Q.Desert plants like Opuntia are able to grow in extreme conditions. Suggest any two adaptations of this plant.
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🔒 Start your 14-day free trial to unlock the full solution →Concept understanding — Adaptations
Adaptation is the ongoing evolutionary process that fits organisms to their environment and improves their fitness, producing phenotypic traits maintained and shaped by natural selection. Adaptive traits fall into three categories. Structural adaptations are physical/bodily features, such as mammals growing thicker fur for winter or camels obtaining water from food. Behavioural adaptations are instinctive or learned actions — chiefly migration (to find resources or evade threats) and courtship (behaviours aimed at securing a mate) — with the scientific study of animal behaviour termed ethology. Physiological adaptations are internal functional adjustments, such as a lion's meat-adapted digestive system, or hibernation and aestivation, where metabolic rate slows enough that an animal can survive extended periods without eating or drinking. Aquatic and terrestri …
Desert (xerophytic) plants like Opuntia face intense heat and very limited water availability, so their leaves and stems are structurally modified to minimise water loss while still allowing photosynthesis. Two of the most characteristic adaptations are described below.
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Opuntia (a cactus) survives the desert by shrinking its leaves to spines to cut water loss, and by turning its stem into a fleshy, photosynthetic, water-storing organ.
Desert (xerophytic) plants like Opuntia show several structural and physiological adaptations that let them survive extreme heat and scarce water; two of the most important are:
- Leaves reduced to spines: Instead of broad leaves (which would lose large amounts of water through transpiration), the leaves of Opuntia are reduced to sharp spines. This drastically reduces the surface area exposed to the sun and drying air, minimising transpirational water loss, and the spines additionally protect the plant from being eaten by herbivores. …
Showing the 12 most recent of 17 on this concept.
- CBSE 2025Set ANNUAL1 markMCQQ.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 …
- CBSE 2024Set E1 markMCQQ.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). …
- CBSE 2023Set ANNUAL1 markMCQQ.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 …
- CBSE 2023Set A1 markQ.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 …
- CBSE 2023Set ANNUAL1 markQ.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 …
- CBSE 2023Set TERM21 markMCQQ.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 …
- CBSE 2023Set TERM21 markMCQQ.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 …
- CBSE 2022Set ANNUAL1 markQ.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. …
- CBSE 2022Set ANNUAL1 markMCQQ.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 …
- CBSE 2021Set D1 markMCQQ.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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- CBSE 2021Set ANNUAL1 markMCQQ.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 …
- CBSE 2018Set ANNUAL1 markQ.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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