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