2nd PUC Biology Important Questions Chapter 13 Organisms and Populations

Karnataka 2nd PUC Biology Important Questions Chapter 13 Organisms and Populations

Question 1.
Define Ecology?
Answer:
Study of interactions, between organisms and their abiotic environment.

Question 2.
Mention the 4 levels of biological organisation?
Answer:
“Ecology studied under 4 different levels of biological organisation.

1. Organisms
2. Populations
3. Community
4. Biome.

Question 3.
What is biome? Mention major biomes of India?
Answer:
Biomes are very large ecosystems, characterized by major vegetation type, Ex: desert, tundra, grass lands etc.

Question 4.
Define Habitat?
Answer:
It is a specific place where species or specific population lives in nature.
[Abiotic factors like temperature, water light and soil along with biotic factors, pathogens, predators, parasites microbes characterize the habitat of an organism].

Question 5.
Explain any three type major abiotic factor influencing the life of organisms.
(b) Name the type of interaction in the following organisms
(i) Fungi-Roots of higher plants
(ii) Cattle-Egret
(iii) Cuckoo-Crow.
Answer:
(a) Temperature: Most ecologically important factor in the environment. The average temp decreases progressively from the equator towards the poles [which ranges from sub-zero in the polar region and more than 50°C in tropical deserts]

• Special, unique Hydrothermal vents have more than 100°C
• In organisms, metabolic activities depend on maximum and minimum temp. In different species, enzyme kinetics in the basal metabolism of an organism depends on temp.

(b) Water: Next to temperature, water is the most important factor which influences the life of organism “Elixir of life”. The productivity and distribution of plants are heavily dependent on water. For aquatic organisms quality [chemicals and pH of water] becomes important. Salt conc.like 5 in land water, 30-35 in sea and greater than 100 in some hyper saline lagoons.

(c) Light: Light responsible for – growth, development, of plants which are autotrophs. Many species of plants in forests are adapted to photosynthesis optimally under low light conditions, because they grow and are over shadowed by tall trees. Many plants require photo period (period of light) for flowering. [Short day, long day, day natural plants]. Animals to depend on light – for foraging, reproductive and migratory activities. Many marine algae and organisms are capable of absorbing certain colour components of the visible spectrum for their survival.

(d) Soil: Property of soil depends on the climate, weathering sedimentary or transported type water holding capability of soil, soil pH, mineral components and topography decides the type of vegetation in any area
which in turn supports different types of animals.
Ex: Benthic animals in water bodies.
(B)

1. Fungi – Root of higher plants. (Mycorrhiza).
2. Cattle – Egret (Commensalism).
3. Cuckoo – Crow (brood parasitism).

Question 6.
Give the significance of temperature on living organisms?
Answer:
(a) Temperature: Most ecologically important factor in the environment.
The average temp decreases progressively from the equator towards the poles [which ranges from sub-zero in polar regions and more than 50°C in tropical deserts].

Special, unique Hydrothermal vents has more than 100°C
In organisms, metabolic activities depend on maximum and minimum temperature. In different species, as enzyme kinetics in basal metabolism of an organism depends on temp. Different animals have different range of temperature tolerance.

Question 7.
Differentiate between Eurythermal and Stenothermal organisms with 2 examples.
OR
What are Eurythermal organisms?
Answer:

Eurythermal: A few organisms can tolerate and thrive in a wide range of temperatures. Eg: cat., dog, tiger etc.

Stenothermal: A few organisms (majority) can tolerate and thrive in a narrow range of temperatures. Eg: coral reefs, insects, seals etc.

OR
Explain the effect of water on life of oranisums?
Answer:
Water: Next to temperature, water is most important factor which influences the life of organism. ‘Elixir of life”. The productivity and distribution of plants is heavily dependent on water. For aquatic organisms quality [chemicals and pH of water] becomes important. Salt conc.like 5 in land water, 30-35 in sea &greater than 100 in some hyper saline lagoons. Based on the tolerance of salt, there are two type or organisms.

