Biological Evolution & Systematics

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Questions and Answers

Considering the principles of Mendelian genetics and the phenomenon of incomplete dominance, what phenotypic ratio would be expected in the (F_2) generation of a monohybrid cross where the heterozygotes display a unique, intermediate phenotype?

All individuals display the intermediate phenotype, with no segregation of parental traits
3:1, with three individuals showing the dominant phenotype and one showing the recessive phenotype
1:2:1, with one individual showing the dominant phenotype, two showing the intermediate phenotype, and one showing the recessive phenotype (correct)
2:1, with two individuals showing the dominant phenotype and one showing the recessive phenotype

In a population undergoing natural selection, a particular allele confers a significant survival advantage during a period of environmental stress, but also results in reduced fecundity (reproductive rate). Assuming all other factors are equal, what is the most likely evolutionary outcome for this allele?

The allele will be quickly eliminated from the population because of the reduced reproductive rate, regardless of its survival advantage
The allele frequency will increase initially, but then stabilize at an intermediate level due to the trade-off between survival and reproduction. (correct)
The allele will rapidly reach fixation within the population due to its survival benefit, overriding the fecundity cost.
The allele frequency will oscillate chaotically, showing no predictable pattern due to the competing selective pressures.

Given the complexities of horizontal gene transfer (HGT), which statement most accurately describes its evolutionary implications?

HGT only transfers genes related to antibiotic resistance, with limited impact on other aspects of bacterial physiology and ecology.
HGT fundamentally challenges traditional phylogenetic models by enabling rapid dissemination of genetic material across distantly related species, thereby blurring the lines of descent. (correct)
HGT strictly adheres to the principle of vertical inheritance, ensuring the preservation of species boundaries and evolutionary lineages.
HGT primarily accelerates adaptation in bacteria and archaea, while having negligible impact on eukaryotic evolution.

Considering the concept of exaptation, which scenario provides the most compelling example?

The evolution of bird feathers initially for insulation, later co-opted for flight. (C) Signup and view all the answers

What is the most significant limitation when using the fossil record to definitively reconstruct ancestral character states and phylogenetic relationships?

Fossilization is a rare event, leading to a biased and incomplete record that can obscure true evolutionary pathways. (D) Signup and view all the answers

How did the independent work of Darwin and Wallace on natural selection challenge the prevailing Linnaean view of species?

It provided a mechanism for how species could change over time, diverging from common ancestors, contradicting the idea of fixity of species. (B) Signup and view all the answers

Given the principles of the Modern Synthesis, how do mutations play their most critical role in evolutionary change?

By providing the raw genetic variation upon which natural selection can act. (A) Signup and view all the answers

If a population of sexually reproducing organisms experiences a drastic reduction in size (a bottleneck event), what is the most likely immediate consequence concerning its genetic diversity?

A decrease in genetic diversity due to the random loss of alleles from the population. (B) Signup and view all the answers

How does coevolution between a parasite and its host typically manifest over evolutionary timescales?

The host and parasite engage in an evolutionary arms race, with each adapting to counter the other's strategies, often leading to increased specialization. (B) Signup and view all the answers

What key insight from Malthus's work on population influenced Darwin and Wallace in formulating their theory of natural selection?

Populations tend to increase exponentially, outstripping available resources, leading to competition and differential survival. (C) Signup and view all the answers

Considering artificial selection through the lens of modern genetics, what is the most critical underlying mechanism that allows for the rapid modification of traits in domesticated species?

The selective breeding of individuals with desired phenotypes, leading to an increased frequency of the underlying favorable alleles in the population. (D) Signup and view all the answers

Given the evidence for endosymbiosis, what is the most parsimonious explanation for the presence of mitochondria within eukaryotic cells with regard to phylogenetic history?

Eukaryotic cells engulfed free-living bacteria, establishing a symbiotic relationship that eventually led to the integration of the bacteria as mitochondria. (D) Signup and view all the answers

Which of the following evolutionary mechanisms is most likely to counteract the effects of genetic drift in a small, isolated population?

Gene flow from a larger, genetically diverse population. (C) Signup and view all the answers

What is the most likely consequence of a species failing to adapt to significant, rapid environmental changes?

The species will face a high risk of extinction. (A) Signup and view all the answers

Considering that sexual selection can sometimes lead to traits that decrease an individual's survival probability, how can such traits persist over evolutionary time?

The reproductive advantage conferred by these traits outweighs the survival cost. (C) Signup and view all the answers

Flashcards

Biological Evolution

Mutation of genetic material through generations of offspring.

Macroevolution

Evolution of species over time, visible in fossils.