Sun	Mon	Tue	Wed	Thu	Fri	Sat
23	24	25	26	27	28	1
2	3	4	5	6	7	8
9	10	11	12	13	14	15
16	17	18	19	20	21	22
23	24	25	26	27	28	29
30	31	1	2	3	4	5

Back to Main Page

Multiple Choice Questions

According to the passage the generation of water bugs hatching during the summer is likely to ........

English (DRDO) (Phase-II) Reading comprehension (P)

Read the passage and answer the following questions:

Three basic adaptive responses—regulatory, acclimatory, and developmental—may occur in organisms as they react to changing environmental conditions. In all three, adjustment of biological features (morphological adjustment) or of their use (functional adjustment) may occur. Regulatory responses involve rapid changes in the organism’s use of its physiological apparatus—increasing or decreasing the rates of various processes, for example. Acclimation involves morphological change—thickening of fur or red blood cell proliferation—which alters physiology itself. Such structural changes require more time than regulatory response changes. Regulatory and acclimatory responses are both reversible.
Developmental responses, however, are usually permanent and irreversible: they become fixed in the course of the individual’s development in response to environmental conditions at the time the response occurs. One such response occurs in many kinds of water bugs. Most water-bug species inhabiting small lakes and ponds have two generations per year. The first hatches during the spring reproduce during the summer, then dies. The eggs laid in the summer hatch and develop into adults in late summer. They live over the winter before breeding in early spring. Individuals in the second (overwintering) generation have fully developed wings and leave the water in autumn to overwinter in forests, returning in spring to small bodies of water to lay eggs. Their wings are absolutely necessary for this seasonal dispersal. The summer (early) generation, in contrast, is usually dimorphic—some individuals have normal functional (macropterous) wings; others have much-reduced (macropterous) wings of no use for flight. The summer generation’s dimorphism is a compromise strategy, for these individuals usually do not leave the ponds and thus generally have no use for fully developed wings. But small ponds occasionally dry up during the summer, forcing the water bugs to search for new habitats, and eventuality that macropterous individuals are well adapted to meet.
The dimorphism of micropterous and macropterous individuals in the summer generation expresses developmental flexibility; it is not genetically determined. The individual’s wing form is environmentally determined by the temperature to which developing eggs are exposed prior to their being laid. Eggs maintained in a warm environment always produce bugs with normal wing, but exposure to cold produces micropterous individuals. Eggs producing the overwintering brood are all formed during the late summer’s warm temperatures. Hence, all individuals in the overwintering brood have normal wings. Eggs laid by the overwintering adults in the spring, which develop into the summer generation of adults, are formed in early autumn and early spring. Those eggs formed in autumn are exposed to cold winter temperatures, and thus produce micropterous adults in the summer generation. Those formed during the spring are never exposed to cold temperatures, and thus yield individuals with a normal wing. Adult water bugs of the overwintering generation brought into the laboratory during the cold months and kept warm, produce only macropterous offspring.

According to the passage, the generation of water bugs hatching during the summer is likely to

be made up of equal numbers of macropterous and micropterous individuals

show a marked inability to fly from one pond to another

exhibit genetically determined differences in wing form from the early spring-hatched generation

contain a much greater proportion of macropterous water bugs than the early spring-hatched generation

छोटे Courses बड़े Results

Master Reading comprehension (P)

Prepare through Micro-courses