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IGCSE Biology 0610
Notes
UYUG
2015 Syllabus
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Page 3 of 68
Biology
Complete compressed notes
For Cambridge International GCSE
Biology (0610)
2015 Syllabus
Page 4 of 68
UYUG
2015 Syllabus
First published: 2014 by
JCHY
AKL
NZ
Republished 2015
© 2014 by JCHY
Images:
© The British Broadcasting Cooperation
All rights reserved. No text in this publication may
be reproduced, stored in a retrieval system, or
copied, without the prior permission of the
copyright owner.
Design and formatting by UYUG
Page 5 of 68
Table of Contents
Section I: Characteristics and classification of living organisms 1
Characteristics of living organisms 1
Classification and diversity of living organisms 1
Concept and use of a classificatory system 1
Viruses, bacteria, and fungi 1
Vertebrates 2
Adaptations of organisms to their environment 2
Flowering plants 2
Arthropods 3
Annelids, nematodes, and molluscs 3
Simple keys 3
Section II: Organisation and maintenance of the organism 4
Cell structure and organisation 4
Cells 4
Functions of parts of a cell 4
Levels of organisation 4
Specialised cells 5
Size of specimens 5
Movement in and out of cells 5
Diffusion 5
Active transport 5
Osmosis 5
Water potential 6
Effects of osmosis on animal and plant tissues 6
Enzymes 6
Temperature and pH 7
Germination of seeds 7
Biological washing powder 7
Enzyme use in food 7
Penicillin 7
Nutrition 8
Nutrients 8
Carbohydrates, fats, and proteins 8
Tests for chemicals 8
Vitamins, mineral salts, fibre and water 9
Microorganisms in the food industry 9
IGCSE Biology 0610 I UYUG
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Food additives 9
Plant Nutrition: Photosynthesis 10
Limiting factor 10
Greenhouse systems 10
Plant nutrition: Leaf structure 11
Parts of a dicotyledonous leaf 11
Plant nutrition: Mineral requirements 11
Minerals 11
Nitrogen fertilisers 11
Animal nutrition: Diet 12
Balanced diet 12
Malnutrition 12
Animal nutrition: Food supply 12
Animal nutrition: Human alimentary canal 13
Alimentary canal 13
Animal nutrition: Mechanical and physical digestion 14
Teeth 14
Chewing, peristalsis and bile 15
Animal nutrition: Chemical digestion 15
Animal nutrition: Absorption 15
Small intestine and colon 15
Villi 15
Hepatic portal vein 15
Animal nutrition: Assimilation 16
Liver 16
Fats 16
Transportation 16
Transport in plants 16
Water uptake 16
Root hair cells 16
Pathway taken by water through a plant 16
Transpiration 17
Factors affecting transpiration 17
Adaptations of leaf, stem and root 17
Translocation 17
Transport in humans 18
Heart 18
Function of the heart 18
IGCSE Biology 0610 II UYUG
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Coronary heart disease 18
Arteries, veins and capillaries 19
Main blood vessels 19
Structure of blood vessels 19
Blood 20
Composition of blood 20
Features of blood cells 20
Immune system 20
Lymphatic system 20
Clotting 20
Respiration 21
Aerobic respiration 21
Anaerobic respiration 21
Gas exchange 22
Function of the lung 22
Mucus and cilia 22
Breathing 22
Excretion in humans 23
Structure of the kidney 23
Dialysis 24
Coordination and response 25
Nervous control in humans 25
Types of nerves 25
Simple reflex arc 25
The eye 26
Hormones 27
Tropic responses 28
Auxin 28
Synthetic plant hormones 28
Homeostasis 28
The skin 28
Maintenance of a constant body temperature 29
Negative feedback 29
Glucose control 29
Drugs 29
Antibiotics 29
Effects of excessive consumption of heroin 29
Effects of excessive consumption of alcohol 30
IGCSE Biology 0610 III UYUG
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Effects of tobacco smoke 30
Section III: Development of the organism and the continuity of life 31
Reproduction 31
Asexual reproduction 31
Sexual reproduction 31
Sexual reproduction in plants 32
Parts of a flower 32
Pollination 32
Sexual reproduction in humans 34
Male reproductive system 34
Female reproductive system 34
Male and female gametes 35
Sexual intercourse 36
Development of new life 36
Sex hormones 37
Methods of birth control 38
Sexually transmitted diseases 38
Gonorrhoea 38
Human immunodeficiency virus (HIV) 38
Growth and development 39
Germination 39
Inheritance 39
Chromosomes 39
Mitosis 40
Meiosis 40
Monohybrid inheritance 40
Variation 41
Selection 41
Genetic Engineering 42
Section IV: Relationships of organisms with one another and with their
environment 43
Energy flow 43
Food chains and food webs 43
Nutrient cycles 44
Carbon cycle 44
Water cycle 45
Nitrogen cycle 45
IGCSE Biology 0610 IV UYUG
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Population size 46
Factors affecting the rate of population growth 46
Sigmoid population growth curve 46
Human population 47
Human influences on the ecosystem 48
Effected ecosystems 48
Agriculture 48
Undesirable effects of deforestation 48
Undesirable effects of overuse of fertilisers 48
Pollution 49
Undesirable effects of pollution 49
Conservation 50
Need for conservation 50
Appendix i
Presentation of data i
Taxonomy i
Genetics ii
Terminology iii
Command words iii
Mathematical requirements iv
Quantities, Symbols and Units v
IGCSE Biology 0610 V UYUG
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IGCSE Biology 0610 VI UYUG
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Section I: Characteristics and classification of living
organisms
Characteristics of living organisms
nutrition – taking in of nutrients which are organic substances and mineral ions, containing raw
materials or energy for growth and tissue repair, absorbing and assimilating them
excretion – removal from organisms of toxic materials, the waste products of metabolism
(chemical reactions in cells including respiration) and substances in excess of requirements
respiration – the chemical reactions that break down nutrient molecules in living cells to
release energy
sensitivity – the ability to detect or sense changes in the environment (stimuli) and to make
responses
reproduction – the processes that make more of the same kind of organism
growth – a permanent increase in size and dry mass by an increase in cell number or cell size
or both
movement – an action by an organism or part of an organism causing a change of position or
place
Classification and diversity of living organisms
Concept and use of a classificatory system
binomial system –a system in which the scientific name of an organism is made up of two
parts showing the genus and species
This method of classification is based on the characteristics of organisms
The genus is always written first, starting with a capital letter, and the species second, starting
with a lower case letter
When written, it just be underlined, as in print it is in italics
Cladistics
This method of classification is based on the genetic similarity/dissimilarity in the DNA or RNA
of an organism
Members of a group will share a common ancestor, and will be more closely related than
members of another group
Viruses, bacteria, and fungi
Viruses Bacteria Fungi
About 100 times smaller than
bacteria
About 1000 times smaller than a
plant cell
Multicellular fungi are composed of
hyphae which forms a network of
mycelium
Do not have a typical cell structure Have a cell wall, made of a material
other than cellulose or chitin
Cell walls made of cellulose or
chitin
Contain a strand of DNA or RNA Have a cell membrane and
cytoplasm, containing glycogen
granules
Cells merge together, with nuclei
spread along cytoplasm
Surrounded by a protein coat
called a capsid
No nucleus, DNA in a single, coiled
chromosome
Secretes enzymes to digest food
outside cells, then absorbs it
Only show one life process,
reproduction (in host cell)
Some have a slime capsule, and/or
flagella(e)
Some produce spores in a
sporangium or cap
IGCSE Biology 0610 1 UYUG
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Vertebrates
Adaptations of organisms to their environment
Flowering plants
Vertebrate
class
Body
covering
Movement Reproduction Sense organs Other details Examples
Fish Scales Fins (also
used for
balance)
Usually
produces
jelly-covered
eggs in water
Eyes but no
ears, lateral
line along
body for
detecting
vibrations in
water
Cold-blooded,
gills for
breathing
Herring,
perch, shark
Amphibians Moist skin 4 limbs, back
feet often
webbed to
make
swimming
more efficient
Produces
jelly-covered
eggs in water
Eyes and ears Cold-blooded,
lungs and skin
for breathing
Frog, toad,
salamander
Reptiles Dry, with
scales
4 legs (apart
from snakes
Eggs with
rubbery,
waterproof
shell - laid on
land
Eyes and ears Cold-blooded,
lungs for
breathing
Crocodile,
python
Birds Feathers,
scales on
legs
Wings, 2 legs Eggs with
hard shell
Eyes and ears Warm-
blooded, lungs
for breathing,
beak
Flamingo,
pigeon
Mammals Fur 4 limbs Live young Eyes and ears
with pinna
(external flap)
Warm-
blooded, lungs
for breathing,
female have
mammary
glands to
produce milk
to feed young,
4 types of
teeth
Elephant,
mouse
Monocotyledon Dicotyledon
Long and narrow leaf Broad leaf
Parallel veins Branching veins
Fibrous roots Tap root
One cotyledon Two cotyledons
Flower parts in 3’s Flower parts in 4’s or 5’s
Vascular bundles scattered, 10% are woody Vascular bundles in a ring, 50% are woody
Grasses, lilies, tulips Oak, lavender, sunflowers
IGCSE Biology 0610 2 UYUG
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Arthropods
Annelids, nematodes, and molluscs
Simple keys
dichotomous key – uses visible features to classify organisms
The key starts with 2 choices, and branches into 2 more in each stage
Insects Arachnids Crustaceans Myriapods
Legs 3 pairs 4 pairs 5 or more pairs 10 or more pairs
Wings Usually 2 pairs – – –
Antennae 1 pair – 2 pairs 1 pair
Structure Divided into head,
thorax and
abdomen
Divided into
cephalothorax and
abdomen
Divided into
cephalothorax and
abdomen
Divided into many
sections, but no
thorax or abdomen
Eyes 1 pair of compound
eyes
Several pairs of
simple eyes
Compound eyes Simple eyes
Gas Exchange Spiracles (tracheal
system)
Book lungs or
tracheal system
Gills Spiracles
Examples Ants, flies, beetles Wolf spider, funnel
web spider
Prawn, crab, lobster Centipedes,
millipedes
Annelids Nematodes Molluscs
Body Elongated, cylindrical
body, covered in mucus
layer
Elongated, cylindrical
body
Most have a shell,
hardened by calcium
carbonate
Segmented body Non-segmented body Have a muscular foot, for
movement or burrowing;
non-segmented body
Mouth and anus present;
bristles (chaetae) usually
present
Body pointed at both
ends
May have eyes on
tentacles
May have clitellum
(reproductive structure)
Examples Earthworm, leech Ascaris Snail, oyster
IGCSE Biology 0610 3 UYUG
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Section II: Organisation and maintenance of the
organism
Cell structure and organisation
Living organisms are made of cells
Cells
Animal cells
The digram shows a liver cell. It is very
active as it has a lot of mitochondria. It
also contains a small temporary vacuole.
Parts of an animal cell
Cytoplasm
Cell membrane
Nucleus
Mitochondria
Small temporary vacuole
Plant cells
The digram shows a palisade cell. It has
a lot of chloroplasts with chlorophyll for
photosynthesis. Plant cells in general are
larger than animal cells.
