Science in Action Notes: Biological Diversity (1.0) | Print |

1.1 .

Ecosystems, Species and Genetic Diversity

A species is a particular group of organisms that have the same structure and can reproduce with each other. Of the 30 - 100 million possible different species of living things, there are over 1.5 million species of animals and 350.000 species of plants that have been identified by biologists. The most successful life form seems to be the insect.

Grade 7 Review) All living things are made up of cells, need energy, grow and develop, reproduce and have adaptations which suit them to the specific habitat in which they live.

The entire collection of living organisms, each with their own unique characteristics, make up the Earth's biodiversity. "Biological diversity refers to the variety of species and ecosystems on the Earth and the ecological processes of they are a part of." The main components of
biodiversity are:

  • Ecosystem diversity - the different types of living communities and the environments, such as marshes, lakes, streams and forests, in which they are found
  • Community (populations of different species living in the same area) diversity - occurs within populations (members of a species that live in a specific area and share the same resources) of organisms living within a particular ecosystem
  • Species diversity - occurs within individual organisms of the same species
  • Genetic diversity - occurs within organisms at a cellular level, as it describes the variety of genetic material in all living things.
  • Species Distribution - Plant and animal species are not distributed evenly throughout the various eco-regions of the world. Most of the different species of plants and animals can be found in tropical regions and, more specifically, in the rainforests. As you move closer to the poles of the Earth, there is less biological diversity.

Biological Diversity Classification

two-name Latin naming system for all living things was developed by Carolus Linnaeus in the 18th century, enabling scientists, around the world, to refer to the same species, by the same name. This classification system was much more reliable than previous systems, because he used structure, rather than habitat. Two words identify each organism. The 1st represents the organisms genus and the 2nd represents the organisms particular species.
Scientists earlier had developed a system which classifies all organisms, based on their structural differences, into 5

  • Animalia (animals)
  • Plantae (plants)
  • Fungi (yeasts, moulds and mushrooms)
  • Protista ( mostly single-celled organisms)
  • Monera (bacteria)

The 5 kingdom classification system can be further subdivided, with each sub-division having its own name.

  • Kingdom
  • phylum
  • class
  • order
  • family
  • genus
  • species

Specialists refer to other sub-divisions as well, such as;
subfamilies, super-orders, and sub-species or varieties.

Biodiversity under the Sea

Coral reefs reflect a great diversity of species. Like tropical forests, coral reefs support many different communities of organisms surviving on a small amount of nutrients, which are very efficiently recycled.

1.2 .


Each and every species depends on many other species within an environment in order to survive and prosper. Food chains and Food webs represent different types of ongoing relationships between and among all the organisms, within a particular environment.


A different type of interdependence is an association, within a certain population, between members of different species.
There are different types of symbiotic relationships:

  • Commensalism - in which one of the participating members benefits, but the other does not, and there is no harm done to that organism.

(a bird using a tree to build its nest in)
(barnacles on a whale)

  • Mutualism - both organisms benefit from the relationship.

(lichen (algae and fungi) growing in the Arctic Tundra benefit each other)
(flower Clusia provides medicine to bees)

  • Parasitism - one organism benefits while the other organism (the victim) is harmed. (the parasite usually doesn't kill the host, because the host represents the parasite's food supply.

(tapeworm in a human host)
(Mexican bean beetle is a plant parasite)

  • Interspecies competition happens when two or more species need the same resource. This type of relationship helps to limit the size of populations, of the competing species.

There are many examples of these types of symbiotic relationships, which show the importance of adaptations, helping particular species survive.


A niche is the role of an organism within a particular ecosystem. An organism's niche includes:

  • What it eats
  • What eats it
  • Its habitat
  • Nesting site, range and habits
  • What effect it has on the other populations
  • What effect it has on the environment

A niche, for a particular organism, can change, depending on the environment in which it is located and the organisms with which it inter-relates.

Resource partitioning is the action which enables competing species to share the resources by accessing these resources in different ways, involving less direct competition.

1.3 .

Variation within Species

Variation within a population, of a single species, is called variability.
Variability is important if the environment, in which the species lives, changes (suddenly or drastically). When a species has a great deal of variation, then, some of the individuals within that species will likely survive when there is change.
Examples of variability include:

  • Red fox (color of coat)
  • Antibiotic resistance (bacteria)
  • Banded snail (color of shell)

Natural selection happens when factors in the environment determines, or 'selects' which individuals, within a species, will be able to survive. If they are able to live long enough to reproduce, then those individuals with their 'survival adaptations (characteristics) will have offspring with similar survival characteristics