1. Niche is
(a) all the biological factors in the organism’s environment
(b) the physical space where an organism lives
(c) the range of temperature that the organism needs to live
(d) the functional role played by the organism where it lives.
Answer (d) : Niche is specific part of habitat occupied by individuals of a species which is circumscribed by its range of tolerance, range of movement, microclimate, etc. Hence, niche refers to the functional role played by the organism where it lives.
2. Presence of plants arranged into well defined vertical layers depending on their height can be seen best in
(a) tropical rainforest (b) grassland (c) temperate forest (d) tropical savannah.
Answer:- (a) tropical rainforest
3. Match mean annual precipitation in column I with the biome in column II and choose the right option.
Column I Column II
(i) 0-50 cm A. Tropical forest
(ii) 50-100 cm B. Coniferous forest
(iii) 150-400 cm C. Grassland
(iv) 50-250 cm D. Desert
(a) (i)-D (ii)-C (iii)-A (iv)-B
(b) (i)-C (ii)-A (iii)-B (iv)-D
(c) (i)-C (ii)-D (iii)-A (iv)-B
(d) (i)-B (ii)-D (iii)-A (iv)-C
Answer :- (a) (i)-D (ii)-C (iii)-A (iv)-B
4. Plants requiring low light intensity for optimum photosynthesis are called
(a) heliophytes (b) pteridophytes (c) sciophytes (d) bryophytes.
Answer (c) : Plants growing in partial shade or low intensity light are called shade plants or sciophytes. In shade plants, the stems are soft, slender with large internodes. Leaves are thin and large sized. They have bright green colour. Cuticle is thin. Stomata are present on both the surfaces. Palisade parenchyma is less developed. There is more vegetative growth as compared to flowering and fruiting. In low light intensity they acquire optimum photosynthesis.
5. –1°C to 13°C annual variations in the intensity and duration of temperature and 50 to 250 cm annual variation in precipitation, account for the formation of a major biome as
(a) temperate forest (b) coniferous forest (c) tropical forest (d) grassland.
Answer (b) coniferous forest
6. Pneumatophores occur in
(a) halophytes
(b) free-floating hydrophytes
(c) carnivorous plants
(d) submerged hydrophytes.
Answer (a) : Pneumatophores are breathing or respiratory roots which are found in plants growing in mangroves or water logged soil or saline swamps. Such plants are called halophytes.
7. Organisms possessing strong and stout forelimbs with clawed digits show _______ adaptations.
(a) arboreal (b) cursorial
(c) fossorial (d) volant
Answer (c) : The fossorial adaptation is adaptation for digging. Organisms showing this type of adaptation have strong and stout forelimbs. They are provided with claws which are useful in digging. They may have a pointed, elongated snout which is also used in digging.
8. Some desert beetles can survive on “metabolic water”, without ever drinking liquid water which
(a) is a breakdown product of pyruvate inside the mitochondria, along with carbon dioxide
(b) was produced as water in the organisms they eat
(c) is a breakdown product from glycolysis in the cytoplasm
(d) is absorbed from the air along with respiratory oxygen.
Answer:- (a) is a breakdown product of pyruvate inside the mitochondria, along with carbon dioxide
9. Which one of the following is the specific xerophytic adaptation?
(a) Presence of spines
(b) Absence of stomata
(c) Presence of long tap root system
(d) Presence of stipular leaves
Answer:- (c) : Xerophytes are the plants living in xeric (dry) habitats. Deserts are the typical xerophytic habitat. Plants growing in xerophytic habitats develop various morphological and physiological adaptations. Roots of these plants are deep tap roots penetrating the soil to great depths so as to absorb water to the maximum. Roots can also be shallow but extensive and spreading so as to collect and hold rain water. In many xerophytes, leaves are reduced to form spines to reduce the transpiration losses as in cacti.
10. Which of the following statements regarding responses of organisms to abiotic factors is false?
(a) All birds and mammals are capable of thermoregulation.
(b) Majority of animals and nearly all plants cannot maintain a constant internal environment.
(c) Shivering is a kind of exercise which produces heat and raises body temperature.
(d) Very small animals are commonly found in polar regions as they have to spend less energy to generate body heat.
Answer:- (d) : 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 and they have to expend much more energy to generate body heat through metabolism. Hence, very small animals are rarely found in polar areas.
11. The success of mammals on earth is largely because
(a) they have the ability to maintain constant body temperature
(b) they can conform to the changes in the environment
(c) they can take care of their young ones as they have mammary glands to suckle them
(d) they can reduce metabolic activity and go into a state of dormancy during unfavourable conditions in the environment.
