Q.Mention the main reasons for Biodiversity conservation. What is ecological niche? (2+1) OR Mention briefly the steps of plant succession.

The Rivet Popper Hypothesis, proposed by Paul Ehrlich, is an analogy that explains the importance of preserving every species in an ecosystem, i.e. biodiversity.

The Rivet Popper Hypothesis compares an ecosystem to an aeroplane held together by thousands of rivets (species). Removing a few rivets (species) here and there may not immediately bring the plane down, but each loss weakens the structure, and beyond a threshold the loss of even one more critical rivet can cause total, catastrophic failure. The analogy is used to argue that ever …

Silent Valley is protected primarily because it is a rare, virgin stretch of tropical evergreen rainforest, harbouring rich and unique biodiversity.

The Silent Valley, located in Kerala's Western Ghats, is one of the very few remaining tracts of pristine, undisturbed tropical evergreen rain forest in India, never having been logged or significantly altered by humans. This intact rain-forest ecosystem is what led to it becoming the centre of the famous 'Save Silent Valley' conservation movement in the 1970s-80s, which ultimately stopped a proposed hydroelectric dam project and led to its declaration as a national park in 1984. While it does host rare species like the lion-tailed macaque, the defining reason for its protection status is that it represents one of the last natural, undisturbed tropical rain-forest ecosystems left in peninsular India.

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The pearl-producing organism is the pearl oyster Pinctada fucata.

A pearl forms when a foreign particle lodges between the mantle and shell of a pearl oyster; the mantle secretes concentric layers of nacre (mother-of-pearl) around it. Pinctada fucata is the classic commercially cultured pearl oyster used in pearl farming.

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The incorrect pair is 'Cochin - Mediterranean breed'; Cochin is actually an Asiatic breed.

Standard poultry classes: Cornish is an English breed, New Hampshire is an American breed, Langshan and Cochin are Asiatic breeds. Mediterranean-class fowls are birds like Leghorn and Minorca. So pairing Cochin with 'Mediterranean' is the error.

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Butterfly fishes occur in the coral-reef waters of the Gulf of Mannar.

Butterfly fishes are small, brightly coloured reef fishes associated with coral. The Gulf of Mannar (a marine biosphere reserve off Tamil Nadu) has rich coral-reef habitats that support them, which is why the TN textbook links butterfly fishes to this region.

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The correct combination is (i) True, (ii) False, (iii) True, (iv) False — option (b).

Evaluating each statement:

1. Raceway culture (rearing fish in running-water channels) is used for carp culture — True (as stated in the TN text).
2. Rohu is NOT used to control mosquito larvae; larvivorous fishes such as Gambusia and Guppy do that — False.
3. Molly and Gourami are popular ornamental (aquarium) fishes — True. …

The silkworm Bombyx mori feeds on mulberry leaves.

Bombyx mori is the domesticated mulberry silkworm used in sericulture. Its caterpillar (larva) eats only mulberry (Morus) leaves, then spins a silk cocoon from which commercial silk is reeled.

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Sterile female bees are the worker bees.

A honeybee colony has three castes: the queen (a single fertile female that lays eggs), drones (fertile males), and workers (sterile females that forage, build comb, feed larvae and defend the hive). The workers develop from fertilised eggs but their reproductive organs stay undeveloped, so they are sterile females.

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Tilapia mosambica shows buccal (mouth) incubation of its eggs.

Mouth-brooding (buccal incubation) is a form of parental care in which the parent keeps the fertilised eggs and hatchlings inside its mouth for protection. Tilapia mosambica is the classic textbook example of a fish that does this.

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