Chapter 3 The Biosphere

3-1 What Is Ecology? Interactions & Interdependence Ecology – study of interactions among organisms & between organisms and their environment Biosphere – the combined portions of the planet in which all life exists Interactions within the biosphere → produce a web of interdependence

Levels of Organization (Sm. to Lg.) Ecologists are scientists who study ecology 1.Species – group of organisms so similar that they breed and produce fertile offspring. 2.Population – group of individuals that belong to the same species and live in the same area. 3.Community – all the different populations that live in a defined area 4.Ecosystem – all organisms that live together in particular place + the nonliving environment 5.Biome – group of ecosystems that have the same climate & similar dominant communities 6.Biosphere

Ecological Methods A.Use a wide range of tools Ex. Microscope, DNA studies, radio tags B.Methods 1.Observing 2.Experimenting 3.Modeling a.Used on ecological problems that occur over long periods of time or are on a large scale b.Use mathematical formulas

3-2 Energy Flow Most important factor in ecosystems – energy flow through the ecosystem Producers Autotrophs – use chemicals or sunlight energy to produce their own food Producer = Autotrophs

Two types of producers: 1.Use solar energy for photosynthesis – process by which plants & some bacteria use light energy to make carbohydrates CO 2 + H 2 O → Carbohydrate + O 2 *done by plants, algae, cyanobacteria 2. Use chemical energy for chemosynthesis Hydrogen Sulfide + O 2 → Carbohydrate *used by bacteria in harsh environments & in tidal marshes

Consumer – acquires energy from other organisms Heterotroph – eat other organisms Heterotroph = consumers

Types of heterotrophs 1.Herbivores – eat producers Ex: Cows, deer 2.Carnivores – eat herbivores & carnivores Ex: Snakes, dogs, owls 3.Omnivores – eat producers & animals Ex: Humans, bears, 4.Detritivore – feed on dead matter Ex: Snails, earthworms, crabs 5.Decomposers – break down organisms Ex: Bacteria, fungi

Feeding Relationships *Energy flows through an ecosystem in one direction using the food network Food chain – series of steps in which organisms transfer energy by eating or being eaten arrows should point to the organism that receives the energy

In most ecosystems, energy doesn’t follow a straight path Food web – network of complex interactions Trophic level – each step in a food chain or web Ecological pyramids – diagram that shows relative amounts of energy or matter contained in each trophic level

3 Types of Pyramids 1.Energy Pyramids Energy consumed: 1. Uses some to live (respiration, movement, etc.) 2. Some lost as heat 3. ~ 1/10 is available for the next level Trophic levels are limited by the energy available Most ecosystems don’t have more than 4 trophic levels because there is not enough energy 2.Biomass Pyramids Biomass – total amount of living tissue in a given trophic level Represents the amount of potential food available for each trophic level 3.Pyramid of Numbers – based on # of individuals organisms at each trophic level

3-3 Cycles of Matter Organisms need H 2 O, minerals & other compounds ~95% of all organisms’ bodies are made up of O,C,H,N Recycling In the Biosphere Matter is recycled within & between ecosystems Elements move in biogeochemical cycles – forms of matter passed from one organism to another & from one part of the biosphere to another

Biological systems convert matter from one form to another Nutrient Cycles Nutrients – all chemical substances an organism needs to live Carbon – the key ingredient of living tissue

4 types of processes that move Carbon 1.Biological processes – photosynthesis, respiration, decomposition 2.Geochemical processes – erosion, volcanic activity 3.Mixed biogeochemical processes – burial & decomposition → coal & oil 4. Human activities – mining, cutting & burning forests, burning fossil fuels

Nitrogen cycle Nitrogen necessary to make amino acids → proteins Forms of naturally occurring N includes: N 2 - ~ 78% of atmosphere Ammonia NitratesWastes & dead organisms Nitrites

Cycle includes these processes: 1.Human activity = plant fertilizer 2. Nitrogen fixation – bacteria change N gas into ammonia 3. Nitrates & nitrites – made by soil bacteria from ammonia & plants use this 4. Decomposers – return N to soil 5. Denitrification – other soil bacteria convert nitrites to N 2 gas

Phosphorus Cycle Phosphorus – important because needed for DNA & RNA Not found in the atmosphere Usually present in soil & rocks where it is worn down & released into rivers Absorbed by plants Continues through the food web

Nutrient Limitation Primary productivity – rate at which organic matter is created by producers Limiting nutrient – a single nutrient that is scarce or cycles slowly controlling growth Growth of Plants is limited by the availability of nutrients Algal bloom – too many nutrients stimulate overgrowth of algae