A4.1 Evolution and Speciation and D4.1 Natural Selection

Hybridization

The interbreeding of two different species to produce a hybrid; often results in sterile offspring, but can lead to new species if followed by polyploid.

Polyploidy

A condition where an organism has more than two sets of chromosomes; common in plants and can lead to sympatric speciation.

Temporal isolation

Occurs when species reproduce at different times, preventing mating.

Adaptive radiation

The rapid evolution of many species from a common ancestor, each adapted to a different ecological niche.

Allopatric Speciation

Speciation that occurs when populations are physically separated by a barrier; over time, natural selection and genetic drift lead to divergence and reproductive isolation.

Abrupt Speciation

Also called instant speciation, it occurs rapidly, often due to polyploidy or hybridization in plants.

Sympatric Speciation

Speciation that occurs without geographic separation; caused by behavioral, temporal, or genetic isolation within the same area.

Geographical isolation

Happens when physical barriers, such as land or water formations, prevent males and females from different parts of a population finding each other.

Niche

The role of a species in its ecosystem, including its habitat, diet, and interactions; includes both abiotic and biotic factors.

Locus

The specific position of a gene on a chromosome; each gene occupies a fixed location on homologous chromosomes.

Behavioral Isolation

Occurs when populations have different mating behaviors or rituals, preventing interbreeding; ex. different bird songs or firefly flash patterns.

Speciation

The formation of new and distinct species through evolutionary processes, often as a result of reproductive isolation or genetic divergence.

Phylogenetic tree

A branching diagram that represents the evolutionary relationships among species based on similarities and differences in genetic or physical traits.

Heritable characteristics

Traits encoded in an organism’s genetic material that can be passed from parents to offspring through reproduction.

Darwinian evolution

the concept proposed that species evolve over time through natural selection acting on heritable variation.

Common ancestery

The idea that different species share a common ancestor from which they have diverged over time through evolutionary processes.

Lamarckism

the outdated theory that organisms can pass on traits acquired during their lifetime to their offspring (e.g., a giraffe stretching its neck and passing on a longer neck)

Reproductive isolation

a situation in which different populations can no longer interbreed successfully, leading to the formation of new species through speciation

Convergent evolution

the independent evolution of similar traits in species of different lineages due to similar environmental pressures or ecological roles

Artificial selection

the process by which humans breed plants or animals for specific traits, influencing the genetic makeup of future generations.

Analogous structures

structures that perform similar functions in different species but evolved independently, not from a common ancestor—an example of convergent evolution.

Homologous Structures

anatomical features that are similar in structure and origin across different species, even if they serve different functions—evidence of common ancestry.

Divergent evolution

the process by which two or more related species become more dissimilar over time, usually due to different environmental pressures or adaptations.

Pentadactyl limbs

limbs with five digits, found in many vertebrates, used as evidence of a shared evolutionary origin.

Gradual evolutionary change

the slow and continuous accumulation of small genetic variations in a population over long periods, leading to the formation of new species.

Extinction

the permanent loss of all members of a species, often resulting from environmental changes, competition, or inability to adapt

Vestigial structure

Shows ancestry but no longer functions

Density dependent factors (PANDA)

Predators, availability resources, nutrient supply, disease, accumulation of waste

Density independent factors (PAWS)

Phenomena, abiotic factors, weather conditions.