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100 questions in this collection · Page 9 of 10
Question 81 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding morphological plant defenses:
I. Thorns are the most common morphological defense structure found in plants such as Acacia and Cactus. II. Thorns act as a physical deterrent that prevents large herbivores from easily browsing on the foliage. III. Nearly all physical plant defenses are highly toxic when ingested by mammals. IV. Some plants develop dense hairs or sticky trichomes on their leaves as morphological defenses against insect pests.
Which of the statements given above are correct?
Statements I, II, and IV are correct. Morphological defenses act mechanically rather than chemically. Statement III is incorrect because thorns and similar structures are physical deterrents, not toxic compounds.
Question 82 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding amensalism:
I. Amensalism is an interaction where one species is harmed and the other is completely unaffected. II. It is represented as a (-, 0) interaction in ecological matrices. III. An example of amensalism is when a tall, wide tree shades out a small seedling growing underneath it, reducing the seedling's growth without affecting the large tree. IV. Amensalism always results in mutual benefit for both species involved after long-term co-evolution.
Which of the statements given above are correct?
Statements I, II, and III are correct. Amensalism is a (-,0) interaction in which one species is harmed while the other remains unaffected. Statement IV is incorrect because amensalism never results in mutual benefit.
Question 83 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding the Monarch butterfly:
I. The Monarch butterfly is highly distasteful to its bird predators due to a special chemical present in its body. II. The butterfly synthesizes this toxic chemical during its adult stage when feeding on nectar. III. The caterpillar of the Monarch butterfly feeds on a poisonous weed to acquire the chemical. IV. This defense mechanism is an evolutionary adaptation to avoid bird predation.
Which of the statements given above are correct?
Statements I, III and IV are correct. The Monarch butterfly becomes distasteful by acquiring toxic cardiac glycosides during its caterpillar stage while feeding on poisonous milkweed. It does not synthesize these toxins from nectar during adulthood. Therefore, statement II is incorrect.
Question 84 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding the limitations of exponential growth:
I. Exponential growth can occur only when resources (food and space) are completely unlimited. II. Unlimited resources are common in stable, climax ecosystems. III. In nature, resource limitation eventually forces populations to follow a logistic growth pattern. IV. J-shaped curves of exponential growth usually end with a rapid crash as resources are depleted.
Which of the statements given above are correct?
Statements I, III and IV are correct. Exponential growth requires unlimited resources, a condition rarely sustained in nature. Stable climax ecosystems have limited resources and generally support logistic growth. Hence, statement II is incorrect.
Question 85 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding epiphytic orchids:
I. An orchid growing as an epiphyte on a mango branch is a classic example of commensalism (+, 0). II. The orchid benefits by getting physical support and better exposure to sunlight. III. The mango tree branch is severely harmed because the orchid acts as a root parasite that drains its sap. IV. The orchid does not absorb any nutrients or water from the host mango tree.
Which of the statements given above are correct?
Statements I, II and IV are correct. Epiphytic orchids use the host tree only for support and better access to sunlight without drawing nutrients or water from it. Therefore, statement III is incorrect.
Question 86 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding barnacles growing on whales:
I. Barnacles growing on the back of whales benefit by being transported to nutrient-rich plankton waters. II. The whale is unaffected by the presence of the barnacles. III. This is a mutualistic relationship because the barnacles clean the whale's skin. IV. This interaction represents commensalism, denoted as (+, 0).
Which of the statements given above are correct?
Statements I, II and IV are correct. Barnacles receive transport and feeding opportunities, whereas the whale is essentially unaffected. Hence, the relationship is commensalism, not mutualism, making statement III incorrect.
Question 87 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding the evolutionary impacts of parasites on hosts:
I. Parasites can drive host evolution, forcing hosts to develop resistance genes. II. If a host becomes resistant, the parasite must evolve new counter-adaptations to survive, representing co-evolution. III. Over evolutionary time, all parasites eventually evolve to become completely harmless to their hosts. IV. Highly specialized parasites are often host-specific, parasitizing only a single species.
Which of the statements given above are correct?
Statements I, II and IV are correct. Host and parasite undergo co-evolutionary arms races. Parasites generally continue to reduce host fitness and do not inevitably become harmless. Therefore, statement III is incorrect.
Question 88 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding parasitic degeneration:
I. Parasites often lose complex organs, such as eyes and digestive systems, that are unnecessary inside a host. II. To compensate for organ loss, they develop specialized structures like suckers and hooks for attachment. III. Parasites typically have extremely low reproductive rates because their survival is guaranteed by the host. IV. The loss of digestive tracts in gut parasites is logical because they directly absorb pre-digested nutrients.
Which of the statements given above are correct?
Statements I, II and IV are correct. Parasites possess high reproductive capacity to ensure transmission to new hosts. Thus, statement III is incorrect.
Question 89 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding host-specific parasites:
I. A host-specific parasite can complete its life cycle on only a single, specific host species. II. Host-specificity increases the parasite's chance of survival if the host species goes extinct. III. Co-evolution ensures that any defense developed by the host is countered by a specific adaptation in the parasite. IV. Parasites that are not host-specific can easily parasitize any taxonomic group with equal efficiency.
Which of the statements given above are correct?
Statements I and III are correct. Host-specific parasites are vulnerable to extinction if their host disappears. Generalist parasites also have physiological limits and cannot parasitize every taxonomic group equally well. Hence, statements II and IV are incorrect.
Question 90 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding lichens:
I. Lichens are mutualistic associations between a fungus and a photosynthesizing alga or cyanobacterium. II. The photobiont (alga/cyanobacterium) provides organic nutrients via photosynthesis. III. The mycobiont (fungus) provides protection, absorbs water and minerals, and anchors the association. IV. The fungus can easily survive and reproduce in nature without its algal partner.
Which of the statements given above are correct?
Lichens are obligate mutualistic associations between a fungus and a photosynthetic alga or cyanobacterium. The algal partner synthesizes food through photosynthesis, while the fungal partner provides protection, water, minerals, and anchorage. The fungal partner is highly specialized and generally cannot survive independently in nature. Hence, statement IV is incorrect.