Human Health and Disease — BIOLOGY STD 12 Science — Question

1. True embryo develops as a result of fusion of:

1. Two polar nuclei of embryo sac.
2. An egg cell and a male gamete.
3. Synergid and male gamete.
4. A male gamete and antipodals.

2. Refer to the given diagram of the embryo of an angiospermous plant with parts labelled P, Q and R. Select the correct statement(s) regarding this.

1. Part 'P' supplies nutrition to the developing embryo.
2. Part 'Q' is the protective sheath of radicle and root cap.
3. Part 'R' is the protective sheath of shoot apex and leaf primordia.
4. The embryo shown in the diagram is present in members of Family Poaceae.

1. (IV) only.
2. (II) and (III) only.
3. (I) and (IV) only.
4. (I), (II), (III) and (IV).

3. Which of the given statements are true?

1. During the development of a dicot embryo, heart-shaped embryo is followed by globular embryo.
2. The part of embryonal axis above the level of cotyledons is epicotyl, while the part below the level of cotyledons is hypocotyl.
3. Monocot seeds possess a single cotyledon, represented by scutellum.

1. (I) and (II).
2. (II) and (III).
3. (I) and (III).
4. (I), (II) and (III).

4. Consider the following parts of an embryonal axis of a dicot seed.

1. Hypocotyl.
2. Epicotyl.
3. Radicle.
4. Plumule.

In which of the following the above parts are correctly arranged from top to base?

1. (III) → (I) → (II) → (IV).
2. (II) → (I) → (III) → (IV).
3. (IV) → (II) → (I) → (III).
4. (III) → (IV) → (II) → (I).

5. In grass family, the cotyledon, is called:

1. Epiblast.
2. Plumule.
3. Scutellum.
4. Perisperm.

1. Kangaroo rat is a:

1. Partial regulators
2. Partial conformer
3. Regulator
4. Conformer

2. Metabolic water refers to:

1. Water required for metabolic activities.
2. Water present in intercellular fluid.
3. Water produced during oxidation of fat or carbohydrate.
4. Water taken in, to promote metabolism.

3. Desert animals minimise water loss by:

1. Producing highly concentrated urine.
2. Promoting maximum reabsorption of water in kidney tubules.
3. Possessing one of the longest loop of Henle in kidney tubules.
4. All of these.

4. Assertion: Kangaroo rat can tolerate and thrive in wide temperature range and is known as stenothermal.

Reason: Kangaroo rats go into hibernation during winter to escape cold weather.

1. Both assertion and reason are true and reason is the correct explanation of assertion.
2. Both assertion and reason are true but reason is not the correct explanation of assertion.
3. Assertion is true but reason is false.
4. Both assertion and reason are false.

5. The adaptations in an organism are meant for:

1. Optimum primary production.
2. Optimum life span.
3. Optimum mobility.
4. Optimum survival and reproduction.

1. Dodo, an extinct taxon, belongs to which country?

1. Mauritius
2. Africa
3. Australia
4. Russia

2. To which of the following categories of IUCN, Berberis nilghiriensis belongs?

1. Extinct.
2. Extinct in wild.
3. Endangered.
4. Critically endangered.

3. Steller's sea cow and passenger pigeon became extinct due to:

1. Alien species invasion.
2. Over-exploitation.
3. Coextinctions.
4. Intensive agriculture.

4. Bali, Javan and Caspian are:

1. Species of tiger.
2. Species of cheetah.
3. Subspecies of cheetah.
4. Subspecies of tiger.

5. Select the correct term for the following definitions (i, ii, iii, iv).

• The taxon is liable to become extinct if not allowed to realise its full biotic potential by providing protection from exotic species/ human exploitation/habitat deterioration/depletion of food.
• The taxon has been completely eliminated or died out from earth, e.g., Dodo.
• The taxon is facing a high risk of extinction in the wild in the near future due to decrease in its habitat, excessive predation or poaching.
• They are species with naturally small populations, either localised or thinly scattered, which are always at risk from pests/ pathogens/ predators/ exotic species.