Plant Kingdom

The Plant Kingdom is a vast and diverse group of organisms characterized by their ability to produce their own food through photosynthesis. They are multicellular eukaryotes with cell walls made of cellulose and possess chlorophyll, a pigment that captures sunlight for photosynthesis.

The Plant Kingdom is divided into five major groups:

Algae: Simple, thalloid, autotrophic organisms that live in water. They are classified based on their pigments and stored food. Examples include green algae (Chlorophyceae), brown algae (Phaeophyceae), and red algae (Rhodophyceae).
Bryophytes:They are commonly found in moist, shaded areas. Examples include mosses and liverworts.
Pteridophytes: Vascular plants with true roots, stems, and leaves, but without seeds. They reproduce through spores.
Gymnosperms: Seed-bearing plants with naked seeds. They do not have flowers or fruits. Examples include pine trees, firs, and cedars.
Angiosperms: Flowering plants that produce seeds enclosed in fruits. Examples include grasses, flowering trees, and shrubs.

Each group of plants has unique characteristics and adaptations that allow them to thrive in different environments. The Plant Kingdom plays a crucial role in the ecosystem, providing food, oxygen, and other resources for life on Earth.

Exercise

1. What is the basis of classification of algae?

Ans :

Algae are classified primarily based on their pigments and stored food. These characteristics help to distinguish different groups of algae and understand their evolutionary relationships.

Here’s a breakdown of the main groups of algae and their key characteristics:

Green Algae (Chlorophyceae):
- Primary pigment: Chlorophyll a and b
- Stored food: Starch
- Cell wall: Cellulose
Brown Algae (Phaeophyceae):
- Primary pigment: Chlorophyll a and c
- Stored food: Mannitol and laminarin
- Cell wall: Cellulose and algin
Red Algae (Rhodophyceae):
- Primary pigment: Chlorophyll a and d
- Stored food: Floridean starch
- Cell wall: Cellulose and agar

2. When and where does reduction division take place in the life cycle of a liverwort, a moss, a fern, a gymnosperm and an angiosperm?

Ans :

Reduction Division (Meiosis) in Plant Life Cycles

Reduction division, or meiosis, is a type of cell division that produces haploid gametes (sex cells) from diploid cells. This is essential for sexual reproduction. Let’s see when and where meiosis occurs in the life cycles of different plant groups:

1. Liverwort

When: During the formation of gametes in the gametophyte generation.
Where: In specialized structures called antheridia (male gamete-producing organs) and archegonia (female gamete-producing organs).

2. Moss

When: Similar to liverworts, during gamete formation in the gametophyte generation.
Where: In antheridia and archegonia.

3. Fern

When: During the formation of spores in the sporophyte generation.
Where: In specialized structures called sporangia, which are usually found on the underside of fern leaves.

4. Gymnosperm

When: During the formation of pollen grains and ovules in the sporophyte generation.
Where: In male cones (strobili) and female cones, respectively.

5. Angiosperm

When: During the formation of pollen grains and ovules in the sporophyte generation.
Where: In the anthers of flowers (for pollen grains) and in the ovules within the ovary of flowers.

3. Name three groups of plants that bear archegonia. Briefly describe the life cycle of any one of them.

Ans :

Three groups of plants :

Bryophytes (mosses, liverworts, hornworts)
Pteridophytes (ferns, horsetails, club mosses)
Gymnosperms (conifers, cycads, ginkgos)

Life Cycle of a Moss (Bryophyte):

Mosses have a distinct alternation of generations, with a dominant gametophyte phase and a reduced sporophyte phase.

Gametophyte: The leafy, green part of a moss is the gametophyte.
Fertilization: Sperm cells from the antheridia swim through water to reach and fertilize the egg cell in the archegonium. This results in the formation of a diploid zygote.
Sporophyte: The zygote develops into a sporophyte, which is a small, stalk-like structure that grows out of the gametophyte. The sporophyte produces spores in a capsule at its tip.
Spore Dispersal: When mature, the capsule opens, releasing spores that are dispersed by wind or water.
Germination: If a spore lands in a suitable environment, it germinates and develops into a new gametophyte, completing the life cycle.

4. Mention the ploidy of the following: protonemal cell of a moss; primary endosperm nucleus in dicot, leaf cell of a moss; prothallus cell of a ferm; gemma cell in Marchantia; meristem cell of monocot, ovum of a liverwort, and zygote of a fern.

