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NCERT Solutions for Class 12 Biology Chapter 13 Organisms and Populations: Ecology is the study of the relationships of living organisms with the abiotic (physicochemical factors) and biotic (other species) factors of their environment. Through evolutionary changes, natural selection takes place at the population level, and hence, population ecology is an important area of ecology.Such facts are explained in the solutions for NCERT Class 12 Biology Solutions Chapter 3. You will also learn about natural selection in this chapter. Some questions from Organisms and Populations Class 12 Solutions are expected in the exam as well, for which there are all the answers. The NCERT Solutions for Class 12 contain solutions provided by subject matter experts, and students can use these solutions to prepare for their board exams. Scroll down to go through the questions and answers given in NCERT Solutions for Class 12 Biology Chapter 13.
In Organisms and Populations Class 12, you will study the fact that populations have attributes that individual organisms do not: birth rates and death rates, sex ratios, and age distribution. You will also find questions related to these topics in . Class 12 Biology Chapter 13 is curated according to the latest CBSE Syllabus for 2023-24. These Class 12 Biology NCERT Solutions will help students score well in the exams. Organisms and Populations Class 12 NCERT Solutions provide explanations in detail with related and representative examples.
Chapter 13 Biology Class 12 are beneficial to enhance the conceptual knowledge of students. Organisms and Populations Class 12 will also help you understand the concepts and topics for the competitive exams. If you are looking for the questions and answers from classes 6–12, then NCERT solutions are there for you, as it's the easiest way to get all the solutions. As well as Chapter 13 Biology Class 12 NCERT Solutions PDF, it can be downloaded.
According to the latest CBSE Syllabus 2023-24, this chapter has been renumbered as Chapter 11.
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NCERT Exemplar for Class 12 Biology Chapter 13 Organisms and Populations
After going through the Organism and Population Class 12 NCERT Solution line by line, you can understand the answer to all questions easily and these are given below:
Organism and Population Exercise:
Q 1. How is diapause different from hibernation?
Answer:
Many insects and other invertebrates go through a period of suspended growth or development known as diapause, during which their metabolic activities are drastically reduced. On the other hand, hibernation is a sleep-like state that some animals, like fish and amphibians, use to get through the winter months in order to survive the cold and lack of food.
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.
Answer:
Some microbes can survive in temperatures as high as because these microbes are adapted to live at high temperatures. These organisms contain enzymes which can work at high temperature. This is why they can be found at thermal vents, hot springs etc. The organisms which are unable to survive high temperatures have enzymes that gats deactivated at high temperatures.
Organisms and Populations Class 12 Solutions:
Q4. List the attributes that populations possess but not individuals possess.
Answer:
The term population refers to a group of individuals of any species living in a well-defined geographical area, sharing or competing for similar kind of resources and potentially interbreed.
Population Attributes: A population has certain attributes that an individual organism does not have. For example, individuals may have births and deaths, but a population has birth rates and death rates. The various population attributes are as follows:
1. 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.
2. Death rate(mortality)- It refers to the live deaths in an area to the population of an area. It is expressed as the number of individuals removes from the population.
3. Sex ratio- It is the ratio of the number of male or female individuals per 1000 individuals.
4. Age distribution- A population at a given time is composed of different individuals belonging to different age groups. If the age distribution is plotted for the population, the resulting structure is called age pyramids. The shape of pyramids reflects the growth status of the population.
5. Population density- The number of individuals of a population present per unit area at a given time.
Organisms and Populations Class 12 NCERT Solutions:
Answer:
Thus, if a population growing exponentially double in size in 3 years, the intrinsic rate of increase (r) of the population will be 0.264.
Organism and Population Class 12 NCERT Solution:
Q6. Name important defence mechanisms in plants against herbivory.
Answer:
The defence mechanisms in plants against herbivory are as follows:
1. Presence of thorns, spines, prickles and bristles
2. Stinging hirs
3. Hairy coating
4. Harbouring ants e.g. Acacia
5. Sticky glandular hairs e.g. Gnaphalium
6. Chemicals like latex, alkaloids and tannins having a bitter taste, offensive smell, silica and poisonous cardiac glycosides which herbivore animals do not like.
Answer:
An orchid that grows on mango tree represents an interaction called commensalism. In this type of interaction, one species is benefitted while another one remains unaffected. Orchid acts as an epiphyte on the mango tree as it does not derive nutrition from it but uses it for support while mango tree remains unaffected.
Chapter 13 Biology Class 12 NCERT Solutions:
Q8. What is the ecological principle behind the biological control method of managing with pest insects?
Answer:
The biological principle involved in the biological control method of managing pest insects is checking their population through predators and parasites. The predators act as biological control by preying upon insect pests.
