DIFFERENCE BETWEEN PLANTS AND ANIMALS

                    Or

How does animal life differ from plant life? 

                      Or

What is the difference between plants and animals

Answer:

Considering the basic structure, both in plants and animals the basic unit of structure is the eukaryotic cell(i.e nucleated cell).

There are mainly two salient features of difference:

(a) animal cell lack chloroplast which is a photosynthetic factory in plant cells.

(b) an animal cell does not have cell walls which are there in plants and is mainly composed of cellulose, furnishing structural rigidity to plants.

Main difference between plants and animals 

Properties	Plants	Animals
Mode of nutrition	Autotrophic ( contain chloroplasts; carry out photosynthesis)	Heterotrophic ( lack chloroplasts; no photosynthesis)
Extent of growth	Indeterminate	Determinate
Cell wall	Cellulose( long glucose chain); rigid, inert	Absent
Nervous System	Absent	Present in most
Mobility	Mostly immobile	Mostly mobile
Primary food reserve	Starch ( unbranched glucose chain); unsaturated oils	Glycogen ( multiple branched glucose chain); saturated fats
Waste products	O2 from photosynthesis, CO2 from metabolism; kidneys not needed since nitrogenous wastes are not generated	CO2 and nitrogenous wastes; kidneys needed in most anim

Owing to the presence of chloroplasts, most plants carry out auto-trophic (self-nourished) nutrition through the process of photosynthesis. 

In this process, the plant (autotroph) builds simple sugars out of carbon dioxide and water, giving off oxygen as a waste product. Here the plant converts the radiant energy into chemical bonding energy.

On the other hand, animals exhibit heterotrophic nutrition. They cannot construct organic molecules out of inorganic substrates. The animals depend on plants and other animals for their nutrition.

Lily moth caterpillar Polytela gloriosa
( animal depending on plants for nutrition)

As a rule, plants grow throughout life ( indeterminate growth), whereas most animals attain a certain adult size and cease to grow (determinate growth). For the quest for food, the compact body of the animal is more compatible with mobility. All but the simplest plants are immobile.

 Most animals have nervous systems and sense organs. The plants usually don't demonstrate such nature but some plant cells, especially at growing tips are sensitive to certain stimuli.

Plants store much of their food reserve as starch, a long unbranched chain of glucose( simple sugar) molecules. Whereas the main carbohydrate food reserve of animals is glycogen, a highly branched chain of glucose, which yields free sugar molecules much more readily than starch does. 

The metabolic rate in animals is so high producing toxic nitrogenous waste like ammonia, urea, etc., due to rapid formation and breaking down. This waste must be excreted out of the body as components of urine. 

On the other hand, plants do not produce urine and do not require kidneys to excrete it.

Next: Animals are important 

About the Author: This educational content on Zoology is written by Rekha Debnath, M.Sc. & M.Phil. in Zoology, with a focus on university-level academic topics. Read the full Author Credentials and Background here.