Biology · Class 12 Science
Ch 13Biodiversity and Conservation — Class 12 Biology, concept-first.
Imagine an alien visitor arriving on Earth from a distant galaxy for the first time — the first thing to strike them would almost certainly be the sheer diversity of life here.
Key concepts
Hover a concept to preview it and jump to its most relevant Q&A.
Three Components Biodiversity
Imagine you walk into a library. A good library doesn't just have a lot of books — it has books on different subjects (variety), a good number of copies of each popular book (abundance), and a sensible way the books are…
Most relevant Q&A
- Name the three important components of biodiversity.Free
- The active chemical drug reserpine is obtained from: (a) Datura (b) Rauwolfia (c) Atropa (d) PapaverPreview
- What accounts for the greater ecological diversity of India?Preview
- How does species diversity differ from ecological diversity?Preview
- Why is genetic variation important in the plant Rauwolfia vomitoria?Preview
Chapter contents
The NCERT structure, section by section. Open a section to see its questions, then read the concept-first solution.
Introduction
Imagine an alien visitor arriving on Earth from a distant galaxy for the first time — the first thing to strike them would almost certainly be the sheer diversity of life here.
Biodiversity
The immense variety of life on Earth is not limited to the number of species. It exists at every level of biological organisation — from the complex molecules inside a single cell, right up to entire…
How Many Species are there on Earth and How Many in India?
The first question that arises when we study biodiversity is a simple one: how many species actually exist on Earth? We have published records of every species that has been discovered and formally na…
Patterns of Biodiversity
The diversity of life on Earth is not spread evenly. Two major patterns help us understand where species are found and why: the latitudinal gradient in diversity and the species-area relationship.
The Importance of Species Diversity to the Ecosystem
Does the number of species in a community actually matter for how the ecosystem works? Ecologists have not been able to give a clear, final answer to this question.
Loss of Biodiversity
While it is uncertain whether new species are still being added to Earth's total through speciation, what is certain is that species are being lost at an alarming rate.
Biodiversity Conservation
Having taken millions of years to accumulate, biodiversity now needs active protection. The book moves directly from naming the problem to addressing it: 13.2.1 lays out why conservation matters — the…
Why Should We Conserve Biodiversity?
The reasons for conserving biodiversity range from the obvious to the subtle, but all carry equal weight. They fall into three broad categories: narrowly utilitarian, broadly utilitarian, and ethical.
How Do We Conserve Biodiversity?
The previous section (13.2.1) laid out why biodiversity is worth conserving. This section turns to how: once we decide to protect biodiversity, we face a practical question — where should we do it? Th…
Summary
- Life on Earth has been diversifying for nearly 3.8 billion years, since it first originated. Biodiversity is the variety of living organisms that resulted, at three levels: genetic (variation within…
Exercises
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- 13.1Name the three important components of biodiversity.Free
- 13.2How do ecologists estimate the total number of species present in the world?Free
- 13.3Give three hypotheses for explaining why tropics show greatest levels of species richness.Free
- 13.4What is the significance of the slope of regression in a species – area relationship?Preview
- 13.5What are the major causes of species losses in a geographical region?Preview
- 13.6How is biodiversity important for ecosystem functioning?Preview
- 13.7What are sacred groves? What is their role in conservation?Preview
- 13.8Among the ecosystem services are control of floods and soil erosion. How is this achieved by the biotic components of the ecosystem?Preview
- 13.9The 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…Preview
- 13.10Can you think of a situation where we deliberately want to make a species extinct? How would you justify it?Preview
Exemplar Problems
Higher-order thinking / exemplar-style practice problems.
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- Q1Which of the following countries has the highest biodiversity? (a) South America (b) South Africa (c) Russia (d) IndiaFree
- Q2Which of the following is not a cause for loss of biodiversity? (a) Destruction of habitat (b) Invasion by alien species (c) Keeping animals…Free
- Q3Which of the following is not an invasive alien species in the Indian context? (a) Lantana (b) Cynodon (c) Parthenium (d) EichhorniaFree
- Q4Where among the following will you find pitcher plant? (a) Rain forest of North-East India (b) Sunderbans (c) Thar Desert (d) Western GhatsPreview
- Q5Which one of the following is not a major characteristic feature of biodiversity hot spots? (a) Large number of species (b) Abundance of end…Preview
- Q6Match the animals given in column I with their location in column II: Column I — Column II A. Dodo — i. Africa B. Quagga — ii. Russia C. Thy…Preview
- Q7What is common to the following plants: Nepenthes, Psilotum, Rauwolfia and Aconitum? (a) All are ornamental plants (b) All are phylogenic li…Preview
- Q8The one-horned rhinoceros is specific to which of the following sanctuary (a) Bhitar Kanika (b) Bandipur (c) Kaziranga (d) Corbett parkPreview
- Q9Amongst the animal groups given below, which one appears to be more vulnerable to extinction? (a) Insects (b) Mammals (c) Amphibians (d) Rep…Preview
