| Biological Diversity | |
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Biological resources constitute all the living organisms on the planet, i.e. the biological diversity or "biodiversity" of the planet. Biological diversity can be divided into three or four areas for discussion purposes, namely;
Mankind has adapted to local environments over time, discovering, using, and altering the local resources to fit our requirements. Many areas that now seem "natural" bear the marks of centuries of human habitation, crop cultivation, and resource harvesting. The domestication and breeding of local varieties of crops and livestock has further shaped biodiversity. It is our growing awareness of our interaction with and dependence on biodiversity that has stimulated world concern. |
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Genetic diversity refers to the variation of genes within species. Genes are the basic building blocks of life and contain all the information for making cells and for programming the work that goes on inside them. It is through the genes that traits are handed down from parents to offspring, in a process called heredity. We are familiar with genes deciding on size, build, colouring, and other features in humans. This also occurs with plants and animals, for example there are thousands of traditional rice varieties in India. We can also compare the degree of genetic variation between species, for example, there are many different varieties of domesticated chicken but very few different types of cheetah. |
| Figure 1. The DNA double helix | |
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Species diversity refers to the vast number of different species within the plant and animal kingdoms, i.e. everything from mammals to insects, fungi, bacteria, reptiles, birds etc. |
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Sometimes referred to as "species richness", species diversity is often used as a measure of biodiversity, by redefining it slightly as; the number of different types of species that occur in a given area. For example there are less different species in a given area of the arctic than the rainforest, i.e. the biodiversity of the rainforest is greater. In fact one estimate of the total number insects in a single tropical tree is 4500! Such diversity can be measured in many ways, and scientists have not settled on a single best method. "Taxonomic diversity," is considered to be a more precise measurement and considers the relationship of species to each other. For example, an island with two species of birds and one species of lizard has greater taxonomic diversity than an island with three species of birds but no lizards. In this way although many more species live on land than in the sea, because terrestrial species are more closely related to each other than ocean species, the diversity of marine ecosystems is considered to be greater than a strict count of species would suggest. Ecosystem diversity is harder to measure than species or genetic diversity because the "boundaries" of communities, associations of species and ecosystems may not be clear. |
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| Task 1: What is an Ecosystem ? Investigate one of the groups listed below, determine the number of sub-groups and describe their characteristics. | |
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For the purposes of discussion ecosystems can be divided into the areas shown below.
Within the oceans category we could consider, coastal, open ocean, estuaries or coral reef habitats. Deserts may be defined as cold or hot and can be arid or semi-arid in places. Geology and mineralogy plays a part in the type of flora (plants) that can be supported and therefore also the fauna (animals). The Mojave Desert for example is bounded by two other deserts and the division might not appear obvious, however the Mojave Desert hosts about 200 endemic plant species found in neither of the adjacent deserts. Besides ecosystem diversity, many other expressions of biodiversity can be important. These include;
More generally it is often important to examine not only compositional diversity i.e. genes, species, and ecosystems, but also diversity in how the ecosystem functions and its structure. |
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| Human cultural diversity could also be considered part of biodiversity although we will not cover this topic within this particular unit. Like genetic or species diversity, some attributes of human cultures (say, nomadism or shifting cultivation) represent "solutions" to the problems of survival in particular environments. And, like other aspects of biodiversity, cultural diversity helps people adapt to changing conditions. Cultural diversity includes differences in language, religious beliefs, land-management practices, art, music, social structure, crop selection, diet, etc. | |