Parts of a plant cell
Cytoplasm
Cell membrane
Cell wall
Nucleus
Mitochondria
Large Permanent vacuole (sap
vacuole)
Chloroplasts
Functions of parts of a cell
cytoplasm – contains cell organelles, location of chemical reactions
cell membrane – prevents cell contents from escaping, controls what goes in and out of the
cell, partially permeable
cell wall – prevents cells from bursting, freely permeable
nucleus – controls cell division, development and activities
mitochondria – produces energy, by respiration
vacuole – contains salts and sugars, helps keep plant cells turgid
chloroplast – contains chlorophyll, traps light for photosynthesis
Levels of organisation
organelle – cell structure that is specialised to carry out a particular function or job
cell – basic structural and functional unit of a living organism
tissue – a group of cells with similar structures, working together to perform a shared function
organ – a structure made up of a group of tissues, working together to perform specific
functions
organ system – a group of organs with related functions, working together to perform body
functions
IGCSE Biology 0610 4 UYUG
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Specialised cells
Size of specimens
Magnification = size of drawing / size of specimen
Units: millimetres (mm)
Movement in and out of cells
Diffusion
diffusion – the net movement of molecules from a region of their higher concentration to a
region of their lower concentration down a concentration gradient, as a result of their random
movement
Diffusion occurs in gaseous exchange in the lungs, and the release of oxygen from plants
Most cells are 75% water, and many substances are dissolved in water; also important
reactions take place in water
Active transport
active transport – the movement of ions in or out of a cell through the cell membrane, from a
region of their lower concentration to a region of their higher concentration against a
concentration gradient, using energy released during respiration
Active transports occurs in the ion uptake by root hair cells, and uptake of glucose by
epithelial cells of villi
Osmosis
osmosis – the diffusion of water molecules from a region of their higher concentration (dilute
solution) to a region of their lower concentration (concentrated solution), through a partially
permeable membrane
Osmosis occurs in the uptake of water by plants
Cell Function Features Appearance
Ciliated cells Move mucus with
bacteria and dust away
from the lungs
Tiny hairs called cilia
move mucus
Root hair cells Absorbs water and
mineral ions; anchors
plant
The hair extends water
and mineral ion reach,
and increases surface
area
Xylem vessels Transports water and
mineral ions; supports
plant; made of lignin
Thin cells, no cytoplasm
or nucleus; arranged end
to end to form a tube;
lignin makes it waterproof
Muscle cells Cause movement Cells merge to form fibres
that can contract; a lot of
mitochondria
Red blood cells Transport oxygen No nucleus, biconcave
shape, contains
haemoglobin
IGCSE Biology 0610 5 UYUG
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Water potential
water potential – the potential of water to move, down a water potential gradient
For plants to take in water, outside the cells must have a high water potential, and vice versa
Effects of osmosis on animal and plant tissues
Enzymes
catalyst – a substance that speeds up a chemical reaction and is not changed by the reaction
enzymes – proteins that function as biological catalysts
Lock and key
Enzymes have a specific shape, which fit specific substrates
There are 2 kinds of reactions
catabolic – breaks down a substrate to form products
anabolic – joins substrates to form a product
Process of lock and key
– Substrate(s) fits into the active site of an enzyme
– Enzyme-substrate complex is formed, in which bonds in substrate are weakened
– Product(s) are formed, and the enzyme can be used again
Condition Animal cell Plant cell
Submerged in hypotonic solution Water is taken in
Concentration of solute outside of the cell < concentration of solute
inside of the cell
Cell will burst, due to lack of cell
wall
Cell will become turgid, but will no
burst because of cell wall
Submerged in isotonic solution No movement of water
Concentration of solute outside of the cell = concentration of solute
inside of the cell
Cell will not change in size
Submerged in hypertonic solution Water leaves the cells
Concentration of solute outside of the cell > concentration of solute
inside of the cell
Cell will become flaccid, shape
changes; they can become
crenated
Cell will become flaccid, cytoplasm
isn’t pressed against the cell wall
IGCSE Biology 0610 6 UYUG
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Temperature and pH
Enzymes have an optimum temperature, where they work best at, usually about 37°C
In abnormally high temperatures, enzymes can denature
This means the shape of the active site has changed, so it cannot act as a catalyst
But in abnormally low temperatures, enzymes can become inactive
Enzymes also have an optimum pH, usually around pH 7, but there are exceptions
pepsin – pH 2, in the stomach
salivary amylase – pH 6.8
catalyse – pH 7.6, in plants
pancreatic lipase – pH 9
In abnormally high or low pH, enzymes can become inactive, they do not denature
Germination of seeds
Seeds contain stored food, usually in the form of starch
Water enters the micropyle and the warmth helps the amylase breakdown the starch
Biological washing powder
Enzymes are used to break down food stains, such as protease (breaks down proteins) and
lipase (breaks down fat/grease)
This saves energy, but high temperatures will make enzymes denature
Enzyme use in food
Baby food – Trypsin pre-digests foods, making it suitable for babies to eat
Baking – Enzymes in yeast converts sugar to ethanol and carbon dioxide, which makes the
dough rise
Brewing – Enzymes in yeast converts sugar to ethanol and carbon dioxide, which makes drink
alcoholic and fizzy
Cheese – Renin clots milk, forming a curd
Confectionary – Isomerase converts glucose to fructose, which enhances sweetness, and
uses less sugar
Fruit juice – Pectinase breaks down cell walls in juice,
thus increasing volume, clarity and lowers viscosity
Penicillin
The fungus penicillium produces penicillin, which
has antibiotic properties, and digests bacterial cell
walls to prevent bacterial growth, which also
bursts the cell
Penicillin is made by fermenting the bacteria which
produce the chemical and then extracting it, the
production can be intra-cellular or extra-cellular
IGCSE Biology 0610 7 UYUG
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Nutrition
nutrition – taking in of nutrients which are organic substances and mineral ions, containing raw
materials or energy for growth and tissue repair, absorbing and assimilating them
Nutrients
Carbohydrates, fats, and proteins
Carbohydrates
– are made of small units of
monosaccharides, as themselves or in
longer chains
Monosaccharides
Glucose
Fructose
Galactose
Disaccharides
Sucrose (glucose +
fructose)
Lactose (glucose +
galactose)
Maltose (glucose +
glucose)
Polysaccharides
Starch
Cellulose
Glycogen
Chitin
Fats
– are made of 3 units of fatty acids,
bonded to one glycerol unit
They are bonded by a ester bond
(oxygen –O–)
Proteins
– are made of long chains of amino
acids
There are about 20 amino acids, and
their patterns and chains can be very
large and complex
Tests for chemicals
Carbohydrates Fats Protein
Elements C, H, O C, H, O C, H, O, N, S
Structure Starch, glycogen, simple
sugars
Fatty acids, try-glycerol Amino acids
Uses Source of energy Source of energy,
insulation, cell
membranes
Growth, tissue repair, cell
membranes, hair, nails,
can be broken down to
provide energy
Sources Rice, potato, yam, bread,
honey
Lard, oil, butter,
margarine, nuts
Meat, eggs, fish, soy
beans, tofu, nuts
Name Method Positive result
Starch Starch test Add a few drops of iodine
solution to sample
Blue/black colour
Reducing sugar Benedict's test Add equal an amount of
Benedict’s solution to
solution, boil carefully
Colour changes from
blue, to green, to orange,
to red, depending on how
much is present
Protein Biuret test Add sodium hydroxide
(NaOH) to sample, then
add a few drops of
copper sulphate (CuSO4)
Mauve (purple) solution
Fats Emulsion test Add ethanol to sample
and shake
White emulsion
IGCSE Biology 0610 8 UYUG
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Vitamins, mineral salts, fibre and water
Microorganisms in the food industry
Yoghurt
Bacteria ferment milk at about 46°C, and produces lactic acid
Lactic acid coagulates milk
Temperature is then reduced to 5°C to prevent further bacterial growth
Single cell proteins
Bacteria, fungi or unicellular algae produce proteins in a fermenter
The microorganisms reproduce quickly, and can make up for a shortage of protein
But it is very expensive to produce and doesn’t taste very nice
There is also Quorn, which is a mycoprotein made of filamentous fungi (which is not a
single cell protein)
It contains 12.2% protein, 6% fibre and low fat
Food additives
Antioxidants
Stops food from reacting with oxygen, which may spoil food or change colour
Bulking agents
Promotes absorption of water in meats
Colourings
Improves appearance of food
Chlorophyll, saffron or synthetic dyes can be used
Some can cause hyperactivity in children and trigger allergic reactions
Flavourings
Enhances taste of food
Monosodium glutamate, sugar, or aspartame (artificial sweetener) can be used
Risks obesity, and tooth decay
Preservatives
Slows down growth of bacteria, extends shelf life
Sulphur dioxide can be added to jams, fruit juice, beer and wine
Can destroy Vitamin B1
Sodium nitrate can be added to meat
Suspected to be a carcinogen
Importance Deficiency Sources
Vitamin C Maintains healthy skin and
gums, helps with absorption
of iron
Scurvy – bleeding under skin
or bleeding gums
Citrus fruits, tomato, mango
Vitamin D Maintains hard bones, helps
with absorption of calcium
Rickets – soft bones
become deformed, may
have bowed legs
Milk, cheese, fish-liver oil,
egg yolk
Calcium Needed to form healthy
bones and teeth, normal
blood clotting
Rickets and slow blood
clotting
Milk, cheese, fish
Iron Formation of haemoglobin Anaemia – constant
tiredness, lack of energy
Red meat, liver, spinach
Fibre Made of cellulose, adds bulk
to undigested food, helps
with peristalsis
Constipation, long-term
deficiency can cause bowel
cancer
Vegetables, wholemeal
bread, fruit
Water Formation of blood, solvent,
chemical reactions
Dehydration Drinks, fruit, vegetables
IGCSE Biology 0610 9 UYUG
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Plant Nutrition: Photosynthesis
photosynthesis – the fundamental process by which plants manufacture carbohydrates from
raw materials using energy from light
carbon dioxide + water → glucose + oxygen
6CO2 + 6H2O → C6H12O6 + 6O2
Carbon dioxide is taken in through the stomata
Water is taken in through the roots, and through the xylem
Chlorophyll (a green pigment) traps light energy and converts it into chemical energy for the
formation of carbohydrates and their subsequent storage
Factors necessary for photosynthesis
Chlorophyll – traps light to form energy
Light – provides energy
Carbon dioxide – source of carbon
Factors affecting rate of photosynthesis
Light intensity
Greater intensity correlates to a higher rate of photosynthesis, only to a certain extent
Carbon dioxide concentration
Higher concentration correlates to a higher rate of photosynthesis,
Temperature
There is an optimum temperature for each plant, which correlates to the enzymes in
the plant
Limiting factor
limiting factor – something present in the environment in such short supply that it restricts life
processes
Limiting factors of photosynthesis
Water
Light intensity
Light of the red and blue wavelength
Magnesium (for chlorophyll)
CO2 concentration
Greenhouse systems
Carbon dioxide enrichment
Atmospheric air contains about 0.04% CO2
Paraffin or fossil fuels can be burnt to increase CO2 concentration
Releasing pure CO2 from a gas cylinder can also increase CO2 concentration
Optimum light
Insufficient light, especially in winter, can be improved by artificial lights
Optimum temperature
Insufficient heat, especially in winter, can be improved by using a heating system
Burning fossil fuels can be burned for heat and CO2 dually
IGCSE Biology 0610 10 UYUG
→ also means light + chlorophyll
Page 21 of 68
Plant nutrition: Leaf structure
Parts of a dicotyledonous leaf
cuticle – made of wax, waterproofing the
leaf; secreted by upper epidermis cells
upper epidermis – thin and transparent,
act as a disease barrier, no chloroplasts
palisade mesophyll – main region for
photosynthesis
spongy mesophyll – loosely packed, to
allow for gaseous exchange; do not
contain as many chloroplasts
vascular bundle – the vein of a leaf,
made of xylem (transports water and
minerals) and phloem (transports sugars
and amino acids) vessels
lower epidermis – protective layer, site of
gaseous exchange
stomata – minute pores surrounded by
guard cells
guard cells – controls gaseous exchange,
and contains chloroplasts
Plant nutrition: Mineral requirements
Minerals
Nitrate ions
Needed for protein synthesis
All protein contain the element nitrogen
Protein used for cytoplasm and enzymes
If there is a deficiency, the stem will become weak, lower leaves will become yellow
and die, while upper leaves turn pale green
Magnesium ions
