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100 questions in this collection · Page 2 of 10
Question 11 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements on life history variations:
I. Organisms evolve to maximize their reproductive fitness, also called Darwinian fitness (high r value), in their habitat. II. Pacific salmon fish and bamboo breed many times during their lifetime. III. Most birds and mammals breed only once in their lifetime. IV. Oysters and pelagic fishes produce a large number of small-sized offspring, whereas birds and mammals produce a small number of large-sized offspring.
Which of the statements given above are correct?
Statements II and III are incorrect. Pacific salmon fish and bamboo breed only once in their lifetime, whereas most birds and mammals breed many times. Statements I and IV are correct.
Question 12 of 100
📘 CLASS XII
Organisms And Populations
Read the statements regarding interspecific interactions between species A and species B:
I. Both species benefit in mutualism, and both lose in competition. II. In amensalism, one species is benefited and the other is neither benefited nor harmed. III. In both parasitism and predation, only one species benefits while the other is harmed. IV. Commensalism is an interaction where one species is benefited and the other is unaffected.
Which of the statements given above are correct?
Statement II is incorrect because in amensalism, one species is harmed while the other remains unaffected. The description given actually represents commensalism. Statements I, III, and IV are correct.
Question 13 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding the roles of predators in ecosystems:
I. Predators act as 'conduits' for energy transfer across trophic levels. II. Predators keep prey populations under control, preventing them from achieving high densities that cause instability. III. The prickly pear cactus introduced into Australia was controlled by introducing a cactus-feeding beetle. IV. In rocky intertidal communities, the starfish Pisaster is an important predator that helps maintain species diversity.
Which of the statements given above are correct?
Statement III is incorrect because the prickly pear cactus was controlled by introducing a cactus-feeding moth, not a beetle. Statements I, II, and IV are correct.
Question 14 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements about predator-prey dynamics:
I. If a predator is too efficient and overexploits its prey, then the prey might become extinct, leading to the extinction of the predator as well. II. Predators in nature are 'prudent' because overexploitation leads to their own food shortage and extinction. III. Herbivores, broadly categorized, are ecologically very different from predators because they consume plant matter. IV. Starfish Pisaster removal from an enclosed intertidal area on the American Pacific Coast led to the extinction of more than 10 species of invertebrates within a year.
Which of the statements given above are correct?
Statement III is incorrect because herbivores are, in a broad ecological sense, not very different from predators. Statements I, II, and IV are correct.
Question 15 of 100
📘 CLASS XII
Organisms And Populations
Consider the statements regarding defensive adaptations in prey species:
I. Some species of insects and frogs are cryptically-colored (camouflaged) to avoid detection by predators. II. The Monarch butterfly is highly distasteful to its bird predator because it synthesizes a toxic cardiac glycoside in its adult body. III. Monarch butterflies acquire their defensive chemicals during their caterpillar stage by feeding on a poisonous weed. IV. Plants cannot run away from herbivores and have evolved morphological and chemical defenses.
Which of the statements given above are correct?
Statement II is incorrect because the Monarch butterfly does not synthesize cardiac glycosides. It acquires these defensive chemicals during its caterpillar stage by feeding on poisonous Calotropis. Statements I, III, and IV are correct.
Question 16 of 100
📘 CLASS XII
Organisms And Populations
Read the statements regarding plant defense mechanisms against herbivores:
I. Thorns in Acacia and Cactus are common morphological means of defense. II. Nearly 25% of all insects are phytophagous, feeding on plant sap and other parts. III. The weed Calotropis produces highly poisonous cardiac glycosides, which is why cattle or goats generally do not browse on it. IV. Nicotine, caffeine, quinine, strychnine, and opium are produced by plants as metabolic waste products that happen to repel grazers.
Which of the statements given above are correct?
Statement IV is incorrect because compounds such as nicotine, caffeine, quinine, strychnine, and opium are produced by plants as defensive chemicals against grazers and browsers, not merely as metabolic waste products. Statements I, II, and III are correct.
Question 17 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding competition:
I. Interspecific competition occurs only between closely related species competing for the same limiting resources. II. Totally unrelated species can compete for the same resource, such as flamingoes and resident fishes competing for zooplankton in South American lakes. III. In interference competition, the feeding efficiency of one species may be reduced due to the inhibitory presence of another species, even when resources are abundant. IV. Competition is best defined as a process in which the fitness of one species (intrinsic rate of increase, r) is significantly lower in the presence of another species.
Which of the statements given above are correct?
Statement I is incorrect because competition is not restricted to closely related species and may occur even when resources are not limiting. Statements II, III, and IV are correct.
Question 18 of 100
📘 CLASS XII
Organisms And Populations
Read the statements concerning ecological evidence for competition:
I. The Abingdon tortoise in the Galapagos Islands became extinct within a decade after goats were introduced due to the greater browsing efficiency of the goats. II. Competitive release occurs when a species restricted to a small area expands its distribution dramatically after its competitor is experimentally removed. III. Connell's experiments showed that the smaller barnacle Chthamalus competitively excludes the larger barnacle Balanus. IV. In general, carnivores appear to be more adversely affected by competition than herbivores and plants.
Which of the statements given above are correct?
Statements III and IV are incorrect. Connell demonstrated that the larger and competitively superior Balanus excludes Chthamalus. Herbivores and plants, rather than carnivores, generally appear to be more adversely affected by competition.
Question 19 of 100
📘 CLASS XII
Organisms And Populations
Consider the statements regarding competitive exclusion and co-existence:
I. Gause's Competitive Exclusion Principle states that two closely related species competing for the same resources cannot coexist indefinitely, and the competitively inferior one will eventually be eliminated. II. Gause's principle holds true whether resources are limiting or unlimited. III. Resource partitioning is a mechanism in which competing species evolve to avoid competition by using different feeding times or foraging patterns. IV. MacArthur showed that five closely related species of warblers living on the same tree were able to coexist because of behavioural differences in their foraging activities.
Which of the statements given above are correct?
Statement II is incorrect because Gause's Competitive Exclusion Principle applies only when resources are limiting. Statements I, III, and IV are correct.
Question 20 of 100
📘 CLASS XII
Organisms And Populations
Read the statements concerning parasitism:
I. Parasites and their hosts tend to co-evolve; if the host evolves resistance mechanisms, the parasite must evolve counter-mechanisms to remain successful. II. Parasites have evolved adaptations such as the loss of unnecessary sense organs, presence of adhesive organs or suckers, loss of digestive system, and high reproductive capacity. III. The malarial parasite depends on two intermediate hosts (a snail and a fish) to complete its complex life cycle. IV. Majority of parasites harm their hosts by reducing host survival, growth, reproduction, and population density.
Which of the statements given above are correct?
Statement III is incorrect because the human liver fluke, not the malarial parasite, depends on two intermediate hosts (a snail and a fish) to complete its life cycle. The malarial parasite requires a mosquito vector for transmission. Statements I, II, and IV are correct.