Answer:- (a) : Mammals are endothermic. Endothermy (maintenance of internal temperature) enable these animals to live at temperatures that other land vertebrates cannot bear.
12. Which one of the following refers to Allen’s rule?
(a) An organism can move from a stressful habitat to a more hospitable area and return when the stressful period is over.
(b) If the stressful conditions are localised or remain only for a short duration, an organism either migrates or suspends itself.
(c) Low atmospheric pressure in higher altitudes results in altitude sickness.
(d) Mammals from colder climates have shorter ears and limbs to minimize heat loss.
Answer:- (d) Mammals from colder climates have shorter ears and limbs to minimize heat loss.
13. Which one of the following is not a parasitic adaptation?
(a) Development of adhesive organs
(b) Loss of digestive organs
(c) Loss of reproductive capacity
(d) Loss of unnecessary sense organs
Answer (c) : Parasitism is a relationship between two living organisms of different species in which one organism called parasite obtains its food directly from another living organism called host. The parasite spends a part or whole of its life either on or inside the body of the host. The general parasitic adaptations are
(i) anaerobic respiration in internal parasites,
(ii) loss of certain organs,
(iii) presence of adhesive organs,
(iv) excessive multiplication,
(v) resistant cysts and eggs for safe transfer of their progeny to new hosts and
(vi) well developed and complicated reproductive organs.
14. The stage of suspended development shown by zooplanktons is called
(a) desiccation (b) diapause (c) hibernation (d) homeostasis
Answer (b) : Environment keeps changing with time and these changes may be unfavourable for an organism e.g., extreme heat or extreme cold. Some organisms migrate from the unfavourable place to the place with favourable conditions e.g., birds. Some organisms, unable to migrate, might avoid the stress by escaping in time. They do so by reducing their metabolic activity and going into a state of ‘dormancy’. Under unfavourable conditions many zooplankton species in lakes and ponds are known to enter diapause, a stage of suspended development.
16. Select the incorrect statement.
(a) An overwhelming majority of animals and nearly all plants maintain a constant internal temperature.
(b) An orchid growing as an epiphyte on a mango branch is an example of commensalism.
(c) In brood parasitism, the parasitic bird lays its eggs in the nest of its host and lets the host to incubate them.
(d) Very small animals are rarely found in polar regions.
Answer:- (a) An overwhelming majority of animals and nearly all plants maintain a constant internal temperature.
17. Match the following and select the correct option.
Column I Column II
A. Bears 1. Diapause
B. Snail 2. Hibernation
C. Zooplanktons3. Dormancy
D. Seeds 4. Aestivation
(a) A -3, B-4, C-1, D-2 (b) A-2, B-1, C-4, D-3
(c) A-4, B-1, C-2, D-3 (d) A-2, B-4, C-1, D-3
Answer:- (d) A-2, B-4, C-1, D-3
18. In a growing population of a country,
(a) pre-reproductive individuals are more than the reproductive individuals
(b) reproductive individuals are less than the post-reproductive individuals
(c) reproductive and pre-reproductive individuals are equal in number
(d) pre-reproductive individuals are less than the reproductive individuals.
Answer:- (a) : In a population where the number of prereproductive individuals or the younger individuals is higher than the reproductive individuals, the population will increase.
19. Asymptote in a logistic growth curve is obtained when
(a) K = N
(b) K > N
(c) K < N
(d) the value of ‘r’ approaches zero.
Answer (a) : Asymptote in a logistic growth curve is obtained when population density (N) reaches the carrying capacity (K), i.e., N = K.
20. Select the correct statement.
(a) In a population, number of births is different from birth rate
(b) A sigmoid growth curve is depiction of exponential growth
(c) In a logistic growth curve the asymptote is beyond the carrying capacity
(d) ‘r’ is equal to the difference between number of births and number of deaths in a population.
Answer:- (a) : Birth, i.e., production of new offspring is an attribute of an individual whereas birth rate i.e., production of new individuals per unit population per unit time is an attribute of population. A sigmoid growth curve is depiction of logistic growth, a more realistic growth model where individuals compete for limited resources and the fittest individual survives and reproduces. In an exponential growth curve (J-shape curve) the asymptote, is beyond carrying capacity as resources are unlimited. ‘r’ is intrinsic rate of natural increase.
21. A biologist studied the population of rats in a barn. He found that the average natality was 250, average mortality 240, immigration 20 and emigration 30. The net increase in population is
(a) 05 (b) zero (c) 10 (d) 15.
