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UNIT 6 PART 1: ORGANIZATION IN THE BIOSPHERE • The biosphere is the part of earth where living things exist. • It is about 20 km thick from the ocean floor through part of the atmosphere. • Includes land, sea, and air. 1 Ecology The branch of biology that deals with the interactions among living things and their environment. ENVIRONMENT LIVING THINGS 2 Biotic Factors • All living things in the environment and their effects on each other Eats fish • Bird Uses grass for nest • Fish Eats insects Eaten by bird, man • Man Eats fish Mows grass • Trees Provide shade Drop leaves • Plants Provide food and oxygen • Insects Eaten by fish 3 Abiotic Factors • Nonliving things in the environment that determine what types of organisms can survive there AMOUNT OF LIGHT AMOUNT OF WATER TEMPERATURE TYPE OF SOIL 4 Organization of Living Things • Population- all the individuals of one species in an area • Community- all the populations in an area • Ecosystem- the community and the environment: all living (biotic) and nonliving (abiotic) things 5 • Variety in a biological community is called biodiversity. • The greater the biodiversity, the more stable the ecosystem. – A rain forest has high biodiversity – A tundra has low biodiversity • Loss of biodiversity may cause the ecosystem to collapse. Biodiversity 6 Limiting Factors and Adaptations • Some things can limit the growth of a population: – – – – – – Food Water Disease Light Competition Predation • Because of variations, some individuals will be better adapted to survive and reproduce than others. • These are called limiting factors. 7 Carrying Capacity • When conditions are good populations increase. • Limiting factors control the size of a population causing growth to slow or reach equilibrium (birth rate = death rate). • The maximum population size that an ecosystem can support (zero growth) is called the carrying capacity. 8 Types of Organisms • Autotrophs (Producers) make their own food by photosynthesis or chemosynthesis. • Green plants and some bacteria • Heterotrophs (Consumers) eat other organisms. • Herbivores eat plants. • Carnivores eat animals. – Predators – Scavengers • Omnivores eat both. • Decomposers eat remains of dead organisms. – Fungi – Bacteria 9 Habitat and Niche • Each organism has a particular part of the environment where it lives- its habitat. – Squirrel – tree – Fox – den – Rabbit - hole • An organism’s role in the ecosystem (its ‘job’) is its niche. • This includes how, where, when it feeds, reproduces, what it eats, where it lives. • Habitat is part of niche. • Each species has its own niche. 10 Competition • Competition occurs when niches overlap. – Eating the same food – Reproducing at the same time • Interspecific competition occurs between members of different species. – Squirrels and chipmunks both eat pine seeds. • Intraspecific competition occurs between members of the same species. – Choosing mates 11 ENERGY AND NUTRIENTS IN AN ECOSYSTEM • Energy does not cycle through an ecosystem but must be constantly supplied because it gets used by organisms. Much of it is lost as heat. • Energy comes from the sun and is made available to all organisms by the producers. • Other materials, like carbon, nitrogen, oxygen, and water, do cycle between living things and their environment. 12 NUTRIENT CYCLES N i t r o g e n Carbon Water 13 Food Chain • Within an ecosystem there is a pathway of energy flow that always begins with the producers. Producers herbivores carnivores 30 (primary, 10) (secondary, 20) 14 Food Web • Many interconnected food chains make up a food web. 15 Pyramid of Energy and Biomass • In a food chain the amount of available energy decreases with each higher feeding level. • Only 10% of the energy in one level is passed to the next. • Since the total amount of energy decreases, the biomass at each level must also decrease.16 Decomposers – organisms of decay • Break down the wastes and remains of dead plants and animals. This changes organic matter into inorganic matter that can be reused by other organisms at all levels. • The final consumers in every food chain: – Fungi – Bacteria • They are nature’s recyclers. 17 Symbiosis is a close relationship between two or more different organisms that live together where at least one benefits from the relationship. Mutualism +,+ Parasitism +,- Commensalism +,0 Symbiote benefits Symbiote benefits Symbiote benefits Host benefits Host harmed Host unaffected Bees & Flowers Leach & Fish Robin & Tree 18 Mutualism • Both organisms benefit from the relationship: – Termites and cellulose-digesting microorganisms – Bees and flowers – Lichens are an alga and a fungus – Legumes and nitrogen-fixing bacteria 19 Commensalism • One organism benefits and the other is unaffected: – Barnacles on whales – Pilot fish and sharks – Cattle egrets and cattle 20 Parasitism • One organism benefits and the other is harmed: – Tapeworms – Lampreys – Mistletoe 21 Ecological Succession • Ecosystems appear stable but they do undergo change. • The living things alter the environment so species change over time: the community is replaced. • One community changes to another until a stable climax community is reached. This is ecological succession. • The climax community stays until there is a catastrophe such as flood or fire. Then succession will begin again. • The different biomes are defined by the climax community. 22 Ecological Succession on Land • Primary succession occurs in an area that has no existing life, such as on a bare rock or hardened lava. • Secondary succession occurs in an area that has been partially destroyed like a cleared forest. • The first organisms to inhabit a community are called pioneers, such as bacteria, fungi and lichens. • Pioneers break down the rock and create soil and humus. 23 Ecological Succession on Land • Eventually grasses and small animals move into the area as the soil improves. • When these die, the soil becomes richer and can support a greater variety of organisms. • The grasses are replaced by small shrubs. • Shrubs are replaced by the taller pines. • After many years the pines may be replaced by oaks, beeches or maples. These are the dominant species that characterize a climax community. 24 Ecological Succession on Land 25 Ecological Succession in Water • Small ponds and lakes undergo succession and gradually fill in. • Sediments such as soil and leaves wash into the pond, slowly filling it in from the edges. • Emergent plants such as cattails and grasses grow around the edges as the pond gets shallower. • Shrubs move into the newly formed soil. • Trees replace the shrubs as the pond shrinks. 26 Ecological Succession in Water Chap 25 27