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Chapter: 12th Zoology : Chapter 11 : Organisms Reproductive and Population

Organisms Reproductive and Population: Questions and Answers (Evaluation)

Zoology : Organisms Reproductive and Population : Book Back Questions Answers: Choose the Correct Answers, Short Answers, brief Answers, Important Questions and Answers



1. All populations in a given physical area are defined as

a) Biome

b) Ecosystem

c) Territory

d) Biotic factors

Answer: a) Biome


2. Organisms which can survive a wide range of temperatuer are called

a) Ectotherms

b) Eurytherms

c) Endotherms

d) Stenotherms

Answer: b) Eurytherms


3. The interaction in nature, where one gets benefit on the expense of other is ______________

a) Predation

b) Mutualism

c) Amensalism

d) Commensalism

Answer: d) Commensalism


4. Predation and parasitism are which type of interactions?

a) (+,+)

b) (+, O)

c) (--, --)

d) (+, --)

Answer: d) (+, --) 


5. Competition between species leads to

a) Extinction

b) Mutation

c) Amensalism

d) Symbiosis

Answer: a) Extinction


6. Which of the following is an r-species

a) Human

b) Insects

c) Rhinoceros

d) Whale

Answer: b) Insects 


7. Match the following and choose the correct combination from the options given below.

Column I :

A. Mutalism

B. Commensalism

C. Parasitism

D. Competition

E. Predation

Column II:

1. Lion and deer

2. Round worm and man

3. Birds compete with squirrels for nuts

4. Sea anemone on hermit crab

5. Bernacles attached to Whales.


a) A- 4,  B-5,  C-2,  D –3,  E-1

b) A- 3,  B-1,  C-4,  D – 2,  E-5

c) A- 2,  B-3,  C-1,  D – 5,  E-4

d) A- 5,  B-4,  C-2,  D – 3,  E-1

Answer: a) A - 4, B - 5, C - 2, D - 3, E -1


8. The figure given below is a diagrammatic representation of response of organisms to abiotic factors. What do A, B and C represent respectively.

Answer: a)


9. The relationship between sucker fish and shark is __________

a) Competition

b) Commensalism

c) Predation

d) Parasitism.

Answer: b) Commensalism


10. What type of human population is represented by the following age pyramid?

a) Vanishing population

b) Stable population

c) Declining population

d) Expanding population

Answer: b) Stable population


11. Which of the following is correct for r-selected species

a) Large number of progeny with small size

b) large number of progeny with large size

c) small number of progeny with small size

d) small number of progeny with large size

Answer: a) Large number of progeny with small size


12. Animals that can move from fresh water to sea called as _____________

a) Stenothermal

b) Eurythermal

c) Catadromous

d) Anadromous

Answer: c) Catadromous


13. Some organisms are able to maintain homeostasis by physical means __________

a) Conform

b) Regulate

c) Migrate

d) Suspend.

Answer: b) Regulate


14. What is a Habitat?

• A habitat can be considered as the address of the organism

• Organisms in a habitat interact with each other and can be part of trophic levels to form food chains and food webs.


15.  Define ecological niche.

• The physical space occupied by an organism and its functional role in the community. The ecological niche of an organism not only defends on where it lives but also includes the sum total of its environmental requirements.

• Charles Elton (1927) was the first to use the term 'niche' as the functional status of an organism in its community.


16. What is Acclimatisation?

Animals are known to modify their response to environmental changes (stress) in reasonably short time spans. This is known as Acclimatization.


17. What is Pedogenesis?

Soil is formed from rocks which are the parent materials of soil, by weathering and is called embryonic soil (called pedogenesis)


18. What is Zero Stress?

This is the level of exposure of plants to environmental factors that leads to neither injury nor reduction in growth and yield of crops.


19. What is soil permeability?

The characteristic of soil that determines that moment of water through pore spores is known as soil permeability.

Soil permeability is directly dependent on pore size. Water holding capacity of the soil is inversely dependent on soil porosity.


20. Differentiate between Eurytherms and Stenotherms.


• Organisms which can survive a wide range of temperature

• Cat, Dog, Tiger, Human are example


• Organisms can tolerate only a narrow range of temperature

• Fish, Frog, Lizard and Snakes are examples


21. Explain hibernation and aestivation with examples.

• In certain conditions, if the organisms is unable to migrate, it may avoid the stress by becoming inactive. This is seen commonly in bears going into hibernation during winter.

• Some snails and fish go into aestivation to avoid summer related problems like heat and desiccation.


22. Give the diagnostic characters features of a Biome?

Characters of a Biome :

• Location, Geographical position (Latitude, Longitude)

• Climate and physiochemical environment

• Boundaries between biomes are not always sharply defined. Transition or transient zones are seen as in case of grassland and forest biomes.

