1. Chapter 3

2. What Is Ecology? Ecology – the study of interactions among organisms and between organisms and their environment – From Greek: oikos (house)

3. Levels of Organization Individual organism Species: a groups of organisms so similar to one another that they can breed & produce fertile offspring

4. Levels of Organization Population – Groups of individuals that belong to the same species and live in the same area

5. Levels of Organization Community – Assemblage of different populations that live together in a defined area

6. Levels of Organization Ecosystem – A collection of all the organisms that live in a particular place, together with their nonliving environment

7. Levels of Organization Biome – A group of ecosystems that have the same climate and similar dominant communities

8. Levels of Organization Biosphere – The combined portions of the planet in which all life exists, including land, water, and air. – Extends from about 8 kilometers above Earth’s surface to as far as 11 kilometers below the surface of the ocean

9. Ecological Methods Scientists conduct modern ecological research using three basic approaches: – Observing First step in asking ecological questions – Experimenting To test hypotheses – Modeling Used to study complex phenomena Tested by further observations & experiments

10. Producers Sunlight – Main energy source for life on Earth – Less than 1% of all the sun’s energy that reaches Earth’s surface is used by living things Autotrophs/Producers – Organisms that can capture energy from sunlight or chemicals and use that energy to produce food – Plants, some algae, certain bacteria

11. Photosynthesis – Process by which some organisms use light energy to convert water & carbon dioxide into oxygen & high-energy carbohydrates such as sugars & starches Chemosynthesis – Some organisms can produce food in the absence of light – Process by which some organisms use chemical energy to produce carbohydrates – Several types of bacteria

12. Consumers Organisms that rely on other organisms for their energy & food supply (heterotrophs) Herbivores: eat plants – Cows, caterpillars, deer Carnivores: eat animals – Snakes, dogs, owls Omnivores: eat both plants & animals – Humans, bears, crows Detritivores: feed on plant & animal remains and other dead matter (detritus) – Mites, earthworms, snails, crabs Decomposers: break down organic matter – Bacteria and fungi

13. Feeding Relationships Energy flows through an ecosystem in one direction: Sun (or inorganic compounds) Autotrophs (producers) Heterotrophs (consumers)

14. Food Chains Series of steps in which organisms transfer energy by eating & being eaten

15. Food Webs Network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem All the linked food chains in an ecosystem Trophic level – each step in a food chain or food web – Producers: 1 st trophic level – Consumers: 2 nd, 3 rd, or higher trophic levels

17. Ecological Pyramids Diagram that shows the relative amounts of energy or matter contained within each trophic level in a food chain or food web – Energy pyramids – Biomass pyramids – Pyramids of numbers

18. Energy Pyramid Only about 10% of the energy available within one trophic level is transferred to organisms at the next trophic level Used by organisms for respiration, movement, reproduction, etc. Some released into the environment as heat

19. Biomass Pyramid biomass – The total amount of living tissue within a given trophic level Represents the amount of potential food available for each trophic level in an ecosystem

20. Pyramid of Number The numbers of individual organisms at each trophic level

21. Recycling in the Biosphere All organisms need more than energy to survive: water, minerals, other life-sustaining compounds Most organisms made up mainly of just 4 elements: O, C, H, N Organisms can’t use these common elements unless they are in a form that cells can take up Unlike the one-way flow of energy, matter is recycled within & between ecosystems Biogeochemical cycles: elements, chemical compounds & other forms of matter are passed from one organism to another and from one part of the biosphere to another

22. Water Cycle Movement of water between the ocean, atmosphere, and land – Evaporation – Transpiration – Condensation – Precipitation

23. Nutrient Cycles Nutrients: all the chemical substances that an organism needs to sustain life – Needed to build tissues & carry out essential life functions Carbon cycle Nitrogen cycle Phosphorus cycle

24. Carbon Cycle Four main type of processes move carbon through its cycle – Biological: photosynthesis, respiration, decomposition – Geochemical: erosion & volcanic activity – Mixed biogeochemical: burial & decomposition of dead organisms & conversion into fossil fuels – Human activities: mining, cutting & burning forests, burning fossil fuels

26. Nitrogen Cycle Nitrogen needed to make amino acids to build proteins Nitrogen fixation: process in which some bacteria convert nitrogen gas into ammonia Other bacteria convert ammonia into nitrates & nitrites Producers use these to make proteins Consumers eat the producers & reuse the nitrogen to make their own proteins Decomposers return nitrogen to the soil as ammonia Ammonia may be taken up by producers Other bacteria convert nitrates into nitrogen gas (denitrification), releasing nitrogen into the atmosphere once again

28. Phosphorus Cycle Phosphorus forms part of DNA and RNA Not very common in the biosphere Remains mostly in rock & soil minerals and ocean sediments

29. Nutrient Limitation Primary productivity – The rate at which organic matter is created by producers – Controlled by amount of available nutrients – Limiting nutrient: single nutrient that either is scarce or cycles very slowly, limiting the growth of organisms in an ecosystem Algal bloom – Immediate increase in the amount of algae & other producers that results from a large input of a limiting nutrient