Q9. Distinguish between the following: (a) Hibernation and Aestivation
Answer:
The differences between hibernation and aestivation are as follows :
Hibernation | Aestivation |
A state of reduction in activity in some organisms to escape winters | A state of reduction in activity in some organisms to escape extreme summers |
E.g. Bears and squirrels | E.g. Fishes and snails |
Q9. (b) Ectotherms and Endotherm
Answer:
The differentiation between ectotherms and endotherms is as follows:
Ectotherms | Endotherms |
These are cold-blooded animals | These are warm-blooded animals |
The change according to the variation in the environment | They maintain a constant internal environment despite the changing environment |
(a) Adaptations of desert plants and animal
Answer:
Plants found in deserts are well adapted to overcome the harsh desert conditions such as water scarcity and scorching heat. Adaptations of desert plants include
1. To reach to underground water, plants have an extensive root system.
2. They bear thick cuticles and sunken stomata on the surface of their leaves to reduce transpiration.
3. In Opuntia, the leaves are entirely modified into spines and photosynthesis is carried out by green stems.
4. A 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.
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
Answer:
Plants found in desserts are well adapted to cope with water scarcity and scorching heat of the desert. Some of these adaptations are as follows:
1. Plants have an extensive root system to tap underground water.
2. They bear thick cuticles and sunken stomata on the surface of their leaves to reduce transpiration.
3. In Opuntia, the leaves are modified into spines and the process of photosynthesis is carried out by green stems.
4. 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.
Class 12 Biology Chapter 13 NCERT Solutions:
(c) Behavioural adaptations in animals
Answer:
Various organisms are affected by various environmental conditions. To overcome these environmental conditions, organisms undergo adaptations such as migration, hibernation, aestivation, etc. The adaptations in the behaviour of an organism are called behavioural adaptations. For example, ectothermic animals and certain endotherms exhibit behavioural 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 plant
Answer:
The ultimate source of energy for plants is sunlight. Plants are autotrophic organisms, which need light in order to perform the process of photosynthesis. Plants need the sun because sunlight is made up of electromagnetic radiations which are given off as energy to the plants. These electromagnetic radiation acts as the key factor in a process that is called photosynthesis. The photons of light energy are received by the chlorophyll molecules and they give off energy in the form of electrons. These electrons are than through a cyclic as well as non-cyclic flow are converted into chemical energy i.e. ATP and NADPH in the process of photosynthesis by which organic substances are formed in plants. Thus, light is a very important factor for plants and for the survival of all the components of Earth.
Class 12 Organisms and Populations NCERT Solutions:
(e) Effect of temperature or water scarcity and the adaptations of animals
Answer:
Effects of temperature or water scarcity and the adaptations of animals: Temperature is considered to be the most important ecological factor. The average temperature varies from one place to another and these variations in temperature affect the distribution of plants as well as animals on the Earth. There are animals which cannot tolerate a wide range of temperature and these animals are called stenothermal animals. The animals which can tolerate a wide range of temperature are called eurythermal animals. Some animals also undergo adaptations to suit their natural habitats. For example, the animals found in colder areas have shorter ears and limbs in order to prevent the loss of heat from their bodies. Similarly, animals like polar bears have thick layers of fat below their skin and thick coats of fur to prevent the loss of heat in polar regions. Some animals show adaptations like hibernation and aestivation to escape harsh winter and summer conditions respectively in order to respond against the temperature conditions.
Water scarcity is another factor that forces animals to undergo certain adaptations to suit their natural habitat. Adaptations of desert animals are mainly to conserve the water. For example, Animals found in desserts 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.
Q11. List the various abiotic environmental factors.
Answer:
Abiotic environmental factors- These are the non-living conditions present in an ecosystem. The various environmental factors are temperature, light, water, wind, humidity, precipitation, soil, minerals etc.
Organisms and Populations Class 12 Questions and Answers:
Q12. Give an example for:
Answer:
Endothermic organisms are those which can regulate their body temperature. Examples of endothermic organisms include birds such as cow, sparrow, pigeons etc and mammals like bears, rats, cows.rabbits etc.
Q12. Give the example for:
Answer:
Ectothermic organisms cannot regulate their body temperature. Examples of ectothermic organisms include sharks, frogs, snakes, lizards, tortoises etc.
Q12. Give an example for:
(c) An organism of benthic zone
Answer:
Benthic zone refers to the floor of a water body. Decomposing bacteria are found in the benthic zone.
Q13. Define population and community
Answer:
Population- A group of individuals belonging to the same species and residing in a particular geographical area at a given period of time is called population. All humans living in a region constitute the population.
Community- A community refers to groups of individuals of different species living in a particular area at a given period of time. Such individuals can not breed with the members of other species.
