Communities and Ecosystems

1. Communities and Ecosystems Chapter 37

2. Principles of Ecology • A. Beginnings of Ecology • 1. This science rose from natural history • 2. Ecology is the study of interactions between organisms and their environment • 3. Information is gathered through a lot of observational studies within the environment (not so much in the lab) • B. Biosphere: portion of the earth that supports life • 1. Biotic Factors – living things in the environment • a. examples: plants, humans, bacteria, animals, fungus • 2. Abiotic Factors – nonliving things in the environment • a. examples: rocks, man-made items, rain, sunlight, temperature, soil, slope of land • b. these factors interact with each other • c. these factors affect the biotic factors

3. C. Hierarchy of life 1. Organism – a single individual of a species 2. Population – a group of organisms that live in the same place at the same time that interbreed. 3. Community – a collection of interacting populations 4. Ecosystem – community + abiotic factors 5. Biosphere – living world + nonliving (bottom of the ocean through the atmosphere)

4. D. Niche – the role a species plays in its community 1. would include what food it eats, how much space it needs, how it finds food, when it is active, reproduction habits etc. 2. The more similar two niches are, the more likely species will compete for at least one resource. There is a limit to how much niches can overlap. Result: a. one species may go extinct b. one species moves to another area, both survive c. one species may adapt to a new niche 3. Competitive Exclusion Principle or Niche Rule – no two species occupying the same niche can exist for long. E. Habitat – where an organism lives

5. F. Interspecific interactions: 1. Symbiosis – “living together”, close and permanent association between organisms of different species a. Commensalism – one species benefits, the other is neither harmed nor benefited from the relationship Examples: b. Mutualism – both species benefit Examples: Facultative mutualism– they can live without each other Obligatory mutualism– they cannot live without each other c. Parasitism – one species benefits, the other is harmed “Host” – the species being harmed Examples: Tissue Parasitism – one species eating the tissue of another Social Parasitism – one species exploits the labors of another 2. Interspecific competition – competing for same limited resource Examples: 3. Herbivory – consumption of plant parts or algae by an animal 4. Predation – leads to diverse adaptations in prey species Examples:

6. G. Trophic structure a. Producer – “autotroph”– organism that makes its own food b. Consumer – “heterotroph” – get energy from the producer directly or indirectly Primary consumer – herbivore (eats producers) Secondary consumer – eats herbivores Tertiary consumer – eats secondary consumers Quaternary consumer – eats tertiary consumers c. Carnivore – eats other heterotrophs d. Scavenger – eats dead animals e. Omnivore – eats both heterotrophs and autotrophs f. Herbivore – eats plants (primary consumer) g. Insectivore – eats insects h. Decompose aka “detritivores” – breaks down dead matter into simple compounds to be reabsorbed.

7. H. Energy flow through an environment 1. Energy originates with the sun 2. Food Chain – simplest feeding relationship a. 4-5 levels maximum (why not 20?) as energy flows through a food chain, it is lost (popcorn demo outside) b. more energy is available at the lower end of the chain 3. Food Web – food chains interlinked and overlapped within a single ecosystem

8. FOOD CHAIN

9. FOOD WEB

10. H. Nutrient Cycles – food chains and food webs show energy being moved in one direction. Energy is lost while nutrients are recycled. 1. Water Cycle: 3 processes involved a. evaporation – liquid to gas (heat) b. condensation – gas to liquid (cool) c. precipitation – falling water

11. 2. Carbon/Oxygen cycle a. sources of carbon – animals exhaling, fire, burning fossil fuels, decomposition b. sources of Oxygen – plants give off c. Carbon leaves environment – plants take in d. Oxygen leaves environment – inhale of animals, fire

12. 3. Nitrogen cycle a. 78% of the air is Nitrogen (in a form plants and animals cannot use) Why do we need nitrogen? Proteins, DNA b. Nitrogen Fixation – process where bacteria in the soil convert atmospheric nitrogen to a usable form called “nitrate” c. Plants absorb nitrates and use them to make protein and DNA d. Nitrogen then goes through the food web as proteins e. Denitrification – process where bacteria in the soil convert proteins (from dead plants and animals) to atmospheric Nitrogen

13. Nitrogen Cycle

14. 4. Phosphorus cycle a. why do organisms need phosphorus? b. rocks are the source of phosphorus for terrestrial ecosystems c. weathering rock adds PO43- d. plants absorb and use them to make organic compounds e. food chain f. decomposers break down animal waste or dead organisms g. phosphorous drains into sea where it may settle and become a part of new rocks h. geologic processes uplift the rocks to expose them to weathering.