Needed for chlorophyll synthesis
Chlorophyll has one magnesium atom in its structure
If there is a deficiency, the leaves will turn yellow, bottom up
Nitrogen fertilisers
Uses
Nitrogen fertilisers increases crop yield
Intensive farming removes nitrates from the soil, which are replenished with fertilisers
Can be replenished by
applying animal manure
crop rotation – growing leguminous plants (peas, beans)
ammonium nitrate
Dangers of overuse
Wilting – caused by causing osmosis, where the water is drawn out of the plant
Eutrophication – destruction of life in rivers or lakes
Please refer to page 48
IGCSE Biology 0610 11 UYUG
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Animal nutrition: Diet
Balanced diet
balanced diet – a diet containing all the needed nutrients in the correct amounts and
proportions
Dietary requirements depends on age, sex and activity of an individual
Generally
Younger children need more energy than adults
Males require more energy than females
Physical work requires more energy than stationary work
Malnutrition
malnutrition – not having a balanced diet, having too little or too much of a nutrient
Effects of malnutrition
Animal nutrition: Food supply
Modern technology has resulted in increased food production
This is achieved by
Modern agricultural machinery – less labour, less workers required
Chemical fertilisers – help crops grow better
Pesticides – kills insects that feed on crop
Herbicides – kills weeds affecting crop
Artificial selection – improves yield, by isolating ones that produce more yield
Problems of world food supply
Not enough food is available in every country
Food may be imported
Fresh food does not last that long
Food can be refrigerated or picked before they’re ripe
Then the food can be ripened by spraying plant auxins
Importing food by air is very expensive
Imported food from a first would country to a poorer one can have a huge impact on
the poorer county’s economy, by reducing the value of food grown by local farmers
Problems which contribute to famine
Unequal distribution of food – depends on wealthiness of country or area
Drought – ruins crops, and prevents them from growing
Flooding – ruins crops, and prevents them from growing
Increasing population – more people to feed, with little food
Cause Effect
Starvation Lack of calories Organ damage
Coronary heart disease Excess fat Poor blood flow, high cholesterol
Constipation Lack of fibre Bowel movements obstructed
Obesity Too much fat of the wrong type Mass increase
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Animal nutrition: Human alimentary canal
ingestion – the taking in substances into the body through the mouth
egestion – the passing out of food that has not been digested, as faeces, through the anus
Alimentary canal
Mouth
Location of ingestion
Teeth grind food and enzymes are secreted by salivary glands
Salivary glands
Produces salivary amylase, which breaks down starch and helps swallowing of food
Oesophagus
Tube shaped organ which passes food down by peristalsis
Stomach
Muscular walls squeeze food to make it a semi-liquid
Gastric juice contains hydrochloric acid and protease
Hydrochloric acid kills bacteria, protease beaks down protein
Small intestine
Duodenum
Receives pancreatic juice
Enzymes break down food
Ileum
Enzymes break down maltose and peptides
Epithelial lining covered in villi, which increases surface area
Pancreas
Produces pancreatic juice, which contains protease, lipase, amylase, and sodium hydrogen
carbonate (to neutralise acid)
Produces hormones insulin and
glucagon
Liver
Produces bile
Bile contains salts that emulsify
fats
Digested foods are assimilated
Glucose is stored as glycogen
Surplus amino acids are
deaminated
Gall bladder
Stores bile
Large intestine
Colon
Reabsorbs water from
undigested food
Absorbs bile salts
Rectum
Stores faeces until it is
egested
Anus
A muscle that controls when
faeces is egested from the body
Digestion occurs in the alimentary canal
Absorption occurs in the small and large intestines
Assimilation occurs in the liver and cells
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Animal nutrition: Mechanical and physical digestion
digestion – the break-down of large, insoluble food molecules into small, water-soluble
molecules using mechanical and chemical processes
physical digestion – the break-down of large pieces of food into smaller pieces
Teeth
Types of human teeth
*a/b; a = lower jaw, b = upper jaw
Tooth structure
Enamel
Covers crown
Hard protective layer made of calcium salts
Dentine
Collagen fibres, sensitive to touch, temperature
and acids
Contains protein which bacteria can feed on
Pulp cavity
Centre of tooth
Contains blood vessels and nerve endings
Cement
Bone like substance that holds tooth in place
Dental decay
A sticky, colourless film of bacteria and
sugars form on the teeth, called plaque
Bacteria feed off plaque, producing
acids, dissolving the enamel
Dentine can dissolve very rapidly once
the enamel is gone, causing toothaches
or infection
Tooth care
Avoid sugary foods, and brush teeth
daily
Use dental floss, or toothpick to remove
remnants of food
Use mouthwash and fluoride toothpaste
Fluoride
Fluoride is absorbed in a child’s diet, and
promotes tooth remineralisation, which
makes teeth stronger
Fluoride in water supplies
Tooth decay decreases; no need
to buy fluoridated toothpaste
Mass medication, no choice
about having treatment; only
benefits growing children; can
cause mottling of teeth
Dental decay
A sticky, colourless film of bacteria and
sugars form on the teeth, called plaque
Bacteria feed off plaque, producing
acids, dissolving the enamel
Dentine can dissolve very rapidly once
the enamel is gone, causing toothaches
or infection
Tooth care
Avoid sugary foods, and brush teeth
daily
Use dental floss, or toothpick to remove
remnants of food
Use mouthwash and fluoride toothpaste
Fluoride
Fluoride is absorbed in a child’s diet, and
promotes tooth remineralisation, which
makes teeth stronger
Fluoride in water supplies
Tooth decay decreases; no need
to buy fluoridated toothpaste
Mass medication, no choice
about having treatment; only
benefits growing children; can
cause mottling of teeth
Incisor Canine Premolar Molar
Position Front Either side of
incisors
Behind canines Back
Description Chisel shaped Cone shaped Blunt and broad; 2
cusps; 1/2 roots*
Blunt and broad;
4/5 cusps*; 2/3
roots*
Function Biting and cutting Tearing Tearing and grinding Chewing and
grinding
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Chewing, peristalsis and bile
Chewing
Form of mechanical digestion
Teeth make food into smaller pieces, which mixes with saliva and creates a large
surface area
Peristalsis
Longitudinal and circular muscles, which contract and relax to move food
This is how food is moved in the alimentary canal
Bile
Emulsifies fats, to increase surface area for the action of enzymes
Animal nutrition: Chemical digestion
chemical digestion – the break-down of large, insoluble molecules into small soluble ones
Enzymes used in chemical digestion
Animal nutrition: Absorption
absorption – the movement of digested food molecules though the wall of the intestine into
the blood or lymph
Small intestine and colon
The region for the absorption of digested food
The small intestine and colon the large pot and absorption of water
Small intestine absorbs 5–10 dm3 per day
Colon absorbs 0.3–0.5 dm3 per day
Villi
Villi cover the surface of the small in
intestine, which increases the internal
surface area
Structure of a villus
Blood capillary
Absorbs glucose and amino acids
Blood movement maintains diffusion gradient
Lacteal
Absorbs fatty acids and glycerol
Epithelial lining
One cell thick wall, which increases diffusion rate
Microvilli increase surface area for absorption
Hepatic portal vein
Transports absorbed food from the small intestine to the liver
After eating, the blood has increased concentrations of glucose, amino acids, vitamins and
minerals, which the liver then reduces the levels back to normal
Enzyme Site of action Conditions Substrate Product(s)
Amylase Mouth, duodenum Slightly alkaline, HCO3−
present
Starch Maltose, glucose
Protease Stomach, duodenum HCl in stomach, HCO3− in
duodenum
Protien Amino acids
Lipase Duodenum Alkaline, HCO3− Fat Fatty acids, glycerol
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Epithelial lining
Lacteal
Blood capillary
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Animal nutrition: Assimilation
assimilation - the movement of digested food molecules into the cells of the body where they
are used, becoming part of the cells
Liver
Metabolises glucose and amino acids
Glucose → glycogen
Amino acids → proteins and
destruction of excess amino
acids
Excess amino acids are destroyed by
deamination
deamination - the removal of the
nitrogen-containing part of amino acids
to form urea, followed by the release of
energy from the remainder of the amino
acid
The liver is also the site of breakdown of
alcohol and other toxins
Fats
Fats are an energy storage substance
Uses
Storing energy, releases twice as
much as carbohydrates do
Insulation in the skin
Myelin sheath on some nerve
cells, to prevent electrical
impulses from leaking
Transportation
Transport in plants
xylem – unidirectional vessel that transports
water and minerals from the roots to the
leaves
phloem – bidirectional vessel transports
sugars and amino acids from the leaves to the
rest of the plant
Positioning of xylem and phloem
In the roots, the xylem is in the centre and the
phloem is around it
In the stems, the xylem is on the inside and
the phloem is outside of it
In the leaves, the xylem is on top and the
phloem is on the bottom
Water uptake
Root hair cells
Absorbs water and ions from the soil
No chloroplasts
Have an elongated shape for increased surface area
Concentration of ions in the vacuoles of root hair cells are high so there is low water potential,
so water enters by osmosis effectively
Pathway taken by water through a plant
Water enters the root hair cell due to high water potential
Water then passes through the cortex cells by osmosis to the xylem
The xylem transports the water and ions from the roots to the leaves
Water passes through the mesophyll and evaporates out of the leaf
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Transpiration
transpiration – evaporation of water at the surfaces of the mesophyll cells followed by loss of
water vapour from plant leaves, through the stomata
mechanism of water uptake – transpiration producing a mention (‘pull’) from above, creating a
water potential gradient in the xylem, drawing cohesive water molecules up the plant
Water vapour loss
Water evaporates due to the irregular shape of the spongy mesophyll, which has a large
surface area, and large air spaces, which them diffuses out through the stomata
Wilting
Occurs when the cells of a plant become flaccid, due to lack of water
Turgid cells help keep the shape of a plant, and do not explode due to a cell wall
Stomata close to prevent water loss
Factors affecting transpiration
Temperature
Higher temperature increases rate of transpiration, as the water molecules gain more
energy to evaporate
Humidity
Lower humidity increases rate of transpiration, as there is a lower concentration of
water molecules outside the leaf, making a steeper concentration gradient for diffusion
Light intensity
Greater intensity of light increases rate of transpiration, as stomata open to allow gas
exchange for photosynthesis
Adaptations of leaf, stem and root
Translocation
translocation – the movement of sucrose and amino acids in phloem:
from regions of production [sources]
to regions of storage OR to regions of utilisation in respiration or growth [sinks]
Transpiration and translocation in different seasons
In spring, sucrose transported from root stores to the leafs
In summer, sucrose is transported from the leafs to the roots stores
Translocation of applied chemicals
If chemicals are sprayed on leaves they get absorbed and enter the plant’s transport system
Systematic pesticides are applied this way so the chemicals are stored in the cell sap
Pests then feed on the plant and become poisoned, and crop yield is increased
Type Adaptations Environment and examples
Mesophytes Stomata on the bottom of the leaf
Waxy cuticle present
Large and thin leaves
Terrestrial plants
Hydrophytes Very thin cuticle
Feathery roots
A lot of stomata on top and bottom of leaf
Aquatic plants
Water lily, elodea
Xerophytes Succulent leaves and/or stem
Extensive root system
Rolled, small or needle leaves
Waxy, few or sunken stomata
Thick waxy cuticle
Desert plants
Prickly pear cactus, pine
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Transport in humans
circulatory system – a system of tubes with a pump and valves to ensure one-way flow of
blood
double circulatory system – a low pressure circulation to the lungs and high pressure
circulation to the body tissues
One circuit has a high pressure because the blood needs to travel from the heart,
around the whole body, and back
The other circuit has a low pressure because the blood only needs to travel from the
heart, to the lungs, and back
The circuit is completed when the blood travels through the heart twice
Heart
Muscular wall
Pumps blood around the body
Thicker on right side
Septum
Divides the left and right sides of
the heart
Chambers
Atriums
Where blood is received
from the vena cava and
pulmonary vein
Ventricles
