Unit 7 Flashcards
What is natural selection and what causes it?
Organisms with better adaptations for the environment have a greater chance of survival and reproduction
How does natural selection affect populations?
Causes microevolution where more fit alleles become increasingly more common in a population
What is artificial selection?
Humans select desirable traits in other species and selectively breed individuals with the desired traits
What is convergent evolution?
Similar environmental conditions select for similar traits in different populations or species over time, results in analogous structures
How do mutations affect a population’s genetics over time?
Mutations create genetic variation which allows for a population to adapt to environmental changes easier
How does genetic drift affect a population’s genetics over time? (Bottlenecks and founder effect)
Genetic drift is the random change in the frequency of an allele
Bottleneck → a bottleneck event causes a large/diverse population to be suddenly reduced to a small population
Founder Effect → Reduces genetic variation due to separation from a larger population
How does gene flow affect a population’s genetics over time?
Gene flow introduces new genes into a population, can either reduce or increase genetic diversity
What are the conditions for Hardy-Weinberg equilibrium?
Large population (no genetic drift), no migration (no gene flow), no net mutation (no genes are modified), random mating (no sexual selection), absence of selection (no natural selection)
What type of data provides evidence for evolution and common ancestry?
Morphological (homologous and vestigial structures), biochemical (compares DNA/amino acid sequences), geological (fossils)
What are homologous structures?
Variation in a structure present in a common ancestor
What are vestigial structures?
Structures that serve little or no purpose now but did in an ancestor
What shows that all eukaryotes descended from a common ancestor?
Membrane-bound organelles, linear chromosomes, genes that contain introns
Why is evolution an ongoing process?
Populations constantly face environmental changes/pressures that cause natural selection and changes in genetic makeup
What is an outgroup?
Represents the lineage that is least closely related to the rest of the organisms
What do the nodes on a cladogram represent?
The most recent common ancestor
Punctuated equilibrium vs gradualism
Punctuated equilibrium → evolution occurs rapidly after a long period of stasis due to changing ecological conditions
Gradualism → evolution occurs slowly along with slow ecological changes
What is divergent evolution?
Adaptation to a new habitat results in different phenotypes
Sympatric vs allopatric speciation
Allopatric → evolution of a new species due to geographic isolation
Sympatric → evolution of a new species due to reproductive isolation
Prezygotic vs postzygotic mechanisms
Pre → prevents production of a fertilized egg
Post → prevents a zygote from developing into a viable, fertile offspring
What leads to the extinction of a population?
Changes in the ecosystem that a population is unable to adapt to
How does extinction connect to species diversity?
High biodiversity = high speciation and low extinction
Low biodiversity = low speciation and high extinction
How does extinction connect to adaptive radiation?
The evolution of new species that fill empty ecological roles or niches that were previously empty due to extinction
How does genetic diversity affect a population’s ability to react to a changing environment?
Diverse populations have individuals with a variety of adaptations, they are more likely to contain individuals who can withstand new environmental pressures
What do all of the variables represent in the hardy-weinberg equations?
p = frequency of the dominant allele
q = frequency of the recessive allele
p^2 = frequency of homozygous dominant
2pq = frequency of heterozygous
q^2 = frequency of homozygous recessive
