Evolution pt.2

The origin of new taxonomic groups (new species, etc.) Speciation is a key process in macroevolution.

Phyletic evolution; transformation of one species to another Anagenesis involves a gradual change in a single lineage.

Branching evolution; new species arise from a population that buds from a parent species Cladogenesis increases biodiversity.

Speciation that occurs due to geographic barriers isolating populations and preventing gene flow This often leads to reproductive isolation.

Inhabiting new environments with new selection factors leading to reproductive isolation This process often follows mass extinctions or the colonization of new habitats.

New species arise within the area of parent populations without geographic barriers Genetic (reproductive) isolation develops in the same location.

Chromosomal changes that occur in plants causing chromosome numbers to multiply in some individuals Polyploidy can lead to speciation in plants.

Factors that prevent different species from mating These barriers can be prezygotic or postzygotic.

Barriers that impede mating between species Types include habitat, temporal, behavioral, mechanical, and gametic isolation.

Barriers that prevent hybrid zygote from developing into viable, fertile adults Types include hybrid infertility and reduced viability.

A region in which members of different species meet and mate Outcomes can include reinforcement, fusion, or stability.

The disappearance of species from Earth Generally occurs gradually, influenced by human actions.

Five Each event wiped out a large proportion of Earth’s species.

The geographical distribution of species Modern species are found where they evolved from ancestors that inhabited those regions.

Preserved evidence of organisms Confirms the existence of earlier species.

Determines the order in which groups of species were present in a sequence of strata It helps establish a timeline of species existence.

Fossils that permit the relative dating of rocks within a narrow time span Trilobites are a common example.

Dating that provides the age of fossils in years Radiometric dating is a common method used.

Study of similar stages in embryonic development among closely related organisms Establishes homology among structures.

Similarity resulting from common ancestry Important for understanding evolutionary relationships.

Similarity not resulting from common ancestry Often results from convergent evolution.

Structures of marginal, if any, importance Examples include the human appendix.