Answer:- (b) : Natality and immigration positively contribute to the population growth while mortality and emigration are negative factors. In the given question,
The net increase in population isnatality + immigration = 250 + 20 = 270
The net decrease in population is
mortality + emigration = 240 + 30 = 270
Thus, net increase in population = 270 – 270 = 0
22. Which of the following is correct?
(a) Population change = (Birth + immigration) – (death + emigration)
(b) Population change = (Birth + immigration) + (death + emigration)
(c) Population change = (Birth + emigration) + (death – immigration)
(d) Population change = (Birth – immigration) – (death + emigration)
Answer:- (a) Population change = (Birth + immigration) – (death + emigration)
23. Which is correctly labelled with respect to the given diagram?
(a) B : Logistic curve
(b) C : Carrying capacity
(c) C : Exponential curve
(d) A : Carrying capacity
25. The formula of growth rate for population in given time is
(a) dt/ dN = rN (b) dt/rN = dN
(c) rN/dN = dt (d) dN/dt = rN.
Answer:- (d) : The population grows in an exponential or geometric ratio. If in a population of size N, the birth rates (not total number but per capita births) are represented as b and death rates (per capita death rates) as d, the increase or decrease in N (growth rate) during a unit time period
t (dN/dt) will bedN/dt = (b – d) × N
Let (b – d) = r, then
dN/dt = rN.
The r in this equation is called intrinsic rate of natural increase.
26. Between which among the following, the relationship is not an example of commensalism?
(a) Orchid and the tree on which it grows
(b) Cattle Egret and grazing cattle
(c) Sea Anemone and Clown fish
(d) Female wasp and fig species
Answer:- (d) : Female wasp and fig species show mutualism.
27.If ‘+’ sign is assigned to beneficial interaction, ‘–’ sign to detrimental and ‘O’ sign to neutral interaction, then the population interaction represented by ‘+’ ‘–’ refers to
(a) mutualism (b) amensalism
(c) commensalism (d) parasitism.
Answer:- (d) : Parasitism is an association in which one organism (the parasite) lives on (ectoparasitism) or in (endoparasitism) the body of another organism (host), from which it obtains its nutrients. This association is beneficial for the parasites as they get continuous supply of nutrients from their host and are able to rapidly multiply their numbers. But it is detrimental for the host organism as parasitic infection leads to various complications and diseases in the host body may also be fatal to him under certain circumstances.
28. Match the following.
Population Example
Interaction
1. Predation A. Cuscuta and hedge plants
2. Commensalism B. Balanus and Chthamalus
3. Parasitism C. Cactus and moth
4. Competition D. Orchid and mango
(a) 1-C, 2-D, 3-A, 4-B (b) 1-D, 2-C, 3-B, 4-A
(c) 1-A, 2-C, 3-B, 4-D (d) 1-C, 2-D, 3-B, 4-A
Answer:- (a) 1-C, 2-D, 3-A, 4-B
29. Connel’s field experiment on the rocky sea coast of Scotland, where larger barnacle Balanus dominates the intertidal area and removes the smaller barnacle Chthamalus. This happened due to
(a) parasitism (b) predation
(c) mutualism (d) competition.
Answer (d) : Competition is a rivalry between two or more organisms for obtaining the same resources.
30. All the following interactions are mutualism, except
(a) plant and animal relation for pollination
(b) association of algae and fungi in lichens
(c) association of cattle egret and grazing cattle
(d) association of fungi and roots of higher plants in mycorrhiza.
Ans:- (c) association of cattle egret and grazing cattle
31. Gause’s principle of competitive exclusion states that
(a) no two species can occupy the same niche indefinitely for the same limiting resources
(b) larger organisms exclude smaller ones through competition
(c) more abundant species will exclude the less abundant species through competition
(d) competition for the same resources exclude species having different food preferences.
Answer:- (a) : Gause’s ‘competitive exclusion principle’ states that if resources are limited, then two closely related species competing for the same resource cannot co-exist indefinitely and the competitively inferior one will be eliminated eventually.
