All Free Biology MCQs with Answers

2281. What is hibernation and aestivation________?

• A. Thermal adaptation shown by animals
• B. wind adaptation shown by animals
• C. adaptation of animals to escape from predators
• D. none of the above

Explanation: Hibernation and aestivation are thermal adaptations in which animals reduce activity and metabolism during very cold or very hot conditions, respectively. Students may choose c because these states can also reduce exposure to danger, but escaping predators is not their defining function.

2282. Bats & humming birds belong to___________?

• A. Endotherms
• B. Ectotherms
• C. Heterotherms
• D. Homeotherms

Explanation: Bats and hummingbirds are heterotherms because their body temperature and metabolic rate can vary, especially during torpor or periods of inactivity, rather than remaining constant at all times. They are endothermic in heat production, but choosing endotherms overlooks the more specific classification based on variable body temperature.

2283. Normal body temperature in mamals like human beings is____________?

• A. 26 - 28°C
• B. 36 - 38°C
• C. 46 - 48°C
• D. 56 - 58°C

Explanation: Human enzymes and cells function best near 37°C, so normal mammalian body temperature is approximately 36 to 38°C. A common mistake is choosing 26 to 28°C, which is far below the temperature maintained by mammalian homeostasis.

2284. Which of the following statement about Homeostasis is incorrect?

• A. There is a definite control system that regulates the homeostatic activities
• B. Homeostatic mechanisms keep the internal environment fixed despite of wide changes in external environment
• C. Because of this the fluctuations of internal environment are of extremely narrow range as compared to that of external environment
• D. All are correct

Explanation: Homeostasis does not keep the internal environment completely fixed; it maintains variables within a narrow range despite external changes. Therefore statement b is incorrect, while students may choose d by overlooking the word fixed and treating all three statements as accurate.

2285. Which adaptation is acquired by plants of cooler areas to prevent lipid crystal formation in cell membrane?

• A. Change in membrane protein composition.
• B. Change in the solute composition of the cell membrane which prevents crystallization.
• C. Increase in proportion of unsaturated fatty acids.
• D. Development of heat shock proteins.

Explanation: Increasing unsaturated fatty acids keeps membrane lipids fluid at low temperatures because their bends prevent tight packing and crystal formation. Students may choose a because membrane proteins can also change during adaptation, but protein composition does not directly prevent lipid crystallization.

2286. In a hot summer after noon, if your body's Homeostatic machinery keep your internal temperature quite lower than that of external than this is an example of____________?

• A. Positive feed back
• B. Negative feed back
• C. Feed back
• D. Osmoregulation

Explanation: Negative feedback opposes a change: when body temperature rises, mechanisms such as sweating and vasodilation lower it toward the normal set point. Students may choose positive feedback because the response follows a temperature change, but positive feedback amplifies the original change rather than correcting it.

2287. Thermostat of human body is present in__________?

• A. Fore brain
• B. Hind Brain
• C. Thalamus
• D. Hypothalamus

Explanation: The hypothalamus contains the body's temperature-regulating centre and compares blood temperature with a set point to coordinate heat-loss and heat-gain responses. Students may choose the thalamus because both names refer to brain regions, but the thalamus mainly relays sensory information and is not the thermostat.

2288. Production of pyrogens is a __________ phenomenon?

• A. Protective
• B. Destructive
• C. Constructive
• D. Aggressive

Explanation: Pyrogens raise the hypothalamic temperature set point and trigger fever, which can hinder the growth or replication of some pathogens and support immune activity. Students may choose destructive because fever can become harmful if excessive, but the production of pyrogens is initially a protective response.

2289. Blubber a thick layer of fat is present in___________?

• A. Fresh water mammals
• B. Terrestrial mammals
• C. Marine Mammals
• D. Flying mammals

Explanation: Marine mammals such as whales and seals possess blubber, a thick fat layer that reduces heat loss in cold water and also provides energy storage. Students may choose terrestrial mammals because some land mammals have substantial body fat, but blubber is the characteristic insulating layer of marine mammals.

2290. Fishes, most of the invertebrates and amphibians are examples of ________ animals?

• A. Endotherms
• B. Ectotherms
• C. Heterotherms
• D. Homeotherms

Explanation: Ectotherms depend largely on environmental heat to regulate their body temperature, so fishes, most invertebrates and amphibians are ectothermic animals. Endotherms generate substantial internal heat, as mammals and birds do. Homeotherms are animals that maintain a relatively constant body temperature, not the group described here.