2nd PUC Biology Question Bank Chapter 13 Organisms and Populations

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Karnataka 2nd PUC Biology Question Bank Chapter 13 Organisms and Populations

2nd PUC Biology Organisms and Populations One Mark Questions and Answers

Question 1.
What are Eurythermal organisms?
Answer:
The organisms which can tolerate and thrive in a wide range of temperatures, e.g., Toad, cyclops, lizards etc.

Question 2.
What are stenothermal organisms?
Answer:
The organisms which can tolerate only a narrow range of temperatures are called stenothermal organisms, e.g: fishes, corals, snail etc.

Question 3.
What is predation?
Answer:
It is an interaction between members of two species in which one species capture, kill and eat up the members of the other species.

Question 4.
What is parasitism?
Answer:
It is an interaction or relationship between two living organisms of different species in which one species (usually smaller) called parasite, obtains its food directly from another living organism (usually larger) called a host.

Question 5.
What is mutualism (Symbiosis)?
Answer:
It is an interaction or relationship between two organisms of different species where both the partners are benefited with none of the two capable of living separately.

Question 6.
What is commensalism?
Answer:
It is a relationship between two living individuals of different species in which one is benefitted, while the other is neither harmed nor benefitted.

Question 7.
What is Amensalism?
Answer:
It is an antagonistic interaction between two individuals of different species in which one organism does not allow other organism to grow or live near it.

Question 8.
What is competition?
Answer:
It is an interaction between two or more organisms for obtaining the same resources.

Question 9.
What is Natality?
Answer:
It refers to the number of births during a given period in the population that are added to the initial density.

Question 10.
What is mortality?
Answer:
The number of deaths in the population during a given period.

Question 11.
What is immigration?
Answer:
It is the number of individuals of the same species that have come into the habitat from elsewhere during the time period under consideration.

Question 12.
What is emigration?
Answer:
It is the number of individuals of the same species who have left the habitat and gone elsewhere during the time period under consideration.

Question 13.
Small animals are rarely found in Polar Regions. Why?
Answer:
Due to higher surface area to volume ratio, the small animals lose heat rapidly in colder regions.

Question 14.
Define ecological niche.
Answer:
A niche can be defined as a defined range of conditions that an organism can tolerate, diversity in the resources that it utilizes and its distinct functional role in the ecological system,
or
The ecological role and space that an organism fills in an ecosystem.

2nd PUC Biology Organisms and Populations Two Marks Questions and Answers

Question 1.
Give two examples each of short day plants and long day plants.
Answer:

Short day plants: Xanthium and chrysanthemum.
Long day plants: Radish and spinach.

Question 2.
Describe habitat and ecological niche.
Answer:
Habitat is the living place of an organism e.g. coastal areas of sea by scoliodon, while ecological niche is the profession of a species and indicates not only its habitat, but also its functional role in the community.

Question 3.
Write the four characteristics of biotic community.
Answer:

Species diversity
Zonation and stratification
Dominance
Succession

Question 4.
What are phenotypic adaptations?
Answer:
Adaptations which enable the organism to respond quickly to a stressful condition.

Question 5.
Mention two causes for rapid growth of human population.
Answer:
Causes:

Decline in the death rate and increase in life span.
Control of several bacterial and viral diseases.

Question 6.
Distinguish between eurythermal and stenothermal organisms with two examples for each.
Answer:
Eurythermal organisms: These are the animals which can tolerate and thrive in a wide range of temperatures.
e.g: Cyclops, toad, man, lizards etc.

Stenothermal organisms: These are the animals which tolerate a narrow range of temperatures and vast majority animals are stenothermal, e.g; fishes, corals and snail.

Question 7.
Distinguish between euryhaline organisms and stenohaline organisms?
Answer:
Based on the tolerance of salt, there are two types of organisms: Euryhaline organisms which tolerate a wide range of salinities and stenohaline organisms restricted to a narrow range of salinities. Many fresh water animals cannot live for long in sea water due to exosmosis of water from the cells and sea water animals cannot live in fresh water due to endosmosis of water.

Question 8.
Distinguish between population and community.
Answer:
1. Population: Population is a local group of individuals of a species. Study of population is called demography, e.g., insect population, reptile population.

2. Community: Community is a localised collection of population of different species of plants and animals, e.g., plant community, animal community.

Question 9.
Distinguish between sciophytes and heliophytes?
Answer:
Certain plants require less intense light for optimum photosynthesis and grow in shady places. They are called shade tolerant species or sciophytes. On the other hand, certain plants require high intensity for optimum photosynthesis. Such plants are called shade intolerant species or heliophytes.

Question 10.
What are homologous organs? Give an example for homologous organs in plants?
Answer:
Organs similar in origin and basic structure but perform different functions are called homological organs.
Example: Thoms of Bougainvillea and Tendrils of Cucurbita.

