Introduction to Natural Selection - AP Biology

Selective breeding by humans to enhance desired traits in organisms. Human intervention replaces natural environmental selection pressures.

Variation, inheritance, high rate of population growth, differential survival and reproduction. These conditions must exist for natural selection to operate effectively.

A cycle of adaptations and counter-adaptations between competing species. Continuous reciprocal adaptations between interacting species.

It leads to competition, ensuring only the fittest survive. Creates resource scarcity that intensifies selection pressure.

Charles Darwin. English naturalist who formulated the theory in the 19th century.

It introduces new genetic variations. Creates novel alleles that provide raw material for selection.

A characteristic that improves an organism's chances of survival. Confers higher fitness compared to alternative trait variants.

An action or behavior that helps an organism survive in its environment. Learned or instinctive responses that increase survival chances.

The role and position a species has in its environment. Defines how an organism interacts with its physical and biological environment.

It determines which traits are advantageous for survival. Environmental factors create selection pressures that favor certain traits.

A sharp reduction in population size due to environmental events. Randomly eliminates genetic variants, reducing overall diversity.

Predation, competition, climate change. Environmental factors that influence which traits are advantageous.

Some organisms are more likely to survive and reproduce than others. Creates unequal reproductive success based on trait advantages.

Organisms best adapted to their environment survive and reproduce. Refers to reproductive fitness, not physical strength or dominance.

Differences in physical traits among individuals of a species. Essential for natural selection as it provides diverse traits to select from.

Through mutations and natural selection over time. Mutations provide variation, selection determines which variants persist.

Selection that favors one extreme phenotype over others. Shifts population characteristics toward one end of the trait spectrum.

Peacock's tail feathers attracting mates. Ornamental display that signals genetic quality to potential mates.

Transfer of genetic variation from one population to another. Migration between populations homogenizes genetic differences.

Increased vulnerability to diseases. Limited genetic variation reduces adaptive potential and disease resistance.

The formation of new and distinct species in the course of evolution. Reproductive isolation leads to divergent evolutionary pathways.

The long neck of a giraffe for reaching high leaves. Physical modification that enhances feeding efficiency and survival.

Speciation that occurs due to geographic isolation. Physical barriers prevent gene flow between diverging populations.

It provides the raw material for natural selection to act upon. Without variation, all individuals would respond identically to selection pressures.

A trait that improves an organism's ability to survive and reproduce. Results from natural selection favoring beneficial characteristics.

It favors average phenotypes and reduces variation. Maintains population stability by eliminating extreme variants.

Artificial selection is human-directed; natural selection is environment-driven. The agent of selection differs between natural and human-controlled processes.

Loss of genetic variation when a new colony is established by a few individuals. Small founding populations carry limited genetic representation.

Evolution of species. Gradual change in species characteristics through accumulated adaptations.