CBSE 12th Standard Biology Subject Biodiversity and Conservation Case Study Questions With Solution 2021
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CBSE 12th Standard Biology Subject Biodiversity and Conservation Case Study Questions With Solution 2021
12th Standard CBSE
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Reg.No. :
Biology
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Read the following and answer any four questions from (i) to (v) given below:
The Kakapo is the world's largest and heaviest parrot, found only in New Zealand. It is unusual in that it is nocturnal, flightless and ground-dwelling. It is an excellent climber of trees, has strong legs that allow it to "jog" several kilometres in a single trip, and has mossy green plumage mottled with brown and yellow. The Kakapo is also critically endangered as of now, there were only few known living individuals left.
(i) Which could be the possible reason for Kakapo to be well-adapted to its environment prior to the arrival of humans in New Zealand?(a) Kakapo was active only in the night when its potential predators would not be out for hunting. (b) The Kakapo would likely be well-camouflaged among the forest foliage due to its greenish plumage. (c) It was able to effectively hunt for food in the night. (d) All of these (ii) When humans started to settle in New Zealand, they took with them non-native animals, including mammals such as cats, dogs and stoats. By which of the following ways, human settlement likely contributed to a near decimation of Kakapo populations in New Zealand?
(a) Habitat destruction (b) Alien species invasion (c) Pollution (d) Both (a) and (b) (iii) All known survived Kakapo have been relocated by the New Zealand government to three predator-free islands, where they are monitored year round by staffs and volunteers to ensure that the birds are safe, healthy and well-fed. The extremely low population of Kakapo is a hurdle to the species becoming viable in the long term, despite such dedicated conservation efforts. This is because
(a) the small population results in very small gene pool (b) there would be very limited genetic diversity among the resulting offspring. (c) of reduced capacity of the species to adapt and survive changes in the environment. (d) All of these (iv) The reasons behind conserving biodiversity have been grouped into which of the following categories?
(a) Narrowly utilitarian (b) Broadly utilitarian (c) Ethical (d) All of these (v) One of the ex situ conservation methods for endangered species is
(a) wildlife sanctuaries (b) biosphere reserves (c) cryopreservation (d) national parks. -
Read the following and answer any four questions from (i) to (v) given below:
Edward Wilson described diversity at all levels of biological organisation ranging from macromolecules inside the cells to biomes. It is of three inter-related hierarchial levels-genetic diversity, species diversity and community ecosystem diversity. Species diversity is the variety in the number and richness of the species of a region. For example, the Western ghats have a greater amphibian species diversity than the Eastern ghats.
(i) The number of species per unit area is called(a) species evenness (b) species richness (c) species equitability (d) both (a) and (c). (ii) The table below gives the population (in thousands) of ten species (A - J) in four areas (I - IV) consisting of the number of habitats given within brackets against each. Study the table and answer the question which follows:
Area and
number of
habitatsSpecies and their population (in thousands) in the area A B C D E F G H I J I(11) 23 12 0.52 6.0 - 3.1 1.1 9.0 - 10.3 II(11) 10.2 - 0.62 - 1.5 3.0 - 8.2 1.1 11.2 III(13) 11.3 0.9 0.48 2.4 1.4 4.2 0.8 8.4 2.2 4.1 IV(12) 3.2 10.2 1.1 4.8 0.4 3.3 0.8 7.3 1.3 2.1
Which are out of I to IV shows maximum species diversity?(a) II (b) III (c) IV (d) I (iii) Study the given populations and choose the correct answer in relation to species diversity.
Population Species Group Individuals Population A I Mammals 3 II Birds 2 III Amphibians 2 Population B I Mammals 2 II Mammals 2 III Amphibians 1 Population C I Mammals 3 II Mammals 2 III Mammals 1
Maximum diversity Minimum diversity
(a) Population B Population C
(b) Population A Population C
(c) Population A Population B
(d) Population B Population A
(iv) The concept of species diversity has two components : evenness and richness. Evenness is based on the relative abundance of species. Richness is based on the total number of species present. Diversity indices combine a measure of richness and evenness. The Simpson index (D) is calculated from the following equations:
\(D=\sum_{i=1}\left(n_{i} / N\right)^{2}\)
where, n = total number of organisms of particular species
N = total number of organisms of all species
Below are data collected in two terrestrial plant communities that represent part of a successional
chronosequence. In this case the values were measured as percent cover.Early Successional Community Late Successional Community Species Percent Cover Species Percent Cover A 83 F 24 B 5 G 20 C 9 H 18 D 2 I 23 E 1 J 15 The data indicate that, relative to the early successional community, the late successional community has which of the following characteristics?
