CBSE Class 6 Science Getting To Know Plants Worksheet Set B

PLANTS

Plants are one group of living things. As all living things do, plants grow, breath, reproduce, respond to stimuli, feed, excrete unwanted products produced in their body and show movement in the form of growth. There is enormous variety of plants around us. Would you list down some of the plants found in your school compound? Are all the same? Or they differ? Plants differ in size, shape and the way they reproduce. Based on certain similarities and differences, plants can be grouped into the following four divisions (phyla).

 Groups of Plants

1.Thallophytes – algae and fungi

2.Bryophytes – Mosses and liver worts

3.Pteridophytes – Ferns and horse tails.

4.Spermatophytes – gymnosperm and angiosperm

• THE THALLOPHYTES

This division includes algae and fungi. The bodies of these plants do not show any differentiation into the stem, leaves and roots. They have undifferentiated simple body called thallus. Algae can make their own food by photosynthesis because they have a green pigment called chlorophyll. On the other hand, fungi do not have chlorophyll and as a result they cannot make their own food by photosynthesis.

Therefore, fungi are either parasitic (feed on the body of other living things) or saprophytic (feed on dead organic matter)

1.Alga

Algae are simple plant like organisms which do not have roots, stems truits, flowers and leaves. They mainly live in water because water is very important for their survival and reproduction. There are different kinds of algae. Some are green while others are red or brown. The green algae consist of green pigment in much amount. In red algae red pigments is dominant and in brown algae brown segment is dominant. All algae are photosynthetic in their nutrition (can make their own food using energy of sun light). Algae lack true vascular tissues (xylem and phloem). They possess great range of size and form, ranging from unicellular (the body is made up of one cell) to multicellular (body is composed of many cells). Cells are the building blocks of the body of living organisms. Because algae are photosynthetic, they serve as producers in aquatic habitat and by being food for consumers.

Examples of algae include Volvox, Chlorella, Chlamydomonas, Spirogyra, Diva etc.

Importance of Algae

Algae are a large group of simple plants which have great biological importance and economic significance to humans. Generally, algae serve as food for aquatic organisms such as fish.

 Thus, some algae

1.Used as food for humans in Asia and North Europe. E.g. Brown algae

2.Used as fertilizers. g. brown algae

3.Source of silica / used in filter/. E.g. Diatoms

4.Indicator of organic pollution of water. E.g. Euglena

5.Source of agar (used as culture medium for microorganisms)E.g. Red algae

6.used in making of ice-cream and cosmetics. E.g. Brown algae

7.Rich sources of iodine and used in pharmaceuticals. E.g. Brown algae

8.Source of reefs/used for building material/. E.g. Red algae

FUNGI /FUNGUS: singular/

Fungi are other group of plants like organisms which do not have stem, leaves and roots. They cannot make their own food by photosynthesis. This is because they do not have the green pigment /chlorophyll/. Thus, fungi are either parasitic or saprophytic in their nutrition. They range from single-celled yeast to multicellular mushrooms and toad stoles in size.

Examples of fungi include

• Yeast D mold

• peculium mushrooms

• Aspergillus Microsporium etc.

Importance of fungi

Fungi are both useful and harmful to the mankind, animals and crops.

Useful fungi

Fungi are biologically very important in the biosphere and have economic and medical significance to humans. For instance

• Some fungi serve as food for humans. g. some mushrooms

• Some fungi are used to make bread rise in bakery and make injera soft. E.g. yeast

• Some fungi decompose dead bodies of plants and animals to recycle materials. E.g. saprophytic fungi

• Some fungi are useful to make antibiotics. E.g. pencillium

• Some fungi are used in making of alcohols. E.g. yeast

Harmful fungi

• Some fungi spoil foods. E.g. molds

• Some fungi cause diseases of plants such as mildews, smut and rusts. e.g. mildew, smut and rust

• Some fungi destroy useful products like papers, leathers and plastics.

• Some fungi cause diseases of animals and humans like ring worm, athlete’s foot,

 Vaginal thrush etc. E.g.

- microsporium

- Tinea-pedis

 THEBRYOPHYTES

Bryophytes are the simplest land plants. They mainly confined to damp and shady places. There are two main reasons for this

• Water is essential for the movement of male gamete/sperm/.

• They lack a true vascular tissues/xylem and phloem/ to transport water, mineral and food.

Bryophytes have root- like thin filaments called rhizoids. They make their own food using energy of sunlight. Bryophytes include two main groups of simple plants.

1. Mosses
2. Liverworts

In a life-cycle of bryophytes there are two distinct types of generations. These are

1. Gametophyte (produces gametes)
2. Sporophyte (produces spores)

1. MOSSES

Mosses are member of bryophytes, found mainly in damp and shady habitats and they are a little bit complex than algae and fungi. They often form dense carpet of cushions on the forest floor. Mosses need little soil to grow. Thus, they are the first colonizer of burned ground, rocks & lava affected areas. Although they do not have true roots, stem or leaves, they have parts that resemble all these parts. The root like structures absorbs water and minerals from soil.

