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NCERT Solutions for Course 12 Biology Chapter xiii – Free PDF Download
Become access to NCERT Solutions for Class 12 Biology Chapter 13 Organisms and Population. Find the NCERT Solutions for Class 12 Biology solved completely by bookish professionals after thorough research and extensive review to present the all-time solutions. All these are created according to the latest term – Two CBSE Syllabus 2021-22 and its marking schemes.
Students tin rely on theNCERT Solutions for Form 12 Biology for solving the textbook questions. The affiliate Organisms and Population briefly describes organisms and their environment, dissimilar abiotic factors, response to these factors, adaptations, population, population growth, and much more. Download the NCERT Solutions for Class 12 Biology PDF of this chapter from the link enclosed below.
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Access Answers to NCERT Class 12 Biology Affiliate 13 – Organisms and Population
1. How is diapause different from hibernation?
Solution:
Diapause is a phase of suspended development to deal with undesirable conditions. Several species of Zooplankton and insects display diapause to laissez passer through extreme climatic weather condition while in their development phase. On the other hand, winter sleep or Hibernation is a resting phase wherein animals escape winters by hiding themselves in their shelters. They do then by entering a state of inactivity achieved past decreasing their metabolism. This procedure of hibernation is observed in squirrels, bats and some rodents.
ii. If a marine fish is placed in a fresh water aquarium, volition the fish be able to survive? Why or why not?
Solution:
The chances of survival of marine fish volition reduce if placed in a fresh water aquarium as their bodies are altered to higher salt concentrations equally provided past marine environments. In a fresh water environment, fishes neglect to regulate the water which enters the trunk through the process of osmosis. Due to the presence of a hypotonic environment outside the fish's body, h2o enters their torso which causes their body to swell leading to the expiry of the marine fish.
three. Most living organisms cannot survive at temperature higher up 45 caste C. How are some microbes able to live in habitats with temperatures exceeding 100 degree C?
Solution:
Thermophiles or Archaebacteria are ancient forms of bacteria that are nowadays in deep sea hydrothermal vents and hot water springs. They are able to withstand the high temperature (exceeding 100 caste C) as their bodies accept adapted to these extreme environmental conditions. Such entities incorporate of specialized thermo-resistant enzymes that perform metabolic functions which practise non become destructed at these extreme temperatures.
4. Listing the attributes that populations possess simply not individuals.
Solution:
A group of entities belonging to the same species, residing in a specific geographical surface area at a particular time, together functioning as a unit can be termed as a population.
Listed beneath are the attributes that a population exhibits:
- Natality or Nativity rate
It can be given past the ratio of live births in a particular surface area to the population of that area. Birth charge per unit can be expressed as the number of individuals added to the population in terms of members of the population
- Mortality or Death charge per unit
Information technology is the ratio of deaths in a region to the population of a region. Death rate tin be expressed equally the loss of individuals in terms of members of the population
- Age distribution
It can be given past the percent of individuals of diverse ages in a given population. A population consists of individuals at any given time, and are present in different age groups. Typically, an age pyramid can be used to depict the age distribution blueprint.
- Sex ratio
It is the count of females or males per m individuals
- Population density
Information technology is given past the number of individuals of a population per unit are at a particular time.
five. If a population growing exponentially double in size in three years, what is the intrinsic rate of increment (r) of the population?
Solution:
If adequate quantity of nutrient resource are available to individuals in a population, information technology grows exponentially. The integral form of exponential growth equation can be used to approximate the exponential growth, which is equally follows:
Nt = No ert ————– equation (1)
Where, Northwardt is the population density after 't' time
No is the population density at time zero
e is the base of operations of natural logarithm = 2.71828
r is the intrinsic rate of natural increase
Let the electric current population density be '10'
∴ The population density afterward 2 years will exist 2x and t given is 3 years
Substituting these values in equation (1)
Therefore, the intrinsic rate of natural increase of the population is 0.2311
half-dozen. Name of import defence mechanisms in plants confronting herbivory.
Solution:
A land of feeding on plants is known equally herbivory. Many plants accept evolved mechanisms both chemical and morphological, to safeguard themselves against the act of herbivory. Listed below are defence mechanisms of few plants:
Chemical defense mechanisms:
- Caffeine, nicotine, opium, and quinine are some chemical substances that are produced in plants in response as office of their defense machinery
- All of the parts of Calotropis weeds consists of lethal cardiac glycosides that demonstrate to be fatal if consumed by herbivores.
