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Ecology Chapter 3 What is an Ecology? • All of the earth’s inhabitants are interwoven in a complex web of relationships • Ecology- the study of the interactions of living organisms with one another and with their physical environment (water, soil, etc.) What is an Ecosystem? • Habitat - place where a particular population of a species lives. Many different species that live together in a habitat are called a community. • Ecosystem - ecological system consists of a community and all the physical aspects of a habitat (abiotic factors, ex. water, rocks) and living aspects (biotic factors,ex. other organisms) Ecosystem Image Item Plant Soil Bacteria Oxygen Fungi Abiotic Biotic Ecosystems support • The number of species living within an ecosystem is a measure of its biodiversity. • What is the biodiversity of Hattiesburg? Biotic factors? Abiotic factors diverse communities Ecological Methods • Ecologist study the ecosystem with 3 approaches • Observation • what species live here? • Experimentation • how do the plants react to different temperatures? • Modeling Energy Flow in Ecosystems • The flow of energy is the most important factor that controls what kinds of organisms live in an ecosystem and how many organisms the ecosystem can support. Primary Energy Source • Most life on Earth depends on photosynthetic organisms, which capture the Sun’s energy and stores it as chemical energy in organic molecules. • The rate at which organic material is produced by photosynthetic organisms in an ecosystem is called primary productivity. This determines the amount of energy available in an ecosystem. • Organisms that first capture the energy (autotrophs) make energy-storing molecules. • All other organisms are heterotrophs (consume plants or other organisms to obtain energy). Trophic Levels • The lowest trophic level are the producers (the base). At the second trophic level are herbivores (organisms that eat mainly plants or other primary producers). • At the third trophic level are consumers called carnivores (animals that eat herbivores). Some animals, such as bears and humans are both herbivores and carnivores: they are called omnivores. • Scavengers are organisms that obtain their energy from the organic wastes and dead bodies that are produced at all trophic levels (vultures). Bacteria and fungi are known as decomposers because they cause decay (puts nutrients back into the soil). • Sometimes you have a fourth level… carnivores eating other carnivores, called a tertiary consumer. • Animals often feed at several trophic levels which creates a complicated food web. Item Bear Squirrel Cheetah Oak Tree Human Grass Eagle Trophic Level (1, 2, 3, or 4) Energy is Lost in a Food Chain • During every transfer of energy within an ecosystem, energy is lost as heat. The amount of useful energy available to do work decreases as energy passes through an ecosystem. • At each trophic level, the energy stored by the organism is about 1/10 of that stored by the organisms in the level below. Pyramid of Energy • Energy (Ecological) Pyramid – diagram in which each trophic level is represented by a block, and the blocks are stacked on top of one another with the lowest trophic level on the bottom. The width of each block is determined by the amount of energy stored in the organisms at that trophic level. • Most pyramids are only 3-4 levels. Too much energy allow more levels. is lost to • Biomass – the dry weight of tissue and other organic matter found in a specific ecosystem. Each higher level on the pyramid contains only 10% of the biomass found in the trophic level below. Ecosystems Recycle Material • All organisms require carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur in relatively large quantities. • The paths of water, carbon, nitrogen, and phosphorus pass from the nonliving environment to living organisms, such as the trees from the atmosphere, water, or soil; stays for a time in the living organism; then returns to the nonliving environment. Carbon Cycle Nitrogen Cycle