Species Richness Evenness
(a) Higher Higher
(b) Higher Lower
(c) Same Lower
(d) Same Higher
(v) Select the incorrect statement regarding species diversity.(a) It results in polymorph formation and is useful in adaptation to changes in environmental conditions. (b) Number of individuals of different species represent species evenness. (c)It influences biotic interactions and stability of the community. (d) It is a trait of the community. -
Read the following and answer any four questions from (i) to (v) given below:
Non-native or alien species are often introduced in advertently for their economic and other uses. They often become invasive and drive away-the local species. Exotic species have proved harmful to both aquatic and terrestrial ecosystems. For example, water hyacinth (Eichhornia crassipes) was introduced in Indian waters to reduce pollution. It was clogged water bodies including wetlands at many places resulting in death of several aquatic plants and animals.
(i) Island water ecosystem are the most vulnerable due to(a) small size (b) small number of species (c) increases reproductive capacity (d) both (a) and (b). (ii) Which of the following is not an alien species?
(a) Lantana camara (b) Periplaneta americana (c) Nile Perch (d) Yucca moth (iii) Second major cause of species extinction is
(a) habitat loss and fragmentation (b) over exploitation (c) alien species invasion (d) co-extinction. (iv) Assertion: Eichhornia crassipes drains off oxygen from water and can be seen growing in standing water.
Reason: Eichhornia crassipes is an indigenous species of India.(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) Both assertion and reason are false. (v) The population of species P in a certain community was constant until a population species Q from a distant land was subsequently introduced into that community. The interaction between the two populations is reflected in the graph below.
What could be the possible reason for the decrease in the population of species P over a number of days?(a) Species Q is a predator of species P. (b) Species Q.is a prey species which wiped out the population of species P. (c) Species P and Q compete for space but feeds on different food. (d) None of these -
Read the following and answer any four questions from (i) to (v) given below:
Wetlands are called Ramsar sites because the first international convention on their conservation was held in Ramsar in Iran in 1971. Wetlands or Ramsar sites are low lying marshy areas which get filled up during rains due to runoff and overflow from other water bodies. They are often considered to be waste lands which are used as dumping area and filled up to recover land for various constructions activities. As a result, a large number of wetlands have disappeared.
(i) Select the incorrect match of wetland and its location.Wetland Location (a) Harike Punjab (b) Chandra Tal H.P. (c) Bhoj M.P. (d) Ashtamudi Odisha (ii) Migratory bird flamingo breeds in which of the following wetlands?
(a) Bhitarkanika Mangroves (b) Rann of Kutch (c) Harike (d) Chandra Tal (iii) Which of the following is not an importance of wetlands?
(a) They are an important source of recharging groundwater. (b) They provide protection from floods. (c) They are good source of siltation and purification of water. (d) None of these (iv) Which of the following wetland ecosystem is highly acidic and has a accumulation of decomposed plants known as peat?
(a) Bog (b) Mangrove (c) Estuary (d) Watershed (v) The mangroves of Bhitarkanika are famous for
(a) rare migratory waterbirds (b) nesting sites for endangered olive ridley turtles (c) prawn cultivation (d) all of these. -
Read the following and answer any four questions from (i) to (v) given below :
Excessive exploitation of species, whether a plant or animal reduces the size of its population so it becomes vulnerable to extinction. Such as Dodo and passenger pigeon have become extinct due to over exploitation by humans. Thus the world is facing accelerated rates of species extinctions, largely due to human interference.
