Case Study Questions Class 12 Biology Organisms and Populations

Case Study Questions Class 12 Biology Chapter 13 Organisms and Populations

CBSE Class 12 Case Study Questions Biology Organisms and Populations. Term 2 Important Case Study Questions for Class 12 Board Exam Students. Here we have arranged some Important Case Base Questions for students who are searching for Paragraph Based Questions Organisms and Populations.

At Case Study Questions there will given a Paragraph. In where some Important Questions will made on that respective Case Based Study. There will various types of marks will given 1 marks, 2 marks, 3 marks, 4 marks.

CBSE Case Study Questions Class 12 Biology Organisms and Populations

Case study 1

What are the key elements that lead to so much variation in the physical and chemical conditions of different habitats? The most important ones are temperature, water, light and soil. We must remember that the physico-chemical (abiotic) components alone do not characterise the habitat of an organism completely; the habitat includes biotic components also – pathogens, parasites, predators and competitors – of the organism with which they interact constantly. We assume that over a period of time, the organism had through natural selection, evolved adaptations to optimise its survival and reproduction in its habitat.

Each organism has an invariably defined range of conditions that it can tolerate, diversity in the resources it utilises and a distinct functional role in the ecological system, all these together comprise its niche.

Que. 1) Organisms has defined many that they can …………………………………………………………………………… range of conditions.

(a) Destroy

(b) Cannot tolerate

(c) Tolerate

(d) Reproduce

Que. 2) When the organism plays role in the ecological system then it is known as ……………………………………………………………………………………..

(a) Ecology

(b) Niche

(c) Survive

(d)  Biotic

Que. 3) For the survival and reproduction, organisms are ………………………………………………………………………………………….

(a) Living free

(b) Interacted

(c) Killed

(d) Adapted

Que. 4) What are the main reason behind so much variation in the physical and chemical conditions?

Que. 5) Write examples of components which characterise habitat of an organism.

Answer Key

Que. 1)(c) Tolerate.

Que. 2) (b) Niche.

Que. 3) (d) Adapted.

Que. 4) Answer: The main reasons behind so much variation in physical and chemical conditions are temperature, soil, water and light.

Que. 5) Answer: Abiotic components such as temperature, soil, water, light and biotic components such as predators, pathogens, parasites and competitors.

Case study 2

Water is another the most important factor influencing the life of organisms. In fact, life on earth originated in water and is unsustainable without water. Its availability is so limited in deserts that only special adaptations make it possible for organisms to live there. The productivity and distribution of plants is also heavily dependent on water. You might think that organisms living in oceans, lakes and rivers should not face any water-related problems, but it is not true. For aquatic organisms the quality (chemical composition, pH) of water becomes important. The salt concentration (measured as salinity in parts per thousand), is less than 5 in inland waters, 30-35 in the sea and > 100 in some hypersaline lagoons. Some organisms are tolerant of a wide range of salinities (euryhaline) but others are restricted to a narrow range (stenohaline).

Many freshwater animals cannot live for long in sea water and vice versa because of the osmotic problems, they would face.

Que. 1) Many ocean living organisms cannot live for long in fresh water due to …………………………………………………………………………………..

(a) Butterfly

(b) Thermal insulation

(c) Osmotic issue

(d) None of them

Que. 2) On the earth, life is unsustainable without ………………………………………………………………………………………….

(a) One tree

(b) A virus

(c) Water

(d) Light

Que. 3) In inland water, salt concentration is less than ………………………………………………………………………………………….

(a) 2

(b) 3

(c) 4

(d) 5

Que. 4) Which factor can affect productivity and distribution of the plants.

Que. 5) Give reason:

Aquatic organisms do face water related issues.

Answer Key

Que. 1)(c) Osmotic issue.

Que. 2) (c) Water.

Que. 3) (d) 5.

Que. 4) Answer: Water is main factor that can affect productivity and distribution of the plants

Que. 5) Answer: The water include chemical composition and pH. Water quality is very important for the aquatic organisms. Also, Salt concentration is different for different water habitat. Hence, aquatic organisms do face water related issues.