Question 8.
Differentiate between Euryhaline and Stenohaline organism give example?
Answer:

1. Euryhaline organisms: Tolerate a wide range of salinities (Salt cone).
   Eg: Avicennia, Salmon Eels.
2. Stenohaline organism: Which tolerates a narrow range of salinities(Salt cone).
   Eg: goldfish, freshwater. fishes.

Question 9.
Fresh water animals cannot live in seawater? Give reason?
Answer:
Many fresh water animals cannot live for long duration in sea water because of osmotic problem

Question 10.
Explain the effects of light and soil on vegetation?
Answer:
Light: Light responsible for – growth, development, of plants which are autotrophs.
Many species of plants in forests are adopted to photosynthesis optimally under low light conditions, because they grow in over shadowed by tall trees.

Many plants require photo period (period of light) for flowering. [Short day, long day, day natural plants]. Animals to depend on light – for foraging, reproductive and migratory activities.

Many marine algae and organisms are capable of absorbing certain colour components of the visible spectrum for their survival.

Question 11.
Name the components of the soil which decides types of vegetation?
Answer:
Soil: Property of soil depends on the climate, weathering sedimentary or transported type water holding capability of soil, soil pH, mineral components and topography decides the type of vegetation in any area which in turn supports different types of animals. Ex: Benthic animals in water bodies.

Question 12.
Define Homeostasis?
Answer:
Organisms have constant internal environment which could be in terms of constant temperature, osmotic cones
of body fluids. This maintenance of constant internal environment is Homeostasis. So, when there is variation in internal environment, organisms develop many adaptations to suit the conditions, following are important examples.

Question 13.
What are regulators? Give examples.
Answer:
REGULATE: Some organisms maintain homeostasis, by maintain constant body temperature, osmotic cone
etc. Ex: All birds, mammals, few vertebrates and invertebrates exhibits thermoregulation and osmoregulation to suit their environment, where they live.

In the case of Human being, body temperature is 37°c, when outside temperature is more, we sweat profusely. In winter in below 37°c, in shivering, a kind of exercise which produce heat and raises the body temperature. In plants it is absent.

Question 14.
What are Confonmers?
Answer:
CONFORM: Majority of animals and plants cannot maintain a constant internal environment and hence their body temperature [Conform = behave according to].
In aquatic animals the osmotic concentration of body fluid varies with ambient water osmotic concentration.

Question 15.
Why small animals are rarely found in polar regions?
Answer:
In case of small animals, they have a larger surface area relative to their volume and they tend to lose body heat very fast when it is cold outside, and they have to produce more energy to generate body heat through metabolism. This is the main reason why very small animals are rarely found in polar regions. If the stressful external conditions are localized or for short duration, organisms have other alternatives.

Question 16.
Explain the strategies by organisms to overcome the temporary stressful external conditions?
OR
Define migration with any 2 examples?
Answer:
Migration: The organism which can move away temporarily, from the stressful habitat to a more hospitable (comfort) area and return back when stressful period is over.
Ex: In every winter the famous keolado National park (Bharatpur) in Rajasthan will be place for Siberian birds, (cranes), coming from extremely cold Siberian Northern regions.
OR
Define suspension?
Answer:
Suspension: Different living organisms tide over very low or very high temperature conditions in various ways is known as suspension.
OR
What is Encystment? Explain with examples.
Answer:
Encystment: In bacteria, fungi and lower plants various kinds of thick walled spores are formed, to overcome unfavourable conditions prefer to germinate in favourable conditions. In higher plants seeds exhibit Dormancy.

In Euglena and Amoeba development of hard covering coat called cyst around their body to overcome unfavourable conditions which is known as encystment.
OR
What is Hibernation? Give example.
Answer:
Hibernation: (winter Sleep): It is the period of dormancy of some animals during winter, [ex: Bears escape in time]. Ex: Cold-blooded animals-Frog, lizards, etc.
Warm-blooded animals – Bear, Squirrel etc.
OR
What is Aestivation? Give examples.
Answer:
Aestivation (summer sleep) : It is a period of dormancy during summer related problems like heat and . dessication. Ex: Fish, Snails, Salamanders etc.
OR
Define diapause?
Answer:
Diapause: Under unfavourable conditions many Zooplanktons in lake ponds exhibits a stage of suspended development.

