Biodiversity Flashcards
biodiversity definition
the variety of living organisms present in an area. Biodiversity includes plants, animals, fungi, and other living things. In fact, it includes everything from gigantic redwood trees to single-celled algae.
the importance of biodiversity
Biodiversity is essential in maintaining a balanced ecosystem for all organisms. All species are interconnected - they depend on one another.
For example, trees provide homes for animals. Animals eat plants, which in turn need fertile soil to grow. Fungi and other microorganisms help decompose dead plants and animals, returning nutrients to the soil. In regions of reduced biodiversity, these connections may not all be present, which eventually harms all species in the ecosystem.
We rely on balanced ecosystems as they provide us with the food, oxygen and other materials we need to survive. Unfortunately, many human activities, such as farming and clearing land for housing, can lead to a reduction in biodiversity.
measuring biodiversity
Tropical, moist regions (that are warm all year round) have the most biodiversity. The UK’s temperate cimate (warm summers and cold winters) has less biodiversity. Very cold areas such as the Arctic, or very dry areas such as deserts, have the least biodiversity. Generaly, the closer a region is to the Equator (the line of latitude of the Earth, halfway between the North Pole and South Pole), the greater the biodiversity. For example, over 40000 plant species live in the Amazon rainforest, whereas less than 3000 live in Northern Canada.
Measuring biodiversity plays an important role in conservation. It informs scientists of the species that are present, thus providing a baseline for the level of biodiversity in an area. From this information, the effect of any changes to an environment can be measured. These may include the effect of human activity, disease or climate change, for example.
Before a major project is undertaken, such as building a new road or the creation of a new nature reserve, an Environmental Impact Assessmen (EIA) is undertaken. This assessment attempts to predict the positive and negative effects of a project on the biodiversity in that area.
Biodiversity can be studied at different levels:
• habitat biodiversity
• species biodiversity -genetic biodiversity.
habitat biodiversity
Habitat biodiversity refers to the number of different habitats found within an area. Each habitat can support a number of different species.
Therefore in general, the greater the habitat biodiversity, the greater the species biodiversity will be within that area.
The UK is home to large number of habitat types, including meadow, woodland, streams, and sand dunes. It has a large habitat biodiversity.
By contrast Antarctica, covered almost entirely by an ice sheet, has a very low habitat biodiversity and very few species live in this region.
On a smaller scale, countryside that is habitat rich, perhaps with a river, woodland, hedgerows and wild grassland, will be more species rich than farmed countryside with large ploughed fields making up a single uniform habitat.
species biodiversity
Species biodiversity has two different components:
• species richness - the number of different species living in a particular area, and
• species evenness - a comparison of the numbers of individuals of each species living in a community. (The community is all the populations of living organisms in a particular habitat.)
Therefore an area can differ in its species biodiversity even if it has the same number of species. For example, a cornfield and a grass meadow may both contain 20 species. However, in the cornfield, corn will make up 95% of the community with the remaining 5% made up of other organisms including weed plants, insects, mice, and birds. In the grass meadow the species will be more balanced in their populations.
genetic biodiversity
Genetic biodiversity refers to the variety of genes that make up a species. Humans have about 25000 genes, but some species of flowering plants have as many as 400 000 genes. Many of these genes are the same for all individuals within a species. However, for many genes, different versions (alleles) exist. This leads to genetic biodiversity within a species (you will learn more about genetic biodiversity in Topic 11.5, Calculating genetic biodiversity).
Genetic biodiversity within a species can lead to quite different characteristics being exhibited. For example, some genes are the same for all breeds of dog - these genes define the organism as a dog. Some of the genes have many alleles - they code for the wide variation in characteristics seen between different breeds of dog, for example coat colour and length.
Greater genetic biodiversity within a species allows for better adaptation to a changing environment, and is more likely to result in individuals who are resistant to disease.