Mosses prevent soil erosion by keeping soil in place and holding large amount of water. They are also very important in the formation of soil. The chemicals produced by root like structures gradually break down rocks into smaller particles (soil). They provide food for birds and mammals. Mosses form peat after death. Examples of mosses include furnaria & sphagnum.

1. Liver Worts

Liver worts are simpler and confined to damp and shady place. They resemble mosses, except that they lie flat on the ground and have a shape. Most liver worts have regular lobes that resemble human liver. They aren’t considered to have true leaves, roots, stem or leaves but they possess structures resemble these plant

organs. They are also without vascular tissues (xylem and phloem,) Examples of liver worts include pellia, marchantia, lophocolea etc.

3. Pteridophytes

Pteridophytes are vascular plants/have vascular tissues-xylem and phloem/. They are plants with true roots, stem and leaves/fronds/. In the life-cycle of pteridophytes there are two distinct generations/organisms/. These are

1. Sporophytes (produce spores in sporangia)
2. Gametophytes (produce gamete-sperm and eggs)

Although pteridophytes have true roots, stem and leaves, they do not have flowers, fruits and seeds.

Ferns

Ferns belong to phylum pteridophyta. They have proper roots, stem and a relatively large leaves called fronds but they do not have flower and fruits. Fronds are site of photosynthesis and bear spores on the undersides. Ferns are mainly found in damp places. They can make their own food by photosynthesis using energy of sunlight. They grow best in environment where warmth, moisture and air content of soil is high.

Ferns need water for reproduction. That is way they prefer to live in damp places.

Importance of Ferns

1. Some ferns have no grazing value and considered to be important weeds.
2. Few ferns propagate for their ornamental value. 

e.g. Dryopteris

1. Some tree-ferns are used for construction purposes.
2. Ferns are important in the formation of coal deposits.
3. Since they are producers they are sources of food for many animals.
4. Their dead body serves as fertilizer

SPERMATOPHYTA/SEED BEARING PLANTS/

Spermatophytes are the most successful group of plants with

1. True stem, leaves and roots
2. Complex vascular tissues /xylem and phloem/
3. Seeds /produce seeds/

They have seeds which contain a baby plant/embryo/ and stored food. Water is not needed for reproduction. There are two main groups of spermatophytes/seed-plants/. These are

1. Gymnosperms/seed bearing non-flowering plants/
2. Angiosperms/Flowering plants/

 Gymnosperms/seed-bearing plants without flowering /

Gymnosperms are also called cone-bearing plants. This is because seeds are enclosed in cones/scaly structure that protect the seeds/. Most gymnosperms are evergreen /keep their leaves throughout the year/. Most of them are found at higher altitudes and further North Pole than any other trees. Conifers are a large group of familiar gymnosperms. They do not bear fruits.

1. Conifers

Conifers account for about one-third / ^rd./of the world forests. They are trees, shrubs, evergreen with needle like-leaves. This group of plants is commercially important as ‘soft wood’. This is because they are used as sources of

- Timber - varnish

- Resins - plastics

- Turpentine - glues

- Wood pulp - rayon etc.

Examples of gymnosperms /conifer/ include

• Pines - Larches
• Firs - Spruces
• Cedars - Junipers
• Podocarps etc.

Angiosperms /Flowering Plants/

Angiosperms include a wide range of plants with

• Seeds /produce seeds/
• Flowers
• Fruits
• Complex vascular tissues /xylem and phloem/
• True leaves, stem and roots. They are better adapted to life on land than any other plants. 

Angiosperms found spread in different habitats. They range from small herbs to massive trees in size. Seeds are protected inside fruits. Flowering plants are very significant in economic and medical importance to humans. Almost all our food comes from flowering plants. They also serve as food for other animals. We obtain cotton, dyes, pigments, medicines, teas, spices etc. from flowering plants.

Flowering plants are divided into two major groups depending on the number of seed leaves or cotyledons. These are

1. Monocotyledons /one seed leaf only/
2. Dicotyledons / two seed leaves/

Comparison of dicotyledons and monocotyledon

Table 4.1 Comparison of dicotyledons and monocotyledon

Reproduction in plant

Reproduction is the mechanism by which new off springs re produced from pre-existing organization. It is a means by which perpetuation of a species is ensured. Reproduction might involve one or two parents one parent it is called asexual otherwise it is called as sexual reproduction. Thus reproduction is categorized into sexual and asexual types.

Flower is the reproductive organ for flowering plants. Reproductive organs other than flower are called vegetative organs and are exemplified by leaves, roots tubers, stems, etc.

Parts of a flower

Flowers are reproductive organ of angiosperms. The flower is made up of different parts that perform different functions. Sepals, petals, stamens, carpel and receptacle are parts of a flower.

1. Sepals

Sepals are the most outer part of a flower. It is green leaf like structure that gives protection to the other parts of the flower.

1. Petals: They are often brightly colored & scented to attract insects for pollination.
2. Stamens: Stamens are the male part of a flower. A stamen consists of anther and filament. The anther produces pollen grains/male gamete/
3. Carpel: Carpel is the female part of a flower. It produces ovules /female gamete/. A carpel is made up of ovary, style and stigma.
4. Receptacle: Swollen part of flower stalk.