Q14. Define the following terms and give one example for each
Answer:
Commensalism- It is a kind of population interaction in which one species gets benefitted while the other one remains unaffected. E.g. Orchid growing on trees.
Q14. Define the following terms and give one example for each:
Answer:
Parasitism- It is the interaction wherein one species (parasite) depends on the other species (host) for food and shelter. This is a kind of negative interaction as parasite gets benefitted but the host is harmed.
E.g . Taenia solium living in the intestine of human
Class 12 Biology Chapter 13 NCERT Solutions:
Q14. Define the following terms and give one example for each:
Answer:
Camouflage- This is an adaptive strategy adapted by prey species to escape the predators. For example, many species of frogs and insects camouflage in their surroundings and escape their predators.
Q14. Define the following terms and give one example for each:
Answer:
Mutualism: The symbiotic relationship between two species in which both species are benefited is called mutualism. For example, lichens show a mutual symbiotic relationship between fungi and blue-green algae, where both are equally benefited from each other.
Q14. Define the following terms and give one example for each :
Answer:
Interspecific competition: In this interaction, both species (different) get negatively affected. For example, the competition between flamingoes and resident fishes in South American lakes for common food resources i.e., zooplankton.
Q15. With the help of suitable diagram describe the logistic population growth curve.
Answer:
Logistic population growth curve
The growth of a population takes place according to the availability of food, presence of predators and parasites, presence of other biotic and abiotic factors affecting a population and other conditions in a particular environment. There are two main types of models i.e. exponential growth model and the logistic growth model.
The logistic growth curve represents the logistic growth model. It represents growth when there is a competition between the individuals of a population for food and space. In this case, the fittest organism survives, reproduces and population growth is seen. In this type of growth, initially, a lag phase is shown which is followed by phases of acceleration and de-acceleration. The different phases of the logistic growth curve are:
1. Lag phase- In this phase, no growth is seen due to the absence of food and other resources.
2. Positive acceleration phase- Limited growth in population is seen as the resources become available.
3. Exponential growth phase- The population grows suddenly and show very rapid growth. The curve rises steeply.
4. Negative acceleration phase- In this phase, environmental resistance increases and growth rate of the population decreases.
5. Stationary phase- In this phase, the growth becomes stationary and becomes stable. The population is said to have reached the carrying capacity of the habitat.
A diagrammatic representation of Population growth curves is given below. The curve a represents exponential growth and curve b represents logistic growth
The equation of the logistic growth curve is as follows:
Where N = Population density at time t
R = Intrinsic rate of natural increase
K = Carrying capacity
Since resources for growth for populations are finite and become limiting, the logistic growth model is considered a more realistic one.
Organism and Population NCERT Solutions:
Q16. Select the statement which explains best parasitism.
(a) One organism is benefited.
(b) Both the organisms are benefited.
(c) One organism is benefited, other is not affected.
(d) One organism is benefited, other is affected.
Answer:
(d) One organism is benefited, other is affected.
In parasitism, one organism lives on the body of another. In this interaction, the parasite gets benefitted while the host is negatively affected.
Q17. List any three important characteristics of a population and explain
Answer:
The term population refers to a group of individuals of any species living in a well-defined geographical area, sharing or competing for similar kind of resources and potentially interbreed. Some characteristics of the population are as follows:
1. 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.
2. Death rate(mortality)- It refers to the live deaths in an area to the population of an area. It is expressed as the number of individuals removes from the population.
3. Sex ratio- It is the ratio of the number of male or female individuals per 1000 individuals.
4. Age distribution- A population at a given time is composed of different individuals belonging to different age groups. If the age distribution is plotted for the population, the resulting structure is called age pyramids. The shape of pyramids reflects the growth status of the population.
5. Population density- The number of individuals of a population present per unit area at a given time.
CBSE NCERT Solutions for Organisms and Population Class 12 is classified under Unit – Ecology and is included in the CBSE Syllabus for the academic session 2022-23. According to previous trends, the unit as a whole receives 14 marks. Thus, in order to easily achieve the 14 marks and deal with any type of question, students must thoroughly review the NCERT Solutions from these chapters including Biology Chapter 13 Class 12.
We have comprehensive answers to every chapter of the NCERT Solutions for Class 12 Biology. Try to attempt all the given questions in Organism and Population Class 12 PDF, and if still confused or in case, you have any doubt then refer to NCERT solutions for Class 12 biology chapter 13. For example, the answer for the question, "what are allopatric species" is A species inhabiting different geographical areas is known as allopatric species. There you will get all the answers to those questions which are mentioned in Ch 13 Biology Class 12 and it will help you to score good marks not only in the board exam even in other competitive exams too.
