bio chp. 22

heritable change in one or more characteristics of a population from one generation to the next

group that share distinctive characteristics In sexually reproducing species, members of the same species can reproduce to produce viable and fertile offspring.

members of the same species that occupy the same location at the same time

1600s - John Ray developed an early classification system for plants and animals. oHelped people perceive similarities and differences between organisms. 1700s - European scientists suggested that life forms are not fixed and unchanging. oSpecies change and adapt to new environments. 1800s - Darwin formulated his Theory of Evolution - Organisms evolve over time to become optimally adapted to their environment

crushing beaks- crush seeds and pull buds from branches small grasping- pick insects from trees heavier grasping- can break apart wood to search for insects probing beaks- search for insects in crevices or open up cactus fruits and take out seeds

• Birds from the South American mainland feed on seeds. There are plenty of seeds of varying size. Variations in beak size are present. • A small population of birds migrates to a new island where resources are limited so not all birds will survive and reproduce. • Seeds on the new island are large. Birds with larger beaks are better at crushing large seeds and are more likely to survive and reproduce (and therefore transfer DNA to next generation). • In the next generation, more birds have larger beaks because large beak alleles were transmitted more frequently than smaller beak alleles.

• Studies on natural selection • Fossils • Biogeography • Convergent evolution • Selective breeding • Comparison of homologies

since natural selection is the best adapted to the environment are more likely to survive and reproduce in daphne major, an island on galapagos had a huge drought and all the small soft seeds disappeared but the bigger ones stayed so they birds with bigger beaks could eat and break down the bigger seeds so they survived. in 1976-1978 scientists measured beak depth in parents and offspring before and after drought- post drought- offspring had larger beaks compared to pre drought offspring

preserved remains of organisms from the past

examples- ▪ T. roseae, discovered in 2005, is a transitional form between fish and tetrapods. oEvidence that tetrapods (4 legged animals) evolved from fish. Early ancestors lived in a wooded environment oThey were smaller, had fleshy paws, and had different tooth morphology. ▪ Modern day horses adapted to live in open grassland oThey evolved to be larger, and to have bony hoofs and different tooth morphology.

species divergence following isolation

Study of the geographic distribution of species.

found in only one location

Australia

Different species independently evolve similar characteristics because they occupy a similar environment. example: The long snouts and tongues of the giant anteater (left) and the echidna (right) allow them to feed on ants.

Two different populations of crickets on different islands independently developed a mutations that abolished chirping to escape parasitic flies. (convergent evolution)

intentional modification of desirable characteristics in domesticated species.

In natural selection nature chooses parents with the most successful traits; in selective breeding/artificial selection, humans choose parents with desirable traits.

evolution of related species from a common ancestor

Similarity due to presumed descent from a common ancestor - Can be analyzed at anatomical, developmental, and molecular level.

similar structures

structures that currently serve no apparent function but are presumed to be remnants from an ancestor that did use the structure. like we have a tailbone but no tail

Species that differ as adults often bear striking similarities during development

Similarity at the molecular level, i.e., genes and metabolic pathways