1. Adaptation, Natural Selection & Evolution
National 5
Adaptation, Natural Selection & Evolution
Mr G Davidson

2. Mutations
A mutation is the random changing of an organism’s genetic material.
Mutations are very rare and they occur randomly.
This mutation can cause a change in phenotype of an organism, and if it does, the individual is said to be a mutant.
Wednesday, 19 September 2018
Mr G Davidson

3. Mutations
Mutations can be brought about by exposing cells to mutagenic agents such as:
Radiation
UV light
Gamma rays
X-rays
Chemicals
Colchinine
Caffeine
Mustard gas
Chemicals in tobacco
Wednesday, 19 September 2018
Mr G Davidson

4. Mutations
Mutations can cause changes that leave the organism better off than it was before.
These are called advantageous mutations.
These are very rare but they do increase variation within the species.
Wednesday, 19 September 2018
Mr G Davidson

5. Mutations
There are some plants which have more than one set of chromosomes.
This is caused by spindle fibre failure.
They are called polyploids and they are normally superior to the normal variety:
Larger fruit
Greater yield
Better disease resistance
Wednesday, 19 September 2018
Mr G Davidson

6. Mutations
Other mutations can have no effect on the organism and these are called neutral mutations.
These mutations can occur in parts of the DNA which don’t code for proteins.
If they do occur in the DNA which codes for protein, the change is so minor that it has no overall effect.
Wednesday, 19 September 2018
Mr G Davidson

7. Mutations
There are, however, mutations called disadvantageous mutations.
If the mutation happens in genes which code for essential enzymes, the organism may be in danger of not surviving.
They may even lead to genes being lost.
Examples of such mutations include cystic fibrosis and sickle cell anaemia.
Wednesday, 19 September 2018
Mr G Davidson

8. Variation Mutations are the only source of new variation.
Without them all organisms would be homozygous and there would be no variation.
Wednesday, 19 September 2018
Mr G Davidson

9. Variation
Because there is variation, the organisms with the advantageous mutations survive and pass them on to the next generation.
This is what causes evolution.
These variations are called evolutionary adaptations and they allow organisms to cope better with environmental changes.
Wednesday, 19 September 2018
Mr G Davidson

10. Adaptations
There are biomes which make life very difficult and if organisms can adapt to live in these places, they will incur less competition.
Deserts are a good example, where it is very arid and hot during the day, but very cold at night.
There are some organisms which have adapted to living in deserts.
Wednesday, 19 September 2018
Mr G Davidson

11. Adaptations There are two types of adaptation organisms can show:
Behavioural adaptations where the organism adapts its behaviour in order to cope.
Physiological or structural adaptations where the organism’s body has adapted through evolutionary changes.
Wednesday, 19 September 2018
Mr G Davidson

12. Desert Rat
The desert rat or kangaroo rat is a small mammal which shows both types of adaptation in order to survive in the desert.
Behavioural adaptations include the rat remaining in an inactive state in underground burrows during the heat of the day in order to conserve water.
They become active at night.
Wednesday, 19 September 2018
Mr G Davidson

13. Desert Rat Physiological adaptations include:
dry mouth and nasal cavities which reduces the amount of water lost when breathing.
No sweating.
Very long kidney tubules to improve the reabsorption of water.
They produce very concentrated urine.
Wednesday, 19 September 2018
Mr G Davidson

14. Camels
Camels have a number of physiological adaptations to help them survive in the desert.
Very thick fur on top of the body to protect it from the heat of the sun.
The have fat in the hump which can be metabolised to release water.
Large feet helps to spread their weight and prevent them sinking into the sand.
Wednesday, 19 September 2018
Mr G Davidson

15. Desert Plants
Plants also have a huge range of adaptations to help them to survive in very dry areas.
They have huge root systems that can go very deep into the ground to find water.
The leaves are reduced to spines to reduce the surface area through which water could be lost.
The stems are fleshy and capable of storing water.
Wednesday, 19 September 2018
Mr G Davidson

16. Natural Selection
All species of organism produce offspring in order to maintain the species.
They all produce more offspring than is required to do so.
This results in some of these offspring being weeded out before they can reproduce.
Wednesday, 19 September 2018
Mr G Davidson

17. Natural Selection
This is called natural selection or ‘survival of the fittest’.
The best adapted individuals will survive at the expense of the “weakest” individuals.
It is natural variation which causes these differences between individuals.
Wednesday, 19 September 2018
Mr G Davidson

18. Natural Selection
Organisms are subjected to “selection pressures” such as:
Starvation
Low disease resistance
Lack of space
Slower (cannot escape from predators)
Competition
Wednesday, 19 September 2018
Mr G Davidson

19. Natural Selection
Natural selection is constantly changing the characteristics of organisms.
This happens over an extended period of time to accommodate the changing environment.
Examples include:
Peppered moth
Antibiotic resistant bacteria.
Wednesday, 19 September 2018
Mr G Davidson

20. Speciation
A species is a group of organisms which can interbreed and produce fertile offspring.
Speciation is the development of a new species.
This is something which happens over a very long period of time.
It starts when a large group of organisms of the same species become separated into 2 or more groups.
Wednesday, 19 September 2018
Mr G Davidson

21. Speciation This may be caused by:
Geographical barriers such as oceans or mountains
Ecological barriers caused by changes in abiotic factors such as temperature, pH, water, etc.
Reproductive barriers such as non-fertilisation, wrong courtship behaviour, etc.
Wednesday, 19 September 2018
Mr G Davidson

22. Speciation
Once the main group have been split, mutations occur within the smaller groups resulting in new alleles.
This can alter the phenotype of the organisms.
As time passes the environment applies slightly different selection pressures on the population and the mutant forms survive better.
Wednesday, 19 September 2018
Mr G Davidson

23. Speciation
These individuals then survive to reproduce and pass on the new alleles.
The individuals without the new alleles will be selected against.
This results in the characteristics of the population changing.
Wednesday, 19 September 2018
Mr G Davidson

24. Speciation
After a long time, even if the barrier is now removed, the 2 populations will differ from each other so much that they are no longer able to interbreed and produce fertile offspring.
Therefore, they are now separate species.
Wednesday, 19 September 2018
Mr G Davidson

25. Speciation Large population of organisms interbreeding
and producing fertile offspring
Wednesday, 19 September 2018
Mr G Davidson

26. Speciation Same environment as before Wetter environment than before
Large population of organisms get
separated by a body of water and can
now no longer interbreed.
Wednesday, 19 September 2018
Mr G Davidson

27. Speciation Same environment as before Mutant forms begin to appear
Over a long period of time some
of the organisms mutate and these
mutant forms survive better in the
wetter environment because they have
bigger feet which stops them sinking.
Wednesday, 19 September 2018
Mr G Davidson

28. Speciation Same environment as before Mutant forms show an advantage
and survive better
Over a long period of time the mutant
individuals numbers increase because
they are surviving in the wetter environment
Wednesday, 19 September 2018
Mr G Davidson

29. Over a long period of time there are now
Speciation
Same environment
as before
New form of organism is
now the dominant form
Over a long period of time there are now
2 different species.
Wednesday, 19 September 2018
Mr G Davidson

30. Two distinct species now exist.
Speciation
If the body of water
now dries up and these 2 varieties can mingle,
they are no longer able to interbreed and
produce fertile offspring.
Two distinct species now exist.
Wednesday, 19 September 2018
Mr G Davidson