kingdoms

The Two Kingdoms : Plantae and Animalia
Carolus Linnaeus placed all the living organisms in two major kingdoms Kingdom Plantae for plants and Kingdom Animalia for animals. This classification was quite reasonable at that period of time since plants and animals could be very clearly distinguished. Plants were stationary, fixed to the soil, absorbed water for growth and could prepare their own food. Animals, on the other hand were capable of movement, and were feeding on plants and other animals for their growth and survival. Apart from this a few other significant differences, particularly at the level of cells, were established between plants and animals by scientists of the later period.

Kingdom Plantae
The original plant kingdom proposed by Linnaeus and subsequent taxonomists of that period included the bacteria, fungi, algae, liverworts, mosses, ferns, conifers and flowering plants. Plants in general are considered to exhibit the following distinguishing characters.

Plants exhibit a great deal of variation in their form and size. Plant body is usually asymmetrical. However, in higher plants structures like leaves and flowers have a definite form and shape.

Plants are rooted mostly and as such are incapable of locomotion. However, certain localized movements may occur in a plant body.

Plants exhibit unlimited growth, almost throughout their life span.

Absence of locomotion.

Plants exhibit largely autotrophic nutrition or saprotrophic nutrition. Particulate matter cannot be absorbed and only materials present in a solution state can be absorbed.

Plant body is composed of cells which have a distinct cell wall, a vacuole filled with sap and plastids of different kinds. The cells do not have centrioles and lysosomes.

Plant cells can synthesize all the amino acids, coenzymes and vitamins necessary for its functions.

Plants have reserve food as starch.

Classification of Kingdom Plantae

The Plant kingdom was initially classified as follows


fig. 7.6 - Classification of Kingdom Plantae

Kingdom Animalia
The original Animal Kingdom proposed by Linnaeus included the protozoans, sponges, jelly fishes, worms, crabs, insects, spiders, snails, starfishes, sharks, bony fishes, frogs, lizards, birds and mammals. In general, animals exhibit the following distinguishing characters.

The animal body generally exhibits a definite symmetry, form and shape.

Animals have the capacity to move from place to place in search of their necessities.

Growth in animals is determined and occurs proportionately in all parts of the body.

Animals are generally heterotrophic, obtaining their food from plants and other animals.

Animals have the property of irritability - the capacity to respond to a stimulus.

The cells, which form an animal's body do not have a cell wall. Plastids and vacuoles are generally absent and centrioles & lysosomes are present.

Animal cells cannot synthesize all the necessary amino acids, vitamins and coenzymes and as such will have to obtain them from external sources.

Reserve food is glycogen.