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ECOLOGY TOPIC 4 4.1 Species, communities, and ecosystems • Species are groups of organisms that can potentially interbreed to produce fertile offspring. • Species: • • • • • Have a common gene pool The basic unit for classifying organisms Have similar physiological and morphological characteristics Are genetically distinct from other species Have a common phylogeny (family tree) Challenges to definition of species • Similar species can sometimes mate and produce offspring. • Examples: • Horse and zebra, donkey and zebra. Don’t have same number of chromosomes so offspring are usually infertile. • Populations that can’t breed due to distance • Populations that don’t interbreed because they reproduce asexually. • What about infertile individuals? Hybrids • When members of different species mate, their offspring are infertile and referred to as an interspecific hybrid. • Examples are mule and liger • Hybrids don’t continue as a population due to being infertile Populations can become isolated • Isolation can cause changes in evolutionary paths creating new species. • Causes for isolation: • Bodies of water • Mountain ranges • Deep canyons • Breeding times • Breeding habits ( songs, dances etc) Autotrophs and Heterotrophs • Autotrophs are capable of making their own organic molecules as a food source. • Photosynthesis converts inorganic molecules into organic molecules. • Examples of Autotrophs (Producers) • Algae, cyanobacteria, grass, trees Autotrophs and Heterotrophs • Heterotrophs cannot make their own food from inorganic molecules and must obtain organic molecules from other organisms. • They obtain their energy from autotrophs or other heterotrophs. Consumers • Ingest other organisms to get the molecules needed for survival. • The only component we can make from sunlight is vitamin D Detritivores • Eat non-living organic matter such as dead leaves, feces, and carcasses. • Examples of detritivores are earthworms, woodlice and dung beetles. • Many bottom feeding organisms in lakes and rivers are detritivores. Saprotrophs • Live on or in non-living organic matter. • Secrete digestive enzymes and absorb the products of digestion. • Examples are bacteria and fungi. • Saprotrophs, bacteria and fungi, are also called decomposers. Communities • A group of populations living and interacting in an area. • Ways of interacting includes feeding on each other, protecting each other, providing habitat for each other. Ecosystems • A community of organisms along with their abiotic environment. • Examples of abiotic components of an ecosystem: • Air, water, soil, light, humidity, pH Systematic Sampling Techniques • Random sampling of an area to determine what is there, how much is there and what abiotic components are there. • A quadrat is a 1 square meter box used to take random samples of an area. • A transect is a line running across numerous environments within an given area. It is used along with a quadrat to show relationships between organisms and the environment they live in. Nutrients • Autotrophs need nutrients to grow and be healthy and they can’t get them from their diets like heterotrophs do. • Nutrients are available to plants from the soil and are taken up by their roots. • The supply of nutrients is maintained by recycling due to decomposers. • Carbon and nitrogen are examples Nutrients • Returned to the system through the action of decomposers. • By returning nutrients to the system, ecosystems can be sustainable. • Nitrogen cycle: N2 as a gas in the atmosphere • Plants and animals can’t use this gas directly • Some bacteria can – nitrogen fixation- take nitrogen from air and create nitrogen compounds that plants and animals can use. 4.2 Energy Flow • Most ecosystems depend on energy from the sun • Photo synthesizers (autotrophs) use light energy to create organic molecules (sugar) from inorganic molecules CO2 • They form the basis or first trophic level of the food or energy chain. Food chains • By feeding on autotrophs, heterotrophs can use the energy of autotrophs to grow and stay healthy. • A food chain is the process of passing energy from organism to organism, trophic level to trophic level. • Only about 10% of the energy contained within a trophic level is used by the next trophic level. • Energy loss in a food chain • Not consumed • Consumed but not used by the consumer • Lost in the form of heat