Ncert Solutions For Class 12 Biology Chapter 13

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Ncert Solutions For Class 12 Biology Chapter 13 Pdf Download

Adda 247 provides NCERT Solutions for Class 12 Biology chapter 13 NCERT solutions which is for the students who want to go ahead in life and achieve great marks in their examinations. The NCERT Solutions for class 12 are provided by the teachers who are experts of their subjects. The solutions are set according to the rules formulated by the NCERT class 12 biology and in the language that can be understood by every student. By these reading the solutions students can build up a strong base easily. The NCERT class 12 Biology solutions covers the chapters 1 to 16 with the important questions and the answers in a detailed way.

Examinations can be threatening for some people, a proper learning of the concepts is the key to crack the examination. Students rely on the solutions of the NCERT provided by Adda 247. The solutions are formulated by the experts of the subjects who have tremendous knowledge in their subjects.

These NCERT Solutions of class 12 chapter 13 help the students to get familiarized with the textbooks. The students can access the solutions anywhere while browsing the web easily. The solutions are very precise and accurate.

NCERT Solutions for Class 12 Biology Chapter 13– Organisms and Populations

The chapter provides information about Organisms and populations. Ecology is the study of the interactions among organisms and between the organism and its physical (abiotic) environment. Ecology deals with four levels of biological organization –Organism- a living entity which can function on its own. Populations- sum of all living organisms of the same species living in a particular geographical area. Communities- a group of people living together in one place. Biomes- a large geographical area of various plants and animals.

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Features of the NCERT Solutions for Class 12 Biology Chapter 13– Organisms and Populations

NCERT Solutions for class 12 biology chapter 13 have been answered based on the important information on the question.

The columns are used wherever necessary.
Solutions are solved point wise and accurately answered point to point.

Important Questions of Ncert Solutions for Class 12 Biology Chapter 13: Organisms and Populations

Question 1. How is diapause different from hibernation?

Answer: Diapause is a condition of suspended development exhibited by species of zooplankton and insects. This is done so that they can pass over the unfavorable conditions which are present during their development.

Whereas hibernation also known as winter sleep is a resting stage shown by bats, squirrels and rodents. This is done to escape the winter season by slowing down their metabolism. Therefore they enter a stage of inactivity by hiding them in shelters.

Question 2. If a marine fish is placed in a fresh water aquarium, will the fish be able to survive? Why or why not?

Answer: Marine water fishes will not be able to survive in fresh water because marine water fishes are adapted to live in salt water conditions. If they are shifted to freshwater, the process of osmoregulation in them will be affected. Due to the internal high salt condition in fish, the freshwater will come inside the body of fish causing fishes to swell up, ultimately bursting.

Question 3. Most living organisms cannot survive at temperature above 45 degree C. How are some microbes able to live in habitats with temperatures exceeding 100 degree C?

Answer: Most living organisms cannot survive at temperature above 45°C because very high temperature causes denaturation of their enzymes. But certain bacteria, cyanobacteria, shelled protozoans, etc. are known to survive even in thermal springs. Tolerance power to the extremes of temperature varies from species to species e.g. Certain bacteria and cyanobacteria have thermal-resistant enzymes and peculiar cell wall.

Question 4. List the attributes that populations possess but not individuals.

Answer: A population can be defined as a group of individuals of the same species residing in a particular geographical area at a particular time and functioning as a unit. For example, all human beings living at a particular place at a particular time constitute the population of humans.

The main attributes or characteristics of a population residing in a given area are:-

(a) Birth rate (Natality): It is the ratio of live births in an area to the population of an area. It is expressed as the number of individuals added to the population with respect to the members of the population.

(b) Death rate (Mortality): It is the ratio of deaths in an area to the population of an area. It is expressed as the loss of individuals with respect to the members of the population.

(d) Age Distribution: It is the percentage of individuals of different ages in a given population. At any given time, the population is composed of individuals that are present in various age groups. The age distribution pattern is commonly represented through age pyramids.

(e) Population density: It is defined as the number of individuals of a population present per unit area at a given time.

Question 5. If a population growing exponentially double in size in 3 years, what is the intrinsic rate of increase (r) of the population?

Answer: A population grows exponentially if enough food resources are available to the individual.

