Question

Water is both a powerful force and critical to an organism’s survival. Explain how this can be true of water, by providing a detailed example of each situation (including the chemistry aspect as needed).

There is a wide variety of survival strategies used by terrestrial organisms. Explain the difference between ectotherms and endotherms, and an example organism for each.

Many organisms live in environments that experience large changes, giving them seasons. Explain the differences between diapause, hibernation, and torpor. Provide a single organism example for each of the three terms and why that species must use this strategy.

Answer 1

Water has different roles in living organisms:

• solvent :

Water is an excellent solvent and it has such propery due to its chemical composition and physical attributes. Polar arrangement of water molecules — positive electrical charge on one side because of hydrogen and negative charge on the other side due to the presence of oxygen. This results in the attraction of different water molecule to each othert.The strong attraction between water molecules is sufficient to break the attractive forces between different molecules like NaCl and dissolve it.

• temperature buffer:

Cells perform a wide range of chemical reactions. Most of them are catalysed by Enzymes. Activity of an enzyme is temperature sensitive only if it occur in a narrow range of temperatures. Water have the capacity to buffer the changes of temperature because it has relatively high specific heat capacity (the heat is used to raise 1 kg of water by 1 ^oC) , enthalpy of vaporisation (heat energy is used to convert a liquid to a gas) as well as enthalpy of fusion (heat energy used to convert a solid to a liquid).

• metabolite :

Chemical reactions occurs in cells together are known as metabolism, i.e. all the physical as well as chemical and physical processes within a cell. The chemicals are known as metabolites. Water is a metabolite in most of the reactions. For example, it's participated in photosynthesis, digestion alsoaerobic respiration.

• living environment :

Many organisms live in water like fish and not survive outside. They have adapted to living in it. The surfaces of water bodies like ponds, river, etc are protected with a 'skin' of water molecules, that support the survival of an aquatic organisms.

Endotherms examples like human, penguine, polar bear, etc produces maximum heat they required internally. During winter, production of metabolic heat is increases to maintain their constant body temperature. Hence, an endotherm's internal  body temperature is not dependent on the environmental temperature.

On the another hand for ectotherms like invertebrates, fishes, amphibians,etc, body temperature majorly depends on external sources of heat. Therefore, body temperature of an ectotherm increases or decreases along with the surrounding temperature. Although ectotherms do produce some metabolic heat—like others— but not increases to maintain a specific internal temperature. Instead of increasing temperature they adopt different strategies, like behavior—seeking sun, shade, etc.—to find suitable environments to meets their needs.