BETTER D4.1 Natural selection

What is natural selection?

A process where individuals with advantageous traits survive and reproduce more

How is evolution defined in the context of natural selection?

Evolution is defined as the change in allele frequency within a population over generations.

What does natural selection act upon?

It acts on phenotypes (observable traits).

What does the process of natural selection explain in a modern context?

It explains today’s biodiversity by operating continually over geological time.

What are the four core postulates of natural selection?

Variation, overproduction, struggle/selection, and inheritance.

What was the paradigm shift regarding the mechanism of evolution?

Darwin’s mechanism of natural selection replaced Lamarck’s theory of the inheritance of acquired traits.

How do mutations contribute to variation?

create entirely new alleles from changes in the DNA

How does meiosis contribute to genetic variation?

Through crossing over (Creating new combinations of alleles on a single chromosome) and independent assortment (shuffling chromosomes into gametes).

How does sexual reproduction increase variation?

Fertilization combines alleles from two different parents to create unique offspring.

What is the relationship between genetic variation and adaptation?

More genetic variation leads to greater adaptive potential for a population.

Do crossing over and independent assortment create new alleles?

No, they only reshuffle existing alleles into new combinations.

What is the consequence of overproduction of offspring?

It leads to intraspecific competition for limited resources like food, water, space, light, and mates.

What is carrying capacity (K)?

The maximum population size an environment can support, set by limiting resources.

What happens to individuals with beneficial traits during competition?

They secure more resources/mates, leading to higher reproductive success.

What are abiotic factors?

Non-living environmental factors such as temperature, salinity, pH, drought, flood, light, and toxins.

How do abiotic factors typically impact a population?

They are often density-independent, meaning their impact does not depend on the population size.

What are examples of adaptations for abiotic stressors?

Tolerance traits such as antifreeze proteins, salt glands, and drought resistance.

How do rapid extremes like wildfires or freezes affect selection?

They can cause strong, fast selection pressures on a population.

What defines an adaptation?

A trait that increases survival and/or mating success in a given environment.

What is biological fitness?

A measure of reproductive success; individuals with higher fitness leave more offspring, causing favored alleles to rise in frequency.

Is fitness a fixed value?

No, fitness is relative and environment-specific.

Is intraspecific compeition a major driver of selection?

yes

What is required for a trait to evolve?

The trait must be heritable (encoded in DNA and passed through germ cells).

Can acquired traits like muscle training or injuries be inherited?

No, only DNA-encoded traits in germ cells are passed to offspring.

Which types of mutations can enter the gene pool?

Germline mutations can enter the gene pool, but somatic mutations cannot.

What is sexual selection?

A selection pressure that favors traits improving mating success rather than just survival.

What is the difference between intersexual and intrasexual selection?

Intersexual selection involves mate choice (e.g., females preferring bright displays), while intrasexual selection involves same-sex competition (e.g., antler combat).

How do costly signals (like heavy antlers) persist in a population?

They persist if the boost in reproductive success outweighs the cost to survival.

What did Endler’s guppy experiments demonstrate?

They showed that selection pressures (predation vs. sexual selection) can rapidly shift population traits.

In the guppy experiment, what happened when there were no predators?

Sexual selection dominated, and males evolved more spots.

In the guppy experiment, what happened under strong predation?

Natural selection dominated, and fewer spots were favored to improve camouflage.