Where blood is pumped,
through the pulmonary
artery and aorta
Valves
Prevent the back flow of blood
Four valves
Pulmonary and aortic
valves (semi-lunar valves)
Tricuspid valve, mitral
valve (bicuspid valve)
Blood vessels
Deoxygenated blood
Vena cava
Pulmonary artery
Oxygenated blood
Aorta
Pulmonary vein
Function of the heart
– Deoxygenated blood fills the left atrium, and oxygenated blood fills the right atrium
– Atria contract, pumping blood through the tricuspid and mitral valves and into the ventricles
– Ventricles contract, pumping blood through the pulmonary and aortic valve
Physical activity makes the heart beat more quickly
This is so that more oxygen and glucose can get to the muscles to provide energy
Coronary heart disease
coronary heat disease – the blockage of coronary arteries
The blockage causes the heart muscle cells to be deprived of oxygen, and waste builds up,
causing a heart attack
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Causes and preventive measures
Arteries, veins and capillaries
Main blood vessels
Pulmonary artery/vein; between the heart and lungs
Hepatic artery/vein; between the heart and liver
Renal artery/vein; between the heart and kidneys
Structure of blood vessels
Capillaries and tissue fluid
Blood enters capillaries from arterioles and slows down, allowing substances in plasma and
oxygen to diffuse
Liquid in plasma also diffuses, forming tissue fluid, bathing the cells
Tissue fluid helps with the diffusion of ions as well
Waste products such as carbon dioxide is diffused back into the plasma
Causes Explanation Preventive measures
Diet Cholesterol builds up in the arteries, and
eventually block it
Cholesterol-free diet
Stress Increases blood pressure, which can result
in fatty materials collecting in arteries
Find ways to relax and identify
causes of stress and avoid them
Smoking Nicotine damages heat and blood vessels Stop smoking
Obesity Excessive weight strains the heart Go on a controlled diet and
regularly exercise
Lack of exercise Heart muscle loses its tone and becomes
less efficient
Take regular exercise
Blood vessel Structure How structure is related to function
Arteries Thick, tough walls with muscle,
elastic fibres and fibrous tissue
Narrow lumen
Valves absent
Prevent bursting and maintains
pressure
Maintains blood pressure
High pressure prevents back flow
Veins Thin wall - mainly fibrous tissue,
little muscle or elastic fibres
Wide lumen
Valves present
Carries blood at low pressure
Reduces resistance to blood flow
Prevents back flow
Capillaries Permeable wall, one cell thick, with
no muscle or elastic fibres
Lumen about one red blood cell
wide
Valves absent
Allows for quicker diffusion
White blood cells can squeeze
between cells
Blood passes slowly for diffusion
Lower blood pressure
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Blood
Composition of blood
Red blood cells
Contains haemoglobin, which
transports oxygen
White blood cells
Responsible for phagocytosis
and antibody formation
Platelets
Causes clotting
Plasma
Transports blood cells, ions,
soluble nutrients, hormones,
carbon dioxide, urea and plasma
proteins
Features of blood cells
Red blood cells
Biconcave discs, with no
nucleus
White blood cells
Lymphocyte
Produces antibodies
Large nucleus
Phagocyte
Fights disease by
surrounding and
engulfing them
Lobed nucleus
Platelets
Made of fragments of cells
Immune system
The body’s defence system against disease and foreign bodies
Antibody production
Antibodies are produced by lymphocytes, which are formed in lymph nodes. They are
produced in response to pathogens present. A different antibody is produces for each
antigen. The antigens clump the bacteria together, in preparation for phagocytes or to
neutralise the toxins.
Tissue rejection
In organ transplants, the body treats the replacement as an invading organism, so the
organ is rejected.
To prevent this, the donor organ needs to have a similar tissue type to the patient.
Immunosuppressive drugs can be used as well, which shuts down the immune
system. Though the patient will be very susceptible to diseases while recovering, so
they need to be kept in isolation.
Phagocytosis
Phagocytes move to the site of infection, surround the pathogen, and engulf the
pathogens. They are killed by digesting them.
Lymphatic system
lymphatic system – the circulation of body fluids, and the production of lymphocytes
The system contains valves and moves slowly around the body by muscle movement
Lymph vessels
Collects excess tissue fluid from the cells
Lymph nodes/glands
Filters lymph, which traps foreign bodies and site of lymphocyte production
Lacteals
Lymph vessels absorb fatty acids and glycerol from the small intestine
Each villus contains a lacteal, which transports the fatty acids and glycerol to the blood
Clotting
Plasma contains soluble protein fibrinogen
When a blood vessel is damaged or exposed to air, fibrinogen is converted to insoluble fibrin
by the enzyme thrombin
Threads are formed to make a blood clot, and late dries to form a scab
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Respiration
respiration – the chemical reactions that breakdown nutrient molecules in living cells to release
energy
Uses of energy in the body of humans
Muscle contraction
Protein synthesis
Cell division
Active transport
Growth
The passage of nerve impulses
Maintenance of a constant body temperature
Aerobic respiration
aerobic respiration – the release of a relatively large amount of energy in cells by the
breakdown of food substances in the presence of oxygen
glucose + oxygen → carbon dioxide + water
C6H12O6 + 6O2 → 6CO2 + 6H2O
Anaerobic respiration
anaerobic respiration – the release of a relatively small amount of energy by the breakdown of
food substances in the absence of oxygen
Equation for muscles during hard exercise
glucose → lactic acid
C6H12O6 → 2C3H6O3
Oxygen debt
Muscles respire anaerobically when
working vigorously, and lactic acid is
produced, and oxygen debt is created
When oxygen is repaid after working
vigorously, the lactic acid is converted to
a harmless substance pyretic acid
Equation for the microorganism yeast
glucose → alcohol + carbon dioxide
C6H12O6 → 2C2H5OH + 2CO2
Brewing
Yeast is added to a source of sugar
(such as grapes), and this is kept in
warm conditions
Yeast respires with the sugar, which is
called fermentation
Ethanol and carbon dioxide is formed,
making is alcoholic and fizzy
Bread-making
Yeast added to water and sugar to
activate it, and mixed in with flour
Dough is then set to rise in a warm
place
When dough is cooked, ethanol
evaporates, yeast is killed, and carbon
dioxide escapes making the bread light
in texture
Amounts of energy released
In aerobic respiration, it produces 38 adenosine triphosphate molecules, for each glucose
molecule
In anaerobic respiration, it produces only 2 adenosine triphosphate molecules, for each
glucose molecule
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Gas exchange
Gas exchange surfaces
Thin – short distance for gasses to diffuse
Moist – allows gasses to dissolve
Large surface area – large area for diffusion
Ventilated – concentration gradient maintained by movement of air and transport/use of
gasses
These surfaces are present in gills and lungs, and skin surfaces
Function of the lung
Inhaling
– External intercostal muscles
contract, pulling ribcage up and
outwards
– Diaphragm muscles contract, and
move down
– Increase of volume decreases air
pressure, so air rushes in
Exhaling
– Internal intercostal muscles
contract, pulling the ribcage down
and inwards
– Diaphragm muscles relax, and
move up
– Decrease of volume increases air
pressure, so air rushes out
Mucus and cilia
Goblet cells in the trachea produce
mucus, to trap particulate matter
and microorganisms
Cilia cells move the mucus up into
the mouth
Breathing
Composition of inhaled and exhaled air
Rate and depth of breathing
Rate and depth of breathing is increased during physical activity
This is to bring more oxygen to the cells and keep carbon dioxide concentration at a safe
levels
The volume of air inhaled or exhaled is the tidal volume
Breathing rate from normal to exercise, is about 12 to 20 breaths per minute
The maximum amount of air inhaled or exhaled is called the vital capacity
This can all be measured by a spirometer
% of Nitrogen % of Oxygen % of Carbon dioxide
Inhaled air 79 21 0.04
Exhaled air 79 16 4
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Link between physical activity and rate and depth of breathing
The changes in the rate at which tissues respire
causes a change in the concentration of carbon
dioxide as well pH in the tissues and blood
Test for carbon dioxide
Use limewater
Breathe in and out from C
Air enters at A
Air leaves at B
Test-tube on left will remain clear
Test-tube on right will turn milky, as there is a
greater amount of carbon dioxide present
Excretion in humans
excretion – removal from organisms of toxic materials, the waste products of metabolism
(chemical reactions in cells including respiration) and substances in excess of requirements
Such substances include carbon dioxide, urea and salts
Function of the liver
Urea is formed in the liver from
excess amino acids
Alcohol, drugs, and hormones are
broken down in the liver
Function of the kidney
The removal of urea and excess
water and the reabsorption of
glucose and some salts
Urinary system
Diagram on the right
Structure of the kidney
Cortex
Outer layer, containing
nephrons
Medulla
Cone shaped areas
containing kine tubules
Ureter
Carries urine from the
kidney to the bladder
Renal pelvis
Where tubules drain
Bladder
Stores urine
Urethra
Carries urine from the
bladder out of the body
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Structure of kidney tubule
Renal capsule (Bowman’s
capsule)
Filters water, glucose,
urea and slats from the
blood
Tubule
Reabsorbs glucose, most
of the water and some
salts back into the blood
This leads to a
concentration of urea,
and a loss of excess
water and salts
[Shown in yellow in the diagram]
Dialysis
dialysis – the maintenance of
glucose and protein
concentration in blood and
diffusion of urea from blood to
dialysis fluid
Application of dialysis machines
– Blood from the patient is
pumped out
– Blood is filtered through the
dialysis fluid, which is similar to
blood plasma
– Urea and excess water and
salts diffuse into the dialysis fluid
– Cleaned blood passes through
air trap, to remove air bubbles
Advantages and disadvantages of kidney transplants, compare with dialysis
Advantages Disadvantages
Kidney transplant Patients can lead a more normal
lifestyle
Cheaper over a long run
Must take immunosuppressive
drugs
Shortage of organ donors
Operation carries risk
Kidney only lasts 8–9 years on
average
Dialysis Available for all kidney patients
No need for immunosuppressive
drugs
Patient must limit salt and protein
intake between dialysis sessions
Expensive over a long run
Impacts lifestyle
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Coordination and response
Nervous control in humans
human nervous system – made of central nervous system (brain and spinal cord) and the
peripheral nervous system which together serve to coordinate and regulate body functions
sense organ – groups of receptor cells responding to specific stimuli: light, sound, touch,
temperature and chemicals
Such organs include ears, eyes, nose, tongue, skin
Voluntary and involuntary actions
Voluntary
Action caused by a conscious thought
Involuntary
Cannot be consciously controlled, automatic
Initiated by sense receptors
Types of nerves
Simple reflex arc
Sensory, relay and motor
neurones, and a reflex
action as a means of
automatically and rapidly
integrating and
coordinating stimuli with
responses
Effectors
Muscles or glands which
respond when they receive
impulses from motor
neurones
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Relay neurone Sensory neurone Motor neurone
Page 36 of 68
Antagonistic muscles
Muscles come in pairs, so when one contracts, the other can contract to return to a normal
position
Biceps and triceps are antagonistic muscles
When the biceps are relaxed, the tricep is contracted
When you bend your arm about the elbow, the biceps contract and the tricep relaxes
The lower arm moves and reaches the scapula
The eye
Parts of the eye
Blind spot
Part of the retina in front of the
optic nerve
Lacks rods and cones
Ciliary muscle
Ring shaped muscle that
controls lens shape
Conjunctiva
Transparent, sensitive layer on
the cornea
Cornea
Transparent layer which refracts
light to help focus it
Fovea
Area of the retina where there is
a high concentration of cones
Light is usually focused here
Iris
Coloured ring of circular and
radial muscle that controls the
size of the pupil
Lens
Transparent, convex and flexible
Focuses light on retina
Optic nerve
Transmits electrical impulses
from the retina to the brain
Pupil
A hole in the centre of the iris
Controls the amount of light
reaching retina
Retina
Light-sensitive layer made of
rods and cones
Sclera
Tough white layer that protects
eyeball
Suspensory ligament
Attaches to the ciliary muscle
Holds lens in place
Vitreous humour
Transparent, viscous liquid which
maintains the shape of the
eyeball
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Rods and cones
Accommodation
The automatic adjustment of the focus of the eye
Viewing distant objects
Ciliary muscles relax, which pulls the suspensory ligaments tense, making the lens thin
