Biology 280: Worksheet 5-15 pts. key

Name: ______________________________

Answer the following questions based on material presented in lecture and in the textbook

1. Briefly explain why it might be difficult to apply the biological species concept in each of the following situations (0.5 pts./answer- 2 pts. total):

1. Fossils of “Java Man” and “Peking Man” are both thought to represent a single species- Homo erectus.

2. A tiger and a lion can interbreed in a zoo and produce a hybrid offspring called a tigon. Female tigons can be fertile.

3. There are many strains and species of Streptococcus bacteria, which reproduce asexually.

4. Many species of bacteria can transfer antibiotic resistance genes to other bacteria of different species.

2. Review the reproductive barriers that separate species by categorizing the following examples as whether it is a pre- or post- zygotic barrier and then the specific kind of barrier it is (0.5 pts./answer- 4 pts. total):.

Pre or Post?	Kind of Barrier?	Example
		Male fiddler crabs (genus Uca) wave their large claws to attract females. Each species has a slightly different wave.
		Two species of mice are mated in the lab and produce fertile hybrid offspring, but the offspring of the hybrids are sterile
		The salamanders Ambystoma tigrinum and A. maculatum live in the same areas. A. tigrinum mater breeds in Feb-March, A. maculatum breeds in April-May
		When different species of tobacco plants are crossed in the greenhouse, the male pollen tube is unable to fuse with the female ovule.

3. Review the differences between intra- and inter-sexual selection by categorizing the following examples as whether it is an example of intra- or intra-sexual selection and then describe the specific type or benefit (i.e., for male-male competition- direct combat, sperm competition, etc. or for female choice- good genes, direct reward, tc.) for each (0.5 pts. each- 4 pts. total):.

Inter or Intra?	Type/benefit?	Example
		Plants that have larger or more brightly colored flowers attract more insects and hence disperse more pollen to other plants than those with smaller, more dull flowers
		In humans, previously deposited sperm within a female will hinder the retention of sperm from later copulations for up to 8 days
		Male mealworm beetles pass a spermless spermatophore containing nutrients to the female during copulation. Females that mate with males that pass along larger spermatophores produce more offspring if they mate with males that produce smaller spermatophores
		Female wild turkeys prefer to mate with males that have larger and redder waddles. Males that have redder waddles tend to have lower levels of parasites than males with smaller, duller waddles

4. Suppose you have two allopatric populations of the same species, recently separated. For each of the micro-evolutionary forces listed below, describe how they would contribute or retard the speciation process (2 pts.).

Genetic drift:

Natural selection:

Mutation:

Migration:

5. Compare and contrast the terms natural selection and sexual selection (3 pts.).