Adaptation

BIOLOGY • ADAPTATION AND EVOLUTION • ADAPTATION

Section 1: Variation

• What is variation?

In biology, variation refers to the differences we

can observe between individuals in a population.
The differences might be physical (height,
DIAGRAM 01:
weight and colour), behavioural (aggression and
obedience) or physiological (disease resistance
and rate of metabolism).

Variation is sometimes classified as continuous

or discontinuous. Continuous variation refers
to differences in a population, which can range
from one extreme to another, such as weight or
height. An individual can be any weight between
the two extremes. In discontinuous variation the
differences are limited and fall within discrete
categories, such as blood groups A, B, AB and O.
Individuals have one of these blood groups and
cannot have some intermediate type of
blood group.

Height is an example of continuous

variation, as an individual can
fall anywhere within a continuous
• Suggested Films
range of heights – Variation
– FactPack: Classification

Extension Question
Q1. Is skin colour an example of continuous or discontinuous variation?
Skin colour is an example of continuous variation. Skin can differ in colour from very pale to very dark.

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 BIOLOGY • ADAPTATION AND EVOLUTION • ADAPTATION

• What causes these variations?

Differences within a population can be caused by genes,

the environment, or a combination of both. Human
blood groups, for example, are determined by the genes
we inherit from our parents, whereas the language we
speak is determined by the environment we grew up
in. Our weight is determined by both our genes and our
environment operating together.

• Suggested Film
– Variation

Differences in blood type are determined by

genes alone, not by our environment

Extension Question
Q2. What causes variation in skin colour?
The differences we see in skin colour are caused by both genes and the environment. Different genes cause different
amounts of pigmentation to be present in the skin, but exposure to sunlight can also have an effect.

• Why is variation important?

Variation in a population is essential in the long term, because it allows a species to adapt to changing conditions. If
conditions change, some organisms will be better suited to those conditions than others, and so they are more likely to
survive and reproduce. If the beneficial differences are caused by genetic factors, these can be passed on to the next
generation, which will therefore be better adapted to the new conditions.

• Suggested Film
– Bizarre Adaptations

Extension Question
Q3. How do bacteria evolve to become resistant to antibiotics?
Antibiotics are chemicals used to kill bacteria. Although they are usually extremely effective at doing this, there are
occasionally bacteria which survive because they show slight differences in their structure and chemistry. Those that
survive are effectively selected for, and they go on to reproduce to form a population of resistant organisms. This is
an example of evolution in action.

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 BIOLOGY • ADAPTATION AND EVOLUTION • ADAPTATION

Section 2: Adaptation

• What is adaptation?

Adaptation refers to the way that organisms are suited to their environment.
They may be suited in terms of their anatomy, behaviour and physiology.
For example, many species of organism have colouration, which helps them
to be less easily seen by predators or their prey. We call this adaptation
camouflage. Similarly, some organisms will play dead when under threat. This
is a behavioural adaptation which helps them to survive. All species show
adaptations to their environment.
This species of bush-cricket has adapted
to camouflage effectively with leaves,
• Suggested Film allowing it to be hidden from both
– Adaptation predators and prey

Extension Question
Q4. Why do polar bears have white fur?
Polar bears have white fur so they can be less easily seen against the snowy background of the Arctic. This is an
adaptation which helps them to catch prey and therefore survive.

• How are organisms adapted to live in the polar regions?

Despite the extreme low temperatures and limited supply of food, many
organisms are able to survive and reproduce in the polar regions.
Most show physical adaptations, which help to reduce heat loss. They
tend to be well insulated with fur, blubber and feathers, and most are large
in order to reduce their surface area to volume ratio. Many also show
behavioural adaptations; some huddle together to conserve heat, while
others hibernate through the coldest periods of the year.

These emperor penguin chicks have • Suggested Film

adaptations that let them survive the – Life in the Freezer
harsh polar climate

Extension Question
Q5. What happens to animals when they hibernate?
Animals usually hibernate when it is very cold and when there is little food to be found. They become very inactive
and their metabolic rate slows down in order to conserve food supplies. They often rely entirely on their body reserves
of fat.

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 BIOLOGY • ADAPTATION AND EVOLUTION • ADAPTATION

• How do organisms survive in the desert?

To survive in the desert, organisms need to stay

cool and conserve water as much as possible. DIAGRAM 02:
Many show remarkable adaptations to these
conditions. Cacti, for example, can store water in
their stems, and do not have leaves in order to
reduce evaporation. Many animals only come out
at night when conditions are cooler, and some,
such as the desert rat, have the ability to lose
very little water in their urine.

• Suggested Film
– Life in Hot Deserts

Extension Question
Q6. Why do some desert organisms have
large ears?

As well as helping to funnel sound, large

ears increase the surface area of an animal.
This can help the organism to lose heat to its
environment.

Section 3: Evolution

• How do organisms evolve to adapt to changing conditions?

Organisms evolve through a process of natural selection.

In any population we can usually observe differences in
Extension Question
the anatomy, behaviour and physiology of the individuals. Q7. Are organisms evolving in response to
Some individuals are therefore likely to be better suited to global warming?
a new set of environmental conditions, and so more likely
to survive and reproduce. Some of their offspring are likely There is substantial evidence that certain species,
to inherit the same features which were advantageous to including some birds and insects, have evolved in
their parents, and so over time more of the population show response to the global warming of the past 150 years.
the beneficial features. This is the process of evolution by Increased temperatures suit some organisms in a
natural selection. population more than others. Those better suited are
more likely to survive and reproduce and thereby pass
on their characteristics to the next generation.
• Suggested Film
– Adaptation

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• What is co-evolution?

