This set of Class 12 Biology Chapter 13 Multiple Choice Questions & Answers (MCQs) focuses on “Organisms and Populations – Adaptations – 1”.
1. What is an attribute of the organism that enables the organism to survive and reproduce in its habitat called?
Explanation: Any attribute of the organism that enables the organism to survive and reproduce in its habitat called adaptation. It is an evolutionary process that takes place from generation to generation. It involves a character or feature or trait that helps an organism in a given habitat.
2. At what height does a person experience altitude sickness?
a) >3500 m
b) <3500 m
c) >500 feet
d) <500 feet
Explanation: A person experiences altitude sickness >3500 m or >8,000 feet. It is also known as mountain sickness. It occurs due to a decrease in pressure around a person due to which there is a decrease in oxygen level.
3. Which of the following is a symptom of altitude sickness?
b) Heart palpitations
Explanation: Among the above-given options heart palpitation is a symptom of altitude sickness. It occurs due to a decrease in pressure around a person due to which there is a decrease in oxygen level. Some other symptoms are nausea, fatigue, etc.
4. By what mechanism does the body compensate for low oxygen availability in altitude sickness?
a) Increasing the binding affinity of hemoglobin
b) Decreasing breathing rate
c) Decreasing the binding affinity of hemoglobin
d) Increasing red blood cell formation
Explanation: The body compensates for low oxygen availability in altitude sickness by increasing red blood cell formation that will increase the uptake of oxygen. A person experiences altitude sickness >3500 m or >8,000 feet.
5. Which one among the following statements is incorrect?
a) Siberian crane is a migratory bird
b) Archaebacteria flourishes in hot springs where the temperature exceeds >95°C
c) Desert lizard has the ability to keep the constant body temperature
d) Fishes can thrive in Antarctic water where the temperature is always below zero
Explanation: Among the above-given sentences, the desert lizard has the ability to keep a constant body temperature is an incorrect statement. This is so because lizards are ectotherms, cold-blooded whose temperature changes as per the temperature of surroundings.
6. What are the plants living in the desert called?
Explanation: Sciophytes are photophobous, shade-loving plants and are found in deserts. They have thinner leaves, large photosynthetic units, and lens-shaped epidermal cells. They also have high chlorophyll content per unit leaf volume.
7. In which plants do stomata open at night?
Explanation: The stomata open during the night in succulents. These plants show an inverted stomatal rhythm as compared to normal plants. The succulents are usually seen in desert areas. To reduce transpiration these plants secrete waxes or resins.
8. Which is the adaptive radiation is used by poikilotherms to protect against extreme heat?
Explanation: The poikilotherms use aestivation as a protective mechanism against extreme heat. The suspension of metabolic activities during summer is called aestivation. It helps in maintaining body temperature and avoids water loss in mostly cold-blooded animals such as snails, bees, tortoise, crocodile, etc.
9. In which region do succulents grow?
Explanation: The succulents are usually seen in desert areas. These are thick, fleshy and retain water in arid conditions. They are drought resistant, follow Crassulacean acid metabolism (CAM) pathway and store water in leaves and stems.
10. In which plants do sunken stomata is seen?
a) Temperate plants
d) Tropical plants
Explanation: Sunken stomata are a feature of xerophytes. It is an adaptation made by desert or icy area plants to avoid water loss. Some examples of xerophytes are some Gymnosperm plants, cacti, pineapple, etc.
11. Through which part does photosynthesis occur in xerophytes?
a) Scaly leaves
b) Modified stems
Explanation: In xerophytes, there is an adaption in which photosynthesis occurs with the help of modified stems to avoid water loss. Roots of xerophytes help in the storage of water. Scaly leaves do not help much in photosynthesis.
12. Which of the following animal excretes solid urine?
c) Kangaroo rat
Explanation: Solid urine is excreted by kangaroo rat to avoid excess loss of water. They are rodents and their kidneys have developed mechanisms to highly concentrate their urine. They have longer papilla in their kidneys.
13. In which plants mechanical tissue is best developed?
Explanation: The mechanical tissue that is collenchyma is best developed in xerophytes. These are enclosed within rigid channels to avoid water loss. Along with this bark of xerophytes is also well developed to retain water.
14. What are plants adapted to grow in the sand called?
Explanation: The plants adapted to live in the sand are called psammophytes. They have an adventitious root system. They are also found along seas, sands along rivers and large lakes where sand is available.
15. Where are stomata present in submerged hydrophytes?
b) On lower surface
c) In the corners
d) On the upper surface
Explanation: In submerged hydrophytes stomata are absent. These are true water plants in which plant cells are used to absorb nutrients, water, and dissolved gases in water. Some examples of submerged hydrophytes are Hydrilla, Potamogeton, Utricularia, etc.
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