Exponential growth equation:

Nt= No ert

Where,

Nt= Population density after time t

Nt= Population density at time zero

r = Intrinsic rate of natural increase

e = Base of natural logarithms (2.71828)

From the above equation, we can calculate the intrinsic rate of increase (r) of a population.

Now, as per the question,

Present population density = x

Then,

Population density after two years = 2x

t = 3 years

Substituting these values in the formula, we get:

⇒ 2x = x e3r

⇒ 2 = e3r

Applying log on both sides:

⇒ log 2 = 3r log e

Hence, the intrinsic rate of increase for the above-illustrated population is 0.2311.

Question 6. Name important defence mechanisms in plants against herbivory.

Answer: Several plants have evolved various mechanisms both morphological and chemical to protect themselves against herbivory.

Morphological defence mechanisms:

Cactus leaves (Opuntia) are modified into sharp spines (thorns) to deter herbivores from feeding on them. Sharp thorns along with leaves are present in Acacia to deter herbivores. In some plants, the margins of their leaves are spiny or have sharp edges that prevent herbivores from feeding on them.

Chemical defence mechanisms:

All parts of Calotropis weeds contain toxic cardiac glycosides, which can prove to be fatal if ingested by herbivores. Chemical substances such as nicotine, caffeine, quinine, and opium are produced in plants as a part of self-defence.

Question 7. An orchid plant is growing on the branch of mango tree. How do you describe this interaction between the orchid and the mango tree?

Answer: The interaction presents between the orchid and the mango tree is an example of commensalism as one species is benefited and other remains unaffected. An orchid plant that is growing on the branch of a mango tree is considered as an epiphyte. So, Epiphytes are the plants which grows on other plants but do not derive nutrition from them. In the given case the orchid is considered

as an epiphyte as it gets support and the mango tree remains unaffected.

Question 8. What is the ecological principle behind the biological control method of managing with pest insects?

Answer: The principle behind using of various biological control methods is the use of predator to control the growth of pest. Predation can be termed as a biological interaction between the two species in which one organism feed on other. The organism that feed on other is termed as predator and the other one is termed as prey. The predators help in regulating the population of preys in a given habitat and helps in the management of pest insects thus preventing the crop from getting damaged. This ecological principle is used in integrated pest management where instead of chemical pesticides, the population of the insect in a farm is controlled by its ecological enemy. This will also not let the insect species to increase to a level where it can damage the crop or decrease to a level where it may disturb the ecological balance.

Question 9. Distinguish between the following:

(a) Hibernation and Aestivation

(b) Ectotherms and Endotherms

Answer: (a) Hibernation and Aestivation

Hibernation	Aestivation
Hibernation is a state of reduced activity in some organisms to escape cold winter conditions.	Aestivation is a state of reduced activity in some organisms to escape desiccation due to heat in summers.
Bears and squirrels inhabiting cold regions are examples of animals that hibernate during winters.	Fishes and snails are examples of organisms aestivating during summers.

(b) Ectotherms and Endotherms

Ectotherms	Endotherms
Ectotherms are cold blooded animals. Their temperature varies with their surroundings.	Endotherms are warm blooded animals. They maintain a constant body temperature.
Fishes, amphibians, and reptiles are ectothermal animals.	Birds and mammals are endothermal animals.

Question 10. Write a short note on

(a) Adaptations of desert plants and animals

(b) Adaptations of plants to water scarcity

(c) Behavioral adaptations in animals

(d) Importance of light to plants

(e) Effect of temperature or water scarcity and the adaptations of animals.

Answer:

(a)Adaptations of desert plants and animals:

(i) Adaptations of desert plants:

Plants found in deserts are well adapted to overcome the harsh desert conditions such as water scarcity and scorching heat.to tap underground water, plants have an extensive root system. They bear thick cuticles and sunken stomata on the surface of their leaves to reduce transpiration. In Opuntia, the leaves are entirely modified into spines and photosynthesis is carried out by green stems. An special pathway that is C4 pathway is found to synthesize food. It enables the stomata to remain closed during the day to reduce the loss of water through transpiration.

(ii) Adaptations of desert animals:

Adaptations of desert animals are done for the same purpose as adaptation in desert plnts. It is done to conserve the water. For example Animals found in deserts 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.

