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CBSE TESTPAPER-03

CLASS - XII BIOLOGY (Organism and Populaion!

1. Name the type of interaction in which one species isharmed while other

is neither benefitted nor harmed?

[1]

2. Why are calotropis plants not browsed by herbivores?[1]

3. What are the two primary requirements of a parasite from host?[1]

. !efine carryin" capacity?[2]

#. $f a marine fish is placed in fresh water aquarium% will thefish be able to

survive. Why or why not?

[2]

&. 'ut of the two population "rowth models% which one ismore realistic (

Why?

[2]

). *ow do +an"aroo rats live in the absence of water inNorth ,merican

deserts?

[3]

-. *ow is diapause dierent from *ibernation?[3]

/. 0ive an eample to show that completely unrelatedspecies can also

compete for same resources?

[#]

1. What is ,"e pyramid? What are the dierent types of a"e pyramid?[#]

11. !ierentiate between re"ulators ( conformers? Why dosmall animals

do not show re"ulations?

[#]

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CBSE TESTPAPER-0"

CLASS - XII BIOLOGY (Organism and Populaion!

[ANSWERS]

,ns.1. ,mmensalism.

,ns. 2. ecause calotropis plant produces a hi"hly poisonous "lycoside

that is a cardiac poison ( thus% directly +ills the predator.

,ns.3. 4ood ( shelter.

,ns.. 5he maimum number of individuals of a population that can be

sustained by a "iven habitat is called its carryin" capacity.

Ans.5. No, marine fish is unable to survive in a fresh water aquarium because they are adapted

to live in saline sea water. They are unable to cope with outside hypotonic environment

because of Osmoregulation problem.

Ans.6. ogistic or !"shaped growth curve is more realistic because no population can continue

to grow e#ponentially, as the resource availability becomes limiting at certain point of

time.

Ans.$. The %angaroo rat in North American deserts is capable of meeting all its water

requirement through its internal o#idation of fat, where water is by"product, it can also

concentrate its urine to a minimal volume.

Ans.&. 'iapauses is the phenomenon of spending unfavourable climatic conditions by insects

during their development whereas. (ibernation is a phenomenon of spending the winter

in a resting or dormant conditions by cold ) blooded animals to escape cold by hiding

them in hollow tree trun% or burro or caves etc, revealing minimum physiological

activity.

Ans.*. +ompletely unrelated species can also compete for same resources for e.g. n certain

shallow la%es of !outh America the visiting flamingoes - the native fishes compete for

the same ooplan%tons as their food.

Ans./0. The geometrical diagrammatic representation of different age groups in a population of

any organism is called Age of pyramids. These are of three types1"

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i2 3#panding pyramid1" t is a broad base, triangular pyramid which represents a

population containing large number of young people. t is rapidly e#panding

population with high birth rate.

ii2 !table pyramid1" t represents a moderate proportion of young to old. As the rate

of growth becomes slow - stable i.e." pre"reproductive - reproductive age groups

becomes more or less equal in sie.

iii2 'eclining 4yramid1" The type of pyramid of population decreasing in sie is

characterised by a narrow base because there are fewer pre"reproductive

individuals than in the other two age categories.

Ans.//. The organisms which maintain homeostasis by physiological or behavioral means -

ensures a constant body temperature - constant osmotic concentration etc. are called

regulators e.g. all birds, mammals some lower vertebrates - invertebrates, for e#ample

in summer, when outside temp is more than our body temperature we sweat profusely

evaporative cooling brings the body temp ) down.

hereas those organisms which cannot maintain a constant internal environment. Their

body temperature changes with ambient temperature e.g. maority of animals - nearly

all plants.

!mall organisms does not show

regulation because

thermoregulation is an energy )

e#pensive process. !ince small

animals have large surface area

relative to volume, they tend to

lose body heat very fast when it

is cold outside they have to

e#pend much energy to generate

body heat through metabolism.