Answer ALL questions please. ALL QUESTIONS 13) You have a small population of be

Question

Answer ALL questions please. ALL QUESTIONS

13) You have a small population of beetles. One day a large rainstorm causes flooding and wipes out 87% of the population. The remaining individuals have much lower genetic variation than the original population. How has the population deviated from Hardy-Weinberg Equilibrium? 14) On the screen in the front of the room is an image showing the phylogeny of Darwin's Finches of the Galapagos Islands, and two related bird species found on the cost of South America (Tiaris bicolor and Loxigilla noctis). What does this phylogenetic tree reveal of the relation between Darwin's Finches and the two continental bird species? What does it reveal about the relationship between C. pallidus and G magnirostris, and the relation between G. magnirostris and G. conirostris_E? Using the map, what factor may have led to the diversification and speciation of these bird species? 1

Explanation / Answer

13). The derivations for a number of population genetic parameters and their strengths and weaknesses in the face of various complexities of natural populations.

Here are some of the essential components which involves in the lower genetic variation than the original population.

I. Total variation over the entire set of populations

II. Within population variation

III. Among population variation

14). This view implies that diversification is rapid early in the radiation and then slows down as ecological opportunities diminish. Some radiations of other organisms elsewhere conform to this pattern.

However, taken at face value, the phylogeny of Darwin's finches shows exactly the opposite pattern: a slow start followed by recent, rapid diversification. The species occupy adaptive peaks, but the fixity of the ecological landscape that allowed them to do so is questionable.

They have sketched a framework for doing this by using molecular genetic information to estimate the finch phylogeny and using geological and climatic information to reconstruct Galápagos environments in the past 2 million to 3 million years.

Reconstruction of finch phylogeny based on microsatellite DNA. Horizontal branch lengths are proportional to units of genetic distance (GST) as indicated by the scale. Numbers refer to percentage bootstrap support for the nodes by two methods.

Mean weights are given on the right, together with symbols of male plumage: fully black, partially black, or brown or green. Alternative reconstructions that use morphology, allozymes, or mitochondrial DNA are similar, differing in relatively small details. Species, from top to bottom Geospiza fuliginosa, Geospiza fortis, Geospiza magnirostris, Geospiza scandens, Geospiza conirostris, Geospiza difficilis, Camarhynchus parvulus, Camarhynchus psittacula, Camarhynchus pauper, Camarhynchus pallida, Platyspiza crassirostris, Certhidea fusca, Pinaroloxias inornata, and Certhidea olivacea.

Morphological Differences. – Principal components analysis (Pimentel, 1979; Ricklefs and Travis, 1980) was used to represent morphological relationships among populations and species.

The advantage of this procedure is that morphological relationships can be represented without distortion using a small number of dimensions. In the first analysis, populations of all 14 species were combined, in order to investigate morphological relationships between the ground, tree, and warbler finches. Components were determined on both the original means for populations and on means transformed using genetic parameters derived from the ground finches.

Relationships among the three groups were similar when data were transformed using the corresponding matrix for the tree finches. Additional analyses were performed on the ground finches and tree finches separately, to more closely investigate patterns of divergence within the two main groups. Factor loadings for the ground finches and tree finches are listed. Mean species positions along the first two components (PC's) are shown for the combined analysis.

Population positions within the tree finches and ground finches are shown In all analyses PC 1 and PC2 together accounted for at least 78% of the total variance among means. Hence PC 1 and PC2 summarize the major trends of variation among populations and species.

In the combined analysis, 97% of the variance among untransformed means is accounted for by these two components. Figure 2 shows that the tree finches and ground finches overlap broadly along these dimensions. However, the two components derived from transformed means account for 85% of the variance but succeed in separating the two main groups.

Computed minimum-length Wagner trees, using the transformed variables, for the tree finches and ground finches separately. Since the original character means were transformed differently in the two groups, the two trees are also presented separately, In practice it is difficult to estimate G, the genetic covariance matrix.

However, since phenotypic correlations tend systematically to underestimate genetic correlations, it will often be possible to estimate G from the phenotypic values. In other cases the observed phenotypic covariance matrix P can substitute for G when estimating selection distance. This assumes the phenotypic matrix to be a simpler scalar multiple of the genetic matrix.

A new measure of morphological distance is used to estimate morphological and phylogenetic relations among the Darwin's finches. The measure, B, is based on a model for multivariate evolution (Lande, 1979), and it estimates the total net force of directional selection acting on characters that is required to bridge the differences between any two species.

This force depends on the amount of genetic variance in traits, and on genetic correlations between traits. "Selection distance" between species is shown to be correlated with biochemical distance, and the method produces a phylogenetic tree similar to the one originally suggested by Lack (1947). The results indicate that, in addition to natural selection, genetic parameters have strongly influenced the direction and rate of morphological divergence in the Darwin's finches.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.