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100 questions in this collection · Page 4 of 10
Question 31 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements comparing exponential and logistic growth:
I. A J-shaped curve is obtained when resource (food and space) availability is unlimited in the habitat. II. A sigmoid curve is obtained when resource availability is finite and becomes limiting. III. The integral form of the exponential growth equation is represented as Nt = N0ert. IV. The base of natural logarithms (e) in the exponential equation is approximately 2.71828.
Which of the statements given above are correct?
All statements are correct. Exponential growth under unlimited resources produces a J-shaped curve and follows Nt = N0ert, whereas logistic growth under limited resources produces a sigmoid (S-shaped) curve.
Question 32 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding the reproductive strategies of organisms:
I. Pacific salmon fish breeds only once in its lifetime and then dies. II. Bamboo species breed many times during their long lifetime. III. Most birds and mammals breed many times during their lifetime. IV. Oysters and pelagic fishes produce a large number of small-sized offspring.
Which of the statements given above are correct?
Statements I, III, and IV are correct. Statement II is incorrect because bamboo species, like Pacific salmon, breed only once during their lifetime and then die.
Question 33 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements about the types of interspecific interactions between Species A and Species B:
I. In mutualism, both Species A and Species B benefit, designated as (+,+). II. In competition, both Species A and Species B lose from the interaction, designated as (-,-). III. In amensalism, one species is harmed (-) and the other is unaffected (0). IV. In commensalism, one species is benefited (+) and the other is unaffected (0).
Which of the statements given above are correct?
All four statements are correct. These represent the standard types of interspecific interactions described in ecology.
Question 34 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding the ecological roles of predators:
I. Predators act as conduits for energy transfer across trophic levels by consuming the energy fixed by autotrophs. II. Predators keep prey populations under control, preventing them from achieving high densities that cause instability. III. The invasive prickly pear cactus introduced into Australia was brought under control by introducing its natural predator, a cactus-feeding moth. IV. Biological control methods adopted in agricultural pest control are based on the ability of predators to regulate prey populations.
Which of the statements given above are correct?
All statements are correct. Predators transfer energy across trophic levels, regulate prey populations, serve as biological control agents, and the prickly pear cactus in Australia was successfully controlled by introducing a cactus-feeding moth.
Question 35 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding the rocky intertidal field experiments:
I. In the rocky intertidal communities of the American Pacific Coast, the starfish Pisaster acts as an important predator. II. When all Pisaster starfish were experimentally removed from an enclosed intertidal area, more than 10 species of invertebrates became extinct within a year. III. The extinction of these invertebrate species occurred because of intense interspecific competition among them in the absence of the predator. IV. Predators in nature are prudent because if they overexploit their prey, the prey might go extinct, leading to the predator's own extinction.
Which of the statements given above are correct?
All statements are correct. Pisaster is a keystone predator whose removal resulted in competitive exclusion of many invertebrate species. Predators are also considered ecologically prudent because excessive exploitation ultimately threatens their own survival.
Question 36 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements on how prey species lessen the impact of predation:
I. Some species of insects and frogs are cryptically coloured (camouflaged) to avoid detection by predators. II. The Monarch butterfly is highly distasteful to predatory birds because of a special chemical present in its body. III. The Monarch butterfly acquires this distasteful chemical during its caterpillar stage by feeding on a poisonous weed. IV. The adult Monarch butterfly synthesizes this toxic chemical internally using its own metabolic pathways.
Which of the statements given above are correct?
Statements I, II, and III are correct. Statement IV is incorrect because the Monarch butterfly acquires the toxic chemical from the poisonous weed consumed during the caterpillar stage rather than synthesizing it.
Question 37 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements regarding herbivory and plant defense mechanisms:
I. Nearly 25 percent of all insects are phytophagous, feeding on plant sap and other plant parts. II. Thorns in Acacia and Cactus are common morphological defenses against herbivores. III. The weed Calotropis produces highly poisonous cardiac glycosides, preventing cattle and goats from browsing on it. IV. Plant-produced chemicals such as nicotine, caffeine, quinine, strychnine, and opium function as defenses against grazers and browsers rather than simple metabolic wastes.
Which of the statements given above are correct?
All four statements are correct. Plants possess both morphological defenses such as thorns and chemical defenses including cardiac glycosides and secondary metabolites that deter herbivores.
Question 38 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding interspecific competition:
I. Darwin was convinced that interspecific competition is a potent force in organic evolution. II. Totally unrelated species can compete for the same resource, such as visiting flamingoes and resident fishes competing for zooplankton in South American lakes. III. In interference competition, resources must be strictly limiting for competition to occur. 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?
Statements I, II, and IV are correct. Statement III is incorrect because interference competition can occur even when resources are abundant, simply due to the inhibitory presence of another species.
Question 39 of 100
📘 CLASS XII
Organisms And Populations
Read the following statements concerning competitive outcomes:
I. The Abingdon tortoise in Galapagos Islands became extinct within a decade after goats were introduced on the island, due to the greater browsing efficiency of the goats. II. Competitive release occurs when a species restricted to a small geographical area expands its distributional range dramatically after its competitor is experimentally removed. III. Goats are competitively superior to Abingdon tortoises because tortoises have extremely slow reproductive rates. IV. In general, herbivores and plants appear to be more adversely affected by competition than carnivores.
Which of the statements given above are correct?
Statements I, II, and IV are correct. Statement III is incorrect because the Abingdon tortoise became extinct due to the greater browsing efficiency of goats, not because of the tortoise's slow reproductive rate.
Question 40 of 100
📘 CLASS XII
Organisms And Populations
Consider the following statements regarding Connell's elegant field experiments:
I. The experiments were carried out on the rocky sea coasts of Scotland. II. The larger and competitively superior barnacle Balanus dominates the intertidal area and excludes the smaller barnacle Chathamalus from that zone. III. The smaller barnacle Chathamalus is the dominant competitor that excludes Balanus from the lower intertidal zone. IV. The evidence for competitive exclusion occurring in nature is always completely conclusive and easily demonstrated in all wild communities.
Which of the statements given above are correct?
Statements I and II are correct. Statement III is incorrect because Balanus is competitively superior and excludes Chathamalus. Statement IV is incorrect because competitive exclusion is not always conclusive or easy to demonstrate in natural communities.