Viewing near objects
Ciliary muscles contract, which removes the tension in the suspensory ligaments (now
slack), making the sense thick
Pupil reflex
The retina detects the brightness of the light entering the eye
Sensory neurones pass an impulse to the brain and back to motor neurones, triggering a
response, either dilating or constricting the pupil
In bright light
Circular muscles are contracted
Radial muscles are relaxed
Pupil is constricted
In dim light
Circular muscles are relaxed
Radial muscles are contracted
Pupil is dilated
Hormones
hormone – a chemical substance, produced by a gland, carried by the blood, which alters the
activity of one or more specific target organs and is then destroyed by the liver
Adrenaline
Secreted by the adrenal gland
Secreted in response to anxiety, exercise or fear
Increases blood glucose concentration and pulse rate
Comparison of nervous and hormonal control systems
Hormones in food production
Hormones are usually used to boost growth rates on animals, such as using oestrogen in
chickens
There are side effects when eating hormone grown animals, such as starting puberty at an
earlier age, or human males developing female characteristics
Function Distribution Comments
Rods Sensitive to low light
intensity
Detects shades of grey
Found in the retina, but
none in the centre of the
fovea or in the blind spot
Provides night vision, to
recognise shapes but not
colours
Cones Sensitive only to high light
intensity
Detects colour
Concentrated in the fovea Three kinds of rods that
detect red, green and
blue light
Nervous system Endocrine system
Speed of action Very rapid Slower
Nature of message Electrical impulses, via neurones Chemical messenger, via
bloodstream
Duration of response Short, until nerve impulse stops Long, until hormone is broken
down
Type of response Muscle contraction Chemical change
Example Blinking, receipting pain Times of anxiety; Growth
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Tropic responses
geotropism – a response in which a plant grows towards or away from gravity
phototropism – a response in which a plant grows towards or away from the direction from
which light is coming
Positive tropisms – the plant grows towards stimulus
Negative tropisms – the plant grows away from stimulus
Auxin
Auxin is the main plant hormone and controls both geotropism and phototropism
Geotropism
In a root placed horizontally, the bottom side contains more auxin and grows less
This makes the root bend downwards in the direction of the force of gravity
In a stem placed horizontally, the bottom side contains more auxin and grows more
This makes the stem bend upwards against the direction of the force of gravity
Phototropism
Auxin makes the shaded side of a shoot grow more, so the shoot will bend towards the light
Investigation for phototropism
Synthetic plant hormones
These hormones can control plant growth
Weedkillers
Weedkillers usually contain a high concentration of hormones
The high concentration upsets normal growth patterns and makes the weed grow too fast,
which then kills the plant
Homeostasis
homeostasis – the maintenance of a
constant internal environment
The skin
Hairs – help with insulation
Sweat glands – secrete sweat
Temperature receptors – detects
temperature
Blood vessels – helps with
vasodilation and vasoconstriction
Fatty Tissue – provides insulation
Seeding A Seeding B Seeding C
Treatment The tips have been
removed
No light reaches the tips More light reaches one
side of the tips
Effect on auxin
concentration
No auxin is produced Equal concentration of
auxin on both sides
Greater concentration of
auxin on shaded side
Result The stems do not grow
longer
The stems grow evenly
and longer on both sides
The cells on the darker
side of the stems grow
longer
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Maintenance of a constant body temperature
Insulation
Fatty tissue prevents heat loss
Hairs can become erect to trap warm air
Temperature receptors in the skin
Sense heat and sends nerve impulses to the hypothalamus
Sweating
Sweat is secreted, and then evaporates, cooling the skin down
Shivering
Muscular activity generates heat
Vasodilation
When it is hot, blood capillaries near the surface dilate, to increase heat loss
Vasoconstriction
When it is cold, blood capillaries near the surface constrict, to reduce heat loss
Hypothalamus
Regulates temperature in the body
Negative feedback
Homeostasis is maintained by negative feedback
If the levels of something (usually hormone levels) rises, the control systems reduce it
If the levels of something falls, the control systems raise it
Glucose control
The pancreas detects the glucose level in the blood and
releases insulin when there is high glucose levels
releases glucagon when there is low glucose levels
The liver then converts
glucose to glycogen if blood glucose is high
glycogen to glucose if blood glucose is low
Drugs
drug – any substance taken into the body that modifies or affects chemical reactions in the
body
Antibiotics
Substances that kill bacteria, by disrupting the reproduction of bacteria
Antibiotics do not work on viruses because they are not living, as they lack the internal
structures antibiotics disrupt in bacteria
Effects of excessive consumption of heroin
A powerful depressant
Problems with addiction
Severe withdrawal symptoms
Crime
Infection, e.g. by sharing needles getting HIV/AIDS
Family breakdown
Sexual promiscuity
Body develops tolerance to the dug
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Effects of excessive consumption of alcohol
Reduced self-control
Depressant
Effect on reaction times
Damage to liver
Social implications
Crime
Sexual promiscuity
Addiction
Financial difficulties
Family problems
Health implications
Damage to liver and brain
Peptic ulcers
Obesity
Effects of tobacco smoke
Tar
A carcinogen, increases risk of lung cancer
Lines the air passages, increasing mucus production and paralysing and damaging
cilia
Nicotine
Addictive, resulting in the addiction to smoking
Raises blood pressure and heart rate
Can lead to a stroke
Stimulates the brain
Can pass to the blood of the fetus
Carbon monoxide
A poisonous gas
Combines with haemoglobin
Smoke particles
Irritate air passages, causing inflammation
Increases mucus production
Coughing in presence of the particles can lead to emphysema (walls of alveoli are
damaged, making large sacs reducing surface area)
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Section III: Development of the organism and the
continuity of life
Reproduction
Asexual reproduction
asexual reproduction – the process resulting in the production of genetically identical offspring
from one parent
Asexual reproduction in bacteria, fungi and potatoes
Bacteria
Reproduce by binary fission
DNA replicates, and then the cell divides into two, forming two daughter cells
Once the daughter cells have grown, they can then reproduce
Fungi
Reproduce by producing spores
Spores are formed inside the sporangium
When it is ripe, it bursts, dispersing the spores
In suitable conditions, the spores germinate and grow
Potatoes
Potatoes are stem tubers
Parent plant photosynthesises and stores the starch in underground tubers
In suitable conditions, the tubers will form shoots and grow
Advantages and disadvantages of asexual reproduction
Sexual reproduction
sexual reproduction – the process involving the fusion of haploid nuclei to form a diploid
zygote and the production of genetically dissimilar offspring
Advantages and disadvantages of sexual reproduction
Advantages Disadvantages
Quick reproduction Lack of genetic variation, less likely to adapt to a
changing or new environment
Only one parent is needed If the parent has no resistance to a disease, the
offspring will not have resistance
No gametes are needed Lack of dispersal can lead to competition for food
All good characteristics are passed on
When there is no dispersal, offspring grow in the
same favourable environment
Advantages Disadvantages
Genetic variation, greater adaption to a changing to
new environment
Two parents needed
New varieties created, which may have resistance to
disease
Growth to maturity is slow
In plants, there are seed dispersal methods, reducing
competition
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Sexual reproduction in plants
Parts of a flower
Petal
Attracts insets
Sepal
Protects the flower as a bud
Stamen (male part)
Anther
Contains pollen sacks,
where pollen is formed
Filament
Supports anther
Carpel (female part)
Stigma
Sticky surface which
receives pollen
Style
Links stigma to ovary,
where pollen tubes grow
Ovary
Contains ovules
Ovule
Develops into seeds
Pollination
pollination – the transfer of pollen grains from the male part of the plant (anther of stamen) to
the female part of the plant (stigma)
Agents of pollination
Insects
Birds
Mammals
Wind
Structural adaptations between insect-pollinated and wind-pollinated flowers
Fertilisation
When the pollen sticks the the stigma, germination is triggered by a sugary solution on the
stigma
The pollen tube then grows from the stigma down the style, and into the ovary, through the
micropyle, and into the ovule
If there are several ovules, they all need to be fertilised individually
Feature Insect-pollinated Wind-pollinated
Petals Large, colourful, scented petals,
with guidelines for insects into the
flower
Absent, or small and
inconspicuous
Nectar Produced in nectaries to attract
insects
Absent, or small and green
Stamen Present inside flower Long filaments hanging freely
Stigmas Small surface area inside the flower Large and feathery hanging
outside, to capture pollen
Pollen Smaller amounts, spiky and sticky Larger amounts, smooth and light
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Structure of a non-endospermic seed
Embryo
Radicle
Becomes the root of the plant
Plumule
Becomes the shoot of the plant
Cotyledons
Energy source
Micropyle
A small opening where water enters
Testa
Protects the seed
Formation of a seed
The zygote divides many times by mitosis, to form an embryo
The ovule wall forms the testa
The ovary wall forms the fruit, which can be fleshy or a dry pod
Wind and animal seed dispersal
Seed and fruit dispersal by wind and animals provides a means of colonising new areas
Wind dispersal
The seed and fruits that use wind dispersal have extensions which act like parachutes
or wings to catch the wind
Plants that use wind dispersal
Dandelion
Sycamore
Internal animal dispersal
The seed and fruits that use internal animal dispersal have brightly coloured and
succulent fruits which contain seeds with indigestible coats which allow the seeds to
pass through the animal undamaged
Plants that use internal animal dispersal
Tomato
Plum
Raspberry
Grape
External animal dispersal
The seed and fruits that use external animal dispersal have hooks which attach them
to the fur of passing animals
Plants that use external animal dispersal
Goose grass
Burdock
Self-pollination and cross-pollination
Self-pollination
Pollen is transferred from the anther to the stigma of the same plant
This makes pollination very efficient, but not much genetic variation
Cross-pollination
Pollen is transferred from the anther to the stigma of the same species
This makes pollination risky, as pollen ay not even reach the stigma, but there is
greater genetic variation
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Sexual reproduction in humans
Male reproductive system
Testes
Produces sperm and hormones
Scrotum
A sac outside of the body containing the testes
Sperm ducts
Carries sperm from the testes to the urethra
Prostate gland
Adds fluid and nutrients to the sperm, in the form of semen
Urethra
Carries urine and semen out of the body
Penis
Passes urine
Used in sexual intercourse and delivers sperm
Female reproductive system
Ovaries
Contains egg and produces hormones
Oviducts
Carries an egg to the uterus by cilia cells
Uterus
Where the baby develops
Cervix
Ring of muscle that separates the uterus and the vagina
Vagina
Where the penis is inserted into during sexual intercourse and semen is deposited
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Menstrual cycle
Day 1–6
FSH released
Endometrium breaks down because
of the lack of progesterone
Day 6–14
Follicle matures
Oestrogen released
Uterus lining builds up
Day 14–15
LH released to trigger ovulation
Progesterone released from the
corpus luteum to maintain uterus
lining
Day 15–28
The lining breaks down because of
the lack of progesterone
If an egg has been fertilised and
implanted, the lining is maintained
and progesterone levels remain high
Hormones in the menstrual cycle
Male and female gametes
Hormine Produces Role
FSH (follicle stimulating hormone) Pituitary gland Causes an egg to mature in an
ovary
Stimulates the ovaries to release
oestrogen
Oestrogen Ovaries Stops FSH being produced (so
that only one egg matures in a
cycle)
Repairs and thickens the uterus
lining
Stimulates the pituitary gland to
release LH
LH (lutenising hormone) Pituitary gland Triggers ovulation (the release of a
mature egg)
Progesterone Ovaries (corpus luteum – the
remains of the follicle)
Maintains the lining of the uterus
during the middle part of the
menstrual cycle and during
pregnancy
Sperm Egg
Size Head about 5 μm by 3 μm and tail
about 50 μm
About 100–200 μm in diameter
Numbers About 300 million per ejaculation 1 every menstrual cycle
Mobility Very mobile (uses tail to move) Very immobile (moves by cilia cells)