Question 17.
What is Adaptation? Explain relating to Kangaroo rat.
Answer:
It is any adjustment or attribute of an organism by having certain morphological, physiological or behavioural
response, which makes it to survive and reproduce in its habitat.
Ex: Kangaroo rat which lives in North American deserts is capable of meeting all its water requirements through fat oxidation cone, urine, where the minimal volume of water is used.

Question 18.
List the characters of desert plants?
Answer:
Thick cuticle on the leaf surfaces. Sunken stomata minimise water loss through transpiration
Special photosynthetic pathway tCrassulacean Acid Metabolism) enables their stomata to closed during day time. Opuntia and other desert plants have no leaves, they are modified into spines. Stems flattened, green and succulent and perform photosynthesis.

Question 19.
State Allen’s rule?
Answer:
According to Allen’s rule “mammals from colder climates have shorter ears and limbs to minimize heat loss”.

Question 20.
How are Seals adopted to live in polar areas?
Answer:
In polar areas aquatic mammals like seals have thick layer of fat [blubber] under their skin that acts as an insulator and reduces loss of body heat. .
ALTITUDE: In some organisms physiological adaptation are observed to respond quickly to a stressful situation. Ex: In man.

Question 21.
Define Altitude sickness? Mention the causes and symptoms of Altitudes sickness.
Answer:
When one moves to a high altitude place experience altitude sickness. “Altitude sickness is the physiological discomfort experienced by the individuals, when they are in high altitude due to low atmos pressure”. Altitude sickness symptoms includes Nausea fatigue ajid rest palpitation.

Because of low atmospheric pressure of high altitude, body does not get enough oxygen, then gradually adjust to the environment by increasing RBC production, decreasing the binding affinity of Hb and by increasing breathing rate. [Note: Most of the animals- narrow range of temperature [Human-37c], But Archaebacteria- live in hotsprings and deep sea hydrothermal vents(>100C temperature). Many Fishes – Antartic water (>0 temperature)

Organisms living in such an extreme conditions show a fascinating array of biochemical adaptations. Behavioural responses are exhibited by some organisms to adjust to variations in their environment].

Question 22.
How does desert Lizards manage their body temperature to in their environment?
Answer:
Desert lizards: They bask in the sun and absorb heat when their body temperature decreases and move to shade when temperature starts increasing. Some species are capable of burrowing into the soil to escape heat.

Question 23.
Define population?
Answer:
Population “The total number of organisms of a specific species present in a specific geographical area at a specific time”. [Note: Population has birth and death rates, The rates can be expressed in a change in numbers with respect to members of the population.
Examples:

1. last year – 20 lotus plants Reproduction – 8 plants are added
   Total = 28
   Birth rate = 0.4 of spring /year
2. Out of 40 fruit files, if 4 died, at a specific time (per week)]
   Death rate = 4/40 = 0.1 per week

Question 24.
Mention attributes shown by a population?
Answer:
Birth rate, Death rate , Sex ratio, Age distribution
[Note: Sex ratio: The no. of female and male per thousands individuals.

• Age structure: A population at any given time is composed of individuals of different ages.
• Age pyramid: “Age distribution is plotted for the population”]
• In a population, these age groups are identified – pre and post-reproductive, reproductive age groups

Question 25.
Explain 3 kinds of population?
Answer:
Expanding, Stable and declining population. The size of the population tells us a lot about its status in the habitat. To determine population size relative densities are measured. Ex: Bacterial culture in petridish, population size is determined indirectly without counting seeing them Eg: pug marks and faecal pellets in case of tiger in National parks.

