Final Exam Flashcards
(26 cards)
Explain how phylogenetic trees are constructed and used to represent ancestral relationships
by analyzing data on the traits or genetic sequences of different species to infer their evolutionary relationships. They visually represent these relationships, showing how species are connected through common ancestry.
Why individuals cannot evolve and why evolution does not lead to perfectly adapted organisms.
Individuals don’t evolve; populations do. Not perfect because it’s limited by available genetic resources, non-adaptive evolutionary forces, and trade-offs between traits.
Two examples of natural selection known to occur in nature.
The evolution of antibiotic resistance in bacteria and the change in beak size of Galapagos finches during drought.
How mutation and sexual reproduction produce genetic variation.
Mutations introduce new genetic material, while sexual reproduction shuffles existing material through mechanisms like crossing over and independent assortment.
Analogous structures
anatomical structures in different species that are similar in function but not necessarily in structure or evolutionary origin
ex: Bird v. Butterfly wings
Homologous structures
physical features in different species that share a common ancestor
ex: Arms of Humans and of Cats
Vestigial structures
anatomical features that were fully functional in an ancestor but have since lost most or all of their original purpose in their descendants.
ex: Tailbones in humans.
Five conditions required for the Hardy-Weinberg equilibrium
no mutation, no gene flow, no genetic drift, random mating, and no natural selection
Genetic drift
a random change in the frequency of gene variants (alleles) within a population, primarily driven by chance events rather than natural selection.
Gene flow
the transfer of genetic material (genes) from one population to another. This movement can be facilitated by the migration of individuals or the transfer of reproductive cells.
How the bottleneck effect influences microevolution
The bottleneck effect occurs when a population experiences a dramatic reduction in size due to a catastrophic event, like a natural disaster or disease. After the bottleneck, the surviving population may have different allele frequencies than the original population, and its genetic diversity might be lower. This can lead to increased vulnerability to future challenges, as the population has fewer options for adaptation.
How the founder effect influences microevolution
a small group of individuals (the founders) establish a new population, carrying with them only a fraction of the original population’s genetic diversity. As a result, the new population may have different allele frequencies and a reduced capacity for adaptation compared to the source population.
stabilizing selection
a type of natural selection where the population mean of a trait stabilizes at a particular value, and extreme variations are less favored
ex: the weight of newborn babies. Babies who are too small or too large have higher infant mortality rates, while those of average weight are more likely to survive.
directional selection
a type of natural selection where one extreme phenotype is favored over both the other extreme and intermediate phenotypes.
ex: Longer necks in giraffes became more common because they allowed them to reach higher food sources.
disruptive selection
a type of natural selection where extreme phenotypes are favored over intermediate phenotypes.
ex: White, Grey, and Black bunnies.
How genetic variation is maintained in populations.
mutation, gene flow, sexual reproduction, and natural selection
Why natural selection cannot produce perfection.
it’s a process of differential survival and reproduction, not a designer creating optimal traits
Microevolution v. speciation.
Microevolution refers to changes in allele frequencies within a population over time, while speciation is the process by which new species arise from an ancestral species.
Prezygotic barriers: Temporal isolation
Species have different breeding seasons or times of day, preventing them from mating even if they are in the same location.
Prezygotic barriers: Habitat isolation
Species live in different habitats and rarely encounter each other, even if they occupy the same geographic area.
Prezygotic barriers: Behavioral isolation
Species have different mating rituals or behaviors, such as courtship displays, that prevent them from recognizing each other as potential mates.
Prezygotic barriers: Mechanical isolation
Incompatible reproductive structures, such as genitalia in animals or flower structures in plants, prevent successful mating.
Prezygotic barriers: Gametic isolation
The gametes (sperm and egg) of different species are incompatible, preventing fertilization even if mating occurs.
Postzygotic barriers: Hybrid Inviability
Hybrid zygotes may fail to develop properly or survive, leading to a reduced or no viability of the offspring.
