D4.1 Natural selection

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What is the basic principle of natural selection?

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

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What is the basic principle of natural selection?

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

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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.

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What is the original source of variation in populations?

Mutation.

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How does meiosis contribute to variation?

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

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What role does sexual reproduction play in variation?

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

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

Mutation.

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What is the carrying capacity of the environment?

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

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What is a biotic factor in natural selection?

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

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What is an abiotic factor in natural selection?

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

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What does density-dependent mean in natural selection?

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

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What does density-independent mean in natural selection?

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

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What is an example of stabilizing selection?

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

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What is an example of disruptive selection?

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

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What is an example of directional selection?

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

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What is a gene pool?

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

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What determines fitness in natural selection?

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

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What are the three patterns of natural selection?

Stabilizing selection, disruptive selection, and directional selection.

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What is intraspecific competition?

Competition between members of the same species.

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What is meant by “survival of the fittest”?

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

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What is the role of acquired traits in evolution?

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

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What is an epigenetic tag?

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

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What does the Hardy-Weinberg equation predict?

Genotypic and allele frequencies in a population under specific conditions.

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What are the conditions for Hardy-Weinberg equilibrium?

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

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

Allele frequencies remain constant, and evolution is not occurring.

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What is artificial selection?

The intentional breeding of individuals with desired traits by humans.

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How does artificial selection provide evidence for evolution?

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

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What is the difference between artificial and natural selection?

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

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What is the definition of a population?

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

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

Random events during meiosis and the specific parents involved.

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What is the role of selection pressures?

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

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What is genetic drift?

Random changes in allele frequencies in small populations.

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What does fitness depend on in evolutionary biology?

Adaptations for a specific niche within an ecosystem.

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What are examples of abiotic selection pressures?

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

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What are examples of biotic selection pressures?

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

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What is the definition of fitness in evolutionary biology?

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

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How is fitness measured?

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

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Why is overproduction of offspring important in natural selection?

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

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What happens to traits that aid survival in a population?

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

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

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

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

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

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

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

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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.

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

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

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What is the typical clutch size of blackbirds?

Between three and five eggs.

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How does mutation enlarge the gene pool of a population?

By producing new alleles.

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

It generates haploid cells with unique combinations of alleles.

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

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

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

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

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How do environmental catastrophes act as selection pressures?

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

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

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

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