- Q10Which one of the following is an endangered plant species of India? (a) Rauwolfia serpentina (b) Santalum album (Sandal wood) (c) Cycas bedd…Preview
- Q11What is common to Lantana, Eichhornia and African catfish? (a) All are endangered species of India. (b) All are keystone species. (c) All ar…Preview
- Q12The extinction of passenger pigeon was due to: (a) Increased number of predatory birds. (b) Over exploitation by humans. (c) Non-availabilit…Preview
- Q13Which of the following statements is correct? (a) Parthenium is an endemic species of our country. (b) African catfish is not a threat to in…Preview
- Q14Among the ecosystem mentioned below, where can one find maximum biodiversity? (a) Mangroves (b) Desert (c) Coral reefs (d) Alpine meadowsPreview
- Q15Which of the following forests is known as the 'lungs of the planet Earth'? (a) Taiga forest (b) Tundra forest (c) Amazon rain forest (d) Ra…Preview
- Q16The active chemical drug reserpine is obtained from: (a) Datura (b) Rauwolfia (c) Atropa (d) PapaverPreview
- Q17Which of the following group exhibit more species diversity? (a) Gymnosperms (b) Algae (c) Bryophytes (d) FungiPreview
- Q18Which of the below mentioned regions exhibit less seasonal variations? (a) Tropics (b) Temperates (c) Alpines (d) Both (a) & (b)Preview
- Q19The historic convention on Biological Diversity held in Rio de Janeiro in 1992 is known as: (a) CITES Convention (b) The Earth Summit (c) G-…Preview
- Q20What is common to the techniques (i) in vitro fertilisation, (ii) Cryo preservation and (iii) tissue culture? (a) All are in situ conservati…Preview
- Q21What characteristics make a community stable?Preview
- Q22What could have triggered mass extinctions of species in the past?Preview
- Q23What accounts for the greater ecological diversity of India?Preview
- Q24According to David Tilman, greater the diversity, greater is the primary productivity. Can you think of a very low diversity man-made ecosys…Preview
- Q25What does 'Red' indicate in the IUCN Red list (2004)?Preview
- Q26Explain as to how protection of biodiversity hot spots alone can reduce up to 30% of the current rate of species extinction.Preview
- Q27What is the difference between endemic and exotic species?Preview
- Q28How does species diversity differ from ecological diversity?Preview
- Q29Why is genetic variation important in the plant Rauwolfia vomitoria?Preview
- Q30What is Red Data Book?Preview
- Q31Define gene pool.Preview
- Q32What does the term 'Frugivorous' mean?Preview
- Q33What is the expanded form of IUCN?Preview
- Q34Define the terms (i) Bioprospecting (ii) EndemismPreview
- Q35How is the presently occurring species extinction different from the earlier mass extinctions?Preview
- Q36Of the four major causes for the loss of biodiversity (Alien species invasion, habitat loss and fragmentation, over-exploitation and co-exti…Preview
- Q37Discuss one example, based on your day-to-day observations, showing how loss of one species may lead to the extinction of another.Preview
- Q38A species-area curve is drawn by plotting the number of species against the area. How is it that when a very large area is considered the sl…Preview
- Q39Is it possible that productivity and diversity of a natural community remain constant over a time period of, say one hundred years?Preview
- Q40There is greater biodiversity in tropical /subtropical regions than in temperate region. Explain.Preview
- Q41Why are the conventional methods not suitable for the assessment of biodiversity of bacteria?Preview
- Q42What criteria should one use in categorizing a species as threatened?Preview
- Q43What could be the possible explanation for greater vulnerability of amphibians to extinction as compared to other animal groups?Preview
- Q44How do scientists extrapolate the total number of species on Earth?Preview
- Q45Humans benefit from diversity of life. Give two examples.Preview
- Q46List any two major causes other than anthropogenic causes of the loss of biodiversity.Preview
- Q47What is an endangered species? Give an example of an endangered plant and animal species each?Preview
- Q48What are sacred groves and their role in biodiversity conservation?Preview
- Q49Suggest a place where one can go to study coral reefs, mangrove vegetation and estuaries.Preview
- Q50Is it true that there is more solar energy available in the tropics? Explain briefly.Preview
- Q51What is co-extinction? Explain with a suitable example?Preview
- Q52Elaborate how invasion by an alien species reduces the species diversity of an area.Preview
- Q53How can you, as an individual, prevent the loss of biodiversity?Preview
- Q54Can you think of a scientific explanation, besides analogy used by Paul Ehrlich, for the direct relationship between diversity and stability…Preview
- Q55Though the conflict between humans and wildlife started with the evolution of man, the intensity of conflict has increased due to the activi…Preview
- Q56What is an ecosystem service? List any four important ecosystem services provided by the natural ecosystems. Are you in favour or against le…Preview
- Q57Describe the consumptive use value of biodiversity as food, drugs and medicines, fuel and fiber with suitable examples.Preview
- Q58Species diversity decreases as we move away from the equator towards the poles. What could be the possible reasons?Preview
- Q59Explain briefly the 'rivet popper hypothesis' of Paul Ehrlich.Preview
- Q60The relation between species richness and area for a wide variety of taxa turns out to be a rectangular hyperbola. Give a brief explanation.Preview
Sample & Board Papers
Sample papers and previous-year board questions for this subject.