1. Name the three important
components of biodiversity.
Ans:
Three components of biodiversity are:
(a) Genetic
diversity
(b) Species diversity
(c) Ecological diversity
2. How do ecologists estimate
the total number of species present in the world?
Ans: Ecologists estimate
the total number of species present in the world by comparing species richness
of some exhaustively studied groups between any two regions (tropics, temperate
or polar regions). Species richness, as a measure of diversity, has been used by
many ecologists. Species density or the number of species per m² is most
commonly used to measure species richness. Species abundance and species
proportional abundance based indices are some other alternative approaches to
the measurement of diversity.
3. Give three hypothesis for
explaining why tropics ’”show greatest levels of species
richness.
Ans: (1) The tropical
area have a more stable climate than temperate zones. Local species continues to
live in absence of natural disturbances.
(2) Warm temperature and high
humidity in most tropical areas provide favourable conditions for growth and
survival of diverse species.
(3) Tropical areas receive more solar energy
over year and thus tropical communities are more productive and can support a
wide range of species.
4. What is the significance
of the slope of regression in a species-area
relationship?
Ans: Slope of regression
or regression coefficient makes it easier to measure species richness along an
area. For a limited area like, a country, it gives a constant value of 0.1 to
0.2 irrespective of the taxonomic group or region. It remains amazingly similar
for all those small regions. On the contrary, for measuring species-area
relationship over large areas like the entire continents, the slope of
regression values in the range of 0.6 to 1.2.
5. What are the major causes
of species losses in a geographical region?
Ans:
Species are lost in a geographical region due to natural
disturbances like forest fires; famine, drought and also due to human
disturbance with over replantation, habitat destruction, habitat displacement,
over specialization, intensive agriculture and pollution.
6. How is biodiversity
important for ecosystem functioning?
Ans:
Biodiversity is important for ecosystem functioning because,
(1) It contributes to productivity.
(2) It cause more efficient recycling of
energy and matter.
(3) It has many alternative pathways for survival under
diverse conditions.
(4) Rich biodiversity provides alternatives available at
each trophic level. All organisms are linked in food chains and interact with
their abiotic environment in such a way so as to keep the natural cycles going
and make the ecosystems self – sustaining units. Disappearance of any link in a
food chain will not affect the ecosystem as other alternatives are there.
7. What are sacred groves?
What is their role in conservation?
Ans:
Sacred forests or sacred groves are forest patches around places
of worship which are held in high esteem by tribal communities. They are the
most undisturbed forest patches which are often surrounded by highly degraded
landscapes. They are found in several parts of India, e.g., Karnataka,
Maharashtra, Rajasthan (Aravalli), Madhya Pradesh (Sarguja, Bastar), Kerala,
Meghalaya. Temples built by tribals are found surrounded by deodar forests in
Kumaon region, Jaintias and Khasjas in Meghalaya. Not a single branch is allowed
to be cut from these forests. As a result many endemic species which are rare or
have become extinct elsewhere can be seen to flourish here. Bishnois of
Rajasthan protect Prosopis cineraria and Black Buck religiously. Some water
bodies are also held sacred in certain places, e.g., Khecheopalri in Sikkim.
Their aquatic flora and fauna are naturally preserved.
8. Among the ecosystem
services are control of floods and soil erosion. How is this achieved by the
biotic components of the ecosystem?
Ans:
Ecosystem services are products or benefits given by ecosystem processes to the
environment for its purification, beauty, biodiversity, protection of natural
resources, habitat to wild life and tribals, protection of soils, CO2
– O2 balance, retention of water against floods, drought and
pollution. Plants play a vital role in the control of floods and soil erosion.
Their roots bind the soil 10. particles firmly and in this way they do not allow
the top soil to be drifted away by winds or moving water. Roots of plants also
make the soil porous and allow water to go into the soil.
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?
Ans: Species
diversity refers to the variety of species within a region which is less in
plants as compared to animals. It is due to greater dispersal/more number of
surviving individuals. Most animals possess simple or complex nervous system to
control and coordinate various activities. They possess receptors to receive
against them. Most of their responses are adaptive and ensure their survival in
changing environmental conditions. They, therefore, have evolved to reveal much
higher species diversity than plants who do not possess nervous system and
respond differently against environment stimuli.
10. Can you think of a
situation where we deliberately want to make a species extinct? How would you
justify it?
Ans: Humans can cause
extinction of species through various means. We are trying to eradicate disease
causing organisms (e.g., poliovirus) from this world to make this world disease
free. Since such micro-organisms are harmful to the human society, such attempt
is justified. Further, such micro-organisms are not essential components
(producers or decomposers) of any ecosystem, and losing one or few such
organisms would not affect the functioning of ecosystem.