Question 26.
Define population growth?
Answer:
It “refers to the increasing in population size”. [It is not a static parameter. The changes of density (Quantity) of population is due to four basic processes.]

Question 27.
List any characters that are employed in human population census? or Mention four basic processes that fluctuate the density of a population in a given habitat.
Answer:

1. Natality
2. Immigration
3. Mortality
4. Emigration

Question 28.
Define Natality, Immigration/Mortality(death rate)/Emigration? or Explain factors responsible for fluctuation in population density.
Or
Define Natality?
Answer:
IN umber of birth during a given period in the population that are added to the initial density
OR
Define Mortality?
Answer:
Number of deaths during a given period in the population.
OR
Define Immigration
Answer:
Immigration (I): Number of individual of the same species that have entered into the habitat from different places during a given period.
OR
Define Emigration?
Answer:
Emigration (E): Number of individuals of the population who left the habitat and gone to different place . during a time period under consideration.

Question 29.
Explain the equation of population density?
Answer:
If N is the population density at time ‘t’ then its density at time t + I is
N_t = N₀ + (B +1 – D + E)
N_t = N_t or + [(B + I) – (D + E)]
N_t = Final population size B = Natality rate
N₀ = Initial population size D = Mortality rate
I = Immigration rate E = Emigration rate population growth
= (Birth + Immigration) – (Deaths + Emigration).

Question 30.
Describe exponential growth with help of a population growth curve?
Answer:
Two types
1. Exponential growth: If resource (food and space) is plenty for an organism and no predators, shows this type of growth. Population grows exponentially till enough food is available after reaching the peak value the population may abruptly decrease to show a J-shaped curve.

If size population is N, the birth rate(b) and death rate(cf), then the increase and decrease in N during a unit time period will be (b – d) × N, let b – d = r, then = r × N [Intrinsic – basic character of an organism]. r = “Intrinsic rate of natural increase” of population growth based on biotic or abiotic factors.

The exponential or geometric growth results in a J shape curve, when plotted with N in relation time.
The integral form of Exponential – growth equation
N_t = N₀ + e^rt
N_t = Population density after time t
N₀ = Population density at time zero
r = intrinsic rate of natural increase
e = the base of natural logarithm (2.71828)

a – exponential growth curve
b – logistic growth curve.

Question 31.
Describe logistic growth?
Answer:
Logistic growth: A population growing in a habitat with limited resources slow initially a log phase (slow growth) followed by Exponential phase (accelerated growth) and finally stationary phase, when the population density reaches the carrying capacity(k).

Note: [A population growing in a habitat with limited resources leads to competition, and the fittest individual will survive and reproduce].

A plot of N in relation to time (t) results in a sigmoid curve. This type of population growth is called as Verhulst – Pearl Logistic Growth \(\frac{d N}{d t}\)= γN
where N = population density at time t
r = rate Intrinsic of natural increase
K = Carrying capacity
= Rate of change in population size
Since the resources for growth for most animal populations are unlimited and becomes limited soon or later the logistic growth model is considered a more realistic one.

Question 32.
What is carrying capacity?
Answer:
Maximum number of individual of a population, which can be supported with optimum resources of their survival.

Question 33.
What is Darwinian fitness? Give any 2 examples.
Answer:
“Population evolve to maximize their reproductive fitness called as Darwinian fitness(high r value), in the habitat in which they live”. They exhibit efficient reproductive strategy under particular set of selection pressures.

Example:
Organisms breed only once in life time – Salmon fish, Bamboo.
Many times – Birds and Mammals.
Production of a large number of small-sized offspring – Oysters, pelagic fishes.
Produce of small number of large-sized offspring – Birds and Mammals.

Question 34.
Mention the different possible interspecific interactions.
Answer:

Question 35.
Mention any FIVE population interaction with an example each
Answer:

Question 36.
Define predator?
Answer:
Predator: Organism which attacks, kills and feeds on other species. [An animal that naturally preys on others],

Question 37.
Define Prey?
Answer:
Animal that is hunted and killed by another for food is known as prey.