Question 11.
Differentiate between Gross Primary productivity and Net primary productivity.
Answer:
Gross Primary productivity is the rate of production of organic matter during photosynthesis.
Net primary productivity is the available biomass to consumption to heterotrophs. (herbivores and decomposers).

2nd PUC Biology Organisms and Populations Three Marks Questions and Answers

Question 1.
List various adaptations in animals.
Answer:
(a) In the absence of external water, the Kangaroo rat in North American deserts is capable of meeting all its water requirements through its internal fat oxidation, in which water is a by product.
Also it can concentrate its urine to a minimal volume.

(b) Mammals living in colder climates have shorter ears and limbs to minimize heat loss. This is called Allen’s Rule.

(c) Aquatic mammals like seals living in polar seas have a thick layer of fat (Blubber) below their skin that acts as an insulator and reduces loss of body heat.

(d) Fishes thriving in Antarctic waters where the temperature is below zero degrees, have an array of biochemical adaptations to such extreme environments.

(e) When human beings go from plains to high altitudes (>3500 m) [eg: Rohtang pass] they experience altitude sickness, due to the low atmospheric pressure and reduced oxygen availability. They develop symptoms like fatigue, nausea and heart palpitations.

But gradually the body gets adjusted by increasing red blood cell production, decreasing binding capacity of hemoglobin and increasing the breathing rate.

Question 2.
Write short notes on :
1. Mutualism
2. Competition
3. Predation
Answer:
1. Mutualism or Symbiosis in which both the species are mutually benefitted but association is obligatory and they cannot live separately under normal conditions.

2. Competition: Competition is defined as an interaction that occurs between two or more organisms when the resources necessary for them are limited and adversely affect them.

3. Predation: It is an interaction between members of two species in which members of one species capture, kill and eat up, members of other species. The killer is called predator and the one getting killed is called prey.

Question 3.
Describe population growth.
Explain the equation of population density.
Answer:
The size of population of any species in not a static parameter. It keeps on changing with time, depending on various factors such as availability of food, predation pressure and prevailing weather. Such changes give some idea of what is happening to the population, whether it is increasing or decreasing.

Though a number of factors affect population size, the density of a population in a given habitat during a given period, fluctuates due to four basic processes-natality, mortality, immigration and emigration.

The population density is the number of individuals of a species per unit area/space at a given time. Mathematically population density is expressed as:
D = \(\frac { N }{ S }\)
where, D stands for the population density, N denotes the number of individuals of a species at a specific time and S represents the number of units of the space.

Natality: It refers to the number of births during a given period in the population that are added to the initial density.
Mortality: It is the number of deaths in the population during a given period.
Immigration: It is the number of individuals of the same species that have come into the habitat from elsewhere during the time period under consideration.
Emigration: It is the number of individuals of the same species who have left the habitat and gone elsewhere during the time period under consideration. Natality and immigration contribute to an increase in population density, while mortality and emigration to a decrease.

Therefore, population growth or change in the size of population in a given time is determined by the above factors.
Change in population size = (Births + Immigration ) – (Deaths + Emigration)
If N is the population density at time t, then its density at time t + 1 is
N_{t +1} = N_t + [(B + I) – (D + E)]
It is clear from the above equation, that population density increases if the number of births plus the number of immigrants (B + I) is more than the number of deaths plus the number of emigrants (D + E), otherwise it will decrease. Under normal conditions, births and deaths are the most important factors influencing population density. If a new habitat is just being colonized, than immigration may contribute more significantly to the population growth than birth rates.

Question 4.
What are polindromk sequences? Discuss the mechanism of action of restriction endonucleases with a schematic representation.

2nd PUC Biology Organisms and Populations Five Marks Questions and Answers

Question 1.
What are adaptations? Discess any four adaptations found in plants and animals,
Answer:
Any attribute of the organism (morphological, physiological or behavioural) that enables the organism to survive and reproduce in its habitat is called adaptation.

Many adaptations have evolved over a long evolutionary time and are genetically controlled. The ultimate aim of all the adaptations is to make the individual fit to obtain food and space for its survival.
Some of the examples of adaptations are given below :

(a) In the absence of external water, the Kangaroo rat in North American deserts is capable of meeting all its water requirements through its internal fat oxidation, in which water is a by product.
Also it can concentrate its urine to a minimal volume.

(b) Mammals living in colder climates have shorter ears and limbs to minimize heat loss. This is called Allen’s Rule.

(c) Aquatic mammals like seals living in polar seas have a thick layer of fat (Blubber) below their skin that acts as an insulator and reduces loss of body heat.

(d) Fishes thriving in Antartic waters where the temperature is below zero degrees have an array of biochemical adaptations to such extreme environments.

