(a) Adaptations of desert plants and animals:
(i) Adaptations of desert plants:
Many desert plants have been well adapted to cope with harsh conditions in the desert, including water adequate and hot. Plants have an extensive root system to tap underground water. There are thick cuticles and sunken stomata on the surface of their leaves to reduce transpiration. Opuntia is a species of plant that has spines entirely as parts of its leaves, Photosynthesis is carried out by green stems. Plants in the desert have special pathways. It is the CAM (C4 pathway) pathway that synthesizes food. To reduce water loss through transpiration, the stomata can remain closed during the day.
(ii) Adaptations of desert animals:
Desert animals such as desert kangaroo rats, lizards, snakes, etc. are well adapted to their habitat. In Arizona, kangaroo rats do not drink water. In order to conserve water, it is capable of concentrating its urine. Desert lizards and snakes bask in the sun throughout the early morning and burrow themselves in the sand during afternoons to escape the heat of the day. Desert animals have developed these adaptations to stop the loss of water.
(b) Adaptations of plants to water scarcity:
Due to water scarcity and heat, desert plants are well adapted to survive in deserts. To obtain water from underground, plants have extensive root systems. They bear thick cuticles and sunken stomata on the surface of their leaves to reduce transpiration. In Opuntia, the leaves form spines, while the green stems are responsible for photosynthesis. Desert plants have special pathways to synthesize food, called CAM (C4 pathway). It enables their stomata to remain closed during the day to reduce water loss by transpiration.
(c) Behavioural adaptations in animals:
There are some organisms that are affected by temperature changes. To cope with environmental stress, these organisms undergo adaptations such as hibernation, aestivation, migration, etc. These adaptations in behavior of an organism are referred to as behavioral adaptations. Some ectothermic animals and certain endotherms exhibit behavioral adaptations. Ectotherms are cold blooded animals such as fish, amphibians, reptiles, etc. Depending on their environment, they have different body temperatures. During the early hours of the day when the temperatures are quite low, desert lizards bask in the sun. As the temperature rises, the lizard burrows into the sand to avoid the scorching sun. Similar burrowing strategies are exhibited by other desert animals. Certain endotherms (warm-blooded animals) such as birds and mammals escape cold and hot weather conditions by hibernating during winters and aestivating during summers. They hide themselves in shelters like caves, burrows, etc. to protect against temperature variations.
(d) 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 plays an important role in generating photoperiodic responses occurring in plants. Plants respond to changes in intensity of light during various seasons to fulfil their photoperiodic 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.
(e) Effects of temperature or water scarcity and the adaptations of animals. Temperature is the most vital 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 temperatures can be referred to as 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. Also, animals found in Polar regions have thick layers of fat below their skin and thick coats of fur to prevent the loss of heat. Some organisms exhibit various behavioural changes to suit their natural habitat. These adaptations present in the behaviour of an organism to escape environment stresses are called behavioural adaptations. For example, desert lizards are ectotherms. This means that they do not have a temperature: regulatory mechanism to escape temperature variations. These lizards bask in the sun during early hours when the temperature is quite low. As the temperature begins to increase, the lizard burrows itself inside the sand to escape the scorching sun. Similar burrowing strategy is seen in other desert animals. Water deficiency is another factor that forces animals to undergo certain adaptations to suit their natural habitat. Animals found in deserts such as desert kangaroo rats, lizards, snakes, etc. are well adapted to stay in 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 in the sand as the temperature rises to escape the heat of the day. Such adaptations can be used to stop the loss of water.