• Predominant plant and animal life. 


23. Classify the aquatic biomes of Earth.

Aquatic biomes of earth :

• Freshwater (Lakes, ponds, rivers)

• Brackish water (Estuaries / wetlands)

• Marine (Coral reefs, pelagic zones and abyssal zones)


24. What are the ways by which organisms respond to abiotic factors?

• Every living organism responds to its environment. There are various ways by which organisms respond to abiotic conditions.

• Some organisms can maintain constant physiological and morphological conditions or undertake steps to overcome the environmental condition, which in itself is a response.


25. Classify the adaptive traits found in organisms.

• Adaptations can be phenotypic or adaptive trait with a functional role is each individual organism that is maintained and has been evolved by natural selection.

The adaptive traits may be

i) Structural adaptation

ii) behavioural adaptation and

iii) Physiological adaptation


26. Differentiate Natality and Mortality.


• Populations increase because of natality

• Natuling is equivalent to birth rate and is an expression of the production of new individual in the population by birth, hatching, germination or fission.

• The two main aspects of reproduction, namely fertility and fecundity play a significant role in a population.

• Natality rate may be expressed in crude birth rate number of organism born per female per unit time

Death rate (b) = number of birth per unit time / average population


• Mortality is the population decline factor and is opposite to natality

• Mortality can be expressed as loss of individuals in unit time or death rate

• Mortality is expressed as specific mortality, that is the number of members of an original population dying after the lapse of a given time.

• The crude death rate of a population can be calculated by the equation.

Death rate (d) = number of deaths per unit time / average population 


27. Differentiate J and S shaped curve.

J shaped Growth Curve

1. Population increases rapidly in an exponential fashion and then stops abruptly due to environmental resistance

2. Rapid exponential growth

3. r - selected species

4. It is observed in many insects

S shaped Growth Curve

1. Population increase slowly at first then more rapidly and gradually slows down due to environmental resistance.

2. Logistic growth

3. k - selected species

4. Most of the small mammals are example.


28. Give an account of population regulation.

• The inherent tendency of all animal population is to increase in number. But it does not increase indefinitely.

• Once the carrying capacity of the environment is reached, population numbers remain static or fluctuate depending on environmetal conditions. This is regulated by many factors which are.

1) Density independent - Extrinsic factors

2) Density dependent- Intrinsic factors

1. Extrinsic factors include availability of space, shelter, weather, food etc.

2. Intrinsic factors include competition, predation emigration immigration and diseases.


29. What is ecological density, crude density and population density?

1. Ecological density :

It is the size of a population in relation to the numbers per unit of habitat space.

Eg. 100 fish in the volume of water in the pond.

2. Crude density :

It is the size of a population in relation to the number per unit of total space.

Eg. 1000 fish in a pond

3. Population density :

It is usually expressed as the number of individuals per unit area or volume.

Eg. 100 trees per acre.


30. Give an account of the properties of soil.

Properties of soil :

1. Texture of soil :

The texture of soil is determined by the size of the soil particles. The types of soil include sand, silt and clay on the basis of their size differences.

2. Porosity :

The space present between soil particles in a given volume of soil are called pore spaces. The percentage of soil volume occupied by pore space or by the interstitial spaces is called porosity of the soil.

3. Permeability of soil :

The characteristic of soil that determines the movement of water through pore spaces is known as soil permeability.

Soil permeability is directly dependent on the pore size. Water holding capacity of the soil is inversely dependent on soil porosity.

4. Soil temperature :

Soil gets its heat energy from solar radiation, decomposing organic matter, and heat from the interior of earth.

Soil temperature effects the germination of seeds, growth of roots and biological activity of soil-inhabiting micro-and macro organisms.

5. Soil water :

In soil, water is not only important as a solvent and transporting agent, but also maintains soil texture, arrangement and compactness of soil particles, making soil habitable for plants and animals.


31. Differentiate between Tundra and Taiga Biomes.

Tundra Biomes

1. Winters are long with little day light, summers are short with long daylight

2. Precipitation is less than 250 mm per year.

3. Dwarf willows, birches, mosses, grasses sedges are the flora here

4. Reindeer, arctic hare, musk ox, lemmings are important herbivores here

Taiga Biomes

1. This area has long and cold winters.

2. Precipitation ranges about 380-1000 mm in a year.

3. Spruce, fir, pine are the important - flora here

4. Moose, elk, deer, reindeer are the important herbivores.


32. List the adaptations seen in terrestrial animals.

• Earthworms, land Planarians secrete a mucus coating to maintain a moist situation for burrowing, coiling, respiration, etc.,

• Arthropods have an external covering over the respiratory surfaces and well-developed tracheal systems.

