Q.Describe briefly the biological effects of light on animal reproduction.

Showing the 12 most recent of 17 on this concept.

1. CBSE 2025Set ANNUAL1 markMCQ
   Q.In desert Plants, leaves modified in to-

   (a) stem

   (b) fruits

   (c) spines

   (d) roots

   ›Reveal solutionSolution

   In desert (xerophytic) plants, leaves are typically modified into spines to conserve water.

   In xerophytic plants adapted to arid, desert conditions — such as Opuntia (prickly pear) and other cacti — the leaves are modified into hard, pointed spines. This drastically reduces the leaf surface area, minimising water loss through tr …

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2. CBSE 2024Set E1 markMCQ
   Q.Which of the following statements is incorrect about temperature?

   (a) Temperature is the most important environmental factor

   (b) Temperature decreases from the equator towards the pole

   (c) Temperature increases with increase in height

   (d) Temperature is low at the summit of a mountain

   ›Reveal solutionSolution

   Temperature falls (not rises) with increasing altitude, so statement (c) is the incorrect one.

   Temperature is the most important ecological/environmental factor because it affects enzyme kinetics, metabolism and the basic physiology of organisms (statement a is correct). Its pattern on Earth:

   • It DECREASES progressively from the equator towards the poles due to the angle of incidence of sunlight (statement b is correct). …

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3. CBSE 2023Set ANNUAL1 markMCQ
   Q.In desert plants, leaves modified into -

   (a) Stem

   (b) Spines

   (c) Fruits

   (d) Roots

   ›Reveal solutionSolution

   In desert plants, leaves are modified into spines to reduce water loss.

   In xerophytic (desert) plants such as cacti, leaves are structurally and functionally modified into spines. This drastically reduces the surface area available for transpiration, thereby conserving water in the water-scarce desert habitat, while the green fle …

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4. CBSE 2023Set A1 mark
   Q.Match the columns. Column A item: Sunken Stomata. Choose the matching term from Column B:

   (a) First antibiotic

   (b) Recessive gene blood disease

   (c) Zoological parks

   (d) Absence of 1 X-chromosome

   (e) Separation of DNA fragments

   (f) Amoebiasis

   (g) Attached DNA fragments

   (h) Adaptation

   ›Reveal solutionSolution

   Sunken stomata are a structural (morphological) adaptation of xerophytic plants that reduces water loss by transpiration.

   Sunken stomata — stomata located in pits below the leaf surface, often accompanied by hairs — are found in plants adapted to dry (xeric) habitats, such as desert and other water-scarce environments. This positioning traps a humid microclimate around the stomat …

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5. CBSE 2023Set ANNUAL1 mark
   Q.Write one adaptation of seals found in polar seas.

   ›Reveal solutionSolution

   Blubber (a thick layer of subcutaneous fat) is the key morphological adaptation that helps seals conserve body heat in the freezing polar seas.

   Organisms living in extreme cold habitats such as polar seas show special morphological/physiological adaptations to cope with the low temperature. In seals, a thick layer of fat (blubber) is deposited under the skin, which acts as an insulator, reducing loss of body heat to the cold surro …

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6. CBSE 2023Set TERM21 markMCQ
   Q.Regulators are the animals which:

   (a) Does not maintain their body homeostasis

   (b) Can maintain their body homeostasis

   (c) Can regulate their heartbeat

   (d) Can regulate their circulation

   ›Reveal solutionSolution

   Regulators are organisms that can maintain constant internal conditions (homeostasis, e.g. body temperature or osmotic concentration) through physiological/biochemical means, regardless of the external environment.

   Organisms respond to environmental variations in different ways. Regulators can maintain homeostasis by keeping the internal environment (temperature, osmotic concentration, etc.) constant through self-regulatory mechanisms, largely independent of external fluctuations — for example, mammals and birds are thermoregulators that maintain constant body temperature. This is in contrast to conformers, whose internal environment changes with the exter …

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7. CBSE 2023Set TERM21 markMCQ
   Q.At high altitude our body compensates for low oxygen availability by:

   (a) Increasing RBC

   (b) Decreasing binding affinity of haemoglobin

   (c) Increasing breathing rate

   (d) All the above

   ›Reveal solutionSolution

   At high altitude, the body compensates for low atmospheric oxygen through several simultaneous adaptive responses: more red blood cells, altered haemoglobin binding, and faster breathing.

