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5.1 Communities and Ecosystems Topic 5: Ecology and evolution Blake Bainou Mr. Evans I.B. Biology SL Period Five May 29th, 2008 Purpose of this presentation: The purpose of this presentation is to provide you with information regarding Bullet 5.1 of the IB Biology SL Detailed Syllabus This document covers 5.1.1 - 5.1.14 5.1.1 Define species, habitat, population, ecosystem, and ecology. Species: a group of organisms that can interbreed and produce fertile offspring. Habitat: the environment in which a species normally lives or the location of a living organism. Population: a group of organisms of the same species who live in the same area at the same time. Community: a group of populations living and interacting with each other in an area. Ecosystem: a community and its abiotic environment. Ecology: the study of relationships between living organisms and between organisms and their environment. 5.1.2 Distinguish between autotroph and heterotroph. Autotroph: an organism that synthesizes its organic molecules from simple inorganic substances. Heterotroph: an organism that obtains organic molecules from other organisms. 5.1.3 Distinguish between consumers, detritivores and saprotrophs. Consumer: an organism that ingests other organic matter that is living or recently killed. Detritivore: an organism that ingests non-living organic matter. Saprotroph: an organism that lives on or in nonliving organic matter, secreting digestive enzymes into it and absorbing the products of digestion. 5.1.4 Describe what is meant by a food chain, giving three examples, each with at least three linkages (four organisms). A food chain shows the progression from producer organisms, to primary, secondary, and then tertiary consumer organisms in an ecosystem. Ex: grass-mouse-snake-hawk Ex: plant-beetle-spider-cat Ex: plankton-whale-shark-human 5.1.5 Describe what is meant by a food web. Food web: a series of organisms related by predator-prey and consumerresource interactions; the entirety of interrelated food chains in an ecological community. 5.1.6 Define trophic level. Trophic level: any class of organisms that occupy the same position in a food chain, as primary consumers, secondary consumers, and tertiary consumers. 5.1.7 Deduce the trophic level of organisms in a food chain and a food web. Students should be able to place an organism at the level of producer, primary consumer, secondary consumer, and so on, as the terms herbivore and carnivore are not always applicable. 5.1.8 Construct a food web containing up to 10 organisms, using appropriate information. Grass Bear Wolf Snake Hawk Rabbit Human Insect Fish Mice Owl 5.1.9 State that light is the initial energy source for almost all communities. light is the initial energy source for almost all communities. 5.1.10 Explain the energy flow in a food chain. Energy losses between trophic levels include material not consumed or material not assimilated, and heat loss through cell respiration. As this energy flows throughout the ecosystem, it is consumed by chemical processes and released as heat. 5.1.11 State that energy transformations are never 100% efficient. Energy transformations are never 100% efficient. 5.1.12 Explain reasons for the shape of pyramids of energy. As energy moves up trophic levels, living organisms only use 10% of the previous trophic level’s energy. This phenomenon creates an energy pyramid, as opposed to an energy rectangle. Consumers Producers 5.1.13 Explain that energy enters and leaves ecosystems, but nutrients must be recycled. Energy enters and leaves and ecosystem in the form of heat and sunlight energy, which is transformed to power chemical processes. Nutrients, however, are recycled throughout the ecosystem because they cannot be replenished. Energy makes it possible for nutrients to be cycled through the biotic and abiotic worlds. 5.1.14 State that saprotrophic bacteria and fungi (decomposers) recycle nutrients. Saprotrophic bacteria and fungi (decomposers) recycle nutrients.