Co-evolution occurs when two species evolve in response to the selection

pressure from each other. This is classically seen in predator-prey
relationships. Only the fastest prey can escape their predators, so over time
the prey population evolves to become faster. Now only the fastest predators
can catch any prey, so over time the predator population becomes faster.

Co-evolution is also seen between viruses and their host. Only those host
organisms with the strongest immune systems might survive an infection,
so over time the population evolves to become more resistant to disease.
However, some viruses are able to survive, and these co-evolve as the
hosts’ defences change. The development of the land iguana’s sharp
claws and climbing skills has led to the
• Suggested Films opuntia cactus evolving a slippery
bark to reduce predation
– Predators and Prey
– FactPack: Super Predators
– FactPack: Super Prey

Extension Question
Q8. Are humans evolving?
Humans are definitely still evolving. Agriculture and modern medicine may have reduced some of the obvious
selection pressures, but factors such as sexual selection and resistance to disease are still at work.

• What is sexual selection?

To pass on its genes to the next generation, an organism has to attract

a mate and reproduce. Any factor which helps to attract a mate, such as
colourful plumage or a courtship display, will be selected for, and if caused
by genes, passed on to the next generation. This explains many of the
bizarre adaptations we see in the natural world.

• Suggested Films
– Sexual Selection
– FactPack: Deadliest Animals

Extension Question
Q9. Why do many male animals fight for a mate?
If you fight other males for mates and win, your genes will be passed on
to the next generation. If you won the fight by being bigger, stronger and
more aggressive, then the genes for those characteristics will be passed
The colourful tail of the male peacock is on to the next generation.
designed to attract potential mates

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 BIOLOGY • ADAPTATION AND EVOLUTION • ADAPTATION

• Quizzes

Adaptation

Basic Advanced

• Cacti store water in their stems. What kind of • What type of adaptation is camouflage an example
adaptation is this? of?

A – physical A – physical
B – behavioural B – behavioural
C – genetic C – genetic
D – reproductive D – reproductive

• What type of adaptation is camouflage an example • Many birds have attractive plumage to attract mates.
of? What type of adaptation is this?

A – physical A – environmental
B – behavioural B – behavioural
C – genetic C – genetic
D – reproductive D – reproductive

• What causes new characteristics to appear? • What causes new characteristics to appear?

A – selection pressures A – selection pressures

B – mutations B – mutations
C – variation C – variation
D – evolution D – evolution

• What is extinction? • What causes species to adapt to

new conditions?
A – the death of an organism
A – death
B – the evolution of an organism
B – mutations
C – the evolution of a species
C – variation
D – the loss of a species
D – evolution

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 BIOLOGY • ADAPTATION AND EVOLUTION • ADAPTATION

Variation

Basic Advanced

• What is the term used to describe differences be- • What is the term used to describe differences be-
tween individuals of a population? tween individuals of a population?
A – appearance A – appearance
B – variation B – variation
C – genetic C – genetic
D – environmental D – environmental

• Body weight is an example of what type • Height in humans is an example of what type of
of variation? variation?
A – genetic A – genetic
B – environmental B – environmental
C – continuous C – continuous
D – discontinuous D – discontinuous

• Gender is an example of what type • Blood group is an example of what type

of variation? of variation?
A – genetic A – genetic
B – environmental B – environmental
C – continuous C – continuous
D – discontinuous D – discontinuous

• What causes inherited variation? • What causes differences in height?

A – genetic factors only A – genetic factors only
B – environmental factors only B – environmental factors only
C – genetic and environmental factors C – genetic and environmental factors
D – neither D – neither

• What causes differences in blood group?

A – genetic factors only
B – environmental factors only
C – genetic and environmental factors
D – neither

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 BIOLOGY • ADAPTATION AND EVOLUTION • ADAPTATION

• Answers

Adaptation

Basic Advanced

• Cacti store water in their stems. What kind of • What type of adaptation is camouflage an example
adaptation is this? of?

A – physical A – physical
B – behavioural B – behavioural
C – genetic C – genetic
D – reproductive D – reproductive

• What type of adaptation is camouflage an example • Many birds have attractive plumage to attract mates.
of? What type of adaptation is this?

A – physical A – environmental
B – behavioural B – behavioural
C – genetic C – genetic
D – reproductive D – reproductive

• What causes new characteristics to appear? • What causes new characteristics to appear?

A – selection pressures A – selection pressures

B – mutations B – mutations
C – variation C – variation
D – evolution D – evolution

• What is extinction? • What causes species to adapt to

new conditions?
A – the death of an organism
A – death
B – the evolution of an organism
B – mutations
C – the evolution of a species
C – variation
D – the loss of a species D – evolution

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 BIOLOGY • ADAPTATION AND EVOLUTION • ADAPTATION

Variation

Basic Advanced

• What is the term used to describe differences be- • What is the term used to describe differences be-
tween individuals of a population? tween individuals of a population?
A – appearance A – appearance
B – variation B – variation
C – genetic C – genetic
D – environmental D – environmental

• Body weight is an example of what type • Height in humans is an example of what type of
of variation? variation?

A – genetic A – genetic
B – environmental B – environmental
C – continuous C – continuous
D – discontinuous D – discontinuous

• Gender is an example of what type • Blood group is an example of what type

of variation? of variation?
A – genetic A – genetic
B – environmental B – environmental
C – continuous C – continuous
D – discontinuous D – discontinuous

• What causes inherited variation? • What causes differences in height?

A – genetic factors only A – genetic factors only

B – environmental factors only B – environmental factors only

C – genetic and environmental factors C – genetic and environmental factors

D – neither D – neither

• What causes differences in blood group?

A – genetic factors only

B – environmental factors only
C – genetic and environmental factors
D – neither