In this problem we will explore some of the many ways that mutations in two different genes can interact to produce different Mendelian ratios. Consider a hypothetical insect species that has red eyes. Imagine mutations in two different unlinked genes that can, in certain combinations, block the formation of red eye pigment yielding mutants with white eyes. In principle, there are two different possible arrangements for two biochemical steps responsible for the formation of red eye pigment. The two genes might act in series such that a mutation in either gene would block the formation of red pigment. Alternatively, the two genes could act in parallel such that mutations in both genes would be required to block the formation of red pigment.

Further complexity arises from the possibility that mutations in either gene that lead to a block in enzymatic activity could be either dominant or recessive. If the crosses between a wild type insect with red eyes and a true breeding white eyed strain with mutations in both genes. Such considerations yield the Pathways in parallel with a recessive mutation in one gene and a dominant mutation in the other, determine the phenotype of the F1 progeny and the expected phenotypic ratio of red to white eyed insects in the F2.

#Question id: 4639

#Unit 9. Evolution & Diversity of Life Forms

If the HMS Beagle had completely bypassed the Galapagos Islands, Darwin would have had a much poorer understanding of the

#Question id: 4640

#Unit 9. Evolution & Diversity of Life Forms

During drought years on the Galapagos, small, easily eaten seeds become rare, leaving mostly large, hard-cased seeds that only birds with large beaks can eat. If a drought persists for several years, what should one expect to result from natural selection?

#Question id: 4641

#Unit 9. Evolution & Diversity of Life Forms

Which of the following statements is an inference of natural selection?

#Question id: 4642

#Unit 9. Evolution & Diversity of Life Forms

Which of Darwinʹs ideas had the strongest connection to Darwin having read Malthusʹs essay on human population growth?

#Question id: 4643

#Unit 9. Evolution & Diversity of Life Forms

The treeʹs horizontal axis is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V—Z) represent various common ancestors. Letʹs say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.

How many separate species, both extant and extinct, are depicted in this tree?

#Question id: 4644

#Unit 9. Evolution & Diversity of Life Forms

The treeʹs horizontal axis is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V—Z) represent various common ancestors. Letʹs say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.

According to this tree, what percent of the species seem to be extant (i.e., not extinct)?