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Ecology. Populations Ecosystems Succession Humans and the Environment. Notes & Key : Ecology Teacher Notes. Population. Population size Refers to the number of individuals in a population Factors that influence this size
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Ecology Populations Ecosystems Succession Humans and the Environment Notes & Key: Ecology Teacher Notes
Population • Population size • Refers to the number of individuals in a population • Factors that influence this size • Abiotic – nonliving, such as temperature, moisture, air, salinity, and pH • Biotic – all the living organisms that inhabit the environment
Population density • Refers to the number of individuals found within a given area • If too wide spread, they rarely encounter each other – difficult to reproduce
Dispersion • Refers to the way in which the individuals of the population are arranged • Even – individuals are located at equal intervals • Clumped – bunched together in clusters • Random – location of each individual is determined by chance
Population Growth – population grows when more individuals are born than die • Carrying capacity – when a population has reached the maximum size that the environment can support • Size is determined by limiting factors • Food, water, shelter
Populations living areas • Habitat = the area in which an organism lives • Niche = the role the organism has in an ecosystem
Population relationships • Symbiosis – close association between two different types of organisms – a scientific ‘living together’ • Mutualism – both organisms benefit (lichen) • Commensalism – one organism benefits and the other is neither harmed nor helped (epiphytes) • Parasitism – one organism benefits and the other is harmed (flea)
Ecosystems • Energy Flow • Producers - make their own food (green plants, algae, some bacteria) • Consumers - obtain their food from others • Herbivores – primary consumers that eat plants • Carnivores – secondary consumers that eat flesh • Omnivores – secondary or tertiary consumers that eat plants and flesh • Decomposers – eat dead and decaying organisms
Food Chain • Trophic levels • Clover • Rabbit • Snake • Hawk
Food Web • Food chains that interconnect • and overlap
Pyramid of biomass • Total mass of organisms at each trophic level • Pyramid of numbers • Number of organisms at each trophic level • Pyramid of energy • Amount of energy at each trophic level • Each trophic level receives ~ 10% from the next higher level
Cycles • Water cycle • Nonliving • Condensation, precipitation, evaporation • Living • Absorption, transpiration
Carbon cycle • Atmospheric carbon • Photosynthesis • Cellular respiration
Nitrogen cycle • Atmospheric nitrogen • Nitrogen-fixing bacteria • Nitrates • Nitrites • Plants • Animals • Decomposers
Oxygen cycle • Oxygen in air and water • Cellular respiration • Water • Photosynthesis
Succession • Populations in an area are replaced by other populations • Organisms make the environment less conducive for their existence and more conducive for the next level
Primary succession – where life did not exist before • Pioneer species • Continuing species change • Climax community • Ex. lichen, grasses, small bushes, small trees, mature softwoods (pines, balsams, firs), mature hardwoods (oaks, hickories)
Secondary succession – where a prior community was destroyed (by fire, flood, volcanic eruption, abandoned farming, mining, logging, etc.) • Pioneer species • Continuing species change • Climax community
Humans and the Environment • Conservation – Wise management of the Earth’s natural resources • Renewable resources • Nonrenewable resources
Renewable resources • Wildlife • Many threatened or endangered • Extinction occurs when a species disappears from Earth • Habitat destruction is major cause
Forests • Becoming smaller due to increased demand for wood and wood products • Deforestation occurs where large areas of forest are cut and cleared. Ex. tropical rainforests • Cut and burned to clear land for farming • Topsoil is thin, good for one, or maybe two, years • Then more must be cleared • When land is cleared, rain ceases as trees caused the rain through transpiration • Land becomes a desert Reforestation is a solution
Soil – good soil is needed to grow plants for food and for fibers to make cloth • Erosion can be prevented • Windbreaks • Contour plowing • Terrace plowing • Strip cropping • Crop rotation
Nonrewable resources • Water • Most important • Cannot live without it • Watersheds • Desalination
Fossil Fuels Coal, natural gas, oil Alternative energy forms solar energy nuclear energy wind power geothermal energy water energy
Pollution • Air pollution • Most comes from burning fossil fuels • Smog – smoke and fog • Acid rain – oxides from burning fossil fuel combine with moisture in air • Temperature inversion • Layer of warm air becomes trapped between layers of cool air • Air pollutants become trapped in cool air • Do not rise form the earth, stay near ground
Water pollution • Agricultural runoff • Industrial waste products • One major example is hot water • Causes thermal pollution • Hot water holds less oxygen than cold water