Question

. Gradualism is an important assumption of evolutionary theory.

A. A complex structure like the eye would be unlikely to emerge from a single large-scale mutation. How does gradualism help evolutionists address the evolution of complex adaptations, such as the eye?

B. How do ring species support a gradualist model of speciation? Explain.

     

2. Use the comparative method to answer the following questions about selection and adaptation, discussed Chapter 8.

A. What are convergent evolution and divergent evolution?

B. Why would selection ever delete a trait after having built it? Explain how cave-dwelling species lost the eyes that had evolved in their ancestors.

C. Why are disabling mutations in an olfactory receptor gene more likely to be “tolerated” by selection in a species with full trichromatic vision than in species without it?

D. Do you see parallels between increased loss of olfactory genes in species with trichromatic vision and the evolution of eyelessness in cave-dwelling species? Explain.

3. Altruistic traits, by definition, harm the individual manifesting the trait and help others.

A. What does Hamilton’s Rule say about the conditions under which kin selection should favor altruism?

B. In the woodpecker nest-helper example from class, explain how it can be in the evolutionary interests of a young bird to help their mother or sister breed when there are not enough nest holes to breed on their own.

C. Even when there are nest holes available, young birds sometimes help their mothers breed instead. How do “Selfish Genes” explain the evolution of behavior that is not in the interests of the individual (not facultative altruism).

     

D. In the case of reciprocal altruism, explain how reciprocity can maintain altruism even without close genetic relatedness.

Answer 1

According to Darwin, process of gradual and stepwise evolution has been called "direct evolution" which resulted in evolution of complex organisms like eyes.

Direct evolution has been further divided into two types :

1. Serial direct evolution

2. Parallel direct evolution

But both of these are not enough for the complete development of complex organs. Hence, it was suggested by darwin as well as other biologists that complex organs and complex system evolve by various indirect routes. Various processes include gene duplication and input of different hormones leading to shift in functioning. Hence, evolution of most complex organs probably involves various processes from different parts of direct and indirect evolutionary continuum.

One of the important process that came up and has been found to be responsible for evolution of complex organs is the process of "gene sharing". It means that there is enhancement or acquiring of new functions without any change in protein coding gene. Also, change in expression of genes at new place lead to formation of new tissues.