Q. 1) Name the three important components of biodiversity.
Ans: Our biosphere is immensely diverse or heterogeneous not only at the species level but all levels of biological organization. Edward Wilson popularised the term biodiversity and explained the three important components of the biosphere:
- Genetic diversity: A single species showing a high level of diversity at the genetic level.
- Species diversity: The variations that exist at species levels.
- Ecological diversity: Large varieties of ecosystems like deserts, mountains, grasslands.
Q. 2) How do ecologists estimate the total number of species present in the world?
Ans: It is a very difficult task to estimate the total number of species present in the world. According to a study, 1.5 million different kinds of species of plants and animals have been reported however, there is no idea about the numbers that have not been identified yet.
More work has been done in temperate regions as compared to tropical regions, thus inventories in temperate regions are more complete and exhaustive for many taxonomic groups. The insect species have been largely studied in both regions.
Ecologists use the statistical means of analysis and comparison of the temperate-tropical species richness of this largely studied group of insects and then try to extrapolate this information/ratio to other plants and animals of tropical regions. This allows them to come up with a gross estimate of the total number of plant and animal species present across the world. Some estimates that have been made by this method range from 10 to 50 million different species.
Q. 3) Give three hypotheses for explaining why tropics show greatest levels of species richness.
Ans: It is well known fact of ecology that species diversity is not uniform across the globe but shows latitudinal diversity. It means that as we move from equator towards the pole, with very few exceptions, tropics (latitudinal range of 23.5° N to 23.5° S) harbor more species diversity than temperate or polar regions.
Given below are three different hypotheses by ecologists for this:
- In the past, temperate regions were subjected to frequent climatic changes such as glaciations. However, tropical regions have remained relatively undisturbed for millions of years. This constant environment allowed species to diversify over millions of years without any environmental disturbances.
- Tropical regions are less seasonal, relatively more constant and predictable in terms of the environment. This helps in greater species diversification over time.
- Tropical regions receive more solar energy throughout the year. This significantly contributes to higher productivity and thus, greater diversity.
Q. 4) What is the significance of the slope of regression in a species–area relationship?
Ans: The slope of regression depicts the relationship between the number of species present in a given area. One of the most fundamental ecological relationships is that, as the area of region increases, so does the number of different species encountered.
It has been found that in smaller areas, where the study is being done, the value of slopes of regression is similar regardless of the taxonomic group or the region under study e.g. the slope of regression for smaller areas remains same across various taxonomic group or region.
However, when a similar analysis is done in larger areas like entire continent (e.g. fruit-eating birds or mammals in the tropical forest across different continents), then the slope of regression is much steeper which means that with the increasing area, the number of species does not increase proportionately.
Q. 5) What are the major causes of species losses in a geographical region?
Ans: The large varieties of plant and animal species that constitute our biosphere are dwindling at an alarming rate. With passing time, the number of species present across the globe is going down or becoming extinct. This is largely due to human activities and interventions with natural phenomenon.
The four major causes of species losses in a geographical region are:
- Habitat loss and fragmentation: Human activities have been largely responsible for habitat loss and fragmentation of existing habitats resulting in a very sharp decline in biodiversity.
- Over-exploitation: Increasing dependence of humans on natural resources has resulted in over-exploitation and extinction of many species.
- Alien species invasion: Introduction of invasive alien species causes decline or extinction of native species.
- Co-extinctions: Extinction of one species leads to extinction of dependent species.
Q. 6) How is biodiversity important for ecosystem functioning?
Ans: An ecosystem which is more diverse is more stable and more productive because of the delicate balance that is maintained between various species existing in that ecosystem.
In a diverse ecosystem, even if one species fails, others can perform similar roles, maintaining stability and productivity under changing environmental conditions.
Q. 7) What are sacred groves? What is their role in conservation?
Ans: Sacred groves are tracts of forests that have been set aside based on the religious and cultural importance of that area and community. All the trees and wildlife within such sacred groves are given total protection by the community.
They form important repositories of forest diversity and provide shelter to many rare and threatened plant species.
Q. 8) Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem?
Ans: Plants play a very big role in the control of floods and soil erosion. The roots of plants bind the soil, increase porosity and allow rainwater to seep into the ground. Loss of green cover leads to soil erosion and floods.
Q. 9) The species diversity of plants (22%) is much less than that of animals (72%). What could be the explanation?
Ans: Animals could relocate to different places under unfavourable conditions, unlike plants. Animals also developed more complex body structures and nervous systems allowing greater diversification.
Q. 10) Can you think of a situation where we deliberately want to make a species extinct? How would you justify it?
Ans: Disease-causing microorganisms such as smallpox virus and polio virus have been deliberately eradicated by humans through well-planned immunisation programmes.
This eradication is justified as these organisms caused large-scale suffering and deaths and their removal has not disturbed ecological balance.