NCERT Solutions for Class 12 Biology Chapter 15
Biodiversity and Conservation Class 12
Chapter 15 Biodiversity and Conservation Exercise Solutions
Exercise : Solutions of Questions on Page Number : 268
Name the three important components of biodiversity.
Answer :
Biodiversity is the variety of living forms present in various ecosystems. It includes variability among life forms from all sources including land, air, and water. Three important components of biodiversity are:
(a) Genetic diversity
(b) Species diversity
(c) Ecosystem diversity
How do ecologists estimate the total number of species present in the world?
Answer :
The diversity of living organisms present on the Earth is very vast. According to an estimate by researchers, it is about seven millions.
Give three hypotheses for explaining why tropics show greatest levels of species richness.
Answer :
There are three different hypotheses proposed by scientists for explaining species richness in the tropics.
(1) Tropical latitudes receive more solar energy than temperate regions, which leads to high productivity and high species diversity.
(2) Tropical regions have less seasonal variations and have a more or less constant environment. This promotes the niche specialization and thus, high species richness.
(3)
What is the significance of the slope of regression in a species - area relationship?
Answer :
What are the major causes of species losses in a geographical region?
Answer :
Biodiversity is the variety of living forms present in various ecosystems. It includes variability among life forms from all sources including land, air, and water. Biodiversity around the world is declining at a very fast pace. The following are the major causes for the loss of biodiversity around the world.
(i) Habitat loss and fragmentation: Habitats of various organisms are altered or destroyed by uncontrolled and unsustainable human activities such as deforestation, slash and burn agriculture, mining, and urbanization. This results in the breaking up of the habitat into small pieces, which effects the movement of migratory animals and also, decreases the genetic exchange between populations leading to a declination of species.
(ii) Over-exploitation: Due to over-hunting and over-exploitation of various plants and animals by humans, many species have become endangered or extinct (such as the tiger and the passenger pigeon).
(iii) Alien species Invasions: Accidental or intentional introduction of non-native species into a habitat has also led to the declination or extinction of indigenous species. For example, the Nile perch introduced in Lake Victoria in Kenya led to the extinction of more than two hundred species of native fish in the lake.
(iv)
How is biodiversity important for ecosystem functioning?
Answer :
An ecosystem with high species diversity is much more stable than an ecosystem with low species diversity. Also, high biodiversity makes the ecosystem more stable in productivity and more resistant towards disturbances such as alien species invasions and floods.
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 one 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.
What are sacred groves? What is their role in conservation?
Answer :
Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem?
Answer :
The species diversity of plants (22 per cent) is much less than that of animals (72 per cent). What could be the explanations to how animals achieved greater diversification?
Answer :
Can you think of a situation where we deliberately want to make a species extinct? How would you justify it?
Answer :
Yes, there are various kinds of parasites and disease-causing microbes that we deliberately want to eradicate from the Earth. Since these micro-organisms are harmful to human beings, scientists are working hard to fight against them. Scientists have been able to eliminate small pox virus from the world through the use of vaccinations. This shows that humans deliberately want to make these species extinct. Several other eradication programmes such as polio and Hepatitis B vaccinations are aimed to eliminate these disease-causing microbes.