Patterns of Evolution

Macroevolution The term macroevolution is used to describe large-scale evolution that takes place over time it is evolution above the species level Six important topics in macroevolution include: extinction, adaptive radiation, convergent evolution, coevolution, punctuated equilibrium, and changes in developmental genes

Extinction Extinction is the disappearance, or dying out, of a species Most extinction occurs when species cannot compete for resources or adapt to changing environments (natural selection at work)

Mass Extinction Mass extinctions occur when entire ecosystems are wiped out and many species go extinct Until recently, researchers looked for a single cause of mass extinctions; however, many paleontologists now think that most mass extinctions are caused by many factors

Significance of Mass Extinctions Each disappearance of so many species left habitats open and provided ecological opportunities for those organisms that survived the result was often a burst of evolution that produced many new species

Adaptive Radiation Adaptive radiation is the process in which one species evolves into diverse species that live in different ways Example: Darwin’s finches → more than a dozen species evolved from a single species of finch

Adaptive Radiation Adaptive radiations can also occur on a much larger scale Example: Dinosaurs vs. Early Mammals The first dinosaurs and mammals evolved at about the same time The dinosaurs went through an adaptive radiation that allowed them to “rule” Earth for millions of years while mammals remained small and were relatively scarce Once the dinosaurs were out of the picture, the mammals went through an adaptive radiation

Adaptive Radiation

Convergent Evolution Convergent evolution is a process in which “unrelated” species come to look alike because they have evolved similar adaptations to similar environments Example: Similarities between sharks, dolphins, and penguins – How did these organisms come to resemble one another? analogous structures - structures which look and function similarly, but are made up of parts that do not share an evolutionary history

Coevolution Coevolution is the process by which two species evolve in response to changes in each other Example: some plants have evolved poisons to protect themselves from insects → in response, insects have evolved ways to protect themselves from the poisons

Punctuated Equilibrium Punctuated equilibrium is a pattern of evolutionary change where long periods of little or no change (in a species) is interrupted by short periods of rapid change * Evolution occurs at different rates for different organisms over time

Developmental Genes Small changes in the development of an embryo can have a large affect on the adult organism