PDF of Mind map of Chapter 13 Organisms and Populations
NCERT Solutions for Class 12 Biology Chapter 13 Organisms and Populations
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1. How is diapause different from hibernation?
Ans. Diapause is a stage of suspended growth where an organism like zooplankton temporarily stop or slow down its growth. Metabolic activities are reduced during this period. Hibernation is also known as winter sleep where an organism reduces it's physical activities and remains in a sleep like state. Hibernation is seen in bears.
2. If a marine fish is placed in a fresh water aquarium, will the fish be able to survive? Why or why not?
Ans. If we place a marine fish in freshwater or in aquarium, the fish will not be able to survive due to large change in salt concentration of water. The salt concentration in freshwater is very low in compared to the sea water.
3. Define phenotypic adaptation. Give one example.
Ans. Phenotypic adaptations refer to changes in the appearance of organisms. For example, evolution of dark winged moth in England was good for their survival after industrialisation, due to increased population.
4. Most living organisms cannot survive at temperature above 45°C. How are some microbes able to live in habitats with temperatures exceeding 100°C?
Ans. Many microbes are able to live in hot springs where temperature can exceed 100 degree Celsius because they have adopted their body according to hot environment. They also have hard cell wall which protect them and also have thermally stable Enzymes that can work at high temperatures.
5. List the attributes that populations but not individuals possess.
Ans: Some attributes that populations posses but not individual are –
(i) Natality
(ii) Mortality
(iii) Population density
(iv) Sex ratio
(v) Age Distribution
6. If a population growing exponentially doubles in size in 3 years, what is the intrinsic rate of increase (r) of the population?
Ans. This answer will be updated soon. We are trying to find some easy way to solve.
7. Name important defence mechanisms in plants against herbivory.
Ans. Since plants cannot move, they develop different types of defence mechanism against grazing animals. For example plants have thorns or spines to prevent grazing by animals. Leaf modification into spines, presence of sharp thorns and spiny leaf margins are also for defence. Similarly poisonous substances produced by plants like poisonous cardiac glycosites in calotropis is also a defence mechanism.
8. An orchid plant is growing on the branch of mango tree. How do you describe this interaction between the orchid and the mango tree?
Ans. Orchid plant growing on the branch of mango tree is a type of commensalism relation. In Commensalism interaction, one species is benefited while other is neither harmed nor benefited.
9. What is the ecological principle behind the biological control method of managing with pest insects?
Ans. Predation is the ecological principle behind the biological control method of managing with pest insects. We introduce the natural predator of the prey species to control it's population. Example - To control butterfly larvae, dragonflies are introduced.
10. Distinguish between the following:
(a) Hibernation and Aestivation
(b) Ectotherms and Endotherms
Ans. Hibernation- Hibernation is also called Winter Sleep. In hibernation, an organism reduces it's physical activities and remains in a sleep like state. Hibernation is seen in bears.
Aestivation - It is also called summer sleep. In Aestivation, the organism highly reduces it's metabolic activities and remains in sleep like state. Aestivation is seen in fish and snails.
Ectotherms - the organism which cannot maintain a constant internal body temperature are known as ectotherms. These are also known as cold blooded animals. For example fishes and reptiles are ectotherms.
Endotherms - the animals which can maintain a constant internal body temperature are known as endotherms. All birds and mammals which are also known as warm blooded animal are endotherms.
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.
Ans.
(a) Adaptation of desert plants and animals - Desert plants generally have very less number of leaves or no leaves at all. Also the leaves are very thick and have a waxy layer called cuticle. This layer prevents loss of water from transpiration. They also have sunken stomata to reduce water loss. Animals have adaptations to reduce water loss and tolerate high temperatures. For example when there is no water the Kangaroo rat complete its need of water by internal fat oxidation in which the water is released as by product. Also animals like camel can store water in their body and use it for up to 6 or 7 days. Camels also have soft legs so that they can easily walk on sand.
(b) Adaptation of plants to water scarcity - Some plants can survive in very lesser amounts of water. They are known as the xerophytic plants. These plants have a thick cuticle to prevent transpiration. These plants have sunken stomata that reduce the loss of water.
(c) Behavioural adaptations in animals - Behavioral adaptation is seen in desert lizard. When the temperature of the surrounding drops down, the desert lizard bask in the sun and absorb heat to its body. After absorbing sufficient heat when the body temperature of the lizard increases more it returns back to a shady place to cool itself.
(d) Importance of light to plant - The intensity and duration of light effects all plants. Light is required for plants to do photosynthesis and produce food. Apart from this, flowering of some plants depends on light this is known as photo-periodism.
(e) Effect of temperature and water scarcity and the adaptation of animals - the warm blooded animals can maintain a constant internal temperature of the body while the cold blooded animals change their body temperature according to the environment. For water scarcity, some animals like Kangaroo rat and camels have developed quite an impressive system to save water and they can survive for many days without water. Camels store water in their hump and Kangaroo rates can get water by internal fat oxidation in their body.
12. List the various abiotic environmental factors
Ans. Temperature, water, light and soil are some of the important factors of environment.
Temperature - Temperature is the ecologically most important factor. Temperature increases when move from pole to equator and decreases when we move from plane to mountain tops. It ranges from subzero level in polar areas and high altitudes to more than 50°C in tropical deserts in summer and exceeds 100°C in thermal springs and deep-sea hydrothermal vents.
Water - Next to temperature, water is the second most important ecological factor. Different animals are adapted to different salt concentration of water. Marine animals can tolerate high salinity while freshwater animals live in water bodies with low salt concentration.
Light - light is important for both plants and animals as it is the ultimate source of energy on earth. Plants use right to do photosynthesis and produce food. Light penetrates up to 500 m deep in ocean. After 500 m depth, ocean is dark.
Soil - Soil formation takes millions of years of time. The type of soil depends upon climate of the area, weathering process and if the soil is sedimentary or transported. Different type of soils have different water holding capacity that depends upon its composition and grain size.
13. Give an example for:
(a) An endothermic animal
(b) An ectothermic animal
(c) An organism of the benthic zone
Ans. Humans and birds are example of endothermic animals. Snake is ectothermic animal. Corals live in benthic zone.
14. Define population and community.
Ans. A number of individuals of the same species living in an area form a population. Community is used for different population living in and area.
15. Define the following terms and give one example for each:
(a) Commensalism
(b) Parasitism
(c) Camouflage
(d)Mutualism
(e) Interspecific competition
Other Questions will be available soon.
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