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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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