• In vertebrate skin, there are many cellular layers besides the well protected respiratory surfaces that help in preventing loss of water.

• Some animals obtain their waste requirement from food as partial replacement of water lost through excretion.

• Birds make nests and breed before the rainy season as there is availability of abundant food. But during drought birds rarely reproduce.

• Camels are able to regulate water effectively for evaporative cooling through the skin and respiratory system and excrete highly concentrated urine, and can also withstand dehydration up to 25% of their body weight. 


33. Describe Population Age Distribution.

• The proportion of the age groups (pre- reproductive, reproductive and post reproductive) in a population is its age distribution attribute.

• This determines the reproductive status of the population at the given time and is an indicator of the future population size.

• Usually a rapidly growing population will have larger proportion of young individuals.

• A stable population will have an even distribution of various age classes.

• A declining population tends to have a larger proportion of older individuals


34. Describe Growth Models/Curves.

• Populations show characteristic growth patterns or forms. These patterns can be plotted and termed as J-shaped growth form and S-shaped growth form (Sigmoid form).

J shaped growth form:

• When a population increases rapidly in an exponential fashion and then stops abruptly due to environmental resistance or due to sudden appearance of a limiting factor, they are said to exhibit J-shaped growth form.

• Many insects show explosive increase in number during the rainy season followed by their disappearance at the end of the season

S-Shaped growth form (sigmoid growth)

• Some populations, as in a population of small mammals, increase slowly at first then more rapidly and gradually slow down as environmental resistance increases whereby equilibrium is reached and maintained. Their growth is represented by S shaped growth curve.


35. Tabulate and analysis of two species population interaction. 

36. Explain parasitism with an example. 

37. Differentiate between predator and prey.


Extra One mark Questions and Answers


1. Which one of the following is most appropriately defined?

a) Host is an organism which provides food to another organism.

b) Amensalism is a relationship in which one species is benefited whereas the other is unaffected.

c) Predator is an organism that catches and kills other organism for food.

d) Parasite is an organism which always lives inside the body of other organism and may kill it.


2. Study the four statements (1 to 4) given below and select the two correct ones out of them.

A) A lion eating a deer and a sparrow feeding on grain are ecologically similar in being consumers.

B) Predator star fish Pisaster helps in maintaining species diversity of some invertebrates.

C) Predators ultimately lead to the extinction of prey species.

D) Production of chemicals such as nicotine, strychnine by the plants is metabolic disorders.

The two correct statements are

a) (B) and (C)

b) (C) and (D)

c) (A) and (D)

d) (A) and (B)


3. Which two of the following changes ( 1 to 4) usually tend to occur in the plain dwellers when they move to high altitudes(3500 m or more)?

A) Increase in red blood cell size

B) Increase in red blood cell production

C) Increased breathing rate

D) Increase in thrombocyte count

a) (B) and (C)

b) (C) and (D)

c) (A) and (D)

d) (A) and (B)


4. Consider the following four conditions (A-D) and select the correct pair of them as adaptation to environment in desert lizards. The conditions:

A) Burrowing in soil to escape high temperature.

B) Losing heat rapidly from the body during high temperature

C) Bask in sun when temperature is low

D) Insulating body due to thick fatty dermis.

a) (A) and (C)

b) (B) and (D)

c) (A) and (B)

d) (C) and (D)


5. People who have migrated from the planes to an area adjoining Rohtang Pass about six months back

a)Have more RBC’s and their haemoglobin has a lower binding affinity to O2.

b) Are not physically fit to play games like football

c) Suffer from altitude sickness with symptoms like nausea, fatigue, etc.

d) Have the usual RBC count but then haemoglobin has very high binding affinity to O2.


6. A biologist studies the population of eats in a barn. He found that the average natality was 250, average mortality is 240, immigration is 20 and emigration to be 30. The net increase in population is

a) 10

b) 15

c) 05

d) Zero


7. An association of individuals of different species living in the same habitat and having functional interaction is:

a) Biotic community

b) Ecosystem

c) Population

d) Ecological niche


8. Gause’s principle of competitive exclusion states that:

a) More abundant species will exclude the less abundant species through competition

b) Competition for the same resources excludes species having different food preferences

c) No two species can occupy the same niche indefinitely for the same limiting resources

d) Larger organisms exclude smaller ones through competition


9. When does the growth rate of a population following the logistic model equal zero? The logistic model is given as dN/dt=rN(1-N/K):

a) When N/K is exactly one

b) When N nears the carrying capacity of the habitat

c) When N/K equals zero

d) When dearth rate is greater than birth rate

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