Ecology

1. Ecology Populations Ecosystems Succession Humans and the Environment Notes & Key: Ecology Teacher Notes

2. 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

3. 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

4. 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

5. 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

7. Populations living areas • Habitat = the area in which an organism lives • Niche = the role the organism has in an ecosystem

8. 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)

9. 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

10. Food Chain • Trophic levels • Clover • Rabbit • Snake • Hawk

11. Food Web • Food chains that interconnect • and overlap

12. 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

13. Cycles • Water cycle • Nonliving • Condensation, precipitation, evaporation • Living • Absorption, transpiration

14. Carbon cycle • Atmospheric carbon • Photosynthesis • Cellular respiration

15. Nitrogen cycle • Atmospheric nitrogen • Nitrogen-fixing bacteria • Nitrates • Nitrites • Plants • Animals • Decomposers

16. Oxygen cycle • Oxygen in air and water • Cellular respiration • Water • Photosynthesis

17. 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

18. 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)

19. 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

20. Humans and the Environment • Conservation – Wise management of the Earth’s natural resources • Renewable resources • Nonrenewable resources

21. Renewable resources • Wildlife • Many threatened or endangered • Extinction occurs when a species disappears from Earth • Habitat destruction is major cause

22. 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

23. 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

24. Nonrewable resources • Water • Most important • Cannot live without it • Watersheds • Desalination

25. Fossil Fuels Coal, natural gas, oil Alternative energy forms solar energy nuclear energy wind power geothermal energy water energy

26. 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

27. Water pollution • Agricultural runoff • Industrial waste products • One major example is hot water • Causes thermal pollution • Hot water holds less oxygen than cold water