Organisms and Populations
Short Questions and Answers
One mark question with answers
1. Symbiosis is
(a) mutually beneficial association
(b) mutually harmful association
(c) harmful to one and beneficial to other
(d) advantageous to one but neutral to other
Answer: (a) mutually beneficial association
2. Community is
(a) Species structure and diversity index of an area
(c) Autotrophic and heterotrophic components
(d) All the above
Answer: (c) Autotrophic and heterotrophic components
3. The relation between algae and fungi in a lichen is
Answer: (a) Symbiosis
4. Ecology is the study of interrelations amongst
(a) soil and water
(b) man and environment
(c) organisms and environment
(d) members of a family
Answer: (c) organisms and environment
5. Study of inter-relationship between a species and its environment is
Answer: (b) autecology
6. Association of animals when both partners are benefitted
Answer: (b) mutualism
7. A trait not found in xerophytes is
(a) thick cuticle
(b) well developed mechanical tissue
(c) sunken stomata
Answer: (d) aerenchyma
8. A parasite living within tissue of host is
(d) none of the above
Answer: (b) endophyte
9. An example of mutualism is
Answer: (b) Selaginella
10. Which take part in symbiosis of lichen?
Answer: (a) alga-fungus
11. The association between ants and some members of family rubiaceae
Answer: (c) myrmecophily
12. Animals undergo inactive stage in winter called
Answer: (c) hibernation
13. 1A high density of elephant population in an area can result in
(a) interspecific competition
(b) intraspecific competition
(d) predation on one another
Answer: (b) intraspecific competition
14. Geometric representation of age structure is a characteristic of
(c) biotic community
Answer: (d) population
Two marks Questions with Answers
1. Define phenotypic adaptation. Give one example.
Answer: Phenotypic adaptation is non genetic change in physical characteristics like external appearance, behaviour and physiology which develops in response to changes in environment and are useful to organisms in adjustment to prevailing environmental conditions.
Example, appearance of mountain sickness at high altitude and its disappearance as one becomes acclimited through increased production of RBCs, decreased binding capacity of hemoglobin and increased rate of breathing.
2. Most living organisms cannot survive a temperature above 45 degrees centigrade. How are some microbes able to live in habitats with temperatures exceeding hundred degree centigrade?
Answer: In most organisms, a temperature above 45 degree centigrade causes denaturation of enzymes and precipitation of protoplasm. Therefore, they die. However, some microbes are found in hot springs and vents where the temperature is of 100° C. These microbes are able to survive at high temperature through (1) occurrence of branched chain lipids that reduce fluidity of cell membranes (2) reduction in amount of free water (3) development of heat tolerant enzymes.
3. Differentiate between hibernation and aestivation.
Answer: Hibernation is the condition of passing the winter in a resting on a dormant condition whereas aestivation is the state of inactivity or torpor during hot and dry summer. In hibernation the animal rests in a warm place and during aestivation the animal rests in a cool, shady and moist place. Hibernation lasts for the whole duration of winter while aestivation generally lasts for hot dry day time because nights are often cooler.
4. Differentiate between natality and mortality.
Answer: Natality is the number of births per unit population per unit time while mortality is number of deaths per unit population per unit time. Natality is meant for continuity of a species while mortality is meant for elimination of aged and infirm. Natality tends to increase population size while mortality tends to decrease population size. Natality increases when the population size is small and decreases when the population size is large while mortality increases when the population size is large and decreases when population size is small.
Three marks Questions with Answers
1. What are halophytes?
Answer: Halophytes are plants of saline environments. They have adaptations to grow in habitats possessing high salt content. Halophytes are able to obtain their supply of water from such habitats because they themselves maintain a high osmotic concentration. Halophytes especially of hot and dry environments possess succulence. Succulent organs may be leaves or stems. They have large cells that store water and mucilage. Succulence has three benefits:
(a) dilution of salts
(b) storage of water which is difficult to obtain
(c) retention of water with the help of mucilage against the forces of evaporation and transpiration.
Halophytes occur in four types of habitats, i.e., saline soils, coastal dunes, tidal marshes and mangroves. They are broadly divisible in two types- saline soil halophytes and mangrove plants.
2. Define the following and give one example for each.
(a) commensalism, (b) parasitism, (c) camouflage, (d) mutualism, (e) interspecific competition.
Answer: (a) commensalism: It is an interaction between individuals of two different species in which one is benefited while the other remains unaffected, example, clone fish living in company of Sea Anemones.
(b) parasitism: It is an interspecific interaction in which small sized organism of one species obtains nourishment and spends a part of whole of its life on or inside the body of large sized organism of other species example, plasmodium (parasite) in humans.
(c) Camouflage: It is the phenomenon of blending with the surroundings due to similar colour, marking and shape as to so as to remain a notice to prey and predator, example, stick insect, leaf insect.
(d) Mutualism: It is an obligatory interspecific interaction of close physical relationship in which both the interacting organisms are benefited, example alga, and fungus in lichens, Rhizobium and legumes in nodulated roots.
(e) Interspecific competition: It is struggle against members of different species for obtaining the same resource which can be food, shelter, minerals, water or light, example, roots of different plant species in the same area of a forest.
3. Define the following:
(a) flora and vegetation, (b) habitat and ecological niche.
Answer: Flora is collective term that is used to describe all the different types of plants or species found in an area.
Vegetation: Plant cover of an area considered generally and not taxonomically.
Habitat: It is a locality alongwith the sum total of all the biotic and abiotic factors of that specific place where an organism lives.
Ecological niche: It is specific part of the habitat utilised by an organism which is circumscribed by the range of its tolerance, resources it utilises and the functional role it plays in the ecological system.
4. Mention four characteristics of biotic community
Answer: Characteristics of biotic community:
(a) species diversity: a community consists of a number of evolutionary unrelated species which, however, show interrelationships and interactions.
(b) Stability: a community which has been living in congenial environment for long time is more stable and has the largest number of species.
(c) Dominance: each community has some plants belonging to a major growth form called dominant plants, example, Pine trees, Oaks, Teak.
(d) Physiognomy: a community has its appearance based on characteristic of dominant plants example, forest, savanna.