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Sexual intercourse
Sexual intercourse involves inserting the erect penis into the vagina
When stimulated, spongy tissue in the the penis fills with blood and the vaginal walls secrete
lubricant
At the climax, semen is ejaculated into the vagina
The sperm then have to swim through the cervix, uterus and into an oviduct
fertilisation – the joining of the nuclei of male gamete (sperm) and the female gamete (egg)
Development of new life
Development of the zygote
The formation of a ball of cells that becomes implanted in the wall of the uterus
Development of the fetus
The zygote continues growth, and starts the development of organs and tissues, this is an
embryo
The placenta develops early on, linking the embryo to the uterus lining
When the organs develop further, and recognisable body parts appear, the embryo is now a
fetus
Amniotic sac and fluid
Amniotic sac – a membrane, formed from the cells of the embryo, which contains the amniotic
fluid and prevents the entry of bacteria
Amniotic fluid – protects the fetus from mechanical shock, drying out and temperature
fluctuations
Placenta
Organ for the exchange of nutrients, gases
and excretory products between the mother
and the fetus
It brings the baby’s blood supply very close to
the mother’s, so the nutrients, gases and
excretory products can diffuse through
The blood does not mix, as the baby and the
mother may have different blood types
Umbilical cord
Umbilical artery
Carries deoxygenated blood, excretory
products and gases to the placenta
Umbilical vein
Carries oxygenated blood, nutrients and gases to the fetus
Ante-natal care of pregnant women
Pregnant women need to have a balanced diet, so the foetus can receive all the nutrients
needed for healthy growth and development
If there is a deficiency in any nutrient, the baby may not develop properly
Extra nutrients needed
Protein – growth
Calcium – development of the skeleton
Iron – forming haemoglobin in red blood cells
Vitamin C and D – blood vessel walls and bones
Some fat – cell membrane
Drugs, chemicals from smoking, alcohol and viruses all can pass through the placenta barrier,
which can put the baby’s health and development at risk
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Labour and birth
Labour
Labour is triggered by the hormone oxytocin
Muscular walls of the uterus contract, and the cervix relaxes
Pressure breaks the amniotic sac and releases amniotic fluid
Expulsion
Contractions become more frequent, cervix dilates, vagina stretches and the baby is
pushed out by the contractions
Afterbirth
The placenta breaks away from the wall of the uterus and passes out
Advantages and disadvantages of breast-feeding compared with bottle-feeding using formula milk
Sex hormones
During puberty, the pituitary gland stimulate the sex organs to produce hormones
In males, the testes produce testosterone
In females, the ovaries produce oestrogen
Secondary sexual characteristics
Site of production and roles of female hormones
Please refer to page 35
Advantages Disadvantages
Breast-feeding Antibodies present in milk, giving
increased immunity to the baby
Mother may not be able to produce
enough milk
Composition of milk is ideal for the
baby
Nipples can become painful
No bacteria, additives or
preservatives, or risk of allergic
reaction
Drugs, chemicals from smoking,
alcohol and viruses can be
transmitted
Develops bond between mother
and baby
Cannot delegate to male partner
Bottle-feeding High quantities is available for the
baby
Lack of antibodies
Either parent can feed the baby Harder to digest for the baby
Cost can be expensive
Testosterone in males Oestrogen in females
Voice becomes lower (breaks) Breasts grow, nipples enlarge
Hair grows on chest, face, under arms and in pubic
area
Hair grows under arms and pubic area
Body becomes more muscular Hips become wider
Penis and testes become larger Uterus and vagina become larger
Testes begin to produce sperm Ovaries start to release eggs and periods begin
(menstruation)
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Methods of birth control
Natural
Abstinence
Rhythm method
Chemical
Contraceptive pill
Spermicide
Mechanical
Condom
Diaphragm
Femidom
Intrauterine device (IUD)
Surgical
Vasectomy
Female sterilisation
Sexually transmitted diseases
Gonorrhoea
Symptoms
Male
Sores on penis
Discharge of pus form penis
Pain when urinating
Inflammation of testicles
Female
Discharge of pus from vagina,
not always obvious
Often no symptoms
Effects
If untreated, it can cause:
Damage to urinary and
reproductive organs, leading to
sterility
Blindness in a baby born to a
mother with the disease
Infection of the heart valves and
joints via the bloodstream
Treatment
Antibiotics
Human immunodeficiency virus (HIV)
Methods of transmission
Unprotected sexual intercourse with an infected person (including homosexuals)
Drug use involving sharing a needle used by an infected person
Transfusions of unscreened blood
Infected mother to fetus
Feeding baby milk from infected mother
Unsterilised surgical instruments
Becoming in contact with an infected person’s blood
Prevention of HIV/AIDS (acquired immune deficiency syndrome)
Condom
Abstinence
Screen blood for transfusions
Use sterilised needles
Feed baby with bottled-milk
Use sterilised surgical instruments
Do not come in contact with a person’s body fluids
How it affects the immune system
HIV attacks certain lymphocytes in the bloodstream
This means antibody count will drop, so the body cannot protect itself if attacked by diseases
such as tuberculosis and pneumonia
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Growth and development
growth – a permanent increase in size and dry mass by an increase in cell number or cell size
or both
development – increase of complexity
e.g change of shape, different types of cells, different or more complex reactions
occurring in a cell
Germination
Seeds require certain conditions for it to germinate
The 3 main factors are water, oxygen, and temperature
Water
Activates enzymes in the seed to turn insoluble food stores into
soluble substances
Makes tissue swell to make testa split
If there is not enough water, it wont be able to support the plants
processes
If there is too much water, it wont allow oxygen to reach the seed for it
to respire
Oxygen
Enters through the gaps of the testa, to be used in aerobic respiration
If there isn’t enough oxygen, the plant cannot undergo respiration,
preventing growth and development
The seed will germinate even if carbon dioxide levels are very low
Temperature
Temperature affects metabolic and growth rates
Depending on the seed, the optimum temperature for germination can
vary hugely, some may stay dormant in optimum temperatures
Inheritance
inheritance – the transmission of genetic information from generation to generation
Chromosomes
chromosome – a thread of DNA, made up of a string of genes
gene – a length of DNA that is the unit of heredity and coeds for a specific protein. A gene
may be copied and passed on to the next generation
allele – any of two or more alternate forms of a gene
haploid nucleus – a nucleus containing a single set of unpaired chromosomes
diploid nucleus – a nucleus containing two sets of chromosomes
Inheritance of sex in humans
2 chromosomes determine the sex of an individual
In a woman, her sex cells are XX
When she produces an egg, the XX is split into 2 haploid cells with a X chromosome
In a man, his sex cells are XY
When he produces sperm, the XY split into 2 haploid cells with a X and Y
chromosome
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Mitosis
mitosis – nuclear division giving rise to
genetically identical cells in which the
chromosome number is maintained by
the exact duplication of chromosomes
Roles of the process of mitosis
Growth
Repair of damaged tissues
Replacement of worn out cells
Asexual reproduction
Meiosis
meiosis – reduction division in which the
chromosome number is halved from
diploid to haploid
Gametes are the result of meiosis
Meiosis results in genetic variation so the
cells produced are not all genetically
identical
Monohybrid inheritance
genotype – genetic makeup of an organism in terms of the alleles present
phenotype – the physical or other features of an organism due to both its genotype and its
environment
homozygous – having two identical alleles of a particular gene. Two identical homozygous
individuals that breed together will be pure breeding
heterozygous – having two different alleles of a particular gene, not pure breeding
dominant – an allele that is expressed of it is present
recessive – an all that is only expressed when there is no dominant allele of the gene present
Punnett squares
These show the possibilities of the genetic composition of the offspring
Punnett squares: ratios
Co-dominance
There could be co-dominance when there are three alleles for a particular gene, such as for
blood types
The A, B and O (genotype denoted as IA, IB, IO respectively) blood groups are alleles that exhibit
both complete and co-dominance
Genotype Phenotype Pattern of inheritance
IAIA A
IAIO A A is dominant over O
IBIB B
IBIO B B is dominant of O
IAIB AB
IOIO O O is recessive to A and B
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1:1 ratio
dominant : recessive
3:1 ratio
dominant : recessive
T – dominant trait t – recessive trait
T t
t Tt tt
t Tt tt
T t
T TT Tt
t Tt tt
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Variation
Continuous variation
This is influenced by genes and the environment, resulting in a range of phenotypes between
two extremes, e.g. height in humans
Discontinuous variation
This is caused by genes alone and results in a limited number of distinct phenotypes with no
intermediates, e.g. A, B, AB, and O blood groups in humans
mutation – a change in gene or chromosome
Mutation is a source of variation
Downs syndrome
It is caused when there is an error in the process of meiosis in the ovaries
When the 21st chromosome does not split and results in cells with 24 and 22
chromosomes
When it is fertilised, it causes the fetus formed will have 47 chromosomes, giving the
baby unusual characteristics
Ionising radiation: A mutagen
Ionising radiation (such as UV/x-rays/gamma rays) can break molecules into smaller
fragments, which are called ions
The ions can then react with other chemical reactions and damage substances and materials
Sickle cell anaemia
A recessive condition where there is a different gene that codes for sickle shaped red blood
cells
Where Hn is the sickle shaped gene, and HN is the normal gene, the HNHn and HnHn
genotypes provide resistance to malaria
Because of this, it is becoming prevalent in countries where malaria is widespread
Selection
Artificial selection
This is when humans select and breed animals and plant which provide economic advantages
Such things that provide economic advantages are keeping twin sheep, or crossing trees/
plants that have a higher yield
Natural selection
natural selection – the greater chance of passing on of genes by the best adapted organisms
Natural selection: A mechanism for evolution
The peppered moth
The peppered moth was light coloured, and so were the trees, free of soot. Once the industrial
revolution began, trees became darker, and dark coloured peppered moths became more
prevalent. The dark coloured moth became prevalent as they had a better chance of survival,
as the trees became darker
Organisms compete for resources
Any trait that increases an organisms competitiveness or survivability or both will be able to
survive, reproduce more often and pass on the favourable offspring
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Antibiotic resistant bacteria
Bacteria reproduce asexually, so a population will have no variation
If the population is treated with an antibiotic, it will be killed
If there is a mutation in the population, the mutated bacteria will not be killed, and is said to be
‘resistant’
Genetic Engineering
genetic engineering – taking a gene from one species and putting it into another species
Producing insulin
Originally insulin was taken from pigs, as insulin from pigs is similar to human insulin
There were several problems with this:
It was expensive
Contamination issues
Allergies
Religious reasons
Current insulin production
Human insulin gene extracted
Gene inserted into the plasmid of the bacteria cell
Bacteria produces insulin to be extracted
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Section IV: Relationships of organisms with one another
and with their environment
Energy flow
The sun is the principal source of energy input to biological systems
Non-cyclic nature of energy flow
Energy flow is not a cycle as it starts from the sun and does not go back there
The energy is then passed on to plants, and then different organisms
At each stage energy is passed into the environment
Food chains and food webs
food chain – a chart showing the flow of energy (food) from one organism to the next
beginning with a producer
food web – a network of interconnected food chains showing the energy flow through part of
an ecosystem
producer – an organism that makes its own organic nutrients, usually using energy from
sunlight, through photosynthesis
consumer – an organism that gets its energy by feeding on other organisms
herbivore – an animal that gets its energy by eating plants
