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Point to Remember for 12 Biology Chapter 15
Reasons for greater biological diversity in tropics
- Tropical latitudes have remained relatively undisturbed for millions of years and thus had a long evolutionary time for species diversification.
- Tropical environments are less seasonal, relatively more constant and predictable which promote niche specialisation and lead to greater species diversity.
- There is more solar energy available in the tropics, which contributes to higher productivity and indirectly leads to greater biological diversity.
Three inter-related levels of Biodiversity
- Genetic diversity: Diversity in the number and types of genes, as well as chromosomes present in different species and the variations in the genes and their alleles in the same species. It helps in speciation.
- Species diversity: Varieties in the number and richness of the species of a region.
- Ecological diversity: Variety in the types of ecosystems.
The importance of species diversity to the ecosystem
- Ecosystems with higher bio diversity are more productive than ecosystems with lower biodiversity. David Tilman showed in his experiments that increased diversity contributes to higher productivity.
- Biodiversity is essential for the stability of an ecosystem. Communities with more species are more stable than those with less species.
- Rich biodiversity is also essential to make an ecosystem more functional and survival of the human race on the earth.
Causes of Biodiversity Losses
- Habitat loss and fragmentation: This is most important cause of plants and animals extinction. For example: Tropical rain forest being destroyed faster. The Amazonian rain forest is called the lungs of the planet. It is being cut for cultivating soya beans.
- Over exploitation: Many species extinctions are due to over exploitation by humans e.g. extinction of Steller’s sea cow, passenger pigeon in last 500 years.
- Co-extinctions: When a species becomes extinct, the plant and animal species associated with it in an obligating way also become extinct.
What is the significance of the slope of regression in a species − area relationship?
Name the three important components of biodiversity.
Give three hypotheses for explaining why tropics show greatest levels of species richness.
Tropical latitudes receive more solar energy than temperate regions, which leads to high productivity and high species diversity.
Tropical regions have less seasonal variations and have a more or less constant environment. This promotes the niche specialization and thus, high species richness.
Temperate regions were subjected to glaciations during the ice age, while tropical regions remained undisturbed which led to an increase in the species diversity in this region.
How do ecologists estimate the total number of species present in the world?
The total number of species present in the world is calculated by ecologists by statistical comparison between a species richness of a well-studied group of insects of temperate and tropical regions. Then, these ratios are extrapolated with other groups of plants and animals to calculate the total species richness present on the Earth.
How is biodiversity important for ecosystem functioning?
If an ecosystem is rich in biodiversity, then the ecological balance would not get affected. As we all know, various trophic levels are connected through food chains. If any organism or all organisms of any one trophic level is killed, then it will disrupt the entire food chain. For example, in a food chain, if all plants are killed, then all deer’s will die due to the lack of food. If all deer’s are dead, soon the tigers will also die. Therefore, it can be concluded that if an ecosystem is rich in species, then there will be other food alternatives at each trophic level which would not allow any organism to die due to the absence of their food resource.
Hence, biodiversity plays an important role in maintaining the health and ecological balance of an ecosystem.