Name/Section __________________________

 

BIO. 140 QUIZ B

 

1. (MANDATORY QUESTION 25 pts.) What are the five levels of selection and what do you think is the appropriate level of selection for behavioral traits and why? Pick the most appropriate level or levels and explain your choice (examples would be an excellent addition to your answer!).

 

genes (2PTS) -> individuals (2PTS) -> kin (2PTS) -> groups (2PTS)-> species (2PTS)

 

have to back up opinion with examples

all examples (5 POINTS) have to be correct, and logic of argument (10 POINTS) must be sound easiest approach to use is to be eclectic and employ all levels as no single level will suffice.

 

2. (CHOOSE 1 OF THE FOLLOWING 2 QUESTIONS TO ANSWER 15 pts.)

a) What are the two critical conditions for sympatric speciation?

 

ASSORTATIVE MATING (3 POINTS) = the non-random pairing of individuals which are more closely alike than the average with respect to one or more traits (matings with like individuals). A key aspect of the theory of sympatric speciation involves the process of natural selection that favors the evolution of discrimination on the part of the female and also the divergence of male traits that females use for mate discrimination. Gene flow between incipient species must be eliminated or severely curtailed, or reproductive isolation is not possible. (4 POINTS)

EXAMPLE (0.5 PTS) Re: in host-plant preference example, male insect A only mates with in female insect A. If insect A mates with insect B, hybrid progeny result (see below).

and

 

HYBRID UNFITTNESS (3 POINTS) = Dobzhansky suggested that natural selection should favor the more finely tuned discrimination mechanisms of the female, in response to the reduced viability that results from hybridization. Thus, a

key component of this theory is some form of disruptive selection that selects against hybrid phenotypes, which then favors evolution of mate discrimination mechanisms. Hybrid unfitness promotes divergence in courtship behavior or mate preference in sympatric compared to allopatric populations. (4 POINTS)

EXAMPLE (0.5 PTS)

OR

 

b) How might an organism be constrained evolutionarily? Can natural selection evolve any behavior imaginable? Describe one factor or process that might limit the action of natural selection.

 

 

NAME (2 POINTS) AND EXPLAIN (5.5 POINTS) A CONSTRAINT.

DESCRIPTION OF A FACTOR/PROCESS/EXAMPLE THAT WOULD PLACE LIMITS ON THE ACTION OF NATURAL SELECTION (7.5 POINTS).

 

PLEITROPY (genetic correlations, one gene has effects on two or more traits.)

EXAMPLE = TESTOSTERONE has an effect on aggression and parental care.

 

PHYLOGENETIC CONSTRAINT AND EXAMPLES:

In addition, organisms are constrained by the effects of history or their own phylogeny. During the evolution of a lineage, adaptations pile on top of one another, and the net result is that closely related organisms share similar constraints on the acquistion of new adaptations owing to functional or sturctural

constraints, and additional development constraints (how the structures are built during embryogenesis). Consider a simple phylogenetic example taken from two lineages of vertebrates -- birds and mammals. For example, all birds lay eggs and this is undoutedly because the common ancestor of birds, some reptile-like dinosaur, also laid eggs. However, most mammals bear live young and this is because in the remote past a new kind of mammal-like reptile evolved a different mode of life and this novel trait was passed on to all subsequent species in the lineage or phylogeny.

OTHER EXAMPLES: PELVIC GIRDLE/NEONATE CRANIAL SIZE = LIMITS EVOLUTION OF BRAIN SIZE IN PRIMATES AND DIFFERENCES IN REPRODUCTIVE MODE OF MAMMALS AND BIRDS CONSTRAINS THE TYPE OF PARENTAL CARE EACH GROUP HAS.