Question 38.
Write a note on significance of predators?
Answer:
Predation as natures way of transferring to higher trophic levels,” the energy” fixed by plants, so they are called as conduits. Predators control the growth and survival chances of prey population. Without predators prey species increase and causes ecosystem instability.

Predators may increase the biodiversity of communities by preventing a single species from becoming dominant.

Question 39.
Predators in nature are prudent why?
Answer:
If predator over exploits(over use) its prey, then the prey might become extinct and in turn predator also become extinct. That is the reason why predator in nature are ‘PRUDENT’ (wise) (Acting wisely).
[Note 1. When certain exotic species are introduced into a geographical area, they spread fastly since they does not have its natural predators].

Question 40.
How prickly pear cactus was controlled biologically?
Answer:
Prickly pear cactus introduced into Australia spreaded widely to million hectares.
It was controlled by cactus feeding moth (predator) which was bought from cactus origin(native) country.
[2. Biological control methods adopted to control agricultural pest based on the ability of predator to control prey pests],

Question 41.
Predators help in maintaining species diversity. Justify it?
Answer:
Predators help in maintaining species diversity in a community, by reducing competition
Ex: Starfish pisaster is an important predator in intertidal communities of American Pacific Coast. In a experiment conducted in sea, when all the starfish were removed, more than 10 species of invertebrates became extinct within a year because of inter specific competition.

Question 42.
How do some species of insects and Frogs avoid being detected by predators?
Answer:
Prey species have evolved to avoid Predators.
Ex: Camouflage (a) Some frogs and insects are cryptically coloured to avoid being detected easily by Predators.
(b) Some species are poisonous to avoid Predators. Ex: Monarch butterfly is highly distasteful to predator bird. This distaste is due to chemical present in the body which is acquired during their caterpillar stage by feeding on a poisonous weed.

Question 43.
How do some plants species avoid herbivores?
Answer:
Plants (prey) avoid herbivores (predators),& phytophagous insects which feed on plants and other parts. Since plants are stationary they have evolved different morphological and chemical defences against herbivores.

Ex: Thoms in Acacia & Cactus.
Chemicals in Calotropis produces poisonous cardiac glycosides where this avoids cattle or goats browsing on them; Various plant extracts which are used as chemical substances like Nicotine* Caffeine, Quinine, opium, strychnine are plant alkaloids produced in plants as defence mechanism against predators.

Question 44.
Define Competition?
Answer:
“Competetion it is An interaction that occurs between two or more organisms for the same necessary resources”

Question 45.
According to Darwin which is the potent force in organic evolution?
Answer:
According to Darwin interspecific competition is a potent force in organic evolution.

Question 46.
Some times totally unrelated species could compete for the same resource? Give examples.
Answer:
Ex: Flamingo birds and Fishes complete for their common food Zooplanktons in South American lakes. Some times the feeding efficiency of one species might be reduced, due to interference of other species even if resources are abundant. [Where competition  fitness of one species will become lower in the presence of other species]

Question 47.
State Gause’s competitive exclusion principle? Give example.
OR
State Gause’s competitive exclusion principle.
Answer:
Cause (1934) p0 forwarded principle, which states that “two closely related species competing for the same resources cannot co-exist indefinitely and competitively inferior one will be eliminated eventually.
Example of competitive exclusion:

1. Abingdon tortoise in Galapagos Islands become extinct within a decade after goats were introduced in to the island due to great browsing efficiency of Goats.
2. Elimination of smaller barnacle chthamalus by superior barnacle Balanus on the rocky sea costs of Scotland.
   [Note: Recent studies do not support this generalization about competition, and but point out that species facing competition might evolve and promote co existence instead of exclusion.].
   Ex: Me Arthur showed that five closely related species of warbler’s (singing birds) living on the same tree.

Question 48.
Define Parasitism?
Answer:
It is an interaction or association between two living organisms, in which one species (smaller) called Parasite gets its food and shelter from another living organism (larger) called Host.

