Biology 11-Topics for the Exam 1 1. Descent with modification: A Darwinian view

Question

Biology 11-Topics for the Exam 1 1. Descent with modification: A Darwinian view of life (Chapter 22) a. Descent with modification b. Key features of natural selection c. Examtples of evolution by natural selection d. Evidence of Descent from a Common Ancestor i. Direct observations, homology, fossil record, biogeography ii. Convergent evolution 2. Evolution of Populations (chapter 23) a. Mutation, sexual reproduction and genetic variation b. Hardy-Weinberg Principle, conditions c. Mechanisms of evolutionary change: Natural selection, genetic drift and gene flow can alter allele frequencies in a population d. Natural selection is the only mechanism that consistently causes adaptive evolution i. Relative fitness, directional, disruptive and stabilizing selection ii. Sexual selection 3. The origin of Species (Chapter 24) a. Definition of Species i. Biological species concept and limitations ii. Morphological, ecological and phylogenetic species concept i. Allopatric speciation 1. reproductive isolation, prezygotic barriers, postzygotic barriers. b. Speciation ii. Sympatric speciation (polyploidy, habitat differentiation, sexual selection) c. Hybrid zone i. Reinforcement: strengthening reproductive barriers ii. Fusion: weakening reproductive barriers ii. Stability: Continued formation of hybrid individuals

Explanation / Answer

b. Key features of natural selection:

i. Traits are often heritable

ii. More offspring are produced than can survive.

iii. Offspring vary in their heritable traits.

Example of evolution by natural selection:

This is a hypothetical example.

A group of mice with heritable variation in fur color as black vs. tan has transferred to a new habitat where the rocks are black. So in the black background the tan mice were easily prayed by the hawks. So a relatively large fraction of the tan mice are eaten, while a much smaller fraction of the black mice are eaten. Since Fur color is a heritable trait. So, fraction of black mice in the surviving group is large and hence there will be blacker baby mice in the next generation. In this way this trait will be naturally selected and the black mice will dominate over tan mice. And with evolution all mice will be black.

d. Evidence of descendant from the common ancestors:

i. Development of different shape beaks in the Galapagos islands birds is such an example of evolution from same species change changes over time.

Another example is the finding of vestigial organs in human like nictitating membrane that shows their similarity with the aquatic animals.

So many fossils found that shows the connecting link between reptiles and birds etc.

ii. Convergent evolution: This is the evolution in which there are similar features in species of different lineages. Analogous structures formation is an important feature of such evolution.It is an independent evolution.

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