(e) Desert plants posses the following adaptations:

Thick cuticle on their leaf surface.
Possess sunken, stomata.
They have a special photosynthetic pathway i.e., CAM pathway that enables their stomata to remain closed during day time.
In opuntia, the leaves are reduced to spines and the photosynthetic functions are taken over by the flattered stems,

(f) Archaebacteria have adaptations to survive at temperatures more than 100°C.

(g) When human beings go from plains to high altitudes (> 3500 m) [e.g: Rohtang pass] they experience altitude sickness, due to the low atmospheric pressure and reduced oxygen availability. They develop symptoms like fatigue, nausea and heart palpitations. But gradually the body gets adjusted by increasing red blood cell production, decreasing binding capacity of haemoglobin and increasing the breathing rate.

Question 2.
Explain the effects of temperature on plants and animals?
Answer:
Temperature: It is the most important ecological factor affecting’ almost all the metabolic activities of the organisms. The metabolic activities begin at a certain minimum temperature and increases with increase of temperature, until they reach a maximum at a temperature called optimum.

Further rise of temperature, is accompanied by a fall in the metabolic activity until it ceases at a maximum temperature. Most of the organisms can survive in a narrow range of temperature (0° – 35°C).

Effects of temperature on plants: The metabolic reactions, transpiration, mineral absorption and water uptake and reproduction in plants are effected by changes in temperture. All metabolic reactions are controlled by enzymes and variation of temperature effects enzyme action.

The rate of transpiration increases with the increase of temperature. When the temperature is low the minerals remain tightly attached to soil. Many species of plant show flowering with low temperature treatment and this, phenomenon is called vernalization.
Equatorial region, tropics, temperate and polar regions have their own particular type of vegetation.

Effect of temperature on animals: The variations of temperature seems to have remarkable effect on metabolism of certain animals. Temperature affects the reproductive capacity of organisms and enzyme linked chemical reactions in the cells. Temperature also effects growth, development and morphology. It shows that different animals have different range of temperature tolerance. Based on this, animals are divided into the following categories.

Eurythermal organisms: These are the animals which can tolerate and thrive in a wide range of temperatures
e.g: Cyclops, toad, man, lizards etc.

Stenothermal organisms: These are the animals which can tolerate only a narrow range of temperatures and the vast majority of animals are stenothermal, e.g: fishes, corals and snail.

Question 3.
Explain the effects of light and soil on vegetation?
Answer:
Light: Light is directly responsible for the growth, development and differentiation of plants. Sunlight is a source of energy for plants to produce food through photosynthesis. Intensity, quality and duration of sunlight controls the activities of both plants and animals.

Certain plants require less intense light for optimum photosynthesis and grow in shady places. They are called shade tolerant species or sciophytes. On the other hand, certain plants require high intensity for optimum photosynthesis. Such plants are called shade intolerant species or heliophytes.

Note: Extremely intense light results in photooxidation of cellular components including photosynthetic apparatus and finally their death. The phenomenon is called solarization.

The duration of sunlight in a day is called photoperiod and response of plants to this is called photoperiodism.
Light also affects movements of plants. Leaves of some leguminous plants fold up or droop at night. These movements are called nictinastic movement.
Light also influences daily movement of animals. Majority of animals are diurnal (active during the day) e.g: Most of birds, man, butterflies etc.
Some animals, such as cockroaches, bats, owls, moths etc hide during the day and become active at night. They are called nocturnal animals.
Photoperiod also affects the breeding cycles of animals.

Question 4.
a) Explain how Mediterranean orchid adapted to achieve pollination.
b) Describe the’importance of predators in an ecosystem.
c) What is Ganse’s ‘competitive exclusion principle’?
Answer:
(a) Mutualism or symbiosis in which both the species are mutually benefitted but association is obligatory and they cannot live separately under normal conditions.

e.g., mycorrhizae with association of fungus (e.g., Boletus) and roots of higher plants. The fungi help the plant in the absorption of water and essential nutrients from the soil while the plant in turn provides the fungi with carbohydrates.

Lichens represent an intimate mutualistic relationship between a fungus and photosynthesising algae or cyanobacteria.
Root nodules of legume plants, Casuarina, Alnus and leaf nodules of Ardisia have symbiotic association of nitrogen fixing bacteria – Rhizobium. The plants provide food and shelter to the bacteria and the bacteria fix free atmospheric nitrogen to the plant.

The most interesting example of mutualism are found in plant-animal relationships. Plants take the help of animals for pollinating their flowers and dispersing their seeds. Animals get rewards or fees in the form of pollen and nectar (for pollinators) and juicy and nutritious fruits (for seed dispersals).

In many species of fig trees, there is a tight one-to-one relationship with the pollinator species of wasp. The female wasp uses the fruit not only as an oviposition (egg laying) site but uses the developing seeds within the fruit for nourishing its larvae. The wasp pollinates the fig inflorescence while searching for suitable egg laying sites. In return for the favour of pollination, the fig offers the wasp some of its developing seeds as food for the developing wasp larvae.

