Explore topic-wise InterviewSolutions in .

Characteristics are:

Population density, population growth, age distribution, birth rate, death rate, sex ratio etc.
(1) Population density:-

Indicates size of population. It is number of individuals of a population found in a unit area or space at a given time. It is found out by total count
Random sampling.

\(D = \frac{N}{S}\)

D – Population Density
N – total number of individuals of given area
S - unit of space or area

(2) Population growth:-

It is increase in size of the population over a period of time.
N_t = N_o + (natality +Immigration) – (Mortality +Emigration)
N_t = N_o + B + I - (D + E)
N_t = Population increase after time t;
N_o = Population at t = 0

(3) Age distribution :-

Pre-reproductive, reproductive, post – reproductive.
it helps to provide information about the population

Expending, Declining or Stable population.

• Population density
• Birth rate
• Death rate
• Sex ratio
• Population growth
• Age distribution
• Population dispersal.

• Parasites that feed on the external surface of the host organism are called ectoparasites. The most familiar examples of this group are the lice on humans and ticks on dogs.

• Endoparasitesare those that live inside the host body at different sites (liver, kidney, lungs, red blood cells, etc.).’”The human liver fluke (a trematode parasite) is an endoparasite.

Since plants produce food through photosynthesis, a process which is only possible when sunlight is available as a source of energy, we can quickly understand the importance of light for living organisms, particularly autotrophs. Many species of small plants (herbs and shrubs) growing in forests are adapted to photosynthesise optimally under very low light conditions because they are constantly overshadowed by tall, canopied trees. Many plants are also dependent on sunlight to meet their photoperiodic requirement for flowering. For many animals too, light is important in that they use the diurnal and seasonal variations in light intensity and duration (photoperiod) as cues for timing their foraging, reproductive and migratory activities.

• The annual variation in the intensity and duration of temperature
• The annual variation in precipitation, account for the formation of major biomes.

Eurythermals show a wide range of distribution as they can tolerate and thrive in a wide range of temperatures.

This is because of the osmotic changes in the body.

Mycorrhiza is a symbiotic association between a fungus and the roots of higher plants.

To maintain the constancy of internal environment despite varying external environmental conditions is called homeostasis.

High altitude areas have brighter sunlight because at high altitude there is a very low concentration of dust particles and atmospheric gases which absorbs the sunlight. There is a low atmospheric pressure at high altitudes. Lower atmospheric pressure results in lower temperatures at high altitudes.

It is the process in which animals spend the winter in an inactive/dormant state, eg: Frogs, polarbear.

It is the process in which animals spend the dry, hot summer period in an inactive state, eg: Snails.

Migration is the temporary, long-distance or short distance movements of animals from the stressful movement to a less stressful or comfortable environment and return to the original habitat when the stressful period is over.

The development of certain features in an organism in response to particular environment which may improve the chances of survivals are called adaptation.

Sigmoid growth curve represents logistic growth where growth is slow initially and then becomes rapid the curve becomes steady due to resources become tending.

(i) Curve (a) – Non-limiting curve

(b) – Limiting and has reached carrying capacity.

(ii) Curve (a) because of absence of controlling factor.

Carrying capacity is the maximum number of individual of a population that can be sustained by a given habitat.

• Some species of frogs and insects are cryptically coloured or camouflaged to avoid being detected easily by the predators.
• Some prey species are poisonous and are avoided by the predators.

Predators help in maintaining species diversity in an ecosystem or community by reducing the intensity of competition among the competing prey species.

Conformers are those organism, which change their body temperature, osmolarity etc. according to the external ‘environmental conditions.

(1) During the course of evolution, the costs and benefits of maintaining a constant internal environment are taken into consideration, when it is not advantageous, the organisms have not evolved mechanisms to maintain homeastasis.

(2) Heat loss or gain is a function of surface area and hence very small animals are not found in polar region i.e. they have become distributed according to the external conditions.

(3) Similarly aquatic animals, that are conformers can change the osmolarity of their body fluid according to the surroundings.

Incorrect:-

Camoflague is blending with the back ground or surroundings due to similar colours, shape or marketing so as to remain unnoticed by predators (for protection) and prey (advantage).

Fig. 1: It is a single population.and all individuals are of the same species, i.e. A—Individual interact among themselves and their environment.

Fig. 2: It is a community and it contains three populations of species A, B and C. They interact with each other and their environment.

Fig. 3: It is a biome. It contains three communities of which one is in climax and other two are in different stages of development. All three communities are in the same environment and they interact with each other and their environment.

A – B

(a) Amensalism – Species A harmed species B unaffected

(b) Predation/parasitism – Species A benefited species B harmed

(c) Competition – Species A and B mutually inhibited

(d) Mutualism – Both A and B benefitted

(e) Commensalism – Species A is benefitted Species B is unaffected.

(i) Figure ‘A’ shows’ mutualism (plant-animal relationship).

(ii) Figure ‘D’ shows predation (leopard killing deer and eating it) 

(iii) Figure ‘C’ shows commensalism (cattle egret and grazing cattle)

(iv) In figure ‘B’ insect is phytophagous that feed on sap of the flower.

(1) Beneficial interaction:-

• The interspecific interaction which is beneficial to both the species is called mutualism.
• Beneficial to one, but neutral to other. 
• Commensalism

(2) Detrimental interaction:-

• Competition is the type of interaction that is detrimental to both the species.
• Parasitism- Beneficial to one and detrimental to the other. 
• Amensatism – Detrimental to one and neutral to the other.

(3) Neutral interaction:-

Commensalism is a type in which interaction is detrimental one and beneficial to the other.

