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Evolution and Biodiversity Chapter 3 Pages 46-62 Evolution: All species descended from earlier ancestral species. Changing genetic makeup in a population over time. Accepted scientific explanation of how animals adapt and survive Evolution and Adaptation • Macroevolution – long term, large scale changes • Microevolution – small genetic changes • Gene pool – all genes in a population • Mutation – random change in structure of DNA. Every so often, a mutation is beneficial for survival. • Natural selection – individuals that have traits that benefit survival. Natural Selection • Microevolution is changes in the gene pool of a population over time that result in changes to the varieties of individuals in a population such as a change in a species' coloring or size. • Macroevolution If the changes are over a very long time and are large enough that the population is no longer able to breed with other populations of the original species, it is considered a different species. Evolution and Adaptation Microevolution Macroevolution Natural Selection Three things must happen: • 1. Genetic variability in a trait within population • 2. Trait is heritable • 3. Differential reproduction – must enable individuals with the trait to leave more offspring than others without the trait. • Adaptive (heritable) trait helps survival and reproduction under current conditions Ecological Niches and Adaptation • Ecological niche – role in ecosystem. Includes interaction with biotic and abiotic factors. • Habitat – physical location • In other words: – Niche – species occupation – Habitat - address Ecological Niches Stratification of niches, habitats allows many different species to coexist. This is biodiversity. Broad and Narrow Niches • Generalist species • Specialist species – What is better? Depends… • Environmental conditions consistent – favors specialists. Fewer competitors, food plentiful • Rapidly changing environmental conditions – favors generalists… More adaptable. Ecological Niches and Adaptation Speciation, Extinction, and Biodiversity How Species Evolve • Speciation • Geographic isolation • Reproductive isolation Fig. 5-7 p. 94 Extinction • When Environmental changes occur, species must evolve to adapt. If not… • Background extinction – slow rate • Mass extinction – quickly, large groups • Mass depletion – higher than mass (Ice Age) – 99% of species that have existed on earth are now extinct. Changes in Earth’s biodiversity – has leveled off during the last 1.8 million Years. Is this due to human influence? Extinction • Adaptive radiation – after mass extinctions, numerous new species evolve to fill vacated niches. Takes 1-10 million years for adaptive radiation to rebuild biodiversity. • Human impacts – accelerated extinction Human Impacts on Evolution • Artificial Selection – artificially selecting superior genetic traits • Agriculture • Hatcheries • pets Genetic Engineering • Gene splicing • Species creation in laboratories • Takes less time than artificial selection • Concerns about Genetic Engineering • Many failures (1% success rate) • Lead to more abortions? Only for the wealthy? Biomes: Life on Land • major vegetation types on land – based on different climates and atmospheric conditions • forests, grasslands, deserts • tropical, temperate, polar • temperature and precipitation determine overall patterns – What biome do we live in? Biomes across 39th parallel Altitude and latitude The two most important factors influencing vegetation in the formation of biomes are precipitation and temperature. Aquatic Life Zones Aquatic Life Zones: Saltwater 71% of the Earth • Coastal zone – majority of marine species (90%) • most commercial fisheries and interaction with land and humans • Open ocean – 90% of ocean area • Estuary – where rivers meet ocean • Coral reefs and mangrove forests Ocean Zones Freshwater Life Zones • Standing water • Flowing water Types of Lakes: Oligotrophic Types of Lakes: Eutrophic Stream Systems • Runoff • Watershed • Drainage basin Estuary • Floodplain