Heat loss or heat gain is a function of surface area.
Since small animals (like humming birds) have a larger surface area relative to their volume, they tend to lose body heat very fast, when it is cold outside.
They spend more energy to generate body heat through metabolism; considering the cost and benefit of maintaining   a constant internal temperature, small animals (humming  birds) are not found in polar regions.

Seals have thich layer of fat, called blubber below their skin.
The blubber acts as an insulator and reduces loss of body heat.

The interaction is called commensalism.
The egrets always, forage close to where the cattle are grazing.
As they move, thJ cattle stir up and flush out from the vegetation the insects which otherwise might be difficult for the egrets to find and catch.
Thus, the egrets are benefitted while the cattle are neither benefitted nor harmed.

Fungi produce various kinds of thick-walled spores to survive under unfavorable conditions; they germinate when conditions become favorable.
Zooplanktons enter diapause, a stage of suspended development, under unfavourable conditions.
Bears go into hibernation during winter to escape in time of unfavourable conditions.

Larger animals such as birds and mammals are able to maintain body temperature by physiological means.These have more volume and smaller surface area as compared to smaller animals.

(i) Relationship between (1) and (2) is of predator-prey relationship.
(ii) Relationship between (3) and (4) is producer and (3) is primary consumer.

Ways to adapt unfavourable conditions are:
(i) Snails undergo aestivation (summer sleep) to avoid summer related problems.
(ii) Bears undergo hibernation (winter sleep) during winter.
(iii) Zooplanktons enter a stage of suspended development called diapause.
(iv) Bacteria and fungi slow down their metabolic rate and from thick-walled spores germinate when the conditions become suitable.

(a) (+) and (+): Mutualism
It is defined as the interspecific interaction in which both the partners are benefitted, e.g. the fungus and algae in a lichen.
(b) (-) and (-): Competition
It is a type of interaction either among the individuals of the same species (intra-specific competition) or between the individuals of two different species (inter-specific competition).
(c) (+) and (-): Predation
It is an interspecific interaction, where one animal, called predator, consumes the other animal, called prey; one is benefitted and the other is harmed, e.g. the lion eating deer.
(d) (+) and (0): Commensalism
It is an interspecific interaction in which one of the species is benefitted and other is neither benefitted nor harmed, e.g. an orchid growing on a mango tree.
OR
(d) (-) and (0): Amensalism
It is an interspecific interaction in which one is harmed and the other is neither benefitted nor harmed, e.g. antibiotic secreted by a fungus kills many bacteria in the vicinity.
(b) (c) (+) and (-): Predation
It is an interspecific interaction, where one animal, called predator, consumes the other animal, called prey; one is benefitted and the other is harmed, e.g. the lion eating deer.
(c) (c) (+) and (-): Predation
 It is an interspecific interaction, where one animal, called predator, consumes the other animal, called prey; one is benefitted and the other is harmed, e.g. the lion eating deer.
(d) (+) and (0): Commensalism
It is an interspecific interaction in which one of the species is benefitted and other is neither benefitted nor harmed, e.g. an orchid growing on a mango tree.
(e)(d) (+) and (0): Commensalism
It is an interspecific interaction in which one of the species is benefitted and other is neither benefitted nor harmed, e.g. an orchid growing on a mango tree.

Mutualism:
Mutualism is defined as the interspecific interaction in which both the interacting species are benefitted, e.g.
(i) Lichens show an intimate mutualistic relationship between a fungus and an alga, where the fungus provides protection and helps the alga to absorb nutrients.
The alga prepares the food for the fungus too.
(ii) Mycorrhizae are mutualistic association between certain fungi and the roots of higher plants.
The fungus helps the plant by making the nutrients available in the vicinity of roots, and stores certain minerals like phosphorus in the mantle of hyphae
The fungus gets food and shelter from the plant.
(iii) Plants depend on insects for pollination; the insects are rewarded in the form of nectar or edible pollen or sometimes place for oviposition.
(iv) Rhizobium in the root nodules of legumes helps in nitrogen fixation and nitrogen nutrition to the plants and in turn gets shelter and food from the plant.

Figure I It is a single population and all individuals are of the same species, i.e., a individuals interact among themselves and their environment intraspecific interaction.
Figure  II It is a community and it contains three populations of species A, Band C. They interact with each other and their environment and is called interspecific interaction.
Figure III 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.