Text Book Back Questions and Answers - Chapter 10 Organisms and Population 12th Biology Zoology Guide Samacheer Kalvi Solutions - SaraNextGen [2024-2025]

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On April 24, 2024, 11:35 AM

Organisms and Population

Text Book Back Questions and Answers

Question 1.
All populations in a given physical area are defined as ___________
(a) Biome
(b) Ecosystem
(c) Territory
(d) Biotic factors
Answer:
(a) Biome

Question 2.
Organisms which can survive a wide range of temperature are called ___________
(a) Ectotherms
(b) Eurytherms
(c) Endotherms
(d) Stenotherms
Answer:
(b) Eurytherms

Question 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

Question 4.
Predation and parasitism are which type of interactions?
(a) (+,+)
(b) (+, O)
(c) (-, -,)
(d) (+, -)
Answer:
(d) (+, -)

Question 5.
Competition between species leads to ___________
(a) Extinction
(b) Mutation
(c) Amensalism
(d) Symbiosis
Answer:
(a) Extinction

Question 6.
Which of the following is an r-species?
(a) Human
(b) Insects
(c) Rginoceros
(d) Whale
Answer:
(b) Insects

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

Dispersal
(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

Question 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) Conformer, Regulator, Partial Regulator

Question 9.
The relationship between sucker fish and shark is ___________
(a) Competition
(b) Commensalism
(c) Predation
(d) Parasitism
Answer:
(b) Commensalism

Question 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

Question 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

Question 12.
Animals that can move from fresh water to sea called as ___________
(a) Stenothermal
(b) Eurythermal
(c) Catadromous
(d) Anadromous
Answer:
(c) Catadromous

Question 13.
Some organisms are able to maintain homeostasis by physical means ___________
(a) Conform
(b) Regulate
(c) Migrate
(d) Suspend
Answer:
(b) Regulate

Question 14.
What is a Habitat?
Answer:
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.

Question 15.
Define ecological niche.
Answer:
Niche of an organism can be defined as the total position and function of an individual in its environment.

Question 16.
What is Acclimatisation?
Answer:
Animals are known to modify their response to environmental changes (stress) in reasonably short time spans. This is known as Acclimatization. This is observed when people who have moved from the plains to higher altitudes show enhanced RBC count within a few days of settling in their new habitat. This helps them cope with lower atmospheric oxygen and higher oxygen demand.

Question 17.
What is Pedogenesis?
Answer:
Pedogenesis is the process of formation of soil (embryonic soil) from the rock materials by weathering.

Question 18.
What is Zero Stress?
Answer:
Stress refers to any environmental factor causing a change in the biological system which is potentially injurious.

Question 19.
What is soil permeability?
Answer:
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.

Question 20.
Differentiate between Eurytherms and Stenotherms.
Answer:
Eurytherms:

1. Organism that can tolerate wide range of temperature.

2. E.g: Human beings

Stenotherms:

Organism that can tolerate narrow range of templerature.

E.g: Fish

Question 21.
Explain hibernation and aestivation with examples.
Answer:
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.

Question 22.
Give the diagnostic characters features of a Biome.
Answer:

1. Location, Geographical position (Latitude and Longitude)

2. Climate and physiochemical environment

3. Predominant plant and animal life

4. Boundaries between biomes are not always sharply defined. Transition or transient zones are seen.

Question 23.
Classify the aquatic biomes of Earth.
Answer:

1. Freshwater (Lakes, ponds and rivers)

2. Brackish water (Estuaries / Wetlands)

3. Marine (Coral reefs, pelagic zones and abyssal zones)

Question 24.
What are the ways by which organisms respond to abiotic factors?
Answer:
The ways by which organism respond to abiotic stress are Regulate, Conform, Migrate and Suspends, etc.

Question 25.
Classify the adaptive traits found in organisms.
Answer:
The adaptive traits may be structural adaptation, behavioural adaptation and physiological adaptation.

Question 26.
Differentiate Natality and Mortality?
Answer:

Question 27.
Differentiate J and S shaped curve.
Answer:
J-shaped growth:

1. Population increase rapidly and exponentally and stops suddenly due to environmental stress.

2. Population declines due to mass mortality.

3. E.g: Insects

S-shaped growth:

1. Population increases slowly at first then more rapidly and then slows down due to this environmental stress.

2. Population is maintained.

3. E.g: Small mammals

Question 28.
Give an account of population regulation.
Answer:
The inherent tendency of all animal populations 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 environmental conditions. This is regulated by many factors which are

· Density independent – Extrinsic factors

· Density dependent – Intrinsic factors

· Extrinsic factors include availability of space, shelter, weather and food, etc. Intrinsic factors include competition, predation, emigration, immigration and diseases.

Question 29.
What is ecological density, crude density and population density?
Answer:

Question 30.

Give an account of the properties of soil.
Answer:

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 cal Ted 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 macroorganisms.

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.

Question 31.
Differentiate between Tundra and Taiga Biomes.
Answer:
Tundra Biome:

1. Tundras are Treeless plains with grasses.

2. Precipitation is less than 250 mm per year.

Taiga Biome:

1. Taiga biome is composed of conifers with needle shaped leaves and scaly leaves.

2. Precipitation is about 380-1000 mm per year

Question 32.
List the adaptations seen in terrestrial animals.
Answer:

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

2. Arthropods have an external covering over the respiratory surfaces and well – developed tracheal systems.

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

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

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

6. 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.

Question 33.
Describe Population Age Distribution.
Answer:
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.

Question 34.
Describe Growth Models/Curves.
Answer:
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). Their growth is represented by S shaped growth curve. 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