carnivore – an animal that gets its energy by eating other animals
decomposer – an organism that gets its energy from dead or waste organic matter
ecosystem – a unit containing all of the organisms and their environment, interacting together,
in a given area
trophic level – the position of an organism in a food chain, food web or pyramid of biomass,
numbers or energy
Trophic levels
There is energy loss between each trophic level
The loss can be transferred in movement, by respiration and by heat loss
Food chains
Food chains usually have fewer than five trophic levels
This is because about 90% of energy is lost between each trophic level
So there is very little energy transferred to the top of the food chain
This also means there tends to be small numbers of animals at the top of the food chain, and
large numbers at the bottom of the food chain
There is increased efficiency in supplying green plants as human food, as the plants are
producers and get their energy directly from the sun
It is relatively inefficient in feeding crop plants to animals, as animals consuming plants cause
more energy loss (90% in each trophic level) and becomes more inefficient as it goes through
many trophic levels
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Pyramid of biomass
Pyramid of biomass shows the total dry mass of one animal or plant species at each trophic
level
The wider the bar, the heavier the dry mass is
Example
Sparrow hawk
Blue tit
Caterpillar
Oak tree
Pyramid of numbers
Pyramid of numbers shows the population of one animal or plant species at each trophic level
The wider the bar, the more organisms there are
Example 1
Sparrow hawk
Tertiary consumer
Thrush
Secondary consumer
Snail
Primary consumer
Clover
Producer
Example 2
Sparrow hawk
Secondary consumer
Insects
Primary consumer
Oak tree
Producer
Nutrient cycles
Carbon cycle
– Carbon dioxide enters atmosphere by respiration and combustion
– Carbon dioxide is absorbed by producers to make carbohydrates in photosynthesis
– Animals eat plants and pass on carbon compounds
– Carbon dioxide is exhaled from the carbon compounds
– Plants and animals eventually die
– Decomposers eat the dead organisms and carbon dioxide is released
– Some dead organisms do not decompose in some conditions, the dead matter then
fossilises due to pressure and heat, and in the future may be used in combustion
Carbon cycle in the sea
– Carbon dioxide is dissolved in the water
– Some marine animals use the carbon in their diet to produce calcium carbonate to make
shells
– Overtime shells and dead organisms collect on the sea floor, and form limestone
– Due to earth movements, the limestone may become exposed to air, where it is weathered
and carbon dioxide is released back into the atmosphere
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Water cycle
Evaporation
Energy from the sun heats
the Earth’s surface and water
evaporates from oceans,
lakes and rivers
Transpiration
Plants release water vapour
into the air from stomata
Condensation
Moist air cools down as it
rises, and condenses into
water droplets, which form
clouds
Precipitation
As the water droplets in the
cloud get bigger and heavier,
the rain, snow or sleet fall
This is precipitation
Nitrogen cycle
Nitrogen-fixation
Nitrogen-fixation bacteria in the root nodules of certain plants (such as legumes)
convert nitrogen gas into nitrate compounds
Lightning can also convert nitrogen gas into nitrate compounds
Haber process converts nitrogen gas into ammonia for use in fertilisers
Nitrifying bacteria convert ammonium ions into nitrates
Absorption of nitrogen compounds
Plants absorbs nitrates form the soil to produce proteins
Animals eat the plants and produces their own proteins
Death and decay
Decomposers breakdown urea, egested materials and dead organisms
Nitrification and denitrification
Nitrogen is returned to the soil as ammonium ions
Nitrifying bacteria convert ammonium ions into nitrates
Denitrifying bacteria break down nitrates and release nitrogen gas back into he
atmosphere
Effects of the combustion of fossil fuels and the cutting down of forests
Less photosynthesis, less oxygen
Increasing numbers of humans, we respire carbon dioxide
Melting of polar ice caps, flooding in low-lying land
Dramatic change and imbalance to weather
Extinction of certain species that cannot survive higher temperatures
Oxygen concentration Carbon dioxide concentration
Combustion of fossil fuels Decreases Increases
Cutting down of forests Decreases Increases
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Population size
population – a group of organisms of one species, living in the same area at the same time
Factors affecting the rate of population growth
Food supply
More food will allow organisms to breed more successfully
Organisms also need to right nutrition as well, or else it will have a deficiency
Shortage to food can result in death to force emigration, reducing population
Predation
If there is heavy predation, the organism may not be able to reproduce fast enough to
replace the eaten population, so the population of the prey will drop
If predator numbers decrease due to limiting factors, the population of the prey will be
able to rise again
Disease
Causes organisms to die, and the disease can possibly spread easily, greatly reducing
the population size and reproduction capabilities
Sigmoid population growth curve
Lag phase
New population takes time to settle and mature
Reproduction rate is low
Population may be dispersed
Exponential (log) phase
Rapid reproduction rate causes exponential growth
Limiting factors do not limit much growth
Stationary phase
Limiting factors start to effect population, such as shortage of food
Environment is holding the maximum number for the population
Rate of reproduction slows down
Birth rate is equal to death rate
Death phase
Limiting factors effect the population hugely
Lack of food, and change of environment causes high death rate
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Time
Population size
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Human population
Human population has been quite stable for 80,000 years
The population started dramatically increasing from 1000 BC
Due to industrialisation, human population has exponentially increased only in the last 100
years
Factors increasing growth
Low infant mortality
Higher life expectancy
Better nutrition
Better housing
Cleanliness
Medical advances
Factors controlling growth
Disease
Famine
War
Factors stabilising growth
Better education (particularly women)
Better living conditions
Family planning
Reduced need for physical labour
Social implications of human population size
Higher demand for all products
Housing
Roads
Cars
Food
Leisure and recreational space
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Human influences on the ecosystem
Effected ecosystems
Tropical rainforests
Deforestation
Urbanisation
Produces more waste
Consumes more energy
Destroys natural habitats
Hunting
Killing animals for skin, tusks,
horns and others
Such animals are tigers,
rhinoceros, and elephants
Oceans
Pollution
Plastic material affect animals
Fishing
Overfishing increases chances of
extinction of certain species
Such animals are whales, atlantic
cod, and herring
Sharks are finned and dumped
back into the ocean, leaving
them immobile
Important rivers
Eutrophication
Agriculture
Undesirable effects of deforestation
Extinction
Reduced habitat area and food sources can lead to extinction
Animal and plant diversity is reduced
Food chains are disrupted
Loss of soil
Removal of trees means the soil becomes loose, due to lack of roots
Soil erosion can can result in leaching of minerals and eventually desertification
Soil erosion can lead to flooding and mudslides and lakes can become silted up
Flooding
Leaching of nutrients can lead to eutrophication
Carbon dioxide build up
Less carbon dioxide is absorbed by the atmosphere, increasing the greenhouse effect
Less oxygen is produced, so atmospheric oxygen levels can drop
Undesirable effects of overuse of fertilisers
Eutrophication of lakes and rivers
When water plants receive too many nutrients, flourishing and creating an imbalance in the
ecosystem
Process of eutrophication
– Nitrates are water soluble,
and are washed into the
water by rainfall, by a
process called leaching
– Extra nitrates cause rapid
algal growth and water plants
flourish
– Algae die, as it blocks light
for algae below
– Bacteria decompose algae,
rapidly using oxygen up via aerobic respiration
– Aquatic animals die from oxygen starvation or suffocation
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Pollution
Undesirable effects of pollution
Water pollution
Sewage
Can result in eutrophication, similar to overuse of fertilisers
Sewage contains high levels of phosphates, organic matter and bacteria
If untreated sewage is disposed, diseases such as cholera and typhoid can be
transmitted
Chemical waste
Heavy metals may be dumped in low concentrations, at non toxic levels
However bioaccumulation occurs if it enters the food chain
Plankton absorb the chemical, and small fish eat it, passing on the toxins which
cannot be excreted
Humans may eat many fish, and accumulated high concentrations of the chemical
Such poisons are mercury and lead
If oil i dumped, it forms a layer over the water
When animals pass through the oil, such as birds, it coats them with oil
The birds will try remove the oil by swallowing it, poisoning them
It can disrupt food chains
Air pollution by sulphur dioxide
Sulphur dioxide is released when fossil fuels are burnt
Then sulphur dioxide dissolves in the water vapour in clouds
When it rains, this is called acid rain
It causes several problems
Increases acidity of lakes, rivers and ponds, and leaches aluminium ions
Damages gills of fish, eventually killing them
Some fish cannot survive more acidic water
Hazard to people with asthma and bronchitis
Corrosion of limestone on buildings
Air pollution by greenhouse gases
Carbon dioxide
Released in combustion of fossil fuels
Methane
Released from livestock, coal mining and natural gas
Pollution due to pesticides
Insecticides
Kills unwanted insects, however it can kill useful insects such as bees
Some insecticides are non-biodegradable and stay in the environment for a long time
Bioaccumulation of toxin DDT can occur
Example of bioaccumulation of DDT
Herbicides
Kills unwanted weeds in a crop, and reduces competition to increase yield
It may kill rare plant species unintentionally
Water Algae Protozoa Small fish Osprey
DDT
concentration in
parts per million
0.000003 0.04 0.2 2 20
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Pollution due to nuclear fall-out
Nuclear fall-out occurs when radioactive
particles are released due to a leak from
a nuclear power plant or from a nuclear
explosion
The radioactive material can be
absorbed by organisms, and
bioaccumulates in food chains
Radioactivity can change DNA, and
cause mutations, cancer, and illness at
every level of a food chain
Effects of non-biodegradable plastics
Trapping/choking birds, fish and other
animals
Collects in rivers and block pathways
Acid rain
Caused by sulphur dioxide and nitrogen
oxides (from furnaces and engines)
Acid rain can be reduced by
Catalytic converters – converts
nitrogen oxides to nitrogen
Using renewable energy over
burning fossil fuels
Using slaked lime to neutralise
acidic oxides in factories
Global warming
The increase of carbon dioxide and
methane cause global warming because
it absorbs heat energy reflected from the
earth and prevents it from escaping into
space
Conservation
Need for conservation
Species and their habitats
Species and animals and plants can be in danger of extinction due to human damage to the
environment
Loss of species means loss of genes, which can be used in genetic engineering
Species have a role in the ecosystem, if it is removed it will cause an imbalance
If there is habitat destruction, poses a huge threat to the survival of the species
Natural resources
Water
Used to grow food, keep clean, provide power, control fires and hydration
Fresh water can come from rain, but the Earth’s freshwater is being used faster than it
can be replenished
Non-renewable materials
Used for transport and a means to provide energy
If not conserved it can run out, and we must use a different means to gain energy
Recycling
Paper
Paper is made of wood, and if it is recycled, less trees are needed to be cut down
Used paper is turned into pulp, sanitised, and printing ink and dyes are removed
The pulp can be rolled into sheets to make recycled paper
Water
Sewage is mostly composed of water, which can be recycled back into water supplies
and systems
Sewage treatment
Large objects screened out of sewage
Sewage sets in grit settling tank, for other matter to sink
Organic matter settle in sludge-settling tank
After digestion in a sludge digester, the can be used as fertiliser
Methane gas can be generated for use as fuel
Remaining liquid sprinkled on to the top of an aeration tank containing stones,
where microorganisms digest remaining organic matter
Water is chlorinated to kill bacteria
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Appendix
Presentation of data
The solidus (/) is to be used for separating the quantity and the unit in tables, graphs and
charts, e.g. time/s for time in seconds
(a) Tables
Each column of a table will be headed with the physical quantity and the appropriate unit, e.g.