The Mediterranean orchid orchid ophrys employs sexual deceit to get pollination done by a species of bee. One petal of its flower bears an uncarry resemblance to the female of the bee in size, colour and markings. The male bee is attracted to what is perceives as a female, ‘pseudo copulates’ with the flower and during that process is dusted with pollan from the flower. When this same bee pseudocopulates with another flower, it transfer pollen to it and thus pollinates the flower.

(b) It is an interaction between members of two species in which members of one species capture, kill and eat up, members of other species. The killer is called predator and the one getting killed is called prey. The predator cannot survive without the prey.

They keep prey population under control. Without the predators, the prey species could multiply and produce high density and cause ecosystem instability. When any exotic species is introduced into a geographical area, they establish and spread fast because the invaded land does not have its natural predators.

When prickly pear cactus (Opuntia) was introduced in Australia in early 1920’s, it started multiplying and spreading rapidly into millions of hectares of rangeland. But, it was controlled, only after a cactus-feeding predator (cochineal insect) introduced from its natural habitat.

(c) Competition is defined as ‘an interaction that occurs between two or more organisms when the resources necessary for them are limited and adversely affect them. Gause’s Competition Exclusion Principle, states that two closely related species competing for the same resources cannot co-exist independently and competitively and the inferior one will get eliminated eventually, e.g. When two species of Paramecium i.e, Paramecium caudatum and Paramecium aurelia are kept together in one habitat for long time, it was observed that one species got eliminated.

The abingdon tortoise in Galapagos Islands became extinct within a decade after goats were introduced on the island, apparently due to the greater browsing efficiency of the goats. The larger and competitively superior barnacle Balanus dominates the intertidal area, and excludes the smaller barnacle Chathamalus from that zone. In general, herbivores and plants appear to be more adversely affected by competition than carnivores.

Question 5.
Define and di&cuss the following terms:
a) Mutualism
b) Competition.
Answer:
(a) Mutualism or symbiosis in which both the species are mutually benefitted but association is obligatory and they cannot live separately under normal conditions.

(b) Competition is defined as ‘an interaction that occurs between two or more organisms when the resources necessary for them are limited and adversely affect them. Gause’s Competition Exclusion Principle, states that two closely related species competing for the same resources cannot co-exist independently and competitively and the inferior one will get eliminated eventually, e.g. When two species of Paramecium i.e, Paramecium caudatum and Paramecium aurelia are kept together in one habitat for long time, it was observed that one species got eliminated.

Question 6.
a) What is biome? Mention any two biomes of India.
b) Compare eurythermal and stenothermal animals with suitable examples.
c) What is altitude sickness?
Answer:
(a) Biome: It is an unit of biosphere with a specific environmental condition to support and sustain a specific interaction of biotic and abiotic factors, e.g., pond biome, marine biome, estuarine biome, forest biome, grass land biome, desert biome.

(b) Eurythermal organisms: These are the animals which can tolerate and thrive in a wide range of temperatures
e.g.: Cyclops, toad, man, lizards etc.

Stenothermal organisms: These are the animals which tolerate only a narrow range of temperatures and the vast majority animals are stenothermal, e.g: fishes, corals and snail.

(c) Any attribute of the organism (morphological, physiological or behavioural) that enables the organism to survive and reproduce in its habitat is called adaptation.

Many adaptations have evolved over a long evolutionary time and are genetically controlled.
The ultimate aim of all the adaptations is to make the individual fit to obtain food and space for its survival.
Some of the examples of adaptations are given below:

(b) Mammals living in colder climates have shorter ears and limbs to minimize heat loss. This is called Allen’s Rule.

(c) Aquatic mammals like seals, living in polar seas have a thick layer of fat (Blubber) below their skin, that acts as an insulator and reduces loss of body heat.

(d) Fishes thriving in Antartic waters where the temperature is below zero degrees, have an array of biochemical adaptations to such extreme environments.

(e) Desert plants possess the following adaptations:

Thick cuticle on their leaf surface.
Posses sunken stomata.
They have a special photosynthetic pathway i.e., CAM pathway that enables their stomata to remain closed during day time.
In opuntia, the leaves are reduced to spines and the photosynthetic functions are taken over by the flattered stems,

(f) Archaebacteria have adaptations to survive at temperature more than 100°C.

(g) When human beings go from plains to high altitudes (> 3500 m) [eg: Rohtang pass] they experience altitude sickness, due to the low atmospheric pressure and non availability of oxygen. They develop symptoms like fatigue nausea and heart palpitations.

But gradually the body gets adjusted by increasing red blood cell production, decreasing binding capacity of haemoglobin and increasing the breathing rate.