Question 49.
Write a note on Parasitic adaptation?
Answer:

• Loss of unnecessary sense organs, loss of digestive system.
• Presence of adhesive organs or suckers.
• High reproductive capacity.
• Complex life cycle
  Ex: 1. liver fluke requires two hosts snail and a fish.
  2. Plasmodium-Mosquito and mar:
• Harmful effect on host: harm the host, reduce life span of host, lastly reduces its population.

Question 50.
Differentiate between Ecto and Endoparasites with examples?
Answer:

Ectoparasites	Endoparasites
1. They feed the external surface of the host	1. They live inside the host body at different sites
2. The life cycle is simple	2. The life cycle is complex
3. Ex: lice on humans, ticks on dogs, cuscuta plant on hedge plants	3. Ex: Plasmodium in RBC of man, Round and Tape worms in the guts of man.

Question 51.
Explain brood parasitism with an example?
Answer:
The parasitic birds lay its eggs in the nest of the host and lets the host incubate them is known as brood parasitism. During the course of evolution the eggs of parasitic bird have evolved to resemble host’s egg to reduce file chances of detecting the foreign eggs and ejecting from the nest. Ex: Cuckoo (koel) lays its eggs io crow’s nest.

Question 52.
Whatis Commensalism? Give an example.
Answer:
“Interaction in which one species is benefited and the other is neither harmed or benefited.
Ex: Epiphytic orchids growing on Mango and other trees.
Barnacles on back of whales. Cattle Egret and grazing cattle (Egrets get insects) clown fish living among tentacles of sea anemone (fish protected), sucker fish and shark.

Question 53.
Define Mutualism? Give examples.
or
Mutualism is a method of population interaction? Explain with examples.
Answer:
Association between two species, and both species are benefited.
Examples:

1. Lichens with fungi and algae or cyanobacteria Fungi – help in the absorption of nutrients from the soil.
   Algae – provides carbohydrates to fungi.
2. Mycorrhizae with fungi and root of higher plants.
   Fungi – Help plants in absorption of nutrients.
   Plants provides carbohydrates to fungi.
3. Plants and pollinators, seed dispersal agents.
4. Fig provide food to wasp, wasp pollinate the fig inflorescence.

Question 54.
Explain co-evolution with a suitable example?
Answer:
Fig and wasp: Fig flower is pollinated by its only one pollinator wasp species. The wasp uses the Fig as an
Oviposition, in turn, pollinates. Fig provides fruit and seeds for nourishing larvae.

Question 55.
Explain sexual deceit as an interaction of species with an example?
Answer:
Mediterranean Orchid Ophrys employs ‘sexual deceit’ to get pollination done by a species of bee. One petal of the flower resembles female bee which attracts male bee to the flower and pseudo copulates which effects pollination. When this same bee pseudocopulates with another flower, it thus pollinates the flower.

Question 56.
Define Ammensalism with an example?
Answer:
Association between two species that is harmful to one of the species, but no effect on the other (niether benefited nor harmed) Ex: Certain plants release toxins that inhibit the growth of other plant species.

→ Ecology – Ernst Haeckel (1869) coined the term Ecology
Oikos = home/place logos = study.

→ Organism And Its Environment:
Variations in temperature, seasons together with variation in precipitation (rain and snow), leads to the formation of major biomes-Desert, Rain forest, Grasslands and Tundra. Changes in each biome lead to the formation of a wide variety of Habitats.

→ Growth Models Or Curves:
Growth of population can be expressed by a mathematical expression called growth curve in which total number of individuals in a population is plotted against time.

→ Population Interactions:
Populations of different species often interact with each other in various possible ways in their habitats. These interactions may be beneficial, neutral or detrimental.
Sign ‘+’ = beneficial interaction
‘-‘ = detrimental interaction
‘o’ = Neutral interaction
The possible outcomes of possible interspecific interaction are shown in the table.

2nd PUC Biology Important Questions with Answers