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100 questions in this collection · Page 10 of 10
Question 91 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding mycorrhizal networks:
I. Mycorrhizal fungi form extensive networks of hyphae in the soil surrounding plant roots. II. These networks increase the effective surface area of the root system for absorption. III. Mycorrhizal associations are parasitic because the fungus drains the plant's carbohydrate reserves without providing any benefit. IV. Plants associated with mycorrhizae show enhanced resistance to root pathogens.
Which of the statements given above are correct?
Mycorrhizae are mutualistic associations. Fungal hyphae increase the absorptive surface area of roots, enhance mineral uptake (especially phosphorus), and improve resistance against root pathogens. In return, plants provide carbohydrates to the fungus. Statement III is incorrect because the interaction is mutualistic, not parasitic.
Question 92 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding the mutualistic rewards in pollination:
I. Plants offer physical rewards such as nectar and pollen to attract animal pollinators. II. Seed-dispersing animals are rewarded with nutritious, juicy fruits. III. These rewards are completely free of cost to the plant and do not require metabolic energy to produce. IV. Cheaters can disrupt these mutualisms by stealing nectar without transferring pollen.
Which of the statements given above are correct?
Plants invest metabolic energy in producing nectar, pollen, and fruits as rewards for pollinators and seed dispersers. Some organisms act as nectar thieves by taking rewards without pollinating flowers. Thus, statement III is incorrect.
Question 93 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding Gause's Competitive Exclusion Principle:
I. Gause's principle predicts that two competing species can coexist if their niches are slightly different. II. If two species compete for the same limiting resource, the competitively superior species will eventually eliminate the other. III. If resources are completely unlimited, Gause's principle still dictates that competitive exclusion must occur. IV. Under unlimited resources, both species can grow exponentially without excluding one another.
Which of the statements given above are correct?
Competitive exclusion occurs when species compete for the same limiting resource. Species can coexist by occupying different niches or partitioning resources. If resources are unlimited, competitive exclusion does not occur, allowing both populations to grow. Hence, statement III is incorrect.
Question 94 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding energy flow and predation:
I. Predators play a vital role in transferring energy fixed by plants to higher trophic levels. II. Without predators, the energy locked in herbivore populations would remain largely static and unavailable to carnivores. III. Decomposers are the only organisms that can transfer energy across trophic levels. IV. Herbivores are ecologically classified as predators because they consume autotrophic biomass.
Which of the statements given above are correct?
Predators function as energy conduits across trophic levels, and herbivores are broadly considered predators of plants because they consume living autotrophic biomass. Decomposers recycle nutrients from dead organic matter rather than being the only pathway for energy transfer. Therefore, statement III is incorrect.
Question 95 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding fitness in population ecology:
I. Ecological fitness refers to an organism's ability to survive in its immediate physical environment. II. Evolutionary fitness (Darwinian fitness) is measured by an organism's lifetime reproductive success (the number of viable offspring left behind). III. High ecological fitness always guarantees high evolutionary fitness, regardless of whether the organism reproduces. IV. Natural selection acts on differences in evolutionary fitness among individuals in a population.
Which of the statements given above are correct?
Statements I, II and IV are correct. Ecological fitness concerns survival, whereas Darwinian fitness depends on successful reproduction. An organism that survives but leaves no offspring has zero evolutionary fitness. Hence, statement III is incorrect.
Question 96 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding the prudence of natural predators:
I. In nature, predators are 'prudent' because they do not hunt their prey to complete extinction. II. Over-exploiting a prey population leads to a food shortage that can cause the predator population to crash. III. Prudent behavior is a conscious, cognitive decision made by individual predators to conserve resources. IV. Prudence is an evolutionary outcome because natural selection eliminates overly aggressive predator lineages that deplete their own food supply.
Which of the statements given above are correct?
Statements I, II and IV are correct. Predator prudence is an evolutionary outcome rather than a conscious decision. Predator populations that overexploit their prey eventually decline due to food shortage. Therefore, statement III is incorrect.
Question 97 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding a stable human population:
I. The pre-reproductive and reproductive age groups are approximately equal in size. II. The birth rate is roughly equal to the death rate, assuming zero migration. III. The age pyramid of a stable population exhibits a classic bell-shaped profile. IV. A stable population is characterized by a rapidly expanding base of young children.
Which of the statements given above are correct?
Statements I, II and III are correct. Stable populations have balanced age groups and nearly equal birth and death rates. A rapidly expanding base is characteristic of a growing population, making statement IV incorrect.
Question 98 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding competition in South American lakes:
I. Visiting flamingoes and resident fishes compete for the same food resource. II. The shared resource they compete for is zooplankton. III. This interaction demonstrates that completely unrelated species can compete for the same resources. IV. Flamingoes and fishes never compete because they belong to completely different taxonomic classes.
Which of the statements given above are correct?
Statements I, II and III are correct. Competition can occur between distantly related organisms when they depend on the same limiting resource, such as zooplankton. Therefore, statement IV is incorrect.
Question 99 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding interference competition:
I. Interference competition occurs when one species physically prevents another from accessing a resource. II. It can occur even if the resource in question is highly abundant. III. The feeding efficiency of one species is reduced due to the inhibitory presence of the other species. IV. It is synonymous with resource exploitation, where one species simply consumes the resource faster than the other.
Which of the statements given above are correct?
Statements I, II and III are correct. Interference competition involves direct behavioral or chemical interactions that reduce another species' feeding efficiency and may occur even when resources are abundant. Statement IV is incorrect because exploitation competition operates indirectly through resource depletion.
Question 100 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding co-evolutionary stability:
I. The fig tree and the pollinator wasp are locked in an obligate, one-to-one mutualism. II. If the fig-wasp undergoes structural changes in its ovipositor, the fig fruit structure must co-evolve to maintain the interaction. III. Co-evolution ensures that the relationship remains mutually beneficial and resistant to evolutionary decay. IV. The fig tree can easily adapt to be pollinated by wind if its specific wasp partner goes extinct.
Which of the statements given above are correct?
Statements I, II and III are correct. The fig-wasp association is an obligate, highly specialized mutualism maintained through co-evolution. Wind pollination cannot readily replace the specific wasp partner, making statement IV incorrect.