32. Match column I with column II and select the correct option from the codes given below.
Column I Column II
A. Commensalism (i) One inhibited, other unaffected
B. Parasitism (ii) One benefitted, other unaffected
C. Mutualism (iii) Both are benefitted
D. Amensalism (iv) One benefitted, other harmed
(a) A-(iv), B-(ii), C-(iii), D-(i)
(b) A-(iii), B-(iv), C-(ii), D-(i)
(c) A-(ii), B-(iv), C-(iii), D-(i)
(d) A-(ii), B-(iv), C-(i), D-(iii)
Answer:- (c) A-(ii), B-(iv), C-(iii), D-(i)
33. Carnivorous animals lions and leopards, occupy the same niche but lions predate mostly larger animals and leopards take smaller ones. This mechanism of competition is referred to as
(a) character displacement
(b) altruism
(c) resource partitioning
(d) competitive exclusion.
Answer (c) resource partitioning
34. A biologist studied the population of rats in a barn. He found that the average natality was 250, average mortality 240, immigration 20 and emigration 30. The net increase in population is
(a) 05 (b) zero
(c) 10 (d) 15.
Answer:- (b) : Natality and immigration positively contribute to the population growth while mortality and emigration are negative factors. In the given question,
The net increase in population isnatality + immigration = 250 + 20 = 270
The net decrease in population is
mortality + emigration = 240 + 30 = 270
Thus, net increase in population = 270 – 270 = 0
35. Select the correct option w.r.t. age pyramids.
(a) A-Expanding, B-Stable, C-Declining
(b) A-Stable, B-Expanding, C-Declining
(c) A-Stable, B-Declining, C-Expanding
(d) A-Declining, B-Stable, C-Expanding
Answer:- (a) : In a growing or expanding population, the number of pre-reproductive individuals is very large, number of reproductive individuals is moderate while post reproductive individuals are fewer. In a stable population, the number of pre reproductive and reproductive individuals is almost equal whereas post reproductive individuals are fewer. In declining population, proportion of reproductive age group is higher than pre-reproductive age group. Number of post reproductive individual is also sizeable.
36. Which one of the following population interactions is widely used in medical science for the production of antibiotics?
(a) Commensalism
(b) Mutualism
(c) Parasitism
(d) Amensalism
Answer:- (d) : Amensalism is a relationship between organisms of different species in which an organism does not allow other organism to grow or live near it. Inhibition is achieved through the secretion of chemicals called allochemics. Antibiotics are a kind of allochemics produced by some microbes which in small concentration can kill or retard growth of harmful microbes without adversely affecting the host.
37. Which of the following statements is false regarding predators?
(a) Predators keep prey populations under control.
(b) Predators help in maintaining species diversity in a community.
(c) If a predator is not efficient, then the prey population would become extinct.
(d) Herbivores (predators) have a greater advantage since the plants cannot run away to avoid predation.
Answer:- (c) : Predators are those organisms that devour other organisms to obtain energy. They may be carnivores (eating other animals) or herbivores (eating plants). Besides acting as ‘conduits’ for energy transfer across trophic levels, predators play other important roles. They keep prey populations under control. Predators also help in maintaining species diversity in a community, by reducing the intensity of competition among competing prey species. But if a predator is too efficient and overexploits its prey, then the prey might become extinct and following it, the predator will also become extinct for lack of food.
38. Which one of the following causes population explosion?
(a) Decrease in infant mortality rate and increase in death rate
(b) Decrease in death rate, maternal mortality rate and infant mortality rate
(c) Decrease in infant mortality rate and decrease in the number of people in reproductive age
(d) Decrease in death rate and increase in maternal mortality rate
Answer:- (b) : Death rate is defined as the number of deaths per 1,000 individuals in a population per year. It decreases population size and population density. Maternal mortality rate is the rate of maternal deaths. Maternal death is the death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of the duration of pregnancy, from any cause related to or aggravated by the pregnancy or its management, but not from accidental or incidental causes.
MMR = Maternal deathsLive births
Infant mortality rate is the number
of deaths per 1,000 infants who die between birth and 1 year of age.
A decrease in all three of these factors can result in population explosion.
39. Which one of the following is most appropriately defined?
(a) Host is an organism which provides food to another organism.
(b) Amensalism is a relationship in which one species is benefitted whereas the other is unaffected.
(c) Predator is an organism that catches and kills other organism for food.
(d) Parasite is an organism which always lives inside the body of other organism and may kill it.
Answer:- (c) : Predation is an interaction between members of two species in which members of one species capture, kill and eat up members of other species ‘Host’ is a term which is specifically related to parasitism. Amensalism is an interspecies interaction in which one species is harmed whereas the other one is unaffected. Parasitic organism can live both over the surface of their host or inside their body.