time/s
There are three acceptable methods of stating units, e.g. metres per sec or m per s or m s-1
The column headings of the table can then be directly transferred to the axes of a constructed
graph
(b) Graphs
Each axis will be labelled with the physical quantity and the appropriate unit, e.g. time/s.
The graph is the whole diagrammatic presentation. It may have one or several curves plotted
on it
Curves and lines joining points on the graph should be referred to as ‘curves’
Points on the curve should be clearly marked as crosses (x) or encircled dots (☼). If a further
curve is included, vertical crosses (+) may be used to mark the points
(c) Pie Charts
These should be drawn with the sectors in rank order, largest first, beginning at ‘noon’ and
proceeding clockwise
Pie Charts should preferably contain no more than six sectors
(d) Bar Charts
These are drawn when one of the variables is not numerical, e.g. percentage of vitamin C in
different fruits
They should be made up of narrow blocks of equal width that do not touch
(e) Histograms
These are drawn when plotting frequency graphs with continuous data, e.g. frequency of
occurrence of leaves of different lengths
The blocks should be drawn in order of increasing or decreasing magnitude and they should
be touching
Taxonomy
Taxonomy is the study of the principles of the organisation of taxa into hierarchies
There are seven levels of taxon – kingdom, phylum, class, order, family, genus and species
These may be used when teaching the concept and use of a classificatory system, the variety
of organisms, and the binomial system
(a) Five Kingdoms are now recognised as
prokaryotes (Prokaryotae), including bacteria and blue-green bacteria
protoctists (Protoctista), including green, red and brown algae and protozoans
fungi (Fungi)
plants (Plantae)
animals (Animalia)
The viruses cannot be fitted into this classificatory system
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(b) The binomial system of naming gives each organism a two-word name, e.g. Homo sapiens. The
first word is the generic name (genus) and the second word is the specific name (species).
(c) Generic and species names are distinguished from the rest of the text either by being set in italics
(in print) or by underlining (when written or typed).
(d) The generic name always takes an initial capital (upper case) letter. It can be accepted as a
shorthand for the specific name where the intent is obvious, e.g. Plasmodium, and in these
circumstances can stand alone. The specific name always has an initial small (lower case) letter when
following the generic name, e.g. Escherichia coli
(e) The scientific name should generally be written in full when it is first used, but may then be
abbreviated when subsequently used, e.g. Escherichia coli becomes E. coli
(f) The common name should not normally be written with an initial capital letter, e.g. cat and dog. The
exception is Man, where it is the common name for a species where the two sexes are distinguished
by the terms man and woman. The generic
(g) A species is not easy to define but an acceptable general definition is as follows: ‘A group of
organisms capable of interbreeding and producing fertile offspring’.
Genetics
(a) The terms gene and allele are not synonymous
A gene is a specific length of DNA occupying a position called a locus
A specific function can be assigned to each gene
An allele is one of two or more different forms of a gene
(b) A standard form of presenting genetic crosses should be adopted. The following symbols should
be used as shown:
P designates the cross of pure-breeding (homozygous) individuals F1 designates the offspring
of homozygous parents
F2 designates the offspring produced by crossing F1 parents.
(c) The format for the course of a genetic cross should be labelled as shown:
parental phenotypes
parental genotypes
gametes
offspring genotypes
offspring phenotypes
etc.
(d) The gene should be designated by a letter or letters so that upper and lower case versions are
easily distinguishable, e.g. B and b. The upper case letter indicates the dominant allele and the lower
case letter indicates the recessive allele.
(e) The symbols for gametes should be circled to indicate the discrete nature of each gamete.
(f) Some form of checkerboard should be used to demonstrate genotypes that can result from
random fusion of gametes. Candidates should understand that genotypes are only possible
combinations and that only a very large number of offspring can result in all combinations being
achieved.
(g) The term incomplete dominance should be discontinued and in the particular case where alleles
are equally dominant it should be called codominance. Thus codominance should be used where the
influence of both alleles is shown in the phenotype, e.g. the AB blood group in humans.
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Terminology
(a) Wherever possible, English terms should be used in preference to Latin or Greek terms, e.g. the
term red blood cell should be used and not erythrocyte
(b) Generalised terms should be stated in English, e.g. small intestine
(c) Where no suitable English terms exist, Latin terms are unavoidable and will need to be used, e.g.
atrium, bronchi, villi
Command words
This is a glossary of terms that could be used in the examination
The list is not exhaustive, and has been kept brief
1. Define (the term(s) ... ) is intended literally, only a formal statement or equivalent paraphrase being
required.
2. What do you understand by/What is meant by (the term(s) ... ) normally implies that a definition
should be given, together with some relevant comment on the significance or context of the term(s)
concerned, especially where two or more terms are included in the question. The amount of
supplementary comment intended should be interpreted in the light of the indicated mark value.
3. State implies a concise answer with little or no supporting argument, e.g. a numerical answer that
can readily be obtained ‘by inspection’.
4. List requires a number of points, generally each of one word, with no elaboration. Where a given
number of points is specified, this should not be exceeded.
5. (a) Explain may imply reasoning or some reference to theory, depending on the context. It is
another way of asking candidates to give reasons for. The candidate needs to leave the examiner in
no doubt why something happens.
(b) Give a reason/Give reasons is another way of asking candidates to explain why something
happens.
6. (a) Describe, the data or information given in a graph, table or diagram, requires the candidate to
state the key points that can be seen in the stimulus material. Where possible, reference should be
made to numbers drawn from the stimulus material.
(b) Describe, a process, requires the candidate to give a step by step written statement of what
happens during the process.
Describe and explain may be coupled, as may state and explain.
7. Discuss requires the candidate to give a critical account of the points involved in the topic.
8. Outline implies brevity, i.e. restricting the answer to giving essentials.
9. Predict implies that the candidate is not expected to produce the required answer by recall but by
making a logical connection between other pieces of information. Such information may be wholly
given in the question or may depend on answers extracted in an earlier part of the question.
Predict also implies a concise answer, with no supporting statement required.
10. Deduce is used in a similar way to predict except that some supporting statement is required,
e.g. reference to a law or principle, or the necessary reasoning is to be included in the answer.
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11. (a) Suggest is used in two main contexts, i.e. either to imply that there is no unique answer (e.g. in
Biology, there are a variety of factors that might limit the rate of photosynthesis in a plant in a
glasshouse)
(b) Suggest may also be used to imply that candidates are expected to apply their general
knowledge and understanding of biology to a ‘novel’ situation, one that may be formally ‘not in the
syllabus’ – many data response and problem solving questions are of this type.
12. Find is a general term that may variously be interpreted as calculate, measure, determine, etc.
13. Calculate is used when a numerical answer is required. In general, working should be shown,
especially
where two or more steps are involved.
14. Measure implies that the quantity concerned can be directly obtained from a suitable measuring
instrument (e.g. length, using a rule, or mass, using a balance).
15. Determine often implies that the quantity concerned cannot be measured directly but is obtained
by calculation, substituting measured or known values of other quantities into a standard formula, e.g.
relative molecular mass.
16. Estimate implies a reasoned order of magnitude statement or calculation of the quantity
concerned, making such simplifying assumptions as may be necessary about points of principle and
about the values of quantities not otherwise included in the question.
17. Sketch, when applied to graph work, implies that the shape and/or position of the curve need
only be qualitatively correct, but candidates should be aware that, depending on the context, some
quantitative aspects may be looked for, e.g. passing through the origin, having an intercept,
asymptote or discontinuity at a particular value.
In diagrams, sketch implies that a simple, freehand drawing is acceptable; nevertheless, care should
be taken over proportions and the clear exposition of important details.
Mathematical requirements
Candidates should be able to:
add, subtract, multiply and divide
understand averages, decimals, fractions, percentages, ratios and reciprocals
recognise and use standard notation
use direct and inverse proportion
use positive, whole number indices
draw charts and graphs from given data
interpret charts and graphs
select suitable scales and axes for graphs
make approximate evaluations of numerical expressions
recognise and use the relationship between length, surface area and volume and their units,
on metric scales
use usual mathematical instruments (ruler, compasses)
understand the meaning of radius, diameter, square, rectangle
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Quantities, Symbols and Units
SI Units
Quantity Name of unit Symbol
length kilometre km
metre m
centimetre cm
millimetre mm
micrometre μm
mass tonne
kilogram kg
gram g
milligram mg
microgram μg
temperature degrees Celsius oC
time year y
day d
hour h
minute min
second s
amount of substance mole mol
Derived SI Units
energy kilojoule kJ
joule J
Recommended units for area, volume & density
area hectare ha
square metre m2
square decimetre dm2
square centimetre cm2
square millimetre mm2
volume cubic kilometre km3
cubic metre m3
cubic decimetre (litre) dm3
cubic centimetre (millilitre) cm3
cubic millimetre mm3
density kilogram per cubic metre kg m-3
gram per cubic centimetre g cm-3
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CIE Science Notes
