Convergent evolution:

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1 Evolution in Action

2 Convergent evolution: -organisms may look similar but are extremely different (each species came from different ancestors but evolved similar adaptations to similar habitats) These organisms face similar environmental demands and will often develop similar structures to meet the demands of the environment.

3 In convergent evolution, organisms that are very distantly related come to resemble each other because they live in similar environments. An example is a shark and a dolphin. These two organisms resemble one another even though they are very distantly related. They were exposed to the same environment, subjected to the same selection pressures and had to solve evolutionary problems in the same way.

4 Divergent evolution, is a process in which the descendants of a single ancestor diversify into species that each fit different parts of the environment (One species evolves into several different types, this process can be called Adaptive radiation) Example: a) Assume that a small number of lizards are introduced on an island. b) The lizards show variations in body types. c) Lizards with thin bodies, short legs and large toe pads survive at a higher rate by living in trees. d) Lizards with longer legs and tails survive better in the grass. e) Eventually, each group may become a separate species.

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6 Coevolution: The process by which two species evolve in response to changes in each other. In coevolution, an evolutionary change in one organism may also be followed by... a corresponding change in another organism.

7 Example: Insects have been feeding on plants since insects evolved. In response, many plants developed toxins or poisons to prevent insects from feeding on them. Plant with new chemical defenses.

8 Natural Variation Scientists used to believe species were perfect and unchanging Darwin argued natural variation (differences among species) is found in all types of organisms Some cows give more milk Some plants give larger fruit

9 Artificial selection Artificial Selection Humans choose individuals that will pass on their traits to the next generation (ex. Dog breeders)

10 Selective Breeding (Artificial Selection) Breeding animals with desired traits in order to increase the expression of those desired traits.

11 Artificial Selection Darwin also studied English farmers and breeders Used selective breeding to breed the best individuals Largest hogs, fastest horses Darwin called this artificial selection Still used today!

12 Selective Breeding takes advantage of naturally occurring genetic variation in plants, animals, and other organisms, to pass desired traits on to the next generation of organisms Nearly all domestic animals and plants have been produced by selective breeding

13 Mutations Genetic Variations are caused by mutations in the genetic code or DNA. Mutations can happen naturally due to errors during meiosis or mitosis. Exposure to radiation, viruses, chemicals can also cause mutations. Some mutations have no effect at all while others can be harmful or helpful. Beneficial mutations may help an individual live longer and pass down the beneficial mutation to more offspring. (This is a driving factor of evolution.) Cancer is caused by a mutation that allows the cells to grow out of control causing a mass or tumor.

14 Common and Uncommon Mutations/Variations It is believed that Blue Eyes originated from a mutation in a single individual 6,000 to 10,000 years ago. Variations/Mutations in our genetic sequences can also lead to high blood pressure, high cholesterol, and diabetes. Polydactyl is an uncommon mutation that causes extra fingers. Heterochromia is an uncommon mutation that causes different colored eyes or one eye of with two different colors.

15 Inbreeding (line breeding) The breeding of closely related individuals. The goal is to maintain the desired characteristics. This is RISKY, because it increases the danger of genetic defect.

16 Hybridization Breeding closely related species in order to bring together the best of both groups. Species: Two individuals that can mate and produce viable (fertile) offspring. Hybrid animals are not viable (fertile).