40. Which one of the following microbes forms symbiotic association with plants and helps them in their nutrition?
(a) Azotobacter (b) Aspergillus
(c) Glomus (d) Trichoderma
Case Based MCQs
Case I : Read the following passage and answer the questions from 41 to 45 given below.
Organism P has thick lips and tongue so that it can easily feed on the commonly available spiny plants. Organism Q has thick layer of insulating fat under the skin. It was strong hooves to walk steadily on steep surfaces and lives in burrows during winters. Organism R has bright colours and sticky pads on its fingers and toes. It lives on trees.
41. Which of the following is correct habitat for organisms P regarding its adaptation?
(a) Grassland biome
(b) Desert biome
(c) Tropical rainforest
(d) Tropical deciduous forest
Answer:- (b) : P is a camel adapted to desert conditions as it has thick lips and tongue so that it can easily feed on the commonly available spiny plants.
42. Which of the following is correct match regarding organism Q and its habitat?
(a) Tundra - Polar bear
(b) Tropical rain forest - Deer
(c) Grassland - Bighorn sheep
(d) Desert - Camel
Answer:- (a) : Q is polar bear as it has thick insulating fat layer under the skin.
43. Which of the following is incorrect regarding organisms R’s habitat?
(a) The vegetation shows stratification
(b) Epiphytic growth is rich
(c) Standing crop is highest
(d) Deep rooted shrubs are common due to abundant sunlight
Answer:- (d) : R could be poison dart frog as it has bright colours and sticky pads on its fingers and toes and its habitat is tropical rainforest. Deep rooted shrubs are not found in tropical rainforest. These are found in deserts. 44. (a) : Habitat of P is desert, so, the dominant plant is Opuntia.
44. The dominant plants in habitat where P lives could be
(a) Opuntia
(b) Nymphaea
(c) Deodar
(d) both (a) and (c).
45. Organisms P, Q and R respectively most likely occur in
(a) F, B and A (b) C, A, E
(c) A, F and C (d) B, D and A.
Assertion & Reasoning Based MCQs
For question numbers 51-60, two statements are given-one labelled Assertion and the other labelled Reason. Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
(a) Both assertion and reason are true and reason is the correct explanation of assertion.
(b) Both assertion and reason are true but reason is not the correct explanation of assertion.
(c) Assertion is true but reason is false.
(d) Assertion is false but reason is true.
51. Assertion : Microclimate generally differs from the prevailing regional climatic conditions.
Reason : Microclimate represents the climatic conditions that prevail at local scale or in areas of limited size.
Answer:- (a) : Microclimate generally differs from the prevailing regional climatic conditions, because the microclimate represents the climatic conditions that prevail at local scale or in areas of limited size, such as the immediate surroundings of plants and animals.
52. Assertion : Aerenchyma is present in the leaves and petioles of hydrophytes.
Reason : Aerenchyma imparts buoyancy to the hydrophytes.
Answer (a) : Plants which remain permanently immersed in water are called hydrophytes. They may be submerged or partly submerged and show the presence of aerenchyma (large air space) in the leaves and petioles. Aerenchyma helps to transport oxygen produced during photosynthesis and permits its free diffusion to other parts, including roots located in anaerobic soils. These tissues also impart buoyancy to the plants.
53. Assertion : Ectotherms are able to remain active under cold conditions.
Reason : Ectotherms are unable to maintain a constant internal temperature.
Answer:- (d) : Endotherms (warm - blooded animals) can regulate their body temperature by physiological means and are able to maintain a more or less constant internal temperature, even when the temperature outside fluctuates (for example - birds and mammals). They have physiological mechanisms for keeping body temperature constant or within tolerance limits. Ectotherms, (cold-blooded animals) cannot regulate their body temperature and are unable to maintain a constant internal temperature. Their body temperature tends to match with the environmental temperature in which they live, (for example-frogs and snakes).
54. Assertion : Many mangrove plants possess high levels of organic solutes.
Reason : This is an adaptation to cope with the conditions of high salt concentration and osmotic potential.
Answer (a) : Mangroves are found in marshy conditions of tropical deltas and along ocean edges. For coping with conditions of high salt concentration and osmotic potential, many mangrove plants have high levels of organic solutes, such as proline and sorbitol. Dunaliella species (green and halophytic algae found in hyper saline lakes) can tolerate saline conditions by accumulating glycerol in the cells, which helps in osmoregulation. Some species of mangroves can excrete salts through the salt glands on the leaves. Some mangroves can exclude salts from the roots by pumping excess salts back into soil.
55. Assertion : With increase in population size, environmental resistance tends to increase.
Reason : This is a nature’s way to check the expression of biotic potential.