Case study 3

Since plants produce food through photosynthesis, a process which is only possible when sunlight is available as a source of energy, we can quickly understand the importance of light for living organisms, particularly autotrophs. Many species of small plants (herbs and shrubs) growing in forests are adapted to photosynthesise optimally under very low light conditions because they are constantly overshadowed by tall, canopied trees. Many plants are also dependent on sunlight to meet their photoperiodic requirement for flowering. For many animals too, light is important in that they use the diurnal and seasonal variations in light intensity and duration (photoperiod) as cues for timing their foraging, reproductive and migratory activities. The availability of light on land is closely linked with that of temperature since the sun is the source for both. But, deep (>500m) in the oceans, the environment is dark and its inhabitants are not aware of the existence of a celestial source of energy called Sun.

What, then is their source of energy? The spectral quality of solar radiation is also important for life. The UV component of the spectrum is harmful to many organisms while not all the colour components of the visible spectrumare available for marine plants living at different depths of the ocean.

Que. 1) Small plants include many species which as adapted to …………………………………………………………………..……………………… light conditions.

(a) Low

(b) High

(c) Continues

(d) Constant 

Que. 2) Light is very important for ………………………………………………………………………………………..

(a) Autotrophs

(b) Heterotrophs

(c) Carnivores

(d) Non-living organisms

Que. 3) In the photosynthesis process, sunlight is required as a source of ……………………………………………………………………………………..

(a) Sugar

(b) Fat

(c) Lipid

(d) Energy

Que. 4) Which organisms are unaware of sun?

Que. 5) Which factor can affect source of light to the organisms?

Answer Key

Que. 1)(a) Low.

Que. 2) (a) Autotrophs.

Que. 3) (d) Energy.

Que. 4) Answer:Organisms that live deep in the oceans with dark environment are unaware of sun.

Que. 5) Answer: Temperature is the factor that can affect source of light because sun is the source of light.

Case study 4

Some organisms are able to maintain homeostasis by physiological (sometimes behavioural also) means which ensures constant body temperature, constant osmotic concentration, etc. All birds and mammals, and a very few lower vertebrate and invertebrate species are indeed capable of such regulation (thermoregulation and osmoregulation). Evolutionary biologists believe that the ‘success’ of mammals is largely due to their ability to maintain a constant body temperature and thrive whether they live in Antarctica or in the Sahara desert. The mechanisms used by most mammals to regulate their body temperature are similar to the ones that we humans use. We maintain a constant body temperature of 370C. In summer, when outside temperature is more than our body temperature, we sweat profusely. The resulting evaporative cooling, similar to what happens with a desert cooler in operation, brings down the body temperature. In winter when the temperature is much lower than 370C, we start to shiver, a kind of exercise which produces heat and raises the body temperature. Plants, on the other hand, do not have such mechanisms to maintain internal temperature.

Que. 1) Homeostatic of an organism is maintained by …………………………………………………………………………………… means.

(a) Behavioural

(b) Modificational

(c) Physiological

(d) Both (a) and (b)

Que. 2) A constant body temperature of ……………………………………………………………………………. °C is maintained by humans.

(a) 37

(b) 90

(c) 60

(d) 200

Que. 3) According to the evolutionary biologist, mammals are successful because they have ability to maintain ………………………………………………………………………………………. of body.

(a) Zero temperature

(b) Low temperature

(c) Constant temperature

(d) High temperature

Que. 4) What will happen if outside temperature will increase more than our body temperature?

Que. 5) Why our body will shiver in winters?

Answer Key

Que. 1)(d) Both (a) and (b)

Que. 2) (a) 37.

Que. 3) (c) Constant temperature.

Que. 4) Answer:Constant human body temperature is 37° C. If outside temperature will increase more than our body temperature then the body will sweat.

Que. 5) Answer: Our body will shiver in the winters because outside temperature will be less than our body temperature.

