- Species richness increases with an increase in the explored area, but only up to a certain limit.
- The relationship between species richness and area follows a rectangular hyperbola and becomes a straight line on a logarithmic scale.
- The relationship is expressed by the equation: log S = log C + Z log A, where Z represents the slope of the line.
- For small regions, Z usually ranges from 0.1–0.2, but for very large areas like continents, steeper slopes (0.6–1.2) indicate a much faster increase in species richness with area.
Definitions [10]
Definition: Biodiversity
- The diversity of life forms present on Earth, including plants, animals, and microorganisms, is called biodiversity.
- Biodiversity is the occurrence of different types of genes among the individuals of species, habitats and ecosystems, both terrestrial and aquatic within a defined area.
Define dichotomous key.
It is a tool used to classify organisms based on their similarities and differences.
Define Hotspots.
Hotspot is a biodegradable region that is both a significant reservoir of biodiversity and is threatened with destruction.
Define Eutrophication.
Eutrophication: The process by which a body of water enriched in dissolved nutrients (such as phosphates) that stimulates the growth of aquatic algae usually resulting in the depletion of dissolved oxygen.
Define Ramsar Sites.
Ramsar Sites: It is a wetland site designed of international importance under the Ramsar convention. It is an inter-governmental environmental treaty established in 1971 by UNESCO and coming into force in 1975.
Define Biodiversity.
Biodiversity is defined as the variety of plant and animal life in the world or in a particular habitat, a high level of which is usually considered to be important and desirable
The sum total of species richness, i.e., the number of species of plants, animals and micro-organisms inhabiting in a given habitat, is known as biodiversity.
Give definitions of Extinct species.
Species that completely disappear from the planet are referred to as extinct.
Give definitions of Invasive species.
Species that are not native to a region or locality but are unintentionally or purposefully introduced and cause harm to the native species already present are referred to as invasive species.
Give definitions of Endangered species.
When a species possesses a very high risk of extinction as a result of rapid population decline of 50 to more than 70 per cent over the previous 10 years, it is said to be an endangered species.
Define cryopreservation.
Cryopreservation is a technique in which organisms, tissue, and cells are preserved and stored at the very low temperature of liquid nitrogen (−196°C) for years. They remain viable in the frozen state for future use.
Key Points
Key Points: Biodiversity
- Biodiversity is the variety of life on Earth — including microorganisms, fungi, plants and animals in both terrestrial and aquatic habitats.
- Diversity exists in size, shape, colour, nutrition, habitat and reproduction. It arises due to adaptations of organisms to different environmental conditions for survival.
- Biodiversity = totality of genes, species and ecosystems in a region (as per IUCN, UNEP and WRI).
- Term coined by Walter Rosen (1982), popularised by Edward Wilson to describe diversity at all levels of biological organisation.
- Today's biodiversity is the result of 3.5 billion years of evolutionary history, influenced by natural processes and human activities.
Key Points: Patterns of Biodiversity
Latitudinal Gradient
- Species richness is high near the equator (tropics: 23.5°N to 23.5°S) and decreases towards the poles. Example: The Amazon rainforest has 40,000 plants, 1300 birds and 427 mammals.
- Tropics have high diversity due to a stable climate, less glaciation, abundant sunlight, higher rainfall and greater niche specialisation.
Altitudinal Gradient
-
Species diversity decreases at higher altitudes due to drastic climatic changes and seasonal variations.
Species-Area Relationship
- Observed by Alexander Von Humboldt, species richness increases with area but only up to a limit. For many species, this forms a rectangular hyperbola.
- Expressed as: log S = log C + Z log A, where S = species richness, A = area, Z = slope, C = Y-intercept. On a logarithmic scale, it gives a straight line.
- Z value for smaller areas = 0.1 to 0.2. For larger areas (continents) = 0.6 to 1.2 (steeper slope — species increase faster than area explored).
Key Points: Importance of Species Diversity to the Ecosystem
- A stable community maintains constant biomass production, withstands disturbances, recovers quickly and resists invasive species.
- David Tilman proved that greater species richness maintains the stability of an ecological community. Rich diversity leads to lesser variation in biomass production — called Productivity Stability Hypothesis.
