Question 11: Write a short note on (a) Adaptations of desert plants and animals (b) Adaptations of plants to water scarcity (c) Behavioural adaptations in animals (d) Importance of light to plants (e) Effect of temperature or water scarcity and the adaptations of animals.
Class 12 - Biology - Organisms and Populations Page 240
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Answer:
(a) Adaptations of desert animals: ... Plants found in deserts are well adapted to cope with water scarcity and scorching heat of the desert. Plants have an extensive root system to tap underground water. They bear thick cuticles and sunken stomata on the surface of their leaves to reduce transpiration.
(b)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 to reduce transpiration.
(c) There are various behavioural adaptation in animals are migration ,hibernation and aestivation. Certain animals change their feeding and foraging time and pattern. some animals like lizard (ectotherms) bask in the sun to absorbs heat and moving to shade when the ambient temperature increases.
(d) Sunlight acts as the ultimate source of energy for plants. Plants are autotrophic organisms, which need light for carrying out the process of photosynthesis. ... Plants respond to changes in intensity of light during various seasons to meet their photoperiodic requirements for flowering.
(e) Effect of temperature or water scarcity on adaptations of animals In conditions of high temperature or water scarcity, the adaptations will be such that help the animals to (i) reduce water loss from the body in breathing and excretion. (ii) utilise water generated internally through metabolic activity.
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a) Adaptations of desert plants and animals-
1. In the desert, the plants are succulent and store water in fleshy leaves, stems or roots. The root system is highly developed for water absorption. In these pants the stem also performs photosynthesis. They have a thick cuticle on stems and leaves which protect from excessive transpiration. Desert plants follow the CAM pathway to prevent excessive water loss.
2. In the desert, animals show various adaptations. Reptiles such as snakes come in the open only at dawn or dusk. Some small desert animals live in burrows to escape the heat. Animals such as camels store fat in their hump. this helps them survive for a long time without food and water.
b) Adaptations of plants to water scarcity
Xerophytic plants are the plants that can survive water scarcity. They have the following adaptations. A thick cuticle on stems and leaves which protect from excessive transpiration. These plants show the presence of sunken stomata which reduce the loss of water. There are certain thick walled cells of hypodermis which do not allow the passage of water and prevents water loss. The leaves are reduced in size and may be modified to form the spines that reduce the surface area for transpiration. The root system is highly developed for water absorption. In these pants the stem also performs photosynthesis.
c) Behavioral adaptations in animals
Animals show various behavioral adaptations depending on the region.
Animals can be endotherms or ectotherms.
The animals that maintain a constant body temperature independent of the environment are called warm-blooded animals or endotherms. The animals that cannot maintain a constant body temperature and change it in accordance with the external environment are said to be cold blooded or ectotherms.
Aestivation and hibernation are also behavioral adaptations. The state of dormancy in some animals during winter is called hibernation. In these animals, the heart rate, metabolic rate and breathing rate is decreased. Aestivation is a response towards high temperature. It is characterized by inactivity and a lowered metabolic rate due to lack of potential to tolerate the heat.
d) Importance of light to plants
Photosynthesis is the process in which autotrophs such as green plants use carbon dioxide and water in presence of sunlight to synthesize nutrients such carbohydrates in the form of glucose and release oxygen. Also, flowering of plants is influenced by photoperiodism.
e) Effect of temperature or water scarcity and the adaptations of animals
1. Animals living in different regions show different kinds of temperature adaptations.
Animals found in colder regions have a large amount of subcutaneous fat and thick fur coat, short ears and limbs to prevent heat loss fro their body.
Animals found in the desert also show various adaptations. Camels store fat in their hump. This helps them survive for a long time without food and water. Reptiles such as snakes come in the open only at dawn or dusk. Some small desert animals live in burrows to escape the heat.
2. Animals that live in the desert have to face water scarcity and high temperatures. Animals such as camels store fat in their hump. This helps them survive for a long time without food and water. Animals such as the Kangaroo rat never drinks water in its entire life.