NCERT Solutions
Class 12 Biology
Organisms and Populations
Q.10
Write a short note on
- Adaptations of desert plants and animals
- Adaptations of plants to water scarcity
- Behavioral adaptations in animals
- Importance of light to plants
- Effect of temperature or water scarcity and the adaptations of animals
- Adaptations of desert plants and animals
Desert plants: Plants found in deserts are well adapted to cope with harsh desert conditions such as water scarcity and scorching heat. Plants have an extensive root system to tap underground water. They bear thick cuticles and sunken stomata on the surface of their leaves are entirely modified into spines and photosynthesis is carried out by green stems. Desert plants have special pathways to synthesize food called Cam. It enables the stomata to remain closed during the day to reduce the loss of water through transpiration.
Desert animals: Animals found in desert such as desert kangaroo rats, lizards, snakes, etc. are well adapted to their habitat. The kangaroo rat found in the deserts of Arizona never drinks water in its life. It has the ability to concentrate its urine to conserve water. Desert lizards and snakes bask in the sun during early morning and burrow themselves in the sand during afternoons to escape the heat of the day. These adaptations occur in desert animals to prevent the loss of water.
- Adaptations of plants to water scarcity
Plants found in deserts are well adapted to cope with water scarcity and scorching heat of the desert. Plants have extensive root system to tap underground water. They bear thick cuticles and sunken stomata on the surface of their leaves to reduce transpiration.
In cactus, leaves are modified to spines and process of photosynthesis is carried out by green stems. Desert plants have CAM pathway to synthesize food. It enables their stomata to remain closed during the day to reduce water loss by transpiration.
- Behavioral adaptation in animals
Certain animals are affected by temperature variations. These organisms undergo adaptations such as hibernation, aestivation, migration, etc. to escape environmental stress to suit their natural habitat. For example: Ectothermal animals are cold blooded animals such as fish, amphibians, etc., their temperature varies with their surroundings.
Desert lizards bask in sun during early hours when the temperature is quite low. As temperature rises, the lizard burrows itself inside the sad to escape the scorching sun. Endotherms such as birds and mammals escape cold and hot weather conditions by hibernating during winters and aestivating during summers. They hide themselves in shelters such as caves, burrow to protect against temperature variations.
- Importance of light to plants
Sunlight acts as the ultimate source of energy for plants. Plants are autotrophic organisms which need light for carrying out the process of photosynthesis. Light also plants an important role in generating photoperiodic response occurring in plants. Plants respond to changes in intensity of light during various seasons to meet their photoperiodic requirements for flowering. Light also plays an important role in aquatic habitats for vertical distribution of plants in the sea.
- Effects of temperature or water scarcity and the adaptations of animals
Temperature is the most important ecological factor. Average temperature on the Earth varies from one place to another. These variations in temperature affect the distribution of animals on the Earth. Animals that can tolerate a wide range of temperature are called eurythermals. Those which can tolerate a narrow range of temperature are called stenothermal animals. Animals also undergo adaptations to suit their natural habitats. For example: animals found in colder areas have shorter ears and limbs that prevent the loss of heat from their body. Animals found in polar region have thick layers of fat below their skin and thick coats of fur to prevent the loss of heat.