Morphological defense mechanisms:
- Opuntia or cactus leaves are contradistinct into thorns or precipitous spines to prevent herbivores from feeding on it
- Margins of leaves in some plants are spiny, having precipitous edges, preventing herbivores to feed on them
- Sharp thorns with leaves are found in Acacia to prevent herbivores from feeding on them
7. An orchid found is growing on the co-operative of mango tree. How do you describe this interaction between the orchid and the mango tree?
Solution:
An epiphyte or air plants are entities growing on other plants. An orchid growing on the branch of a mango tree is an epiphyte. Such plants derive their diet and moisture from air, water and rain or from the droppings around it and non from the establish on which it is growing. Hence, the relationship between a mango tree and an orchid is an case of commensalism wherein one species receives its benefits and the other stays unaffected. In the given interaction, the orchid is benefitted every bit it gets physical support from the mango tree but the mango tree is unaffected.
8. What is the ecological principle behind the biological control method of managing with pest insects?
Solution:
Predation is the ecological principle behind the biological control method of managing with pest insects. Predation is referred to as the biological interaction between a predator and a prey wherein the predator feeds on the prey, thereby regulating the population of pest insects. Case – The Gawbusia fish checks the mosquito larvae in h2o bodies.
9. Distinguish between the post-obit:
(a) Hibernation and Aestivation
(b) Ectotherms and Endotherms
Solution:
The differences are as follows:
(a) Hibernation and Aestivation
| Hibernation | Aestivation |
| Also known as wintertime sleep, it is a country of reduced activeness observed in some entities to escape the farthermost common cold climatic conditions | Likewise known every bit summer sleep, it is a land of reduced action noticed in some entities to escape the dehydration as a outcome of heat in summers |
| Examples – Squirrels and bears found in cold regions hibernate in winters | Case – Snails and fishes aestivate in summers |
(b) Ectotherms and Endotherms
| Ectotherms | Endotherms |
| The body temperature varies with their surroundings | Body temperature remains constant |
| They are cold blooded-entities | They are warm-blooded entities |
| Examples – reptiles, fishes, amphibians | Instance – mammals and birds |
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) Consequence of temperature or water scarcity and the adaptations of animals.
Solution:
(a) Adaptations of desert plants and animals
Desert plants:
Some of the severe conditions typically found in a deserts are scorching heat and water scarcity. Plants that are found in deserts have suitably adjusted to this as they have an all-encompassing root organisation to tap the cloak-and-dagger water. These plants possess sunken stomata on foliage surfaces and thick cuticles to decrease transpiration. A plant known as Opuntia has leaves that are completely alerted into spines where photosynthesis is performed by the green stems. These plants of deserts have specialized pathways known as CAM or the C4 pathway to manufacture food which facilitates the stomata to stay closed during the twenty-four hours to subtract the h2o loss acquired through the transpiration process.
Desert animals:
Lizards, kangaroo rats, snakes are some animals found in deserts which have adapted appropriately to their habitat. For instance, the Kangaroo rat inhabiting the Arizona deserts never drinks water in its life and has the potential to concentrate its urine to conserve water. Snakes and Desert lizards accept adapted in a style that they lounge in the dominicus early on in the morn and burrow themselves in sand in the afternoons to escape the heat of the day, to foreclose water loss.
(b) Adaptations of plants to h2o scarcity
Some of the severe atmospheric condition typically found in a deserts are scorching heat and h2o scarcity. Plants that are found in deserts have suitably adapted to this equally they have an extensive root organisation to tap the undercover water. These plants possess sunken stomata on leaf surfaces and thick cuticles to decrease transpiration. A institute known every bit Opuntia has leaves that are completely alerted into spines where photosynthesis is performed by the green stems. These plants of deserts have specialized pathways known as CAM or the C4 pathway to manufacture nutrient which facilitates the stomata to stay airtight during the day to subtract the water loss caused through the transpiration process.
(c) Behavioral adaptations in animals
Some entities that are affected past the fluctuations in temperature experience adaptations namely aestivation, hibernation, migration to escape ecology pressure to adapt to their natural habitat. These adaptations in the behavior of an entity is termed as behavioral adaptations. For case, ectothermal and a few endothermal animals display these adaptations.
