Ecology Populations Ecosystems Succession Humans and the Environment

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 p. H • 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