Study Questions Week 5

1.How does the study of ontogeny and development help to elucidate our understanding evolution. Also compare and contrast Haeckle’s and Von Baer’s views on the importance of development and its relationship to evolution.

Ontogeny, the study the embryonic stages of development, can show us that changes in the early stages of development can lead to the evolution of different body plans. Heakle said that ontogeny recapitulates phylogeny, meaning that it retraces the evolution from a simple to a complex form, while Von Baer said that changes in early stages of development can lead to drastically different body plans.

2.Define the term neoteny. Explain how neoteny can lead to speciation and give an example.

Neoteny is the retention of juvenile morphology in the adult stages of life.

3.Give examples of gene suppression and gene duplication that illustrates their role in speciation.

Gene suppression for segmentation in the back half of the body of a millipede lead to the small number of segments in the abdomen of hymenoptera. Gene duplication of the thorax gene in hymenoptera lead to the development of two thorax segments, which is why they have two rather than one pairs of wings.

4.What is an exaptation.

An exaptation is a trait that evolved to serve one function and which later becomes useful for a novel function.

5.What is an example of an atavistic trait and how can you induce the presence of an atavistic trait?

An atavistic trait is a trait that was lost, or almost lost in the evolution of a species by suppression of the trait’s expression. For example the fibula in birds barely exists. If you knock out the suppression genes or block cellular communication in the area of the fibula, you get the development a slightly larger fibula!

6.Compare the Out of Africa hypothesis versus the MultiRegional Hypothesis. Give the two lines of evidence which support one of these hypotheses.

Out of Africa suggests that Homo sapiens sapiens first evolved in Africa and then radiated to other areas of the world. The Multi Regional Hypothesis suggests that Homo sapiens sapiens evolved in a number of regions simultaneously. Analysis of neutral mutations in mitochondrial DNA and the Y chromosome of humans supports the out of africa hypothesis.

7.Draw a flowchart indicating the evolution of Homo sapiens beginning the chart with the divergence of chimpanzees, gorillas, and Australopithicenes. Indicate major morphological and behavioral innovations.

Chimps à Australiopithicus africanus à A. afarensis and A. robustus then A. afarensis à Homo habilis à H. erectus à H. sapiens (both neanderthalis and sapiens)

8.Contrast the allometric relationship between brain size and body size among homonids, Australopithecines, and apes (gorillas, chimps, etc.).

Homo: slope of allometric relationship is 1.73

Australiopithecus: slope of allometric relationship is 0.34 (but the Y-intrercept is higher than the apes)

Apes: slope is 0.34

9.Draw a timeline indicating the origin of each of the different kingdoms.

See your text on pages 512 and 542

10.Define cephalization and tagmatization.

Cepalization: the evolution of the head and head sensory organs

Tagmatization: Increasing segmentation (often with specialization of the segment)

11.What is the importance of the Burgess shale?

The Burgess shale is an extremely well preserved fossil region from the Cambrian explosion. It includes many of the modern species that we see today including sponges, crustaceans, polycheates.

12.How might preservational biases (i.e. the fossil record) influence our understanding of metzoan evolution.

The metazoan had atmospheric conditions that were not ideal for fossilization on land, som we may not see evidence for many of the forms that could have existed. We are also restricted in our knowledge of fossils by what we happen to find!!

Hardy-Weinberg revisited: You find a population of wild chickens on Borneo that has three feather morphs: blue, yellow, and green. A preliminary DNA analysis shows that the feather color gene is coded by two alleles at one locus. You also note that green is intermediate between yellow and blue. You survey the population and find 100 blue, 700 green, and 200 yellow chickens. Give the allele and genotype frequencies of the current population. Assuming that the population undergoes H-W mating to produce the next generation what is the allele and phenotype frequencies of the next generation. Was the population originally in Hardy-Weinberg equilibrium??

Genotype of the population you find: Blue (BB): 100/1000 = .1; Green (Bb): 700/1000 = .7; yellow (bb): 200/1000 = .2 Allele frequency: B = (2x100 + 700)/2000 = .45 ; b = (2x200 + 700)/2000 = .55

If it now meets HW assumptions, the next generation will give genotype and phenotype frequencies:

BB = pxp = (.45)(.45) = .2025

Bb = 2pq = 2(.45)(.55) = .495

Bb = qxq = (.55)(.55) = .3025

Compare this to the genotype frequencies of the original population: since it only takes one generation to get to equilibrium if the pop meets HW assuptions, and you see that they are different; so the population was not in HWE!