3.+Individual+organisms+and+species+evolve

MAJOR UNDERSTANDINGS

3.1a The processes of sexual reproduction and mutation have given rise to a variety of traits within a species. 3.1b Changes in environmental conditions can affect the survival of individual organisms with a particular trait. 3.1c Human activities such as selective breeding and advances in genetic engineering may affect the variations of species. 3.2a In all environments, organisms with similar needs may compete with one another for resources. 3.2b Extinction of a species occurs when the environment changes and the adaptive characteristics of a species are insufficient to permit its survival. 3.2c Many thousands of layers of sedimentary rock provide evidence for the long history of Earth and for the long history of changing lifeforms whose remains are found in the rocks. 3.2d Although the time needed for change in a species is usually great, some species of insects and bacteria have undergone significant change in just a few years.