Biodiversity And Conservation Class 12th Biology CBSE Solution

Class 12th Biology CBSE Solution

Exercises
Question 1.

Name the three important components of biodiversity.


Answer:

Biodiversity refers to the variability of living organisms on Earth. The main biological components or levels of biodiversity are:

• Genetic diversity: It is the genetic variability among a species.


• Species diversity: It refers to the number of species that live in a particular place.


• Ecological diversity: It refers to the variation in ecosystems in a particular region or variation in ecosystem across the planet.



Question 2.

How do ecologists estimate the total number of species present in the world?


Answer:

• According to International Union for Conservation of Nature (2004), more than 1.5 million species of plants and animals have been described so far. Robert May have estimated the global species diversity to be around 7 million.


• Species inventory is more complete in temperate than in tropical countries and hence, more species are yet to be discovered in the tropical area.


• Biologists make a statistical comparison of temprate-tropical species richnes of an intensively studied group of insects and extrapolate this ratio with other groups of plants and animals to come up with a gross estimate of total species on the planet.


• This conventional taxonomic method is not suitable for estimating microbial species.



Question 3.

Give three hypotheses for explaining why tropics show greatest levels of species richness.


Answer:

Scientists have proposed various hypotheses to justify the higher species diversity in tropics. They are as follows:

• Tropical regions have been relatively undisturbed for millions of years compared to temperate region which have been subjected to glaciations in past which led to higher species diversification as it got more evolutionary time.


• Tropical regions have more constant and predictable climate compared to temperate which can promote niche specialization and higher species diversity.


• Solar energy is available more to tropics causing higher productivity and leading to higher diversity.



Question 4.

What is the significance of the slope of regression in a species – area relationship?


Answer:

• German naturalist and geographer, Alexander von Humboldt observed that within a region, the species richness increased utpo a limit with increased explored area. The relation between species richness and area is a rectangular hyperbola. On a logarithmic scale, it is straight line where Z is the slope of line (slope of regression).


• Z ranges from 0.1 to 0.2 for all taxa and regions except very large areas like continents.


• For larger areas, the slope of regression is steeper and Z ranges from 0.6 to 1.2.



Question 5.

What are the major causes of species losses in a geographical region?


Answer:

There are four major causes that can lead to species loss in an area.

• Habitat loss and fragmentation: Changes caused in a habitat due to uncontrolled and unsustainable human activities such as deforestation, slash and burn agriculture, mining, and urbanization can result into breaking up of the habitat into small pieces, which effects various species and the movement of migratory animals. This leads to decrease in the genetic exchange between populations leading to decreased population of species. It is the most important cause leading to species extinction.


• Over-exploitation: Human greed has led to over-exploitation of various natural resources which has led to endangering and extinction of various species over years.


• Alien species Invasions: Alien species that the introduced unintentionally or delibrately can become invasive and can cause declination or extinction of indigenous species.


• Co-extinctions: Various species can be connected to each other in an obligatory way. When one species gets extinct, other plants or animal species associated with it also gets extinct.



Question 6.

How is biodiversity important for ecosystem functioning?


Answer:

• Biodiversity gives ecosystem services such as photosynthesis and pollination that the nature provides.


• The higher the diversity, more stable is the ecosystem.


• If an ecosystem is rich in biodiversity, then the ecological balance would not get affected.



Question 7.

What are sacred groves? What is their role in conservation?


Answer:

• Sacred grooves are communally protected forest fragments that usually have a religious importance attached to it.


• In India sacred groves are found in certain regions of Rajasthan, Western Ghats of Karnataka, Maharashtra, Meghalaya, and Madhya Pradesh.


• Sacred grooves help in protection of various rare and threatened species as deforestation is strictly restricted in such areas.



Question 8.

Among the ecosystem services are control of floods and soil erosion.

How is this achieved by the biotic components of the ecosystem?


Answer:

• The biotic components of an ecosystem refers to the living organisms.


• Trees help soil become more porous by creating minuscle channels which helps seeping rain water in soil much faster and hence prevent flooding.


• Plants slow down water flow and roots hold soil which helps in preventing soil erosion.



Question 9.

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:

• Animals are more diverse than plants because they have adapted better to the changing environment.


• Animals have more complex body structure and brain capacity as compared to the plants.


• Animals are locomotive and can migrate.


Hence, species diversity of plants is less compared to that if the animals.



Question 10.

Can you think of a situation where we deliberately want to make a species extinct? How would you justify it?


Answer:

There are various disease causing microbes in humans that we would like to eliminate. Small pox causing virus have already being eradicated by using vaccines to prevent humans from the deadly disease. There are programs that are on to eliminate deadly microbes such as Polio virus and hepatitis B virus.


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