Plant Kingdom | Introduction | Short Note For NEET BIOLOGY

Chapter 3: Plant kingdom

Plant Kingdom | Introduction | Short Note For NEET BIOLOGY

5 kingdom classification by R.H. Whittaker in 1969

Monera

Protista

Fungi

Animalia

Plantae

Plant kingdom:

Algae 

Bryophytes

Pteridophytes

Gymnosperms

Angiosperms

2 Problems in older classification 

️Earlier classification had only 2 types

One who had cell wall (plants)

One who did not have cell wall (animals)

So fungi and some members of Monera and Protista who had cell walls were classified under plantae. Which is not correct. 

Because fungi is different than plants and others are prokaryotic organisms whereas plants are eukaryotic organisms.

️ Cyanobacteria: earlier it was called blue green algae and classified under algae. 

The reason of this misunderstanding was the green color and photosynthetic character of the organism. 

It has green and blue pigment which makes it imparts blue-green color as well as they help in photosynthesis.

But as these organisms are not eukaryotic but prokaryotic organisms, hence they are now removed from Plantae and listed under Monera kingdom.

Types of classification and their evolution by time:

Artificial classification:

Earliest classification system

Used only gross superficial morphological characteristics i.e. habit, color, number and shape of leaves etc

Aristotle: divided plants only through their height(vegetative character) i.e. herbs, shrubs or trees.

Linneus: used androecium structure for classification.

Also called as sexual classification of plants

Androecium is part of flower which contains whirl of stamens

Drawbacks of artificial system:

Separated closely related organisms because it did not include more characters

It gave equal weightage to vegetative and sexual characters which is not acceptable. Because.. 

Vegetative characters change and evolve faster according to the habitat and surroundings

Sexual characters are more conservative and don’t change quickly with changing environment 

Natural classification system 

Classification of flowering plants by George Bentham and Joseph Dalton Hooker (Bentham & Hooker)

Depends on natural affinities among organisms

Includes external characters as well as internal characters

Internal characters 

Ultra structure: detailed structure of internal organs

Anatomy: study of internal structures

Embryology: study of embryo of plants, how the embryo develops etc

Phytochemistry: Study of special chemicals released by plant such as alkaloids(in opium, cannabis etc), tannins(in tea) etc

Phylogenetic Classification systems: 

Phylogenetic: relating to evolution 

This system includes evolutionary relationships of organisms for classification

Uses fossil records/data and or DNA sequence of organisms

Assumes that organisms belonging to same taxa have common ancestor – this classification system puts organisms with common ancestor under one group(taxa/taxonomic group)

Different sources of information is used – helpful when fossil evidence are not available

Numerical taxonomy 

Other names- Phenetics , taximetrics

Uses computers- softwares 

Uses all observable characters

Number and codes given to a characters and then data are processed for comparison

If a character is present code '+' or number '1’, if absent code '–’ or number '0’ given by software. 

If manually done this can take very long to compare and classify thousands of animals using hundreds of characteristics. Hence computers are used. 

Pros- 

Each character is given equal importance

Hundreds of characteristics at a same time can be included in classification 

Cytotaxonomy 

Uses cytological information i.e.

Chromosome numbers

Structure

Behaviour of cells

Chemotaxonomy

Used by taxonomist in current times

Used chemical constituents of plants e.g. 

DNA sequences

Presence of alkaloids 

It resolves confusion in classification.

FOR NEET BIOLOGY DAILY CHECK

Urvi Bhanushali

Manish Mevada