NCERT Book Class 11 Biology Chapter 3 Plant Kingdom

PLANT KINGDOM 23

C HAPTER 3
PLANT KINGDOM
3.1 Algae In the previous chapter, we looked at the broad classification of living
organisms under the system proposed by Whittaker (1969) wherein he
3.2 Bryophytes
suggested the Five Kingdom classification viz. Monera, Protista, Fungi,
3.3 Pteridophytes Animalia and Plantae. In this chapter, we will deal in detail with further
classification within Kingdom Plantae popularly known as the ‘plant
3.4 Gymnosperms
kingdom’.
3.5 Angiosperms We must stress here that our understanding of the plant kingdom
has changed over time. Fungi, and members of the Monera and Protista
having cell walls have now been excluded from Plantae though earlier
classifications placed them in the same kingdom. So, the cyanobacteria
that are also referred to as blue green algae are not ‘algae’ any more. In
this chapter, we will describe Algae, Bryophytes, Pteridophytes,
Gymnosperms and Angiosperms under Plantae .
Let us also look at classification within angiosperms to understand
some of the concerns that influenced the classification systems. The
earliest systems of classification used only gross superficial morphological
characters such as habit, colour, number and shape of leaves, etc. They
were based mainly on vegetative characters or on the androecium
structure (system given by Linnaeus). Such systems were artificial; they
separated the closely related species since they were based on a few
characteristics. Also, the artificial systems gave equal weightage to
vegetative and sexual characteristics; this is not acceptable since we know
that often the vegetative characters are more easily affected by
environment. As against this, natural classification systems developed,
which were based on natural affinities among the organisms and consider,