- Paul Ehrlich (Stanford) proposed the Rivet Popper Hypothesis — an ecosystem compared to an aeroplane and species to rivets. Loss of one species may not cause immediate damage, but gradual loss seriously threatens the ecosystem.
- Loss of key species causes rapid and serious damage, showing that diversity and ecosystem well-being do not share a linear relationship.
- Loss of species disturbs food chains, food webs, energy flow and natural cycles — affecting the entire balance of the ecosystem.
Categories of Species Assessment by the IUCN
| Category | Meaning |
|---|---|
| Extinct (EX) | No individuals left alive |
| Extinct in Wild (EW) | Survive only in captivity |
| Critically Endangered (CR) | Extremely high risk (≤ 50 individuals) |
| Endangered (EN) | Very high risk; 50–70% decline (last 10 years) |
| Vulnerable (VU) | High risk; 30–50% decline (last 10 years) |
| Near Threatened (NT) | Likely to become threatened soon |
| Least Concern (LC) | Abundant and widespread species |
| Data Deficient (DD) | Insufficient data available |
| Not Evaluated (NE) | Not assessed by IUCN |
Key Points: Loss of Biodiversity
- Loss of biodiversity causes ecosystem imbalance and may lead to extinction of species (natural, mass, and anthropogenic).
- Natural causes include forest fires, earthquakes, and volcanic eruptions, while human causes include habitat destruction, hunting, and overexploitation.
- The present biodiversity loss is considered the 7th mass extinction, occurring 100–1000 times faster due to human activities.
- Loss of biodiversity reduces plant productivity, disturbs environmental processes, and lowers resistance to disturbances.
- The “Evil Quartet” causes biodiversity loss: habitat loss, over-exploitation, alien species invasion, and co-extinction.
- Invasive species can harm or eliminate native species due to a lack of natural predators (e.g., Parthenium, water hyacinth).
- Conservation status is maintained in the IUCN Red Data Book; endangered species have declining populations, while extinct species are completely lost.
Key Points: Conservation of Biodiversity
- Conservation of biodiversity means protection and proper management of species to maintain balance and ensure benefits for the present and the future.
- Narrowly utilitarian value: biodiversity provides food, shelter, medicines, and industrial products; many species are used in traditional and modern medicine.
- Broadly utilitarian value: biodiversity supports ecological processes like oxygen production, pollination, seed dispersal, and also provides recreational benefits.
- Bioprospecting involves searching for useful biological resources like new medicines, genes, and economically important products.
- Ethical reason: all living organisms have an equal right to live, so humans should not destroy biodiversity.
Key Points: Biodiversity Conservation Methods
- Biodiversity can be conserved by sustainable use of natural resources through two methods: in situ and ex situ conservation.
- In situ conservation means protecting species in their natural habitat (e.g., national parks, wildlife sanctuaries, biodiversity hotspots).
- Biodiversity hotspots are regions with high species richness; protecting them can significantly reduce extinction rates.
- Ex situ conservation involves protecting species outside their natural habitat (e.g., zoos, botanical gardens, seed banks, tissue culture).
- Modern techniques like cryopreservation and captive breeding help in conserving endangered species.
Key Points: Patterns of Biodiversity (Species–Area Relationship)
Key Points: The importance of Species Diversity to the Ecosystem
- Communities with higher species diversity are generally more stable, showing less year-to-year variation in productivity and better resistance to disturbances and invasions.
- Experimental studies (e.g., David Tilman’s work) show that increased species diversity leads to higher productivity and stability in ecosystems.
- Loss of species can weaken ecosystem functioning, even if the effects are not immediately visible.
- The rivet popper hypothesis explains that continuous loss of species can critically damage ecosystems, especially when key species are lost.
Key Points: Need for Biodiversity Conservation
- Biodiversity provides direct economic benefits such as food, fuel, fibre, industrial products and medicines (narrowly utilitarian value).
- A large proportion of modern and traditional medicines are derived from plants, with many more potential resources yet to be discovered.
- Biodiversity supports vital ecosystem services like oxygen production, pollination, climate regulation and nutrient cycling (broadly utilitarian value).
- Nature offers important aesthetic, cultural and recreational benefits that improve human well-being.
- Ethically, every species has intrinsic value, and humans have a moral responsibility to protect biodiversity for future generations.
