Natural Selection
Population Genetics and HWE
Evidence for Evolution
Phylogeny
Speciation and Extinction
100
What is fitness?
An organism's ability to successfully survive and reproduce.
100
_________ __________ happens when alleles are transferred between populations due to immigration.
Gene Flow
100
Identify one primary source of evidence for evolution.
The fossil record, comparative morphology, biogeography, molecular homology, embryonic homology
100
What does a "node" represent in a phylogeny?
Nodes (the brown dots) represent common ancestors from which species evolve from.
100
Which type of speciation involves a barrier that completely separates a small population from the main population?
Allopatric Speciation
200
Draw and label the three modes of selection
200
During the 1800s, the bison population in North America drastically declined due to extensive hunting, habitat destruction, and competition with domestic livestock. This resulted in the population reducing to fewer than 1,000 individuals. What did the bison population experience?
Bottleneck effect
200
Whales have small, internal pelvic bones that are not connected to the rest of their skeletal structure. These bones resemble the pelvic bones found in land mammals, such as wolves and deer. In land mammals, these pelvic bones are necessary for supporting their hind limbs. Whales, however, do not use these bones for walking or supporting their body weight. Which morphological structure is being described?
Vestigial Structures
200
True or false - the basal taxa is the lineage that evolved from the root and remains unbranched, while the sister taxa represents two clades that emerge from the same node.
True!
200
Two species of frogs live in the same forest but breed in different seasons. As a result, they do not interbreed, even though they are geographically close. What mechanism maintains reproductive isolation between these two species?
Temporal Isolation
300
(1) Is this an example of natural selection?
(2) Why or why not?
A homeowner plants peppermint plants in her backyard to deter ants. Ants recognize the peppermint scent as unpleasant and avoid the plants by staying several feet away. Ants that approach the scent cannot tolerate it and move further away. The offspring of these ants also avoid the peppermint plants. Based on this scenario, is this an example of natural selection in the ant population?
(1) Nope!
(2) This is not an example of natural selection because the ants’ avoidance behavior is not the result of genetic changes in the population.
300
If 30 out of 50 individuals exhibit a dominant phenotype in a population, what is the frequency of the recessive allele?
q≈0.632
300
A researcher observes a cell under a microscope and notes that it lacks membrane-bound organelles and contains circular chromosomes. Based on these observations, what can be inferred about the evolutionary ancestry of this cell?
The cell shares a more recent common ancestor with prokaryotes than with eukaryotes, because it lacks structural features associated with eukaryotic common ancestry.
300
Both phylogenetic trees and cladograms are hypotheses about the history of evolution, but what differentiates phylogenetic trees from cladograms?
Phylogenetic trees indicate the approximate time of evolutionary change/events while cladograms represent lineages.
300
The figure to the right illustrates how evolutionary changes occur over time in primates, mammals, and carnivores. What do the peaks for each species represent?
Rapid bursts of change, following relative stability (aka Punctuated Equilibrium)
400
A population of peppered moths in industrial England had two phenotypes: light-colored moths and dark-colored moths. Before industrialization, light-colored moths were more common because they camouflaged into light, lichen-covered trees and were therefore better at hiding from predators. After industrialization, soot darkened the trees, making dark-colored moths more camouflaged. Over time, the dark-colored phenotype became more prevalent. What does this example illustrate about natural selection?
Natural selection favors phenotypes that increase fitness in specific environments.
400
In a certain dog species, the allele for wire hair (H) is dominant over the allele for smooth hair (h). In a large, randomly mating population, 15% of the dogs exhibit the smooth hair phenotype. Assuming the population is in Hardy-Weinberg equilibrium for this gene, which of the following values is closest to the number of dogs expected to be heterozygous for the trait?
2pq = 0.48
400
Due to similar environmental pressures, organisms from different lineages may develop similar traits or behavioral strategies, even though they evolved independently. (1) What are these structures called and (2) which pattern of evolution leads to this?
(1) Analogous structures
(2) Convergent evolution
400
The table below represents the amino-acid differences amongst a species of various bovine. Which one is the out group?
Syncerus caffer
400
During the Cretaceous-Paleogene extinction event, many species, including the non-avian dinosaurs, went extinct. This mass extinction created opportunities for mammals to diversify and occupy ecological niches previously held by dinosaurs. What evolutionary process is described in this example?
Adaptive radiation follows mass extinction.
Adaptive radiation - if a new habitat or niche becomes available, species can diversify rapidly
500
Predict how the population of grasshoppers might change if drought conditions persisted over many generations given the following information:
In a population of grasshoppers living in a grassy meadow, two distinct phenotypes are observed: green and brown coloration. Green grasshoppers blend well with the grass, while brown grasshoppers are more visible to predators like birds. During a year of normal rainfall, the grass is lush and green. However, in a drought year, much of the grass turns brown, making the brown grasshoppers less visible. The table below shows the survival rates of green and brown grasshoppers over two consecutive years: one with normal rainfall and one with a drought.
The frequency of brown grasshoppers will increase because they have a higher survival rate in drought conditions, which allows them to produce more offspring.
500
Identify ALL 5 conditions of the HWE.
No mutations
Random mating
No natural selection
Extremely large population size
No gene flow
500
Which line of evidence relies on the presence of ultraconserved elements in non-coding regions of the genome that remain nearly identical across distantly related vertebrate species, suggesting deep evolutionary constraints and a shared ancestry despite functional redundancy.
Molecular homology/biochemistry/comparative genomics
500
Construct a cladogram using the table illustrating the amino acid differences among various venomous snake species.
500
Genetic studies indicate that lions and tigers diverged from a common ancestor approximately two to three million years ago. Despite this, lions and tigers can interbreed to produce hybrid offspring such as ligers or tigons. These hybrids, however, often experience a wide range of issues. Identify and describe one postzygotic mechanism that likely contributes to the challenges observed in hybrids between lions and tigers.
Reduced hybrid viability: The genes of different parent species may interact in ways that impair the hybrid’s development or survival/ hybrid embryos or offspring fail to develop properly or die early in development.
Reduced hybrid fertility: a hybrid can develop into a healthy adult, but it is sterile.
Hybrid breakdown: the hybrid of the first generation may be fertile, but when they mate with a parent species or one another, their offspring will be sterile.