Some common cold blooded animals, ectotherms such as amphibians, fish, reptiles have their temperatures varying with their environs as seen in Desert lizard, where they lounge in the sun in the early hours of the solar day and burrow themselves in sand when the temperature begins to ascent in the noon. Some warm-blooded animals or endotherms such equally mammals or birds escape the hot and cold atmospheric condition conditions by hibernating in winters and aestivating in summers. They take shelter in burrows, caves etc to safeguard against these temperature variations.
(d) Importance of calorie-free to plants
The ultimate source of energy for plants is sunlight. Plants are referred to every bit autotrophic entities. They crave light to perform photosynthesis. Light has a critical function in producing photoperiodic response that takes place in plants. These plants respond to the changes in the lite intensity in different seasons to be able to run into their photoperiodic requirements for the process of flowering. Besides, light has a significant role in aquatic habitats for vertical distribution of plants in the body of water.
(due east) Effect of temperature or water scarcity and the adaptations of animals
One of the most of import ecological factors is temperature which varies from place to identify. The variation in temperature affects the distribution of animals on the planet. Eurythermals are the animals that can tolerate a range of temperatures while stenothermal animals are the ones which can withstand only a narrow range of temperature. In order to suit their natural habitats, animals besides undergo adaptations. For example, animals in cooler regions have brusque limbs and ears, helping to preclude heat loss from the body. Animals that are found in colder regions accept thick fat layers underneath their skin, thick fur coats to prevent rut loss.
Some entities that are affected past the fluctuations in temperature experience adaptations namely aestivation, hibernation, migration to escape environmental pressure to adapt to their natural habitat. These adaptations in the behavior of an entity is termed as behavioral adaptations. Instance, the Desert lizards are ectotherms, this ways to say they practice non possess a temperature regulatory mechanism to escape the variations in temperature. These lounge in the sun in the early on hours of the day and burrow themselves in sand when the temperature begins to rise in the noon.
Another factor that expels animals to experience several adaptations to familiarize to their natural habitats is water scarcity. Lizards, kangaroo rats, snakes are some animals establish in deserts which have adapted appropriately to their habitat. For case, the Kangaroo rat inhabiting the Arizona deserts never drinks h2o in its life and has the potential to concentrate its urine to conserve water. Snakes and Desert lizards take adapted in a way that they lounge in the sun early in the forenoon and burrow themselves in sand in the afternoons to escape the estrus of the mean solar day, to prevent water loss.
11. List the various abiotic environmental factors.
Solution:
Abiotic environmental factors are formed past all the not-living components of an ecosystem which includes the following:
- Temperature –
It is i of the most significant factors which varies seasonally on land, progressively decreases from the equator towards the poles, from plains to the mountain tops. From sub-naught levels in polar areas to temperatures greater than fifty degree Celsius in tropical deserts in summers, their range is wide. Some unique habitats such every bit deep body of water hydrothermal vents, thermal springs sees average temperature exceeding more than 100 caste Celsius. Entities who can withstand a range of temperatures are termed every bit eurythermals instance – birds and mammals whereas stenothermals are entities who tin bear a narrow range of temperature, example – polar bears.
- Water –
Life cannot sustain without water. For marine entities, pH, water temperature, chemical limerick etc is significant. It is also afflicted by water salinity that is less than five parts per thousand in inland water, thirty-35 parts per thousand in sea etc
Euryhaline are entities which can bear a wide salinity range whereas stenohaline are entities that tin can tolerate a narrow range of salinity. Most of the fresh water animals cannot sustain in body of water h2o for long due to osmotic problems that arise due to loftier salinity and vice-versa
- Soil –
Properties and nature of soil varies from place to place, depending on the post-obit factors
-climate
-soil development procedure
-Weathering procedure
Characteristics such every bit grain size, assemblage, soil limerick determine the h2o holding capacity and percolation of soil. Along with these, some other features such equally pH, topography, mineral composition etc determine the type of institute that tin grow in a specific habitat.