(b) 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 an extensive root system to tap underground water. They bear thick cuticles and sunken stomata on the surface of their leaves to reduce transpiration. In Opuntia,the leaves are modified into spines and the process of photosynthesis is carried out by green stems. 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

Various organisms are affected by various environmental conditions. To overcome the situation, organisms undergo adaptations such as migration, hibernation, aestivation, etc. These adaptations in the behaviour of an organism are called behavioural adaptations. For example, ectothermal animals and certain endotherms exhibit behavioral adaptations. Ectotherms are cold blooded animals such as fish, amphibians, reptiles, etc. Their temperature varies with their surroundings. For example, the desert lizard basks in the sun during early hours when the temperature is quite low. However, as the temperature begins to rise, the lizard burrows itself inside the sand to escape the scorching sun. Similar burrowing strategies are exhibited by other desert animals.

(d) Importance of light to plants:

The ultimate source of energy for plants is sunlight. Plants are autotrophic organisms, which need light for carrying out the process of photosynthesis. Plants need the sun because sunlight is made up of electromagnetic radiation which is given off as energy as the sun burns through its stores of hydrogen many millions of miles away from Earth. The electromagnetic radiation that plants receive from the sunlight that reaches Earth and penetrates its atmosphere is the key ingredient in a process that is called photosynthesis. Photosynthesis is important because it is the way in which plants derive their energy.

(e) Effects of temperature or water scarcity and the adaptations of animals:

The most important ecological factor is temperature. From one place to another the average temperature is varies. These variations in temperature affect the distribution of animals on the Earth. Animals which can tolerate a narrow range of temperature are called stenothermal animals. 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 environmental 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

Water scarcity is another factor that forces animals to undergo certain adaptations to suit their natural habitat. Adaptations of desert animals are done for the same purpose as adaptation in desert plnts. It is done to conserve the water. For example Animals found in deserts 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.

Frequently Asked Questions on NCERT Solutions for Class 12 Biology Chapter 13

What are the advantages of referring NCERT Solutions for class 12 Biology chapter 13?

Students referring the ncert solutions for class 12 biology chapter 13 pdf download by Adda 247 find the solutions helpful during the exams. The solutions are prepared by the experts in an interactive manner keeping in mind the students. The students’ perspective is kept in mind while preparing the solutions. It helps in completing the syllabus on time and also provides notes for the revision prior to the exam.

What are the advantages of referring NCERT in competitive exams like JEE and AIPMT?

Most of the competitive exams like NEET, JEE etc. follow the basic NCERT books for designing their question papers. NCERT serves as the base for every book prepared for NEET and JEE. The competitive exams are based on the CBSE syllabus applied in XI and XII classes and NCERT books strictly follow CBSE syllabus. In addition to this, NCERT books play an important role in clearing out the theoretical concepts. Every topic given in NCERT books is explained in such a way to help students make their basics and fundamentals strong and clear.

How To Use NCERT Solutions For Class 13 Biology?

i) Study the chapter topic wise and understand the various concepts.
ii) First, try to solve the questions by yourself and then look at the solutions.
iii) Use them as a reference guide while revising the chapter
iv) If you get stuck at any question, you can check the step by step solution from the PDF from ncert solutions for class 12 biology chapter 13 pdf download by Adda 247.

Is it mandatory to solve all the NCERT questions mentioned at the end of each chapter?

The questions and answers mentioned in NCERT textbooks at the end of each chapter are quite important not only for examination but also for understanding the concepts in a better way. These questions aim to test the students’ understanding and learning over the topics that they have learned in the chapter.

Solving the NCERT exercise problems will help to

clear all the concepts and formulae you learned in a chapter
get comfortable with different types of questions that might be asked in exams
get enough practice which is key to succeed in Mathematics exam
improve your accuracy and speed

What are the important concepts covered in the Chapter 13 of NCERT Solutions for Class 12 Biology?

The concepts involved in the chapter 13 of NCERT Solutions are –

13.1 – Organisms and its environment

13.2 – Major abiotic factors

13.3 – Responses to abiotic factors

13.4 – Adaptations

13.5 – Populations

13.6 – Population attributes

13.7 – Population growth

13.8 – Life history variation

13.9 – Population interactions

These concepts are created by the faculty at Adda 247. The solutions are available at Adda 247 in the PDF format which can be downloaded by the students.