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Transcript
Ecosystem Populations Continued http://www.whale-images.com/endangered-mammals-80-pictures.htm Exponential Growth Earths Human Population Carrying Capacity • It’s the largest population of a species that an environment can support. • Food supply, competition, and predators can affect population size. http://www.rareconservation.org/blog/index.php?paged=2 • Seychelles Paradise Flycatcher requiring about one hectare of mixed woodland per breeding pair. Lives on small island north-east of Madagascar. 4 Limiting Factors that determine the carrying capacity 1) MATERIALS AND ENERGY • Limited by amount of energy from the Sun • Supply of water, carbon and other materials http://www.condorjourneysadventures.com/costarica_nature.asp http://weathersavvy.com/Q-Climate_DesertsHot.html 4 factors that determine the carrying capacity of an ecosystem 2) FOOD CHAINS • Biomass in all levels affects the length of the chain. • Limited by amount food supply (so trophic level below) • Limited by predators (so trophic level above) 4 factors that determine the carrying capacity of an ecosystem 3. COMPETITION • Competition for food, water, mate and space. • Intraspecific competition: among members of the same species • Interspecific competition: between species. 4 factors that determine the carrying capacity of an ecosystem 4) Population density : How many individuals that can live in an area at one time. Density-dependent factors • When density increases beyond suitable level: • Overcrowding may : – increase stress and spread of diseases or parasites – Increase aggression and neglect of offspring • Therefore decreases population Density-independent factors Limit a population regardless of its size. -Forest fire -Earthquake -Volcanic eruption -Tornado Feeding People Productivity • The average amounts of new plant biomass produced each year per unit area. Productivity of ecosystems • Productivity is influenced by many factors Factors that can increase productivity • Add water and fertilizer to deserts • Very expensive Factors that can increase productivity. • Clear cutting rain forest • Introduce good farm plants and animals into rainforest conditions. • Not a good idea. • Disease, pests, weather fluctuations. Food and Population Size • Canadians consume more calories and more animal products per day than others in the world. • 80% of the Earth’s population consumes grains as primary source of nutrition. Food and Compeitiors • Natural ecosystem – hundreds of species are interconnected. • Agricultural – produces short, simple food chains, that link plants to people. Factors that increase productivity. • Monoculture • A single crop (wheat, corn or rice) is often grown on huge areas of land. • How does monocultural affect populations of primary consumers? Costs of monoculture – pests This peel represents the surface, the skin of the earth's crust, the topsoil on which humanity depends. It's less than 5 feet deep and can produce only a fixed amount of food. Due to erosion and overfarming, we lose 24 billion tons per year. It takes 100 years for one inch of topsoil to form