Key Points: Methods of Biodiversity Conservation
| Aspect | In situ Conservation | Ex situ Conservation |
|---|---|---|
| Meaning | Conservation of species in their natural habitats | Conservation of species outside their natural habitats |
| Level protected | Protects whole ecosystems and communities | Protects individual species |
| When used | When species can survive in natural conditions | When species are endangered or near extinction |
| Main methods | Biosphere reserves, national parks, sanctuaries | Zoos, botanical gardens, seed banks |
| Indian examples | Western Ghats, Himalayas, sacred groves | Zoological parks, botanical gardens |
| Advanced techniques | Habitat protection, hotspot conservation | Cryopreservation, tissue culture |
| Importance | Maintains natural evolution and interactions | Prevents immediate extinction |
Key Points: Patterns of Biodiversity (Latitudinal Gradient)
- Species diversity is highest in the tropics and gradually decreases from the equator towards the poles.
- Tropical regions (23.5°N–23.5°S) harbour far more species than temperate and polar regions, as seen in birds, plants and other organisms.
- The Amazon rainforest shows the greatest biodiversity on Earth, with thousands of plant, animal and insect species.
- Higher tropical diversity is due to long uninterrupted evolutionary time, stable and less seasonal climate, and greater solar energy leading to high productivity.
Important Questions [31]
- “India has greater ecosystem diversity than Norway.” Do you agree with the statement? Give reasons in support of your answer.
- Identify ‘a’ and ‘b’ in the figure given below representing proportionate number of major vertebrate taxa.
- Name the type of biodiversity represented by the following: 50,000 different strains of rice in India.
- Mention the Kind of Biodiversity of More than a Thousand Varieties of Mangoes in India Represent. How is It Possible?
- Explain the effect on the characteristics of a river when urban sewage is discharged into it.
- Write the Difference Between Genetic Biodiversity and Species Biodiversity that Exists at All the Levels of Biological Organisation.
- Given below is a 'pie chart' representing the global biodiversity: proportionate number of species of major taxa. Identify (X) and (Y) in the given 'pie chart'.
- The following graph shows the species-area relationship. Answer the following questions as directed. (a) Name the naturalist who studied the kind of relationship shown in the graph.
- The species-area relationship is represented on a log scale as ______.
- Study the graph given below: As per Alexander von Humboldt, what do the symbols S, A, Z and C in the graph stand for, in respect of a species and area relationship?
- Given below is an equation describing the Species-Area relationship between species richness and area for a wide variety of taxa as angiosperm plants, birds, bats etc. S = CAz
- Explain, giving three reasons, why tropics show greatest levels of species diversity.
- Write the inference drawn by Alexander von Humboldt after his extensive explorations of South American jungle.
- The sixth extinction in progress currently is different from all previous extinctions on earth as it is ______.
- Substantiate with the Help of One Example that in an Ecosystem Mutualists (I) Tend to Co-evolve and (Ii) Are Also One of the Major Causes of Biodiversity Loss.
- Suggest two practices giving one example of each, that help protect rare or threatened species.
- Explain the concept of "co-extinction" by taking two examples.
- Enlist two criteria that are used to identify a region for maximum protection as 'Biodiversity hotspots'.
- Name any two biodiversity hot spots in India.
- "Forests provide intangible benefits to us." Explain by taking three different areas, how.
- The IUCN Red Data List (2004) in the last 500 years documents the extinction of nearly 784 species including ______.
- Which one of the following groups faces maximum threat of extinction?
- 'in-situ' Conservation can help endangered/threatened species. Justify the statement.
- List six advantages of the "ex-situ' approach to conservation of biodiversity.
- Why should we conserve biodiversity ? How can we do it?
- "Biodiversity plays a major role in many ecosystem services that nature provides." State one ethical reason for conserving biodiversity.
- List Any Four Techniques Where the Principle of ex-situ Conservation of Biodiversity Has Been Employed.
- There Are Many Animals that Have Become Extinct in the Wild but Continue to Be Maintained in Zoological Parks. (I) What Type of Biodiversity Conservation is Observed in this Case?
- Name and Describe Any Three Causes of Bio-diversity Losses.
- Why are scared groves highly protected?
- "Biodiversity plays a major role in many ecosystem services that nature provides." Describe any two broadly utilitarian arguments to justify the given statement.