Answer:- (a) : The inherent maximum capacity of an organism to reproduce or increase in number is termed as biotic potential (designated by the symbol ‘r). Biotic potential is realised only when the environmental conditions are non-limiting, so that natality rate (birth- rate) is maximum and mortality rate (death - rate) is minimum. Under these conditions, population size increases at the maximum rate. However, nature keeps a check on the expression of biotic potential. For example, if a pair of flies is allowed to reproduce unchecked, the fly population may outweigh the earth in a few years. The environmental check on population size, or its biotic potential is called environmental resistance. With increase in population size, the environmental resistance (against the population) tends to increase. The environmental resistance represents the limiting effect of abiotic (e.g., water, space) and biotic factors (e.g., food, competition) that do not allow organisms to attain their biotic potential and keep the population size at a much lower level.
56. Assertion : The soil profiles of grassland, forest and desert biomes differ from each other.
Reason : Soil profile develops due to weathering process, accumulation of organic matter and leaching of mineral matter.
Answer:- (b)
57. Assertion : Heliophytes, generally have low photosynthetic, respiratory and metabolic activities.
Reason : Heliophytes are the sun adapted plants which are adapted to high intensity of light.
Answer (d) : Plants have special traits that help them to enlarge their tolerance limits to light regimes. Individual plants, as well as plant communities, adapt to different light intensities by becoming shade tolerant or sun adapted. Heliophytes are the sun adapted plants which are adapted to high intensity of light, and have higher temperature optima for photosynthesis,as well as have high rate of respiration. On the other hand, shade adapted plants also called as sciophytes generally have low photosynthetic, respiratory and metabolic activities. Plants such as ferns and several herbaceous plants growing on the ground under the dense canopy of trees, are shade tolerant plants.
58. Assertion : Mycorrhizal relation exists between Boletus and Pinus.
Reason : Mycorrhizal association is a symbiotic interaction.
Answer:- (b) : Mycorrhiza is a mutualistic or symbiotic interaction in which a fungus (e.g. Boletus) and a root of plant (e.g. Pinus) are involved. The root provides food and shelter to the fungus. The fungus helps the plant in solubilisation and absorption of minerals, water uptake and protection against pathogenic fungi.
59. Assertion : Mimicry is the resemblance of one organism to another.
Reason : Mimicry may be protective or aggressive.
Answer:- (b) : Mimicry is defined as the resemblance of one organism to another or to any natural object for the purpose of concealment, protection or for some other advantage. Mimicry employed by a prey is known as protective mimicry while the other used by a predator is termed as aggressive mimicry.
60. Assertion:Phytoplanktons grow in abundance in the profundal zone of lake.
SUBJECTIVE TYPE QUESTIONS
Very Short Answer Type Questions (VSA)
1. Soil horizons A and B represent solum. Why?
Answer:- Only A and B horizons of soil represents solum or true soil because they have weathered products of the parent rock.
2. Plants like Calotropis have evolved adaptations for defence against grazers. Explain.
Answer:- In order to keep predators or herbivores away from grazing, certain plants like Calotropis produce highly poisonous cardiac glycosides that can make herbivores sick when eaten.
3. Name the type of interaction that exists between barnacles and whale.
Answer:- Commensalism
4. When and why do some animals like frogs hibernate?
Answer:- When animals are exposed to low temperatures, hibernation is necessary for cold-blooded animals like frogs to prevent their metabolic rate from getting slow down.
5. In a population, per capita birth rate is 0.025 and per capita death rate is 0.008 during a unit time period. What is the value of intrinsic rate of natural increase, ‘r’ for the population?
Answer:- Intrinsic rate of natural increase,
6. When and why do some animals like snails go into aestivation?
Answer:- When animals like snails are exposed to lethal high temperatures, they go into aestivation to avoid the heat of summer.
7. Give one example where population estimation of an organism is done indirectly without actually counting the organism.
Answer:- Sometimes population size is indirectly estimated without actually counting them, for example, tiger census in our National parks and tiger reserves is often based on pug (animal’s foot print) marks and faecal pellets.
8. What is an interaction called when an orchid grows on a mango plant?
Answer:- Commensalism
9. Give example of an organism that enters ‘diapause’ and why.
Answer:- Bombyx mori (silk moth) is an insect that enters diapause due to some adverse environmental conditions such as drought, extreme temperature, reduced food availability which, in turn, delays the overall development. The physiological and metabolic activities diminish at this particular time. 10. Emphemerals are drought escapers xerophytic plants, for example: Tribulus terrestris.