Case study 5

An overwhelming majority (99 per cent) of animals and nearly all plants cannot maintain a constant internal environment. Their body temperature changes with the ambient temperature. In aquatic animals, the osmotic concentration of the body fluids change with that of the ambient air, water osmotic concentration. These animals and plants are simply conformers. Considering the benefits of a constant internal environment to the organism, we must ask why these conformers had not evolved to become regulators. Recall the human analogy we used above; much as they like, how many people can really afford an air conditioner? Many simply ‘sweat it out’ and resign themselves to suboptimal performance in hot summer months. Thermoregulation is energetically expensive for many organisms. This is particularly true for small animals like shrews and humming birds. Heat loss or heat gain is a function of surface area. Since small animals have a larger surface area relative to their volume, they tend to lose body heat very fast when it is cold outside; then they have to expend much energy to generate body heat through metabolism. This is the main reason why very small animals are rarely found in polar regions.

During the course of evolution, the costs and benefits of maintaining a constant internal environment are taken into consideration. Some species have evolved the ability to regulate, but only over a limited range of environmental conditions, beyond which they simply conform. If the stressful external conditions are localised or remain only for a short duration, the organism has two other alternatives for survival.

Que. 1) The conformers are ……………………………………………………………………………………… to become regulators.

(a) Not evolved

(b) Evolved

(c) Resistant

(d) None of above

Que. 2) In the ……………………………………………………………………………, temperature of body changes with the ambient temperature.

(a) Ocean

(b) Plants

(c) Birds

(d) Insects

Que. 3) Which of the following is unable to maintain a constant internal environment?

(a) Mammals

(b) Birds

(c) Tigers

(d) Plants

Que. 4) In the polar region, very small animals rarely found. What will be the main reason?

Que. 5) Which region has very small animals rarely?

Answer Key

Que. 1)(a) Not evolved.

Que. 2) (b) Plants.

Que. 3)(d) Plants.

Que. 4) Answer: Very small animals can lose body heat fast when they have larger surface area. These animals generate body heat through metabolism when there is cold outside. Hence, They found rarely in the polar region.

Que. 5) Answer: Polar region has very small animals rarely.

Case study 6

The size of a population for any species is not a static parameter. It keeps changing with time, depending on various factors including food availability, predation pressure and adverse weather. In fact, it is these changes in population density that give us some idea of what is happening to the population – whether it is flourishing or declining. Whatever might be the ultimate reasons, the density of a population in a given habitat during a given period, fluctuates due to changes in four basic processes, two of which (natality and immigration) contribute to an increase in population density and two (mortality and emigration) to a decrease.

 (i) Natality refers to the number of births during a given period in the population that are added to the initial density. (ii) Mortality is the number of deaths in the population during a given period. (iii) Immigration is the number of individuals of the same species that have come into the habitat from elsewhere during the time period under consideration. (iv) Emigration is the number of individuals of the population who left the habitat and gone elsewhere during the time period under consideration.

Que. 1) For any species, size of ………………………………………………………………………………….. is not a static parameter.

(a) Population

(b) Area

(c) Temperature

(d) Soil

Que. 2) Which of the following are responsible for the fluctuation of density of population?

(a) Mortality

(b) Natality

(c) Emigration

(d) All of them

Que. 3) In the population, the number of death during a given period is known as ………………………………………………………………………………………..

(a) Immigration

(b) Mortality

(c) Natality

(d) Emigration

Que. 4) Define the following term: Mortality and Immigration

Que. 5) Which two basic process can decrease population density? 

Answer Key

Que. 1)(a) Population

Que. 2) (d) All of them

Que. 3) (b) Mortality

Que. 4) Answers:

Natality: In the population, the number of births which occurs during a period of time and which are added to initial density is known as Natality.

Immigration: During the time period under consideration, the individuals number of same species which have come into the habitat from elsewhere is known as Immigration.

Que. 5) Answer: Emigration and Mortality are the two basic processes that can decrease population density.

Updated: February 20, 2022 — 1:52 am

Leave a Reply

Your email address will not be published. Required fields are marked *