B3 Revision (New Specification)
• LI: To revise all of the B3 unit in preparation for the
GCSE exam.
1. To start: describe what is happening at each letter
in the diagram
Can you answer this question? (3 marks)
Topics you need to know:
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Species and adaptations
Extinction
Energy Transfer in food chains/webs
The Carbon Cycle
The Nitrogen Cycle
Indicators of environmental change
Life on Earth and when it originated
Variation and Evolution
Natural Selection
Lets go through
Evidence for Evolution
each of these
Biodiversity
topics in more
Sustainability
detail!
Species and Adaptations
• Can you answer the following:
1. What is the definition of a
species? (1 mark)
2. What is an adaptation? (1 mark)
3. How is a cactus adapted to
survive in hot and dry climates?
(3 marks)
4. List 4 things animals/plants can
compete for? (4 marks)
5. What does a food web show?
(2 marks)
6. What is interdependence?
(1 mark)
Extinction
• A species can become extinct if it is unable to
adapt to a change in the environment, what
could these changes be? (think of 4)
Energy transfer in food chains
• Almost all organisms are dependent on energy from the sun.
• Plants absorb a small percentage of the energy from the sun to
produce their own food via photosynthesis – the energy is then
stored in the plant tissue.
• Other organisms get energy from eating the plants and almost
EVERY food chain starts with a plant.
1.
Not all of the energy is passed on to the next organism in food
chain, list 3 ways that this energy can be lost? (3 marks)
2. Why is their rarely a 4th level in a food chain?
Remember:
Percentage efficiency = energy in tissues
Energy in food eaten x 100
The carbon cycle
• Carbon is a key element in all living things and
is continually recycled as follows:
1. Carbon enters the cycle as carbon dioxide from the
air
2. Plants fix the carbon into their tissues by
photosynthesis and these plants are eaten by
animals or die and decompose
3. Carbon is returned to the air by respiration from
plants and animals, decomposition by MO’s and by
combustion of organic materials (fossil fuels)
The Nitrogen Cycle
• Nitrogen is essential to all living things.
Nitrogen in
air
A
Proteins in
plants
B
D
C
Proteins in
animals
E
F
Nitrates in
soil
Describe what is happening at points A-F
Indicators of environmental change
• Non living and living indicators exist
Non – Living
Levels of Carbon Dioxide
Temperature
Nitrate levels in soil
Living
Phytoplankton
Lichens (fungus and alga
living together)
Mayfly larvae
• Scientists monitor change locally and globally
• Living indicators provide accurate information about
levels of pollution and environment changes e.g.
Mayfly larvae need high levels of oxygen in water so
if they are present suggest that there is little
pollution
Life of Earth
• Life on earth began 3500 million yrs ago
and the 1st life forms were very simple
• Over many yrs these have formed the
variety of organisms today via evolution
• The changes to organisms over time is
due to variation caused by their
environment and their genes
1. What are the 2 pieces of evidence for
evolution and which is more reliable?
2. Why are there some gaps in the
records?
Variation and Evolution
1. What causes variation in
species?
2. What is a mutation?
3. Are all mutations harmful?
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Evolution involves the
development of new species
In a population of organisms
the genes in the population will
change due to mutations, this
is known as the GENE POOL
Natural Selection
• This is the mechanism that Charles Darwin used to
describe how evolution happens.
How evolution happens (Copy and complete)
• Variation exists between members of the same
species. This is caused by their _______ , _______
and _______. Some individuals are born with
characteristics that help them _________. These
individuals will be more likely to _____ and pass on
the ________ __________ to the next generation.
This is an example of ______ __________
Natural Selection
environment
survival feature
survive
mutations
breed
genes
How quickly does evolution happen?
• Over a long period of time advantageous genes become
the norm in a population.
• There are examples of natural selection happening
much faster:
1. Bacteria becoming resistant to antibiotics
2. Head lice becoming immune to medication
Question:
• What would happen to a group of the same species if
they became isolated from each other on separate
islands, would they be able to reproduce after many
years apart? (3 marks)
Charles Darwin Vs
Lamarck
Task:
List the
similarities and
differences
between their
theories!
Believed that species evolved
over time via natural selection
Believed that species had an
‘inner urge’ to change and so
acquired new characteristics
during their lifetime that were
passed to offspring
Biodiversity
This is the variety of life on Earth including:
• The number of species
• The range of different types of
plant/animal/microorganism
• The genetic diversity (Variation)
• The rainforest is very biodiverse and could be
valuable for finding new medicines
Question:
• Species are becoming exist more rapidly than would
be expected, what could be causing this? (4 marks)
Sustainability
• This is meeting the needs of
people today without harming
the resources for future
generations
• BIODIVERSITY must be
maintained to ensure
sustainability!
1. Why is a monoculture not
sustainable?
2. What can manufacturers do
to make products as
sustainable as possible?