Short Answer Type Questions (SA-I)
11. What type of interaction is seen when koel lays eggs in crow’s nest?
Answer:- Koel or cuckoo laying its eggs in crow’s nest is an example of brood parasitism. In brood parasitism, the parasitic bird lays its eggs in the nest of its host, and the host incubates them. Here, the eggs of the parasitic bird have evolved to resemble the host’s egg (in size and colour) so as to avoid being detected.
13. Draw and explain expanding age pyramids of human population. Why is it so called?
Answer:- An age pyramid for expanding human population is as follows:
Pyramid with broad base or triangular shape indicates a rapidly expanding population with a high percentage of prereproductive individuals followed by reproductive then postreproductive individuals. Thus, in rapidly growing population, birth rate is high and population keeps growing.
14. Differentiate between the mutualism and competition.
Answer
15. What does the given age pyramid signify about the status of a population? (The bar at the base represents pre-reproductive individuals.)
Answer:- Given is a bell-shaped age pyramid which signifies that the population is stable. Such age pyramid is formed when the number of pre-reproductive and reproductive individuals is almost equal and the post-reproductive individuals are comparatively fewer. It implies that the population is neither decreasing nor increasing, instead is maintained at a stable level.
16. Shark is eurythermal while polar bear is stenothermal. What is the advantage the former has and what is the constraint the later has?
Answer:- Sharks being eurythermal can tolerate wide range of temperature variations and thus have wider distribution on earth, on the other hand, polar bear being stenothermal can tolerate only narrow range of temperature and is restricted to specific regions only.
17. Explain why very small animals are rarely found in polar region.
Answer:- Very small animals have large surface area to body volume ratio. It results in excessive heat loss from exposed body surface. Such a great extent of heat loss makes it impossible for very small animals to survive in cold polar regions. Large animals have small surface area to body volume ratio, reducing heat loss and making temperature maintenance easier for them. This effect of temperature on the absolute size of an animal and the relative proportions of various body parts is also known as Bergmann’s rule.
18. Explain parasitism and coevolution with the help of one example of each.
Answer:- Parasitism is the interspecific interaction where one of species (called parasite) depends on the other species (host) for food and shelter and damages the host. E.g., malarial parasite in blood cells of humans. Coevolution in parasitism refers to the process in which parasite evolves mechanism to interact and neutralise the mechanism evolved by the host to reject or resist parasite.
19. Why do clown fish and sea anemone pair up? What is this relationship called?
Answer:- Mutualism is the interaction between clown fish and sea anemone. The clownfish lives among the stinging tentacles of sea anemone and gets protection from its predators. Clownfish has a slimy mucus covering that protects it from the poisonous tentacles of sea anemone. Also clown fish makes its meals from the anemone’s leftover. In return clown fish helps anemone in catching its prey by luring other fish towards it. It also eats the dead tentacles keeping the anemone and the area around it clean.
21. Why the plants that inhabit a desert are not found in a mangrove? Give reasons.
Answer:- Plants inhabiting desert (xerophytes) are not found in mangroves, because xerophytic plants are adapted to dry and hot environment. They possess various physical modifications to tolerate extreme water scarcity and heat, like extensive root system, succulent organs, leaf reduced to spine, etc. Mangrove swamp is a region of vegetation where soil is highly saline and water logged. Only halophytes can survive in such regions as they possess aerial roots called pneumatophores through which gaseous exchange occurs. Roots of xerophytes are positively geotropic and will suffocate and die in such badly aerated soil ultimately leading the whole plant to death.
Short Answer Type Questions (SA-II)
22. Refer to the given graph and answer the following questions.
(a) What does the graph represent? Identify A, and C.
(b) Differentiate between A and B.
(c) How organism C regulates their body functions?
Answer:- (a) The given graph represents various ways of organismic response i.e., possibilities of living organisms to cope with stressful conditions. A represents the conformers, B represents regulators and C represents partial regulators.
(b) Differences between A (conformers) and B (regulators) are as follows:
23. Define the following:
(a) Ecological niche
(b) Gause’s competitive exclusion principle
(c) Mimicry
Answer :- (a) Ecological niche (Grinnel, 1917) is a specific part of habitat occupied by individuals of a species which is circumscribed by its range of tolerance, range of movement, microclimate, type of food and its availability, shelter, type of predator and timing of activity.
24. (a) How are herbs able to grow on forest floors?
