Section 15-3 Evolution in Action

1. Section 15-3 Evolution in Action

2. Convergent Evolution Convergent Evolution occurs when different species evolve similar traits based on living in similar environments. Examples include wings of birds, bats & insects, hydrodynamic bodies of sharks and marine mammals and body shape in twig-dwelling anoles. The structures of these animals are analogous, meaning they are derived from different DNA mutations but share the same functions.

3. Convergent Evolution Convergent evolution can be seen in species that become adapted to habitats on different continents. There are various forms of anteater-like animals around the world. There are many parallels between marsupials on Australia and placental mammals on other continentents.

4. Divergent Evolution Divergent Evolution occurs when one ancestral species evolves into different species based on living in different environments. Examples include limbs of vertebrate animals and Proboscidmammals that include current day elephants as well as extinct lineages. The structures of these animals are homologous because they are derived from the same recent ancestor but have different functions.

5. Divergent Evolution A specialized case of divergent evolution is called adaptive radiation. This occurs when a new population in a new environment like an island undergoes many forms of specialization to fill available niches. Examples include Darwin’s finches and Caribbean anoles.

6. Artificial Selection Artificial Selection involves humans selecting and breeding organisms with desirable characteristics over generations to shape their evolution. Over centuries this has resulted in the domesticationof plants to improve traits like size, taste and nutrition in crops.

7. Artificial Selection For tens of thousands of years humans have been domesticating labor and livestock animals for their benefit. Humans have also artificially selected pets for both jobs and companionship.

8. Artificial Selection Sometimes humans unintentionally drive natural selection by creating an artificial situation. Peppered moth populations were shaped by pollution. Fish size is being decreased as a result of the removal of large fish, so the small fish that can fit through nets have an adaptive advantage.

9. Coevolution Coevolution is the parallel evolution of two species in response to one another’s needs. After many generations the organisms in the partnership would not be able to function without their symbiotic species. Examples include flowers and their pollinators and clownfish and the sea anemone.

10. Coevolution Coevolution can involve many species simultaneously as seen in humans. We are referred to as a superorganism. We have a microbiome that consists of various bacteria and fungi living symbiotically within us.

11. Coevolution Coevolution often results in an evolutionary arms race when it involves the benefit of one species and the harmof another one. Examples include pesticide and antibiotic resistance in insects and bacteria to chemicals designed to kill them.

12. Coevolution Host specificity by parasites also occurs. The parasite has to evolve in such a way as to weaken but not kill the host. There is also a coevolutionary response of a prey to its predator. An example is seen in the newt that makes a toxic chemical and the garter snake that has evolved to eat it.