Organism and population NCERT will also tell you about the growth rate, birth rate, death rate, and immigration of the population. The proportion of males and females of different age groups in a population is graphically presented as age pyramid, and its shape indicates whether a population is stationary or growing or declining. This has been explained in Biology Chapter 13 Class 12. So, you must practice each and every question related to this and if you have any doubt or problem in getting the correct answers by your own then, don't worry organism and population NCERT PDF will help you. But don't forget to try at least once, so that you can answer those questions from Chapter 13 Biology Class 12 by yourself. Then check your answers with the help of NCERT solutions for Class 12 biology chapter 13 organisms and populations.
Important topics from Class 12 Biology Chapter 13 are given below:
Section Name | Topic Name |
13 | ORGANISMS AND POPULATIONS |
13.1 | Organism and Its Environment |
13.2 | Populations |
13.3 | Summary |
If you have any doubt or unable to answer by yourself then, organism and population NCERT solutions are there for you to help you out.
Class 12 Biology Chapter 13 NCERT Solutions Key features are given below:
NCERT Exemplar Class 12 Chemistry Solutions |
NCERT Exemplar Class 12 Mathematics Solutions |
NCERT Exemplar Class 12 Biology Solutions |
NCERT Exemplar Class 12 Physics Solutions |
Chapter 1 | Reproduction in organisms |
Chapter 2 | Sexual Reproduction in Flowering Plants |
Chapter 3 | Human Reproduction |
Chapter 4 | Reproductive Health |
Chapter 5 | Principles of Inheritance and Variation |
Chapter 6 | Molecular basis of inheritance |
Chapter 7 | Evolution |
Chapter 8 | Human Health and Disease |
Chapter 9 | Strategies for Enhancement in Food Production |
Chapter 10 | Microbes in Human Welfare |
Chapter 11 | Biotechnology: Principles and Processes |
Chapter 12 | Biotechnology and its Applications |
Chapter 13 | Organisms and Populations |
Chapter 14 | Ecosystem |
Chapter 15 | Biodiversity and Conservation |
Chapter 16 | Environmental Issues |
NCERT solutions for Class 12 Maths |
NCERT solutions for Class 12 Chemistry |
NCERT solutions for Class 12 Biology |
NCERT solutions for Class 12 Physics |
We hope you will ace your board examination with the help of NCERT Solutions for Class 12 Biology Chapter 13 Organisms and Populations.
The important topics of organism and population ncert are:
Population Attributes:
The differentiation between ectotherms and endotherms is given below:
Ectotherms | Endotherms |
These are cold-blooded animals | These are warm-blooded animals |
The change according to the variation in the environment | They maintain a constant internal environment despite the changing environment |
Hibernation is the state in which animals slow down their metabolic activities in order to go dormant during the winter. Fish, amphibians, and reptiles all exhibit this. These animals consume a lot of food and store it as extra fat in order to combat the issue of food scarcity during hibernation. During sleep, this is provided in the form of energy. To understand the key ideas, students of Class 12 are encouraged to consult NCERT Solutions. The main goal of the solutions is to aid students in their board exam preparation. The step-by-step explanations in plain language give students more confidence to take the board exam without being intimidated.
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Hello there! Thanks for reaching out to us at Careers360.
Ah, you're looking for CBSE quarterly question papers for mathematics, right? Those can be super helpful for exam prep.
Unfortunately, CBSE doesn't officially release quarterly papers - they mainly put out sample papers and previous years' board exam papers. But don't worry, there are still some good options to help you practice!
Have you checked out the CBSE sample papers on their official website? Those are usually pretty close to the actual exam format. You could also look into previous years' board exam papers - they're great for getting a feel for the types of questions that might come up.
If you're after more practice material, some textbook publishers release their own mock papers which can be useful too.
Let me know if you need any other tips for your math prep. Good luck with your studies!
It's understandable to feel disheartened after facing a compartment exam, especially when you've invested significant effort. However, it's important to remember that setbacks are a part of life, and they can be opportunities for growth.
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If you have uploaded screenshot of your 12th board result taken from CBSE official website,there won,t be a problem with that.If the screenshot that you have uploaded is clear and legible. It should display your name, roll number, marks obtained, and any other relevant details in a readable forma.ALSO, the screenshot clearly show it is from the official CBSE results portal.
hope this helps.
Hello Akash,
If you are looking for important questions of class 12th then I would like to suggest you to go with previous year questions of that particular board. You can go with last 5-10 years of PYQs so and after going through all the questions you will have a clear idea about the type and level of questions that are being asked and it will help you to boost your class 12th board preparation.
You can get the Previous Year Questions (PYQs) on the official website of the respective board.
I hope this answer helps you. If you have more queries then feel free to share your questions with us we will be happy to assist you.
Thank you and wishing you all the best for your bright future.
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