Transcript review ch5
G. Tyler Miller’s Living in the Environment 13th Edition Evolution and Biodiversity: Origins, Niches, and Adaptations Chapter 5 Evolution and Adaptation Natural selection • Process in by which individuals of a population acquire genetically based traits that increase their chances of survival and their ability to produce offspring. Adaptation (n.) – A heritable trait that enables an organism to better survive and reproduce under a given set of environmental conditions Artificial selection • Humans select one or more desirable genetic traits in the population of a plant or animal. Natural Selection Conditions necessary for natural selection: – variability – heritability – differential reproduction Fig. 5-5 p. 101 Climate Change and Natural Selection • Changes in climate throughout the earth’s history have shifted where plants and animals can live. Figure 4-6 Limits on Adaptation through Natural Selection • A population’s ability to adapt to new environmental conditions through natural selection is limited by its gene pool and how fast it can reproduce. – Humans have a relatively slow generation time (decades) and output (# of young) versus some other species. Evolution and Adaptation • Co-Evolution – Populations of two different species interacting over a long period of time – Changes in the gene pool of of one species changes the gene pool of another species • Predator-Prey Relationships • Plant defense mechanisms Ecological Niches and Adaptation Occupation • Ecological niche – Total way of life or functional role of a species in an ecosystem. Address • Habitat – Physical location of a species Ecological Niches and Adaptation • Fundamental niche – Full potential range of the physical, chemical, and biological factors a species can use if there were no direct competition from other species. • Realized niche – Part of a species fundamental niche that are actually used. Broad and Narrow Niches • Generalist species – Species with a broad ecological niche. • Live in many different places. • Eat a variety of food. • Tolerate a wide range of environmental conditions. (flies, mice, deer, catfish, humans) • Specialist species – Species with a narrow ecological niche. • Live only in one type of habitat • Use only a few types of food • Tolerate only a narrow range of climatic and other environmental conditions. (tiger salamander, red-cockaded woodpecker, spotted owls, pandas) Generalist and Specialist Species: Broad and Narrow Niches • Generalist species tolerate a wide range of conditions. • Specialist species can only tolerate a narrow range of conditions. Speciation, Extinction, and Biodiversity Speciation - formation of two species from one species because of divergent natural selection 1) Geographic isolation – groups of the same species become physically separated Geographic Isolation …can lead to reproductive isolation, divergence of gene pools and speciation. Speciation, Extinction, and Biodiversity 2) Reproductive Isolation – isolated populations become so genetically different they cannot . . . Interbreed, or produce live, fertile offspring Extinction: Lights Out • Extinction occurs when the population cannot adapt to changing environmental conditions. The golden toad of Costa Rica’s Monteverde cloud forest has become extinct because of changes in climate. Figure 4-11 Extinction: Lights Out • 99.9 % of all species that ever existed are now extinct Figure 4-11 How do speciation and extinction affect biodiversity? Speciation – Extinction = Biodiversity Effects of Humans on Biodiversity • The scientific consensus is that human activities are decreasing the earth’s biodiversity.