Answer:- (a) Sciophytes or shade plants like herbs and shrubs survive under the shadow of big canopied trees or sun plants or heliophytes in forests as they are perfect shade tolerant plants which show better growth in lower level of light intensity. They grow in a manner, that they are arranged in different strata according to their shade tolerance.
(b) What are osmoconformers?
Answer:- (b) Osmoconformers are those organisms which cannot maintain constant osmolarity of their body fluids and it varies according to their surrounding medium.
25. Predation is usually referred to as detrimental association. State any three positive roles that a predator plays in an ecosystem.
Answer:- Predators play important role in ecosystem. These are discussed as follows:
27. Name and explain the type of interaction that exists in mycorrhizae and between cattle egret and cattle.
Answer:- Mycorrhiza is a mutualistic interaction between fungus and roots of higher plants. The root provides food and shelter to the fungus. The fungus helps the plant in solublisation and absorption of minerals, water uptake and protection against pathogenic fungi.
29. When you go for a trek/trip to any high altitude places, you are advised to take it easy and rest for the first two days. Comment, giving reasons.
Answer:- Atmospheric pressure is low at higher altitudes as compared to plains. When we go for a trek/trip on high altitude, then due to low atmospheric pressure our body does not get enough oxygen, as a result of which we experience nausea, fatigue and heart palpitation (altitude sickness). But by taking rest for first two days, body gets acclimatised to high altitude conditions. The body compensates low oxygen availability by increasing red blood cell production, decreasing binding capacity of haemoglobin and increasing breathing rate. Hence, we automatically stop experiencing altitude sickness.
30. During a school trip to ‘Rohtang Pass’, one of your classmates suddenly developed ‘altitude sickness’. But, she recovered after sometime.
(a) Mention one symptom to diagnose the sickness.
(b) What caused the sickness?
(c) How could she recover by herself after sometime?
Answer:- (a) Heart palpitation
(b) Sickness is due to low atmospheric pressure of high altitudes, as body does not get enough oxygen.
(c) After sometimes, body compensates for low oxygen availability by increasing red blood cell production, decreasing binding capacity of haemoglobin and by increasing breathing rate.
31. Water is very essential for life. Write any three features both for plants and animals which enable them to survive in water scarce environment.
Answer:- Water is very essential for life. Plants and animals show modifications according to availability of water in the area. Some of the adaptations seen in plants which enable them to survive water scarce environment are as follows:
– Plants of hot deserts are adapted to survive in dry conditions of soil and high temperatures. The plant which evade dry conditions are known as ephemerals. Some plants have deep tap root which are capable of absorbing water from deep soil e.g., Prosopis, Acacia, etc.
– In case of cacti and succulents, the presence of fleshy leaves and stems to store water (succulence) is an adaptation to dry environment. In cacti, leaves are reduced to spines, where stems are modified to fleshy structures.
– Many tropical plants, particularly grasses which grow in hot and arid climates possess C4 pathway of photosynthesis. So, these plants perform better in low soil water environments. Such plants, use less water to achieve higher rates of photosynthesis.
Some of the adaptations seen in animals which enable them to survive water scarce environment are as follows:
– Desert lizards lack the physiological ability that mammals have to deal with the high temperature. They keep their body temperature fairly constant by behavioural means. They enjoy in the sun and absorb heat when their body temperature drops below the comfort zone but move into shade when the surrounding temperature starts increasing.
– The Kangaroo rats conserves water by excreting solid urine and can live from birth to death without even drinking water. Loss of water is minimised by producing nearly solid urine and faeces.
– The camels show tolerance to wide fluctuations in body temperature and are able to maintain blood stream moisture even during extreme heat stress.
32. Differentiate between hibernation and aestivation. Give one example of each.
Answer:- The differences between hibernation and aestivation are as follows:
33. Some organisms suspend their metabolic activities to survive in unfavourable conditions. Explain with the help of any four examples.
Answer:- To tide over unfavourable conditions, some organisms suspend their metabolic activities. These are discussed as follows :
34. (a) List any three ways of measuring population density of a habitat.
(b) Mention the essential information that can be obtained by studying the population of an organism.
Answer:- (a) The different methods to study population size are as follows:
35. Name and explain the kind of interaction in the following:
(i) Algae and fungi in lichens
(ii) Hermit crab and sea anemone
(iii) Head louse and humans
Answer (i) Mutualism is found between algae and fungi in lichen. Lichen is a composite entity which is formed jointly by an alga and a fungus. The fungus provides water, minerals and shelter to the alga. In return alga provides food to the fungus.