(i) Which of the following cause of biodiversity loss is not included in evil quartet?(a) Coextinction (b) Pollution (c) Alien species invasion (d) Habitat loss and fragmentation (ii) Identify the species that have become extinct due to over exploitation
(a) Stellar sea cow (b) Yucca moth (c) Blatta orientalis (d) Nile Perch (iii) Factors which make species susceptible to extinction are
(a) large population size (b) lack of genetic variability (c) lower status of trophic level (d) ability to switch over to alternate foods. (iv) Assertion: Pollution reduces species biodiversity.
Reason: Spillover of oil in sea causes death of several marine animals.(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) Both assertion and reason are false. (v) __________ is the first major cause of species extinction.
(a) Coextinction (b) Over exploitation (c) Habitat destruction (d) Alien species invasion.
Case Study Questions
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CBSE 12th Standard Biology Subject Biodiversity and Conservation Case Study Questions With Solution 2021 Answer Keys
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(i) (d) : Since the Kakapo is nocturnal, it was active only in the night when its potential predators would not be out for hunting. With its greenish plumage, the Kakapo could likely be well camouflaged among the forest foliage in the daytime when it is resting hence evading detection by its predators. It was able to effectively hunt for food in the night given its ability to climb trees and travel significant distances over land despite lacking the ability to fly.
(ii) (d): As humans settled in New Zealand, they would have cleared the land to make way for their own needs e.g., farmland, hence shrinking the natural habitats of the Kakapo. The new mammals that were introduced into the Kakapos habitats might have out-competed the Kakapo for the limited food resources available. The new mammals that were introduced might also have easily preyed on the Kakapo (e.g., by using their sense of smell), as the KakapoIikely lacked the necessary adaptations to defend itself given that such predators were never present in the past. For instance, many mammals such as cats are nocturnal and hence would prey on Kakapo when the latter are also active at night.
(iii) (d) : The small populations results in a yery small gene pool, i.e., a very limited variety of alleles / traits among surviving individuals of the species. Even if the existing birds manage to breed and multiply significantly, there would be very limited genetic diversity among the resulting offspring. This would lead to reduce capacity of the species to adapt to and survive changes in the environment. There may also be reduced fitness in the offspring given increased likelihood of homozygosity of recessive harmful! deleterious alleles, which would result in these alleles being expressed to bring about unfavourable phenotypes.
(iv) (d) : We should conserve biodiversity. The reason for this can be broadly divided into three categories:
(i) Narrowly utilitarian (Humans derive a major part of their requirement from organisms). (ii) Broadly utilitarian (Biodiversity is fundamental to ecosystem services of nature).
(iii) Ethical (Every living species has an intrinsic value, it is our moral duty not to destroy them).
(v) (c): Ex situ (off site) conservation is conservation of selected rare plants/animals in places outside their natural homes. It is a desirable approach to save threatened or endangered plant or animal species from extinction. Ex situ conservation includes offsite collections, gene banks, in vitro fertilisation, cryopreservation techniques and tissue culture. -
(i) (b) : The number of species per unit area is called species richness.
(ii) (b)
(iii) (b)
(iv) (d)
(v) (a) : Genetic diversity results in polymorph formation and is useful in adaptation to changes in environmental conditions. -
(i) (d)
(ii) (d) : Pronuba yuccasella shows obligatory mutualistic relationships with Yucca.
(iii) (c) : Alien species invasion is considered to be second major cause of extinction of species.
(iv) (c): Eichhornia crassipes is an aquatic plant, native to Amazon basin. This plant was introduced into India for its beautiful flowers and shape ofleaves.
(v) (a) -
(i) (d) : Ashtamudi is located in Kerala.
(ii) (b): Migratory bird flamingo breeds in Rann of Kutch.
(iii) (d)
(iv) (a): The rate of peat formation is sufficiently high to create a bog in hydrosere. A bog is a permanently waterlogged raised site that receives all its water and nutrient inputs from rainfall or other precipitation.
(v) (b) -
(i) (b) : Evil quartet, i.e., four major causes of biodiversity loss are habitat loss and fragmentation, over exploitation, alien species invasion and co-extinction.
(ii) (a)
(iii) (b) : Population traits which make species susceptible to extinction are: small population, higher status of trophic level and inability to switch over to alternate foods.
(iv) (a)
(v) (c)
Case Study Questions
