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Biodiversity and Conservation - Importance and Loss of Biodiversity

Grade 12CBSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Biodiversity refers to the combined diversity at all levels of biological organization. The term was popularized by sociobiologist Edward Wilson.

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Genetic Diversity: Diversity at the genetic level within a single species. Example: Medicinal plant Rauwolfia vomitoria shows variations in the concentration of the active chemical reserpine (C33H40N2O9C_{33}H_{40}N_2O_9).

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Species Diversity: Diversity at the species level. For example, the Western Ghats have a greater amphibian species diversity than the Eastern Ghats.

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Ecological Diversity: Diversity at the ecosystem level, such as deserts, rain forests, mangroves, coral reefs, wetlands, estuaries, and alpine meadows.

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Global Species Diversity: Robert May's global estimate places the total number of species on Earth at approximately 7 million7 \text{ million}.

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Latitudinal Gradients: Species diversity decreases as we move away from the equator towards the poles. Tropical regions (latitude range of 23.5∘N23.5^\circ N to 23.5∘S23.5^\circ S) harbor more species than temperate or polar areas.

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Species-Area Relationship: Proposed by Alexander von Humboldt; he observed that within a region, species richness increases with increasing explored area, but only up to a limit.

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Rivet Popper Hypothesis: Proposed by Paul Ehrlich. He compared the ecosystem to an airplane and species to rivets. Removing 'rivets' (extinction) weakens the structure, and losing 'key rivets' (keystone species) causes immediate critical danger.

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The Evil Quartet: The four major causes of biodiversity loss: (1) Habitat loss and fragmentation, (2) Over-exploitation, (3) Alien species invasions, and (4) Co-extinctions.

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Sixth Extinction: We are currently in the 'Sixth Episode' of mass extinction, which is anthropogenic (human-caused) and is occurring at a rate 100100 to 10001000 times faster than pre-human times.

📐Formulae

S=CAZS = CA^Z

log⁡S=log⁡C+Zlog⁡A\log S = \log C + Z \log A

Where: S=Species richness, A=Area, Z=Slope of the line (regression coefficient), C=Y-intercept\text{Where: } S = \text{Species richness, } A = \text{Area, } Z = \text{Slope of the line (regression coefficient), } C = \text{Y-intercept}

💡Examples

Problem 1:

In the species-area relationship equation log⁡S=log⁡C+Zlog⁡A\log S = \log C + Z \log A, what is the generally observed value of ZZ for small areas regardless of the taxonomic group or the region? How does this value change when analyzing the relationship in very large areas like entire continents?

Solution:

For small areas, the value of ZZ lies in the range of 0.10.1 to 0.20.2. For very large areas like entire continents, the slope of the regression line is much steeper, with ZZ values in the range of 0.60.6 to 1.21.2.

Explanation:

The value of ZZ represents the regression coefficient. In smaller areas, the rate of finding new species decreases quickly, leading to a flatter slope (0.10.1 to 0.20.2). In larger areas, the variety of habitats increases significantly, leading to a much steeper increase in species richness per unit area (0.60.6 to 1.21.2).

Problem 2:

According to the IUCN Red List (2004) documents, how many species have become extinct in the last 500500 years?

Solution:

784784 species.

Explanation:

The total extinction includes 338338 vertebrates, 359359 invertebrates, and 8787 plants. Notable recent extinctions include the Dodo (Mauritius), Quagga (Africa), Thylacine (Australia), Steller's Sea Cow (Russia), and three subspecies of tiger (Bali, Javan, Caspian).

Importance and Loss of Biodiversity Revision - Class 12 Biology CBSE