Adaptations, Natural Selection & Evolution

1. Adaptations, Natural Selection & Evolution

2. 1. Mutations • MUTATION = change in structure or composition of an organism’s DNA • MUTANT = an organism that displays the genotypic mutation in its phenotype

3. Mutations are random events that tend to be recessive so appear in a low number of the population • Mutations are the source of new variation • Variation is the differences between members of a species • Mutagenic agents that can increase mutation rates There are 2 main categories of mutagenic agents: • Chemicals & Radiation • Chemical Mutagenic Agents: • Mustard Gas • Colchicine • Caffeine • Formaldehyde • Radiation Mutagenic Agents: • X-rays • UV Light • Gamma Rays

4. Mutations can be: • Advantageous for the organism- the mutation has caused the mutant to be better than the original organism. It is the source of new variation. • E.g. polyploidy in plants • Disadvantageous for the organism- the mutation causes harm to the organism • E.g. cystic fibrosis/sickle cell anaemia • Neutral- the mutation causes no change to the organism, it is neither beneficial or harmful

5. 2. Adaptations • An adaptation is a characteristic possessed by an organism which makes it well suited to its environment • Adaptations are favoured by natural selection as they increase the individual’s chance of survival • Adaptations can be: • Structural • Physiological • Behavioural

6. 2. Adaptations The Galapagos Islands lie west of South America in the Pacific Ocean On these islands live 13 different species of Finch In order to survive, each Finch species has adapted to occupy a particular niche (role)

7. 2. Adaptations Different Finch species have: • different beak shapes and sizes • different habitats/niche Can you think which finch lives near bark containing burrowing insects? Which lives on the ground near trees that produce thick walled seeds?

8. Bee pollinated plants Bee pollinated flowers often have UV colouring, invisible to the human eye but visible to the bee. To the bee this is a target signalling where the nectar is, and promotes pollination.

9. Cacti Succulent tissue, deep root and superficial roots, no broad leaves.

10. Polar bear Camouflaged, dark skin for insulation, blubber, wide feet.

11. African Bullfrog Uses spade-like hind-legs to burrow away from predators.

12. Sea dragon Camouflaged to protect from predators.

13. Camel

14. Elephant

15. 3. Natural selection • What examples of variation can you think of in humans? • Can you think of other examples of variation in other species? • An organism that is ‘struggling for survival’ means that only the best adapted organisms will survive to pass on their genes • Organisms that are best adapted are said to have a ‘selective advantage’ over other members of the species Charles Darwin

16. Sexual reproduction produces more offspring than environment can support Some slower rabbits are caught Some weaker rabbits die Inherited variation is expressed in phenotypes Healthiest, strongest, fastest etc survive & breed Poorly adapted die More offspring produced than the environment can support, best adapted survive to pass on genes Poorly adapted die

17. Natural selection in action: The Peppered Moth Peppered moth exists in 2 colours, light and melanic. Each have selective advantage in different environments.

18. Before the industrial revolution: • light moths had a selective advantage • well camouflaged against the lichen-covered trees, they were better able to avoid predation • During the 19th century pollution killed off some of the lichens and soot deposits caused the tree bark to appear darker • Light moths = no longer camouflaged and more likely to be eaten by birds Light is favoured

19. Dark moths had a greater chance of reproducing and passing on the alleles that made them dark • caused a gradual increase in the proportion of dark moths until light moths became very rare in industrial areas • The moth populations in these areas had evolved • This change from predominantly light to dark forms in industrial areas is called industrial melanism Melanic is favoured Note that this change was not due to pollution making the moths darker. The dark variety had always existed in small numbers, but only had a selective advantage when the selection pressure changed.

20. Resistance to antibiotics a. One mutant bacteria arrives spontaneously in the population. b. Mutant bacteria has selective advantage and survives. c. Resistant bacteria reproduces to make more resistant bacteria.

21. Resistance to antibiotics d. One of these bacteria may be resistant to a 2nd antibiotic. e. Mutant bacteria has selective advantage and survives to reproduce more like bacteria.

24. 4. Speciation • A species is a group of organisms that can interbreed to produce fertile offspring • All of the members of the same species make up a population • the gene pool refers to the different genes within an interbreeding population • Speciation is the name given to the process where two new species are formed from one original species

25. 4. Speciation • Speciation requires some sort of isolation barrier (something that causes the original population to become divided) • These barriers can be: • Geographical (seas, rivers, mountains/deserts) • Ecological (temperature, water availability, pH) • Reproductive (sex cells unable to fuse, unsuccessful mating displays, flowering at different times of year

26. Population separated by an isolation barrier Different mutations occur in each new sub-population Variation is displayed in each new population & natural selection occurs where those with the selective advantage will survive & pass on their genes After many generations, mutations and natural selection changing the gene pool of each population, even if the isolation barrier is removed, these sub-groups will no longer be able to interbreed to produce fertile offspring