- Light –
All autotrophs depend on light to carry out photosynthesis, releasing oxygen during the procedure. In forests, pocket-size herbs and shrubs are adapted to photosynthesis under very low light intensities as they are overshadowed by tall copse. Also, near plants depend on sunlight to come across their photoperiodic necessities for flowering. Several animals are dependent on diurnal and seasonal differences in light intensity equally prompts for timing their reproductive, foraging and migratory activities. Light availability on state is closely associated with that of temperature, every bit Sun is the ultimate source. In deep oceans, information technology is dark perpetually. Spectral quality of solar radiation is necessary for life. For many entities, UV component of calorie-free is harmful. Unlike components of visible spectrum is available for marine plants active at different oceanic depths. Hence, dissimilar algae types such every bit brown, dark-green and reddish algae occur at various depths in the middle, upper and everyman levels of h2o respectively.
12. Give an example for:
(a) An endothermic animate being
(b) An ectothermic animal
(c) An organism of benthic zone
Solution:
(a) An endothermic beast – Crows, sparrows, cranes, cows, rabbits, rats etc
(b) An ectothermic creature – Fish such as amphibians, sharks, frogs, snakes, tortoise, lizards
(c) An organism of benthic zone – decomposing bacteria is an organism of benthic zone
13. Define population and community.
Solution:
Population – information technology can be defined as a grouping of individuals of the aforementioned species inhabiting a particular geographical surface area at a given fourth dimension, functioning as a unit.
Community – it can exist defined as a group of individuals of various species, living in a certain geographical region. These individuals can be different or like, just cannot reproduce with members of other species.
xiv. Define the post-obit terms and give ane example for each:
(a) Commensalism
(b) Parasitism
(c) Cover-up
(d) Mutualism
(e) Interspecific competition
Solution:
(a) Commensalism
The interaction between ii species wherein one species is benefited and the other remains unaffected in known as commensalism. Examples – Barnacles attached to a whale'due south body and an orchid growing on the branches of a mango tree
(b) Parasitism
The interaction between two species wherein 1 species is positively affected (typically the smaller ane) and the other is negatively affected (typically the larger one) is known as Parasitism. Case – Liver fluke is a parasite living within the body of the host and deriving diet from it. Here, the parasite benefits from the host, every bit it derives nutrition from it while the host is affected negatively as the parasite reduces the host fitness causing its body to get weak.
(c) Cover-up
It is a tactic taken upward by the prey to escape from predators. Intrinsically, organisms are colored to easily alloy with their surroundings and escape from their predators. Several insects and frog species cover-up to escape their predators.
(d) Mutualism
An interaction betwixt two species wherein both species involved are benefited is Mutualism. Instance – lichens exhibit a mutual symbiotic relationship betwixt blue greenish algae and fungi. Hither, both are equally benefited from each other.
(e) Interspecific competition
An interaction between individuals of dissimilar species wherein both are negatively affected is interspecific competition. Case – The competition betwixt resident fishes and flamingoes in South American lakes for shared food resource, that is, zooplankton
fifteen. With the help of suitable diagram draw the logistic population growth curve.
Solution:
The logistic population growth curve is usually observed in yeast cells cultivated in laboratory weather condition and includes five phases, namely:
- The lag phase – the population of yeast cell is small initially as resource are limited in the habitat
- Exponential phase – in this stage, the population of the yeast jail cell suddenly rises as a issue of rapid growth leading to an exponential population growth due to availability of plenty food resources, consistent favorable ecology conditions without whatsoever interspecific contest. This results in the curve rise upwards steeply.
- Positive acceleration stage – at the get-go of this phase, the cell growth is limited. The yeast cell adjusts to the new surround and grows its population
- Negative dispatch phase – the environmental resistance increases and the growth rate of the population declines as a result of an increased competition between the yeast cells for shelter and food.
- Stationary phase – The population is stable in this phase. The count of cells generated in a population is equivalent to the number of cells that die out. Additionally, the species' population is said to have touched nature's carrying-chapters in its habitat. S-shaped growth bend is also referred to as the Verhulst- pearl logistic bend.
16. Select the statement which explains best parasitism.
(a) Ane organism is benefited.
(b) Both the organisms are benefited.
(c) Ane organism is benefited, other is not affected.
(d) One organism is benefited, other is afflicted.