(a) Migratory animal—Siberian crane, Salmon 

(b) Camouflaged animal—Frog, insects

(c) Predator animal—Tiger, sparrow

(d) Biological control agent—Moth (against prickly pear cactus) 

(e) Phytophagous animal—Insects like Locusta

(f) Chemical defense agent—Cardiac glycosides produced by Calotropis

Population Nearly/relatively permanent aggregation or grouping of interbreeding individuals of the same species present in a particular space or area at a given time who share the same gene pool.

Community (Biotic or Biological Community) Assemblage of different species present in the same area at the same time which show interactions and interdependence through trophic and spatial relationships.

(a) An endothermic animal – Monkey (mammal)
(b) An endethsmml animal Frog (amphibian), snake (reptile)
(c) An organism of benthic zone – Angle Fish

Because temperature affects the basal metabolism/ physiological function of the organism//not adapted to low temperature of temperate climate.

Bears undergo hibernation to get rid of the stressful time in winter.

Plants that inhabit rainforest are not adapted to survive in wetlands or aquatic conditions because in wetlands the soil is deficient in oxygen. So the plants develop above ground roots called pneumatophores for respiration. Such an adaption is not found in roots' of plants growing in rain forest.

In seed - bearing plants, seed and some other vegetative reproductive structures serve as a means to tide over periods of stress besides helping in dispersal. They do so by reducing their metabolic activity and going into a state of 'dormancy'. They germinate to form new plants under favourable moisture and temperature condition.

Commensalism is the interaction in which one species benefits and the other is neither harmed nor benefited.

• Commensalism:- 

It is the interspecific interaction in which one species is benefited while the other is neither benefited nor affected.

• Amensatism:-

It is an interspecific interaction in which one species is affected, while the other species is neither benefited or affected.

In interference competition, even if the resource is abundant, the feeding efficiency of one species is reduced by the interfering and inhibitory presence of other species.

Eg:

The Abingdon tortoise in Galapagos islands become extinct with in a decade due to the introduction of goat in that island.

Submerged plants receive weaker illumination than exposed floating plants in a lake because on passing of light through water much more amount of light is lost.

Calotropis plants possess a highly poisonous cardiac glycoside, which is fatal to animals.

Animals living in arid areas are adapted to manage with scarcity of available water and reduce water loss to minimum.

Eg: Kangaroo rat feeds on dry seeds. Animals protect themselves from excessive cold by hibernation, thick for, constriction of peripheral blood vessel.

Phenotypic adaptation:-

It is non-genetic change in physical and physiological characteristics which develops in response to changes in environment and are useful to organisms in adjustment to prevailing Pvt. conditions.
eg:-

• Mountain sickness in normal people in high attitudes but tribes living in himalayas do not have mountain sickness
• Euphorbia hirta plant species.

Brood parasitism is a phenomenon in which one species (parasite) lays eggs in the nest of other species (host) of bird and lets the host incubate them,

eg: Cuckoo lays eggs in crow’s nest Cuckoo’s eggs shows resemblance with the eggs of crow in colour size etc which failed to identify by the crow with their eggs.

(1) Algae and fungi in lichens:-

• This is an example of mutualism in which both are benefited
• Fungi provide protection and helps in absorbing water and minerals where as the algae prepare food for the fungus.

(2) Head louse and human: 

This is an example of ectoparasitism the parasite gets shelter as well as food from human’s head.

(3) Hermit crab and sea anemone:- 

This is an example of commensalism in which sea anemone gets benefit for moving to places rich in nutrients while the hermit crab neither benefitted nor harmed.

In accordance with their life styles, parasites evolved special adaptations such as the loss of unnecessary sense organs, presence of adhesive organs or suckers to cling on to the host, loss of digestive system and high reproductive capacity. The life cycles of parasites are often complex, involving one or two intermediate hosts or vectors to facilitate parasitisation of its primary host.

Allen’s rule refers to the minimising of heat loss in animals by possessing shorter ears and limbs.

To compensate for the low atmospheric pressure and low oxygen content of air prevailing at high attitudes, people have higher, RBC count or total haemoglobin.

Shark: tolerates wide range of temperature so wide spread / survives in all waters. 

Polar bear : restricted occurrence in narrow range of temperature so constraint to live in very cold icy environment.

Mammals from colder climates generally have shorter ears and limbs which minimize heat loss (Allen's rule). 

In polar region seals have thick layer of fat (blubber) below their skin that acts as insulator and reduce loss of body heat.

(a) The frogs hibernate during very cold season and reduce their metabolic activities.

(b) The kangaroo rat has the ability to concentrate its urine and can live from birth to death without drinking water, thereby conserving water. 

(c) Barnacles and molluscs, living in very cold intertidal zones of northern shores, show their reduce activities. 

(d) Some animals go to summer sleep.

Detailed Answer:

(i) Polar bear : They hibernate during winter to escape the cold weather.

(ii) Snails/fishes : They go into aestivation during summer to avoid heat related problems and desiccation. 

(iii) Seeds of higher plants/spores of bacteria/fungi : They become dormant in unfavourable conditions and in case of Amoeba, cyst formation takes place. 

(iv) Some species of zooplankton : They undergo diapause.

Small animal like hummingbird/shrew, have a larger surface area relative to their volume, they tend to loose heat when it is cold outside, hence spend much energy to generate body heat through metabolism.

Humans maintain a constant body temperature of 37°C. In summer, when outside temperature is more then our body temperature, we sweat profusely. The resulting evaporative cooling, similar to what happens with a desert cooler in operation, brings down the body temperature. In winter when the temperature is much lower than 37°C, we start to shiver, a kind of exercise which produces heat and raises the body temperature.