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Ecology 1: Ecosystems Levels of Organization • Organism • Ex. an elephant • Population – A group of individuals in the same species, living and interacting in one area • Ex. a herd of elephants in the Serengeti • Community – Multiple populations interacting in one area • Ex. grazing antelope, elephants and giraffes in the Serengeti • Ecosystem – All populations in one area interacting with each other and their non-living environment. • Ex. the Serengeti (all organisms plus climate, nutrients, etc.) Levels of Organization • Biosphere – All areas of the earth from the ocean depths to the atmosphere that support life. Ecological roles • Autotrophs - Producer • makes own food (through photosynthesis or chemosynthesis) • Heterotrophs - Consumer • must eat other organisms for food; • primary (mouse), secondary (fox), tertiary (bobcat) – Herbivore (eats plants) Carnivore (eats meat) Omnivore (eats both) – Detritivore • Organisms that feed on animals remains and dead material (crabs, earthworms) – Decomposer • An organism (ex. fungi or bacteria) that completes the final breakdown of materials in an ecosystem • End of 3.1 How does energy enter the ecosystem? – Energy hits the earth in the form of sunlight – Autotrophs convert sunlight (or chemical) energy into organic molecules – Less than 1% of the sun’s energy is converted into organic material – Eventually all energy is lost back to the atmosphere as heat. How does energy move through an ecosystem? • Energy trapped in autotrophs (producers) then gets transferred to heterotrophs (consumers) as one organism eats another • The easiest way to show this is by using a food chain, food web, or food pyramid. • Food chain – series of steps in which organisms transfer energy by eating and being eaten. Food Web links all ecosystems in a food chain together Food Pyramids • A food pyramid is designed to show the organisms in an ecosystem, grouped by their feeding position or trophic level (1st=prod, 2nd=herbivores, etc) • Both food chains and food pyramids show that only 10% of the energy at one trophic level makes it to the next trophic level (from the 2nd law of thermodynamics). Primary Productivity • The rate at which new organic material is created in an ecosystem by producers is called the Primary Productivity • The more energy entering the food chain (from producers), the more that can pass up through the levels (only 10% moves up at each level), and as result, the more levels there can be. • Therefore, the ecosystems with the most productive producers have the most levels (ex. rain forest) – In most cases, there are only 3-4 levels. – End of 3.2 How do nutrients cycle? • Energy follows a ONE-WAY path – Sun living organisms heat atmosphere • Matter CYCLES through living organisms endlessly • Biogeochemical cycles – Water – Carbon and Oxygen – Nitrogen Water Cycle Carbon and Oxygen Cycle Nitrogen Cycle Niches • Niches vs Habitats – A habitat is the location where a species lives. • Ex. tall grassland/prairie – A niche includes all of the species’ requirements plus its role in the ecosystem. It is determined by all the the abiotic and biotic factors relevant to the species. • Ex. Top predator in prairie areas where gophers live, and the temperature is never below freezing. Niche differences • Organisms can be identified as either – Generalists • • • • Organisms with a broad niche Eat lots of types of food Live in many types of environments Ex. house mice – Specialists • • • • Organisms with a narrow niche Eat a narrow range of food items Live in few, specific types of habitats Ex. panda bear Mutualism • Mutualism occurs when both species benefit – – – – – Rhinos and oxpeckers trees and mycorrhizae, ants and acacia Termites and protist Pollination (Yucca and yucca moth) Parasitism – one organism feeds on/lives on another species – typically host is bigger than parasite – parasites usually do not kill host (weaken them) – parasites need host for food, shelter, etc. – ex. fleas on dog, tapeworm in human, mistletoe, lamprey Commensalism • Commensalism occurs when one species benefits, and the other neither benefits, or is harmed • examples: – clownfish and anemones – epiphytes and trees – Cattle egrets and ungulates Predation • Predation - one organism feeds upon the other – predator usually bigger than prey – ex. lion eating zebra Prey Strategies Competition • When two species use the same resources, they are said to compete and their interaction = competition. – ex. lions and hyenas compete for food in Africa • Competition does not necessarily involve contact; interaction may be only by means of effects on the resources. • No two organisms can occupy exactly the same niche at the same time What determines where species can live? • All species have requirements for many factors/conditions. – Abiotic factors – non-living factors; ex. temperature, precipitation, pH – Biotic factors – other species; ex. prey species, competing species • For each of these factors, species exhibit a range of tolerance. – For example, a fish species may only be found within a pH range of 4.5 to 6 in lakes. Biomes • A major terrestrial community that is found in different areas with similar climate is called a biome. A biome’s structure and appearance are similar throughout its distribution. • The world’s biomes are tropical rain forest, tropical dry forest, temperate woodland and shrubland (Chaparral), temperate deciduous forest, boreal/coniferous forest (taiga), desert, temperate grassland, tropical grassland (savanna), and tundra. Biome distribution Freshwater Habitats • These habitats are distinct from both marine and terrestrial habitats and are very limited in area. – make up about 2% of earth’s surface – can be divided into • Flowing water (rivers) standing water (ponds and lakes) and wetlands (seasonal coverage) Freshwater Habitats • Estuaries – These are very important for • Breeding grounds for fish • Filtering water – Very productive ecosystems! – Disappearing fast (flat land near the ocean) Ocean • 75% of earth’s surface • Continental shelf - shallow ocean waters - smallest area; large number of species (kelp forests) – Intertidal zones • Along our coast • Species can tolerate being in and out of water • Sea stars, algae, sea anemones – Coral Reefs • The “rain forests” of the ocean • High diversity • In tropical waters Ocean • open sea surface contains plankton (freefloating microscopic organisms), bacteria, algae, fish larvae; responsible for 40% of world’s photosynthesis • Benthic zone - deep sea waters - below 1000’ feet animals adapted to dark; some blind/bioluminescent What happens when ecosystems are disturbed? • When a disturbance impacts an ecosystem, it recovers through a process known as succession. • Succession on newly formed habitat is called primary succession. – No remaining organisms or soil – Examples, lava flow, sand dune, glacier retreat – It can take 1000+ years from sand dune to forest.