MCQ Questions for Class 12 Biology: Ch 13 Organisms and Populations

1. The plants of this group are adapted to live partly in water and partly above substratum and free from water
(a) Xerophytes
(b) Thallophytes
(c) Hydrophytes
(d) Helophytes
► (d) Helophytes

2. Which of the following would necessarily decrease the density of a population in a given habitat?
(a) Immigration > emigration
(b) Natality and immigration
(c) Natality > mortality
(d) Mortality and emigration
► (d) Mortality and emigration

3. Biotic components of the ecosystem :
(a) Share and compete for resources
(b) Only compete for resources
(c) Only share their resources
(d) Neither share nor compete for resources
► (a) Share and compete for resources

4. When the number of immigration and births is more than emigration and deaths, the growth curve of the population will show
(a) Declining phase
(b) Steady phase
(c) Exponential phase
(d) Lag phase
► (c) Exponential phase

5. In a population, unrestricted reproductive capacity is called
(a) Biotic potential
(b) Birth rate
(c) Fertility
(d) Carrying capacity
► (a) Biotic potential

6. All of the following do not harm their host except:
(a) Pilot fish
(b) Pediculus
(c) Orchids
(d) Balanus
► (b) Pediculus

7. Two opposite forces operate in the growth and development of every population. One of them relates to the ability to reproduce at a given rate. The force opposing to it is called
(a) mortality
(b) fecundity
(c) biotic control
(d) environmental resistance
► (d) environmental resistance

8. The population growth curve is sigmoid if the growth pattern is
(a) Geometric
(b) Accretionary
(c) Logistic
(d) Exponential
► (c) Logistic

9. Which should be considered more realistic growth model?
(a) Verhulst-Pearl logistic growth
(b) Geometric growth
(c) Exponential growth
(d) None of the above
► (a) Verhulst-Pearl logistic growth

10. An example of predation is :
(a) Cuckoo laying eggs in crow’s nest
(b) Biological control of pest population
(c) Penicilliumwhose toxins kill bacteria
(d) None of the the above
► (b) Biological control of pest population

11. The number of births in polygamous population is often directly related to :
(a) number of males
(b) number of females
(c) both (a) and (b)
(d) none of these
► (b) number of females

12. Genetic drift operates in
(a) Large isolated population
(b) Slow reproductive population
(c) Small isolated population
(d) Fast reproductive population
► (c) Small isolated population

13. The rate of individuals born per 1,000 individuals per year is called
(a) Mortality rate
(b) Growth rate
(c) Vital rate
(d) Natality rate
► (d) Natality rate

14. Human population follows the
(a) J-shaped growth curve
(b) Z-shaped growth curve
(c) S-shaped growth curve
(d) All of the above
► (c) S-shaped growth curve

15. The semilog of per minute growing bacteria is plotted against time. What will be the shape of graph?
(a) Sigmoid
(b) Hyperbolic
(c) Ascending straight line
(d) Descending straight line
► (c) Ascending straight line

16. In which of the following interactions both partners are adversely affected ?
(a) Predation
(b) Parasitism
(c) Mutualism
(d) Competition
► (d) Competition

17. What is true about the isolated small tribal populations?
(a) There is a decline in population as boys marry girls only from their own tribe
(b) Hereditary diseases like colour blindness do not spread in the isolated population
(c) Wrestlers who develop strong body muscles in their life time pass this character on to their progeny
(d) There is no change in population size as they have a large gene pool
► (a) There is a decline in population as boys marry girls only from their own tribe

18. Excessive aerenchyma is a characteristic feature of
(a) Mesophytes
(b) Heliophytes
(c) Hydrophytes
(d) Xerophytes
► (c) Hydrophytes

19. Migration is an adaptation that should be categorised under:
(a) Behavioural attribute
(b) Physiological attribute
(c) Anatomical attribute
(d) Morphological attribute
► (a) Behavioural attribute

20. In a population curve, the rate of growth becomes steady towards the end of the exponential curve due to
(a) Reproductive power is reduced
(b) Environmental stress
(c) Migration
(d) All of the above
► (b) Environmental stress

21. Growth of the population of an area depends on
(a) Natality rate
(b) Immigration
(c) Environmental resistance
(d) All of the above
► (d) All of the above

22. Just as a person moving from Delhi to Shimla to escape the heat for the duration of hot summer, thousands of migratory birds from Siberia and other extremely cold northern regions move to:
(a) Western Ghat
(b) Meghalaya
(c) Corbett National Park
(d) Keoladeo National Park
► (d) Keoladeo National Park

23. Choose the correct sequence of stages of growth curve for bacteria
(a) Lag, log, stationary, decline phase
(b) Lag, log, stationary phase
(c) Stationary, lag, log, decline phase
(d) Decline, lag, log phase
► (a) Lag, log, stationary, decline phase

24. If in a population, natality is balanced by mortality, then there will be
(a) Decrease in population growth
(b) Increase in population growth
(c) Zero population growth
(d) Overpopulation
► (c) Zero population growth

25. Xerophytes are mostly
(a) Succulents
(b) Water related
(c) Mesophytes
(d) None of the above
► (a) Succulents

26. Edaphic factors will include:
(a) pH, humidity and air
(b) topography and water
(c) pH, topography and substratum
(d) pH, temperature and rain
► (c) pH, topography and substratum

27. Organisms capable of maintaining constant body temperature are
(a) Poikilothermal
(b) Conformers
(c) Stenothermal
(d) Homeothermal
► (d) Homeothermal

28. Which of the following will not be considered a predator?
(a) Paramecium
(b) Tiger
(c) Vultures
(d) Starfish
► (c) Vultures

29. An interesting modification of flower shape for insect pollination occurs in some orchids in which a male insect mistakes the pattern on the orchid flower for the female species and tries to copulate with it, thereby pollinating the flower. This phenomenon is called:   
(a) mimicry  
(b) pseudocopulation
(c) pseudopollination       
(d) Pseudoparthenocarpy
► (b) pseudocopulation

30. Niche overlap indicates
(a) two different parasites on the same host
(b) sharing of one or more resources between the two species
(c) mutualism between two species
(d) active cooperation between two species
► (b) sharing of one or more resources between the two species

31. Penicillin and streptomycin are responsible for:
(a) neutral interactions
(b) beneficial interactions
(c) positive interactions
(d) negative interactions
► (d) negative interactions

32. The maximum growth rate occurs in
(a) stationary phase
(b) senescent phase
(c) lag phase
(d) exponential phase
► (d) exponential phase
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