Ch. 21 - Microevolution

How does sexual reproduction contribute to genetic variation?

by rearranging alleles into new combinations through crossing over, independent assortment, and fertilization.

What is gene flow?

the transfer of alleles between populations through migration, which can reduce genetic differences over time.

What is sexual selection?

a form of natural selection where certain traits increase an individual's chance of mating and reproduction.

What limitations does natural selection have in producing 'perfect' organisms?

it can only act on existing variations, is limited by historical constraints, and adaptations are often compromises.

What is the Hardy-Weinberg equation used for?

to test whether a population is evolving by measuring changes in allele frequencies.

What is natural selection?

a mechanism of evolution where individuals with favorable traits are more likely to reproduce, leading to a change in allele frequencies.

What is stabilizing selection?

favors intermediate phenotypes, reducing variation by eliminating extreme forms of a trait.

What are examples of conservation issues related to bottlenecking?

reduced genetic diversity in endangered species, such as cheetahs, leading to lower adaptability and survival rates.

What is genetic variation's role in microevolution?

provides the raw material for microevolution, allowing populations to adapt and evolve.

What is balancing selection?

maintains multiple alleles in a population due to the heterozygote advantage, such as in the case of sickle-cell anemia and malaria resistance.

How does inbreeding affect genetic diversity?

reduces genetic diversity, increases the chance of recessive genetic disorders, and lowers overall fitness in a population.

What is genetic drift?

causes allele frequencies to change unpredictably due to chance events, particularly in small populations.

What are the mechanisms of microevolution?

natural selection, genetic drift, and gene flow, which can alter allele frequencies in a population.

What is the significance of allele frequency?

indicates how common an allele is in a population, influencing genetic diversity and adaptability.

What is genetic equilibrium?

a theoretical state where a population's allele frequencies remain constant, indicating no evolution.

What is the role of environmental factors in gene expression?

can modify the expression of genes, affecting phenotypes without altering the underlying genotype.

What is polymorphism in genetics?

the presence of two or more distinct forms of a trait within a population.

What is the role of mutations in evolution?

Mutations introduce new genetic variations, which can be beneficial, harmful, or neutral, influencing the evolutionary trajectory of populations.

What is the definition of a population in evolutionary biology?

a group of individuals of the same species that occupy a given area and can interbreed.

What are the five conditions for Hardy-Weinberg equilibrium?

no mutations, random mating, no natural selection, large population size, and no gene flow.

How does natural selection lead to adaptive evolution?

by increasing the frequency of alleles that allow a survival advantage in a specific environment.

What is artificial selection?

the human-driven process of breeding organisms for specific desirable traits.

What does the term 'gene pool' refer to?

the collection of all alleles in a population, representing the genetic diversity available for future generations.

What is the only source of new alleles?

Mutations are the only source of new genes or alleles, altering the DNA sequence.

What is an adaptation?

a characteristic that enhances an organism's survival and reproduction in its environment.

What is fitness in the context of natural selection?

an organism's ability to survive and reproduce in a specific environment, often determined by inherited traits.

What are the two main types of genetic drift?

Founder effect and bottleneck effect

What is the bottleneck effect?

a drastic reduction in population size due to environmental changes, resulting in altered allele frequencies and the loss of genetic diversity.

What is the significance of mutation in evolution?

Mutations are the only source of new alleles, introducing genetic variation that can be beneficial, harmful, or neutral.

What is polymorphism in genetics?

the presence of two or more distinct forms of a trait within a population.

What is the founder effect?

when a small group starts a new population, leading to different allele frequencies than the original population.

What are the consequences of genetic drift in conservation biology?

reduced genetic variation in endangered species, impacting their adaptability and survival.

What is directional selection?

favors individuals at one end of the phenotypic range, shifting allele frequencies in a consistent direction.

What is gene flow?

the transfer of alleles between populations through the movement of individuals or gametes, reducing genetic differences.

What is fitness in the context of natural selection?

the reproductive success of an individual, determined by its ability to survive and reproduce in its environment.

How does genetic drift affect small populations?

causes unpredictable changes in allele frequencies, reducing genetic variation and potentially stabilizing harmful alleles.

What is microevolution?

small-scale evolutionary changes within a population, primarily through changes in allele frequencies.

What factors can alter allele frequencies in a population?

Natural selection, genetic drift, and gene flow are primary factors that can alter allele frequencies in a population.

What is balancing selection?

maintains two alleles in a population due to the heterozygote advantage, such as in sickle-cell anemia.

What is an adaptation?

a trait that enhances an organism's survival and reproductive success in a specific environment.

What is disruptive selection?

favors individuals at both extremes of the phenotypic range, leading to the elimination of intermediate forms.

What is the role of environmental pressures in natural selection?

determine which traits are favorable, influencing the survival and reproductive success of individuals.

How does natural selection lead to adaptive evolution?

increases the frequency of alleles that allow advantages in survival and reproduction, driving adaptive evolution.

What are the limitations of natural selection in producing perfect organisms?

Natural selection acts on existing variations and is constrained by historical factors, leading to compromises in adaptations.

What occurs when the Hardy-Weinberg conditions are not met?

If Hardy-Weinberg conditions are not met, it indicates that evolution is occurring within the population.

What is the importance of the gene pool?

the collection of all alleles in a population, crucial for understanding genetic variation and evolution.