Natural Selection
What mechanism did Darwin propose as the primary driver of evolution, in which organisms with favorable traits are more likely to survive and reproduce?
Natural selection
What happens to the overall genetic diversity of a population when many of its alleles become "fixed" (reach 100% frequency)?
It decreases significantly
What does p2 mean in the Hardy-Weinberg equations?
The percent of the population that is homozygously dominant.
Antibiotic resistance in bacteria and insect resistance to pesticides are examples of what?
Evolution
The Biological Species Concept defines a species based on its ability to do what?
Interbreed in nature and produce viable, fertile offspring.
Extinctions have occurred naturally throughout Earth’s history. According to our unit, during what specific conditions do extinction rates become rapid?
During times of ecological stress.
If selective pressures favor extreme light and dark fur colors but eliminate intermediate shades, what specific mode of natural selection is occurring?
Disruptive Selection
What are the two types of genetic drift, and briefly explain what each one means?
The two types are the bottleneck effect (a severe, random reduction in population size due to a sudden event) and the founder effect (when a small group of individuals breaks off from a larger population to establish a new colony).
What are the two equations of Hardy-Weinberg?
p+q= 1 and p2+2pq+q2 = 1?
While Darwin relied heavily on morphological and geological data, modern biologists use a more precise type of evidence to determine evolutionary relationships. What is this modern evidence, and how does it actually work to show how closely related two species are?
The evidence is molecular (or biochemical) data. It works by comparing the sequences of DNA, RNA, or proteins between species; the fewer differences there are in the sequences, the more recently the two species shared a common ancestor.
When constructing a cladogram to analyze the evolutionary relationships of closely related waterfowl (the in-group) at a local estuary like Lake Merritt, a biologist also includes the DNA sequence of a distantly related hawk. What is the specific term for the hawk in this scenario?
Out-group
What type of speciation occurs when a population becomes geographically isolated by a physical barrier like a river or canyon?
Allopatric speciation.
What specific factor greatly influences a population's ability to respond to changes in the environment, making them more resilient to environmental perturbation?
The level of genetic diversity in the population.
What does fitness mean in terms of Natural Selection?
the ability to survive and reproduce.
What random cellular process is the ultimate source of entirely new genetic variation in a population?
Mutation
In a population at Hardy-Weinberg equilibrium, if 16% of the individuals express the recessive phenotype, what is the frequency of the recessive allele in the gene pool?
0.04
sqrt(0.16)
What is the specific anatomical term for useless structural remnants, like the pelvic bones in modern whales?
Vestigial structures.
Older classification systems grouped all reptiles together but excluded birds. However, modern phylogenetics shows that birds share a more recent common ancestor with crocodiles than crocodiles do with turtles. Because the traditional "Reptile" group excludes birds, it is scientifically invalid. What is the specific term for a valid evolutionary group that includes an ancestor and all of its descendants?
A monophyletic group (or clade).
A mating call that is not recognized by a closely related population is an example of what specific type of reproductive isolating mechanism?
A prezygotic barrier (specifically, behavioral isolation).
Modern extinction rates are exceptionally high, primarily due to ecosystem changes driven by what?
Human activity.
Darwin based his theory of natural selection on two key observations: traits are heritable, and populations produce more offspring than the environment can support. This overproduction leads to what outcome?
Competition for limited resources, resulting in differential survival and fitness.
When individuals migrate between previously isolated populations and successfully interbreed, they introduce new alleles. What is this evolutionary mechanism called, and what is its general effect on the genetic differences between the two populations?
This is called gene flow, and it tends to reduce the genetic differences between the populations.
Name at least three of the five theoretical conditions required for a population to remain in Hardy-Weinberg equilibrium.
(Any three) A very large population size, no migration (gene flow), no net mutations, random mating, and no natural selection.
All eukaryotes share membrane-bound organelles, but mitochondria and chloroplasts are unique because they contain their own circular DNA and ribosomes. According to evolutionary theory, what specific process does this structural evidence support regarding the origin of eukaryotes?
The Endosymbiotic Theory (or that early eukaryotes evolved by engulfing free-living prokaryotes).
You are trying to determine the evolutionary relationship between a shark, a dolphin, and a bony fish. If you only look at their body shape, you might incorrectly group the shark and dolphin together. What is the specific evolutionary concept that explains this physical similarity, and what is the explanation for how it occurs?
The concept is convergent evolution. The explanation is that similar selective pressures in their shared aquatic environment resulted in similar phenotypic adaptations (like a streamlined body shape), even though they do not share a recent common ancestor.
If closely related leopard frogs mate but their embryos die before hatching, this represents what specific type of postzygotic barrier?
Reduced hybrid viability.
In a large, isolated population of peacocks, there is no mutation and no predators. However, the peahens strictly choose to mate only with the males that have the longest, most vibrant tail feathers. Is this population in Hardy-Weinberg equilibrium? Explain your reasoning.
No, it is not. The population violates the condition of "random mating," because individuals are actively selecting mates based on specific phenotypes, which will alter allele frequencies over time.
When new habitats become available in an ecosystem, speciation rates can become exceptionally rapid. What is this period of rapid speciation called, and what happens during this process?
This period is called adaptive radiation. During this process, a single ancestral species rapidly diversifies into multiple distinct new species as they undergo divergent evolution to fill different, newly available ecological niches.
A population of organisms has a specific allele that makes them highly successful in their current habitat. If the environment suddenly changes, why might this exact same allele suddenly cause the population to decline?
Alleles that are adaptive in one environmental condition may become deleterious (harmful) in another because of different selective pressures.