   At high altitudes, atmospheric pressure (and hence available oxygen) is low, causing altitude sickness with symptoms like nausea and fatigue. The body gradually acclimatises through several physiological changes acting together: increased red blood cell production (to carry more oxygen per unit blood), an increase in breathing rate, and changes in the oxygen-binding affinity …

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8. CBSE 2022Set ANNUAL1 mark
   Q.In polar seas, seals have a thick layer of fat. Name the fat layer seen below their skin.

   ›Reveal solutionSolution

   Seals and other marine mammals of the polar seas possess a thick sub-cutaneous fat layer called blubber, which is a physiological/morphological adaptation for insulation against extreme cold.

   Organisms living in extreme, cold environments such as the polar seas show specific adaptations to cope with low temperatures, since very few organisms can tolerate such conditions. One well-known adaptation seen in aquatic mammals like seals is the presence of a thick layer of fat immediately below the skin, called blubber. This layer:

   • Acts as an effective thermal insulator, reducing heat loss from the body to the surrounding icy water/air, and helps maintain a stable internal (core) body temperature.
   • Also serves as an energy (fat) reserve and provides buoyancy while swimming. …

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9. CBSE 2022Set ANNUAL1 markMCQ
   Q.Which mammal excretes concentrated urine to conserve water?

   (a) Kangaroo rat

   (b) Camel

   (c) Squirrel

   (d) Polar bear

   ›Reveal solutionSolution

   The kangaroo rat is famously adapted to survive in the desert without drinking water, by producing highly concentrated urine.

   Desert animals show specific physiological adaptations to survive extreme water scarcity. The kangaroo rat, found in North American deserts, is a classic example — it is capable of meeting all its water requirements through internal fat/metabolic oxidation, and can concentrate its urine so much (far more concentrated than even a camel's) that it does not need to drink water at all. The camel is also well adapted to deserts (tolerating large body temperature fluctuation, producing r …

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10. CBSE 2021Set D1 markMCQ
    Q.Which one is hydrophytic plant ?

    (a) Trapa

    (b) Opuntia

    (c) Dalbergia

    (d) Acacia

    ›Reveal solutionSolution

    Trapa is an aquatic plant adapted to grow in water, so it is the hydrophyte; the answer is (A).

    Hydrophytes are plants that grow wholly or partly in water and show adaptations such as floating leaves, reduced roots and abundant air spaces (aerenchyma).

    …

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11. CBSE 2021Set ANNUAL1 markMCQ
    Q.Animals undergo inactive stage during winter. It is called

    (a) acclimatisation

    (b) hibernation

    (c) aestivation

    (d) adaptation

    ›Reveal solutionSolution

    Hibernation is winter dormancy (vs. aestivation, which is summer dormancy).

    Many animals cannot cope with extreme environmental conditions and instead escape by avoidance, entering a state of dormancy. Hibernation refers to the inactive, low-metabolism state some animals (e.g., bears, several rodents, bats) enter to pass through winter, avoiding cold stress and food scarcity. Aestivation is the analogous dormancy some animals (e.g., snails, fish like lungfish) undergo to avoid s …

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12. CBSE 2018Set ANNUAL1 mark
    Q.Define Allen's rule.

    ›Reveal solutionSolution

    Allen's rule is a morphological adaptation to climate: shorter extremities in cold climates reduce the surface area available for heat loss.

    Allen's rule is an ecological/morphological rule of adaptation which states that in warm-blooded (endothermic) species, animals living in colder regions generally have shorter, more compact ears, limbs, tails, and other protruding extremities compared to individuals of the same or related species living in warmer regions. Shorter extremities reduce the surface area-to-volume ratio, minimising heat loss to the cold surroundings and helping the animal conserve b …

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