Ecosystem Structure: Biotope, Biocenosis, and Global Biomes

Biotope and Biocenosis: Defining Ecosystem Components

Biotope

A term that literally means living environment and applies to a physical space, natural and limited, in which a biocenosis lives. The biotope and biocenosis together form an ecosystem.

The biotope concept can be applied to all levels of the ecosystem:

• General Biotope: Can be considered large areas, such as the sea, formed by the plant, animal, and microorganisms it supports.
• Local Biotope: Such as a coral reef, with its characteristic vegetation and associated fauna.

Therefore, the biotope may be uniform from an ecological viewpoint, or it may comprise a set of distinct ecological residences, such as a river and its upper, middle, and lower reaches, where different plant and animal communities live in each section.

Biocenosis

A term encompassing all communities—plant (phytocoenosis), animal (zoocenosis), and microorganism (microbiocenosis)—which develop in a given biotope.

Examples of Biocenosis

• The coral reef and its accompanying characteristic fauna.
• Posidonia beds (marine monocotyledonous plants) and the species of bryozoans and crustaceans living with them.

Species Interactions within a Biocenosis

The species constituting a biocenosis display various forms of interaction:

• Competition: The struggle for space and food.
• Parasitism: Food exploitation of one organism by another.
• Predation: Consumption of one species by another.

These relationships are complex. Each organism plays a certain role in the food chain (producers, consumers, decomposers), and disruption of these relationships may cause a disturbance in its equilibrium.

Ecological Imbalance Example: Alien Species

An example of imbalance is the introduction of alien species, such as the introduction of rabbits in Australia. Because they found no predators that controlled their reproduction, they became an epidemic that decimated the vegetation of the colonized areas, causing a severe ecological imbalance.

Ecosphere or Biosphere

It is the thin mantle of life that covers the Earth. Different approaches are used to classify its regions.

Biomes

Major vegetation units are sometimes called vegetation biomes by European and North American ecologists. The main difference between the two terms is that biomes include associated animal life, although major biomes are often named after the dominant forms of plant life.

Terrestrial Biomes

Under the influence of latitude, elevation, and associated regimes of temperature and humidity, terrestrial biomes vary geographically from the tropics to the Arctic. They include various types of:

• Forests
• Grasslands
• Scrublands
• Deserts

These biomes also include associated freshwater communities: streams, lakes, ponds, and wetlands.

Marine Biomes

Ecologists also consider marine environments as biomes, which include:

• The open ocean
• Coastal areas (shallow water)
• Benthic regions (ocean bottom)
• Rocky coasts, beaches, estuaries, and associated tidal flats.