Pedicle: Flower stalk that bear the other floweral parts.

6.2 Pollination

The transfer of pollen grains from anther to stigma of a flower is called pollination. It is two types

1. Self-pollination
2. Cross-pollination
   • Self-pollination is the transfer of pollen grains from anther to stigma of the same flower.
   • Cross-pollination is the transfer of pollen grains from anther to stigma of different flower of the same species.

6.2.1 Agents of pollination

Pollination does not occur by itself most of the time. Therefore, a pollinating agent is necessary to carry pollen grains from anther to stigma. Insects, wind, water and animals are agents of pollination.

Among the above agents of pollination, wind and insects are among the major ones.

1. Wind pollination

Wind is an agent of pollination which carries pollen grains from anther to stigma. Wind pollinated flowers have the following characteristics.

1. Generally small.
2. Petals are green or dull color and reduced in size.
3. Do not produce nectar.
4. Produce large number of pollen grains.
5. Pollen grains are light and dry.
6. Insect-pollination

Insects such as bees, moths, butterflies etc. Visit flowers to feed on the nectar. They are the major agents of pollination. Insect-pollinated flowers have the following characteristics.

1. Have brightly colored petals.
2. Emit sweet scent.
3. Produce nectar which is food of insects.
4. Generally larger.
5. Smaller numbers of pollen grains are produced.

Fertilization

Fertilization is the fusion of male gamete /pollen grains/ with female gamete /ovule/. Once a pollen grain has reached on a stigma, a pollen tube starts to grow down the style. The pollen tube carries male gametes /pollen grain/ to ward the female gamete /ovule/. The pollen grain fuses with ovule to become seed. The ovary becomes fruit.

Vegetative Reproduction in plants

Vegetative reproduction /vegetative propagation/ is a form of asexual reproduction in plants. It involves the development of a new plant from the main plant organs like roots, stems and leaves.

The plant organ that serves as vegetative propagation must contain buds that develop into a new plant capable of independent existence. These vegetative organs that contain buds are called perennating organs. They included bulbs, corms, rhizomes tubers and stolen. Asexual reproduction /vegetative propagation/ in plants involve four methods. Cutting, layering, grafting and budding.

1. Cutting

This is a simple method of vegetative propagations in which part of a healthy plant is removed by cutting and placed in a suitable soil for growth. It produces roots and grows into a new plant of independent existence. Plants such as rose, grape wine, strawberry, bamboo, geranium, chrysanthemum etc. propagate through this method.

1. Layering

Layering is used for plants that produce runners. A young branch/runner/ is bent down and pressed into the soil around parent plant until roots grow out from the covered part of the plant. Once roots are grown out the branch can be cut to detach it from the parent plant.

1. Grafting

Grafting is the transfer of part of one plant on to another plant. Once the two cut surfaces have been brought together, the two plants should be bound and the joint covered with wax. Plants such as apple, plum, peach etc. propagate by drafting

1. Budding

Budding is a type of grafting in which a bud of a plant is transferred to another plant. Then the two tied together and protected. Rose plants propagate by this method.

Both sexual and asexual reproductions in plants have advantages and disadvantages

 Sexual and asexual reproductions in plants

Seed and its Germination

The ovule develops into seed after fertilization. Therefore, seed is a matured ovule.

Structure of a seed

A seed consists of a baby plant /embryo/, a protective covering (seed coat/ testa) and one or more fleshy structure (cotyledons)

- Embryo is a mini /baby plant/ that develops into a new plant. It consists of an axis that differentiated into two parts, the radical and plumule. The radicle develops into roots while the plumule becomes the shoot. (the part of plant above the ground)

- Seed coat/testa is a tough covering that protects the seed from damage by any condition.

- Cotyledon is fleshy structure that contains stored food used up by the embryo during at time of germination.

Germination of a seed: The development of a new plant from a seed is called germination. Moisture (water), oxygen (air) and suitable temperature are necessary conditions for the germination of a seed

Plants as source of food

Pants are the main source of food for humans. We depend on plants for the food we eat directly or indirectly. The different parts of plants such as seed, leaves, stems, roots, fruits and flowers are used as food by humans. The food we get from plants gives us energy, protect us against diseases, strengthen our bones, teeth and muscles & help us to grow.

            Questions

            Very Short Answer

Q1)      What is parallel venation?

Q2)      What is veins and midrib?

Q3)      What are lateral roots?

Q4)      Define leaf venation?

Q5)      Name the parts of a flower?

           

            Short Answer

Q6)      What do you understand by the ovary?

Q7)      Distinguish between parallel venation and reticulate venation?

Q8)      What do you mean by pistil?

Q9)      How roots absorb water and minerals from soil?

Q10)    What do you mean by ovules?

           

            Long Answer

Q11)    Explain about pistil and parts of pistil?

Q12)    Distinguish between stamens and pistil?

Q13)    Explain why flower is important to a plant and parts of the flowers?

Q14)    State the difference between tap root and fibrous root?

Q15)    State the difference between petals and sepals?

 

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