Maharashtra Board Class 9 Science Chapter 6 Classification of plants PDF Download

Classification Of Plants

You have already studied the kingdoms Monera, Protista and Fungi of the 'Five Kingdom' classification system proposed by Robert Whittaker (1959) for the study of living organisms.

What are the hidden secrets of the Kingdom plantae which impart this green freshness to our surroundings? Just how much diversity is there in this Kingdom? Let us see!

Kingdom Plantae

The group of autotrophic living organisms having eukaryotic cells with cell walls is the group of plants. Plants have become autotrophic as they can perform photosynthesis with the help of chlorophyll. Living organisms of kingdom plantae are the main source of food for all other living organisms.

Basis For Classification

The presence or absence of organs is the first criterion for classification of plants. The presence or absence of separate conducting tissues for conduction of water and food is the next consideration for classification. Do the plants bear seeds? If they do then, whether the seeds are enclosed in a fruit or not is also an important criterion for classification. Finally, plants are grouped depending upon the number of cotyledons in the seeds.

At the higher levels of plant classification, different characteristics are considered for classification. For example, depending upon the absence or presence of flowers, fruits and seeds, plants are classified as cryptogams or phanerogams. Depending upon whether seeds are enclosed within a fruit or not, phanerogams are classified as gymnosperms and angiosperms. Angiosperms are further classified as monocots or dicots depending upon the number of cotyledons in seeds.

Teacher's Note

Plants are very important for our life. They give us food, oxygen and medicines. You can see different plants in your school garden like tulsi, neem and mango trees.

Exam Trick

Remember: Cryptogams = no flowers and no seeds. Just like hidden things, their reproductive organs are hidden. Phanerogams = has flowers and seeds. You can see them clearly.

Points to Remember

Plants are autotrophs. They make their own food by photosynthesis.
The five kingdoms are: Monera, Protista, Fungi, Plantae and Animalia.
Plant classification is based on organs, tissues, seeds and flowers.
Cryptogams have no flowers. Phanerogams have flowers and seeds.
Seeds can be monocots (one part) or dicots (two parts).

Cryptogams

Division I - Thallophyta

These plants grow mainly in water. This group of plants, which do not have specific parts like root-stem-leaves-flowers but are autotrophic due to the presence of chlorophyll, is called algae. Algae show great diversity. They may be unicellular or multicellular, and microscopic or large. Examples of algae are Spirogyra, Ulothrix, Ulva, Sargassum, etc. Some of these are found in fresh water while some are found in saline water. These plants usually have a soft and fibre-like body. Various types of fungi like yeasts and moulds which do not have chlorophyll are also included in this group.

Observe

Search for a pond with greenish water. Collect some of the green fibres from the water. Put the fibres in a Petri dish and wash them clean with water. Put one of the fibres in a drop of water on a glass slide and spread it out straight.

Put a cover-slip over the slide and observe under a compound microscope. Do you see the spirally arranged green thread-like chloroplasts in the cells in that straight fibre? This plant is known as Spirogyra.

Teacher's Note

Algae are found in ponds and rivers. You can see green water in ponds during summer. This green color comes from algae like Spirogyra.

Exam Trick

Remember: Thallophyta = Thallus body. No real roots, stems or leaves. Just like jelly, it is soft.

Points to Remember

Algae are green plants that live in water.
Spirogyra has spiral chloroplasts like a spring.
Algae can be one cell or many cells.
Algae are autotrophs. They make their own food.
Some algae live in salt water and some in fresh water.

Division II - Bryophyta

Observe and Discuss

You may have seen a lush green soft carpet on old walls, bricks and rocks in the rainy season. Scrape it gently with a small ruler, observe it under a magnifying lens and discuss.

This group of plants is called the 'amphibians' of the plant kingdom because they grow in moist soil but need water for reproduction. These plants are thalloid, multicellular and autotrophic. They reproduce by spore formation. The structure of the plant body of bryophytes is flat, ribbon-like long, without true roots, stem and leaves. Instead, they have stem-like or leaf-like parts and root-like rhizoids. They do not have specific tissues for conduction of food and water. Examples are Moss (Funaria), Marchantia, Anthoceros, Riccia, etc.

Teacher's Note

Moss grows on wet rocks and walls during the rainy season. You can see green moss on the walls of old houses near water.

Exam Trick

Remember: Bryophyta = Amphibians of plants. They need water like frogs. They live in moist places.

Points to Remember

Bryophytes are small plants. They are usually green.
They grow in wet and moist places.
They do not have real roots, stems or leaves.
They have leaf-like and root-like parts called rhizoids.
They reproduce by spores.

Division III - Pteridophyta

Observe and Discuss

You may have seen ferns among the ornamental plants in a garden. Take a leaf of a fully grown fern and observe it carefully.

Plants from this group have well-developed roots, stem and leaves and separate tissues for conduction of food and water. But, they do not bear flowers and fruits. They reproduce with the help of spores formed along the back or posterior surface of their leaves. Examples are ferns like Nephrolepis, Marsilea, Pteris, Adiantum, Equisetum, Selaginella, Lycopodium, etc.

These plants reproduce asexually by spore-formation and sexually by zygote formation. They have a well-developed conducting system.

Use Your Brain Power

What is the similarity between the plants of the groups Thallophyta, Bryophyta and Pteridophyta irrespective of differences in their body structure?

Teacher's Note

Ferns are beautiful plants. You can see ferns in gardens and near water bodies. They have long green leaves with patterns on the back.

Exam Trick

Remember: Pteridophyta = Ferns and club mosses. They have real roots and stems. They reproduce by spores, not seeds.

Points to Remember

Pteridophytes are ferns. They have real roots, stems and leaves.
They have conducting tissues for water and food.
They do not have flowers or fruits.
They reproduce by spores on the back of leaves.
Examples are ferns, Selaginella and Lycopodium.

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