D4.1 Natural selection

What is the basic principle of natural selection?

Organisms produce more offspring than the environment can support, leading to a struggle for existence.

Why is variation essential for natural selection?

Natural selection can only occur if there is variation within a population, as some variants are more likely to survive and reproduce.

What is the original source of variation in populations?

Mutation.

How does meiosis contribute to variation?

Meiosis produces new combinations of alleles through crossing over and independent orientation of bivalents.

What role does sexual reproduction play in variation?

It combines alleles from two parents, bringing together mutations from different individuals.

What is the only source of variation in species that do not reproduce sexually?

Mutation.

What is the carrying capacity of the environment?

The maximum population size that the environment can support based on limiting resources.

What is a biotic factor in natural selection?

A selection pressure caused by other organisms, such as food availability or predation.

What is an abiotic factor in natural selection?

A selection pressure caused by non-living environmental factors, such as temperature or natural disasters.

What does density-dependent mean in natural selection?

Selection pressures that intensify as population density increases, such as competition for food.

What does density-independent mean in natural selection?

Selection pressures that are unrelated to population density, such as extreme weather or natural disasters.

What is an example of stabilizing selection?

Human birth weights, where average weights are favored over extremes.

What is an example of disruptive selection?

In coho salmon, both small “sneaker” males and large “fighter” males are favored over intermediate-sized males.

What is an example of directional selection?

In Gough Island mice, body size increased rapidly due to strong selection pressure.

What is a gene pool?

All the genes and their different alleles present in a population.

What determines fitness in natural selection?

An individual’s ability to survive, reproduce, and contribute to the gene pool of the next generation.

What are the three patterns of natural selection?

Stabilizing selection, disruptive selection, and directional selection.

What is intraspecific competition?

Competition between members of the same species.

What is meant by “survival of the fittest”?

The individuals best suited to their environment are more likely to survive and reproduce.

What is the role of acquired traits in evolution?

Acquired traits are not heritable and do not contribute to evolutionary change.

What is an epigenetic tag?

A chemical marker that establishes a pattern of gene expression and can be passed to offspring.

What does the Hardy-Weinberg equation predict?

Genotypic and allele frequencies in a population under specific conditions.

What are the conditions for Hardy-Weinberg equilibrium?

No mutation, random mating, no migration, large population size, and no natural selection.

What does it mean if a population is in genetic equilibrium?

Allele frequencies remain constant, and evolution is not occurring.

What is artificial selection?

The intentional breeding of individuals with desired traits by humans.

How does artificial selection provide evidence for evolution?

It demonstrates how selection can cause changes in populations over short periods.

What is the difference between artificial and natural selection?

Artificial selection is driven by human preference, while natural selection is driven by environmental pressures.

What is the definition of a population?

A group of organisms of the same species living in the same area.

What determines the combination of an individual’s inherited genes?

Random events during meiosis and the specific parents involved.

What is the role of selection pressures?

They favor certain phenotypes over others, influencing survival and reproduction.

What is genetic drift?

Random changes in allele frequencies in small populations.

What does fitness depend on in evolutionary biology?

Adaptations for a specific niche within an ecosystem.

What are examples of abiotic selection pressures?

Freezing temperatures, floods, earthquakes, fires, or extreme climates.

What are examples of biotic selection pressures?

Competition for food, predation, or disease caused by other organisms.

What is the definition of fitness in evolutionary biology?

How well-adapted an individual is to survive and reproduce in its specific environment.

How is fitness measured?

By an individual’s contribution to the gene pool of the next generation.

Why is overproduction of offspring important in natural selection?

It leads to competition for resources, which drives the selection of the fittest individuals.

What happens to traits that aid survival in a population?

They are disproportionately inherited by successful offspring, increasing in frequency over time.

Why are Himalayan rabbits an example of gene-environment interaction?

Cold temperatures change gene expression, causing darker fur growth without altering base sequences.

What is the main cause of differences in cold tolerance in plants?

Variation among individuals in their tolerance to abiotic factors like freezing weather.

Why does natural selection not cause acquired traits to be inherited?

Acquired traits do not alter the base sequence of genes in gametes.

What is an example of a species with a slow breeding rate?

The southern ground hornbill, which raises one fledgling every three years on average.

What is an example of a species with a fast breeding rate?

The fungus Calvatia gigantea, which produces up to 7 trillion spores.

What is the typical clutch size of blackbirds?

Between three and five eggs.

How does mutation enlarge the gene pool of a population?

By producing new alleles.

What is the role of meiosis in breaking up existing allele combinations?

It generates haploid cells with unique combinations of alleles.

Why are traits in artificial selection often different from their wild ancestors?

They are shaped by repeated human selection for specific uses or preferences.

What is the role of random mating in Hardy-Weinberg equilibrium?

It ensures no phenotype preferentially mates with another, maintaining stable allele frequencies.

How do environmental catastrophes act as selection pressures?

They are density-independent factors that influence survival regardless of population size.

What is the relationship between phenotypes and alleles in natural selection?

Favored phenotypes result in increased frequency of their corresponding alleles in the population.