ECOSYSTEMS AND BIOMES

Definition of Concepts

Ecology: The study of the interrelationships between living organisms and the living and non-living components and processes in an environment

Biosphere: The worldwide system within which all life functions. It occurs at the interface between the atmosphere (air), hydrosphere (water) and the lithosphere (soils, rocks).

Biome: A major ecological region within which plant and animal communities are similar in general characteristics and in their relationships to the physical environment. Eg. Such vegetation zones as the Tundra, Desert & Rainforests.

Ecosystem: The collection of all living organisms in a geographic area, together with all the living and non-living things with which they interact.

· Acquatic Ecosystems (water-based) ecosystems

· Terrestral Ecosystems (land-based) ecosystems.

Population: A group of organisms of the same kind living in a given area

Natural Community: Populations of different plant and animal species interacting among themselves in an area.

Habitat: The specific physical location where a particular organism lives or is adapted to live in a community.

Ecological Niche: An organism’s role or occupation within a community.

The Competitive Exclusion Principle: This principle states that no two species can occupy the same niche (food or space) successfully in a stable community. Closely related species therefore live far from one another.

The Environment: All the surroundings that affect an organism or groups of organisms in a given area

Bio-geography: the study of the distribution of plants and animals, the diverse spatial patterns they create, and the physical and biological processes (past & present) that produce this distribution.

STRUCTURE OF ECOSYSTEMS

1. Boitic and Abiotic Structure

Every ecosystem is composed of two parts:

a) Biota: the living organisms - all plant & animal species

b) Abiotic: the non-living physical and chemical component consisting of wind, temperature, water, soil, precipitation etc.

The single abiotic factor most lacking in a particular environment is termed a Limiting Factor. e.g. lack of water- deserts, excess water – bog, low temperature -Tundra. The variation in physical factors that a population can withstand and continue to thrive in an environment is termed Range of Tolerance.

2. Categories of Organisms

PRODUCERS: Green plants that carry on photosynthesis. Producers are auto-trophs because they are self-nourished – they do not depend on other species to feed. These plants use their chlorophyll to capture light energy which they use to convert carbon dioxide and moisture (absorbed from air) into sugar and release oxygen in the process. Every major ecosystem has its particular green plants 9algae, plankton) that carry on photosynthesis and release chemical energy (carbohydrates, protein etc.) on which non-producers feed.

CONSUMERS:

· Consumers are heterotrophs (other-nourished) for they rely on chlorophyll-containing plants or the products of such plants for nourishment.

· Consumers are subdivided into groups according to their food source.

i) Primary consumers: Species that feed directly on producers (plant-eating species). They are also called Herbivores. E.g. elephants, goats, cattle

ii) Secondary Consumers: Species that feed on primary consumers. Secondary and higher order consumers are called Carnivores. E.g. fox, cat.

iii) Tertiary and higher level Consumers: Species that obtain their nourishment by eating other meat-eating species. E.g. tiger

iv) Multiple level Consumers: Species that obtain their nourishment from eating both plants and animal species. Also called Omnivores

DECOMPOSERS:

They are the final link in the food chain. Comprise of organisms that feed on dead matter and break it down to release chemical energy back into the soil for plants to re-use them. E.g. fungi, bacteria, insects, worms and others. Detritivores: feed on detritus matter (dead plants and animals) e.g. crab, vulture, termites, wood beetle and crayfish. They are also called scavengers.

THE FOOD CHAIN

A food chain or food web is represented by a sequence of organisms through which energy and nutrients flow. Organisms that share the same basic foods are said to be at the same trophic (feeding) level. Only about 10% of the calories in plant matter survive from primary to the secondary trophic level.

PRINCIPLES OF ECOLOGY

Law of Conservation of Matter

“Although matter can be changed from one form to another it can neither be created nor destroyed by ordinary physical and chemical changes”.

The Laws of Energy

i) First Law of Energy: “energy can be converted from one form to another but cannot be created or destroyed”

ii) Second Law of Energy: “Whenever energy is converted from one form to another, a certain amount is lost in the form of heat.

BIOGEOCHEMICAL CYCLES

Processes through which elements that sustain life (water, carbon, phosphorus and nitrogen) are continuously made available to living organisms. Well known chemical cycles include:

a) Nitrogen Cycle,

b) Hydrological cycle,

c) Carbon cycle, and …

d) Phosphorus cycle

ECOLOGICAL SUCESSION

A natural process by which plant and animal communities that are more complex replace older, usually simpler ones. Changes in plant communities usually move toward a stable, mature and self-sustaining community called the Climax community. When the succession occurs in an area that is not previously occupied by organisms it is called primary succession. Secondary succession occurs in an area previously occupied by organisms. Acquatic Succession: Lakes and ponds exhibit ecological succession as they gradually become filled with nutrients, sediments and plants eventually disappearing to form a forest community. This gradual enrichment of water bodies is termed Eutrophication.

THE NATURAL BOIMES

1. Equatorial and Tropical Rain Forest

a) evergreen broadleaf forest (Selva)

2. Tropical Seasonal Forest and Scrub

a) Tropical monsoon forest

b) Tropical deciduous forest

3. Tropical Savanna

a) Tropical grassland b) Savanna woodland

4. Mid-latitude Broadleaf and Mixed Forest

a) Temperate broadleaf

b) Midlatitude deciduous forest

5. Needleleaf Forest & Montane Forest

a) Taiga, b) Boreal forest, Montane forest

6. Temperate Rain Forest

a) West coast Forest, b) Coast redwoods

7. Meditarranean Shrubland

a) Sclerophyllous shrubs

b) Australian eucalyptus forest

8. Warm Desert and Semi-Desert

a) Subtropical desert and scrubland

9. Cold Desert and Semi-Desert

a) Midlatitude desert, scrubland and steppe

10. Arctic and Alpine

a) Tundra