Ecology.

Ecology

the branch of biology that deals with the relations of organisms to one another and to their physical surroundings

Organisms depend on their environment for:

• food

• shelter

• breeding site

Species

A group of organisms that can potentially interbreed to produce fertile, viable offspring

Population

A group of organisms of the same species, living in the same area at the same time

Community

A group of populations living together and interacting with each other within a given area

Habitat

The environment in which a species normally lives, or the location of a living organism

Ecosystem

A community and its abiotic environment (i.e. habitat)

Biomass

•The total mass of a group of organisms – consisting of the carbon compounds contained in the cells and tissues

Biotic factors

Other living things in the environment

• mates

• prey

• predators

Abiotic factors

Non-living factors in the environment

• Physical: •Oxygen and Carbon Dioxide ,Light Intensity and Water Availability

• Climatic: temperature, humidity

Autotrophes

•organisms that make their organic molecules out of inorganic molecules (plants and some bacteria, via photosynthesis)

Heterotrophic organisms

•Organisms that get their organic molecules by eating other organisms, (animals, fungi and certain bacteria)

Trophic levels

The position an organism occupies within a feeding sequence

•Producers always occupy the first trophic level in a feeding sequence

•Primary consumers feed on producers and hence occupy the second trophic level

- Further consumers (e.g. secondary, tertiary, etc.) may occupy subsequent trophic levels

Heterotrophy - consumers

Ingest organic matter which is living or recently killed

Heterotrophy - detritivores

Ingest non-living organic matter

Heterotrophy - Saprotrophs

Feed on non-living organic matter by secreting digestive enzymes and absorbing the products

Food chain/web

A food chain shows the linear feeding relationships between species in a community

Rule of 10

Energy transfer between organisms is never 100% efficient, usually, the energy transfer from one trophic level to the next is 1/10 of the previous one.

Mutualism

Both species benefit

Commensalism

One benefits, one doesn’t care

Parasitism

One benefits at the other’s expense

Ecological pyramids

Quantitative representations of energy flow

Pyramid of numbers

The relative number of organisms at each stage or trophic level.

Problem: Pyramid can look odd, due to difficulties drawing to scale and enormous numbers of some organisms.

Pyramid of biomass

The total mass of organisms at each stage of a food chain

Each level in the pyramid will be roughly one tenth the size of the preceding level as energy transformations are ~10% efficient

Pyramid of energy

Shows the amount of energy trapped per area in a given time period at each stage of a food chain

These pyramids are always upright in shape, as energy is lost along food chains (either used in respiration or lost in digestion)

Carbon

•Raw material for growth of the cells (fats and proteins)

•Source of energy ( released via oxidisation during respiration eg: carbohydrates and fats)