Solution:
(d) One organism is benefited, other is affected
Parasitism is a blazon of interaction between ii species wherein i species (parasite) gets benefited while the other species or the host is negatively afflicted/harmed. Example – Lice or ticks(parasites) found on human body(host) is an example wherein lice derives its nutrition by feeding on the humans' blood causing the fitness of the individual(host) to reduce, harming the human trunk.
17. List any iii important characteristics of a population and explain.
Solution:
A group of entities belonging to the aforementioned species, residing in a specific geographical area at a particular time, together functioning every bit a unit of measurement can be termed as a population. Example – All humans living in a item expanse at a specific time contain the population of humans.
Listed below are the attributes that a population exhibits:
- Natality or Birth rate
It can be given past the ratio of live births in a particular area to the population of that area. Nascence rate tin be expressed as the number of individuals added to the population in terms of members of the population
- Mortality or Death rate
Information technology is the ratio of deaths in a region to the population of a region. Death rate can be expressed as the loss of individuals in terms of members of the population
- Age distribution
Information technology can be given past the percent of individuals of diverse ages in a given population. A population consists of individuals at any given fourth dimension, and are nowadays in different age groups. Typically, an age pyramid tin exist used to describe the age distribution pattern.
In previous classes, students accept learnt about Ecology as a subject, which deals with the interaction betwixt entities and between organisms and their physical environment. Typically, ecology is concerned with four levels of biological organisation – populations, organisms, communities and biomes. In this class, students explore ecology at the levels of organisms and population. Utilize the NCERT Solutions to develop a firm grip over the key concepts of Class 12 Biology.
NCERT Solutions for Class 12 Biology Chapter xiii – Organisms and Population
NCERT Solutions for Course 12 Biology Chapter thirteen – Organisms and Population is classified under Unit – Environmental and is included in the term – Ii CBSE Syllabus for the session 2021-22. The unit of measurement, on the whole, holds 14 marks equally per previous trends. Hence, students are required to revise NCERT Solutions from these chapters thoroughly so that students can easily achieve the 14 marks and face any type of question.
Typology of questions are as follows:
- Application type of question
- Knowledge-based
- High order thinking skill (HOTS) questions and many more
Key concepts covered in this chapter are given below:
- Organism and Its Environment
- Populations
Students tin can use the NCERT Solutions for Course 12 Biology Chapter 13 for whatsoever quick reference to comprehend complex topics.
Cardinal Features of NCERT Solutions Class 12 Biological science Affiliate xiii – Organisms and Population
- NCERT Solutions are framed by field of study experts
- Solutions are bachelor to download for complimentary in pdf format
- Promotes conceptual based learning
- Ultimate prep tool for students
- Serves as a perfect reference guide to refer anywhere, someday
Ofttimes Asked Questions on NCERT Solutions for Class 12 Biological science Chapter xiii
How tin can I score full marks in Affiliate thirteen of NCERT Solutions for Class 12 Biological science?
The NCERT Solutions for Class 12 Biological science Chapter 13 is prepared by the highly experienced faculty after conducting vast research on each concept. While solving the textbook questions, students can refer to these solutions to get an overall thought well-nigh the topics covered in this chapter. The solutions can be accessed in both online and offline style as per the needs of students. The PDF format of solutions is available on BYJU'S which tin exist downloaded and used by the students to get their doubts cleared instantly.
How to first reading NCERT Solutions for Grade 12 Biology Affiliate thirteen?
Very first learn and understand organisms populations with the help of BYJU'S website. And so go through the solutions provided by BYJU'S experts at their site. By solving these exercises one tin can be thorough in all the concepts nowadays in NCERT Solutions for Class 12 Biological science Chapter thirteen.
Explain the concept of hibernation covered in Chapter xiii of NCERT Solutions for Course 12 Biology.
Hibernation is the condition in which the animals go dormant during winters by lowering their metabolic activities. This can be seen in reptiles, fish and amphibians. To combat the trouble of nutrient shortage during hibernation, these animals eat a lot of nutrient and store information technology in the grade of excess fat. This is supplied in the form of energy while sleeping. Students of Class 12 are advised to refer to the NCERT Solutions from BYJU'S to gain a grip on the of import concepts. The solutions are prepared with the main aim of helping students with their 2nd term test training. The stepwise explanations in unproblematic language boost the confidence amid students to appear for the term – II exam without fear.
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