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Ecology
• Definition: the scientific study of interactions among organisms and their environment
– Branch of biology that was developed from natural history
– Study reveals the relationships between living and non-living parts of the
world
Ecology
• Abiotic – Physical factor such
as: air, temperature, moisture, soil, light
– These factors make up an organism’s habitat
• Habitat: the area where an organism lives
• Biotic: – All living or once living
components of an ecosystem
– Includes dead organisms and the waste of organisms
The environment is divided into living and non living parts:
Levels of Organization in Ecology
• Biosphere
• Ecosystem
• Community
• Population
• Organism
To help ecologists understand the interactions of the biotic and abiotic parts of the world, scientists have organized the living world into levels:
Levels of Organization
• Biosphere– The part of the Earth’s covering where life is
possible
• Goes from the top of the atmosphere to the bottom of the ocean; about 12 miles high!
• Supports a wide variety of organisms
• If the earth were shrunk to apple size, the biosphere would be thinner than the apple skin
Levels of Organization
• Ecosystem– A community of organisms and their living
and non living surrounds
• Living components of an ecosystem are the biotic factors
• Non living components of an ecosystem are the abiotic factors
Levels of Organization
• Community – A group of various species that live in the same
habitat and interact with each other
• Population– group of organisms of one species that interbreed
and live in the same place at the same time
• Organism– living member of species
Levels of Organization
In a desert…..
• Organism: coyote• Population: pack of coyotes• Community: pack of coyotes, hawks, owls,
snakes, scorpions, & reptiles• Ecosystem: populations of animals listed
above, cacti, shrubs, sand dunes, climate, rocks, temperature
• Biosphere: the earth
Biodiversity
• Includes:– The variety of organisms within a given area– The genetic variation within a population– The variety of species in a community – The variety of communities in an ecosystem
– Both abiotic and biotic factors help to determine the biodiversity of an area
In an Ecosystem
• Habitat: a place where an organism lives out its life
• Niche: the specific role and position a species has in its environment.
– Organisms may share parts of their niche, but never the whole thing!
In an Ecosystem
• Fundamental Niche: the entire range of conditions where a species can survive– Shaped by competition for resources between species
• Realized Niche: the actual niche that an organism occupies within an ecosystem
The establishment of a niche allows for several organisms to live in the same habitat while reducing competition for resources!!
Changes in an Ecosystem• Succession: the replacement of one community by
another at a single location over a period of time• First organisms to appear are pioneer organisms
– Primary Succession occurs after natural disasters• Volcanic eruptions, fires, hurricanes, tornadoes, etc
– Secondary Succession occurs after HUMAN involvement
• Clearing of land for development, clear cutting the forest, etc
• Symbiosis– Two species live in close association with each other.
Can be positive or negative• Mutualism: both species benefit
– Ex: cleaner shrimp/fish• Commensalism: one species benefits, the other
does not, but is not harmed– Ex: orchids growing on trees
• Parasitism: one species is helped while the other is hurt
– Ex: Ticks on a dog. – The tick is the parasite and the dog is the host
Relationships in an Ecosystem