Ans :

Here’s the ploidy of the cells you mentioned:

Protonemal cell of a moss: Haploid
Primary endosperm nucleus in dicot: Triploid (3n)
Leaf cell of a moss: Haploid
Prothallus cell of a fern: Haploid
Gemma cell in Marchantia: Haploid
Meristem cell of monocot: Diploid
Ovum of a liverwort: Haploid
Zygote of a fern: Diploid

5. Write a note on economic importance of algae and gymnosperms.

Ans :

Algae

Food: Algae are a rich source of nutrients and are used as a dietary supplement or directly consumed in various cuisines.
Biofuels: Algae can be processed to produce biofuels like biodiesel and bioethanol.
Pharmaceuticals: Many algae produce compounds with medicinal properties, used in the production of drugs for various diseases.
Industrial products: Algae are used in the production of agar, alginic acid, and carrageenan, which have applications in food, pharmaceuticals, and cosmetics.
Environmental benefits: Algae play a crucial role in aquatic ecosystems, providing oxygen and serving as a food source for other organisms. They also help in water purification and carbon sequestration.

Gymnosperms

Timber: Gymnosperms, particularly conifers, are a major source of timber for construction, furniture, and paper production.
Pulp and paper: The wood of gymnosperms is used to produce pulp and paper.
Resins and oils: Gymnosperms produce resins and oils that have applications in various industries, including adhesives, paints, and varnishes.
Ornamentals: Many gymnosperms, such as pine trees and Christmas trees, are cultivated for ornamental purposes.
Ecological importance: Gymnosperms play a vital role in forest ecosystems, providing habitat for wildlife and contributing to soil conservation.

6. Both gymnosperms and angiosperms bear seeds, then why are they classified separately?

Ans :

While both gymnosperms and angiosperms bear seeds, they are classified separately due to the structure and arrangement of their seeds.

Gymnosperms: These plants have “naked” seeds, meaning the seeds are not enclosed in an ovary or fruit. They are usually borne on cones or scales. Examples include pine trees and firs.
Angiosperms: These plants have “covered” seeds, which are enclosed within a fruit. The ovary of the flower develops into the fruit, protecting the seeds. Examples include flowering plants like roses, apples, and grasses.

7. What is heterospory? Briefly comment on its significance. Give two examples.

Ans :

Heterospory is a term used to describe plants that produce two different types of spores: microspores and megaspores.

Microspores: These are smaller spores that develop into male gametophytes (pollen grains).
Megaspores: These are larger spores that develop into female gametophytes (ovules).

Significance of Heterospory:

Evolutionary Advantage: Heterospory is considered an evolutionary advancement as it allows for the development of more complex reproductive structures and mechanisms.
Increased Genetic Diversity: The production of separate male and female gametophytes can lead to greater genetic diversity through cross-pollination.
Seed Formation: In seed plants (gymnosperms and angiosperms), heterospory is essential for the formation of seeds, which provide protection and nourishment to the developing embryo.

Examples of Heterosporous Plants:

Ferns: Most ferns are heterosporous, producing microsporangia and megasporangia on different parts of the plant.
Gymnosperms: All gymnosperms, such as pine trees and firs, are heterosporous. They produce male cones (microstrobili) that contain microspores (pollen grains) and female cones (megastrobili) that contain megaspores.

8. Explain briefly the following terms with suitable examples:- (i) protonema (ii) antheridium (iii) archegonium (iv) diplontic (v) sporophyll (vi) isogamy

Ans :

(i) Protonema

Definition: A thread-like, green structure that develops from a moss or fern spore.
Example: The green, filamentous growth that first appears from a moss spore.

(ii) Antheridium

Definition: A male reproductive organ in plants that produces sperm cells.
Example: The small, sac-like structures found on the underside of fern leaves.

(iii) Archegonium

Definition: A female reproductive organ in plants that produces an egg cell.
Example: The flask-shaped structures found on the underside of fern leaves.

(iv) Diplontic

Definition: A life cycle where the diploid stage is dominant.
Example: Most animals, including humans.

(v) Sporophyll

Definition: A leaf that bears spores.
Example: The scales of a pine cone, which bear pollen grains (microspores).

(vi) Isogamy

Definition: A type of sexual reproduction where the gametes (sex cells) are identical in size and structure.
Example: Many algae and fungi exhibit isogamy.

9. Differentiate between the following:-

(i) red algae and brown algae

(ii) liverworts and moss

(iii) homosporous and heterosporous pteridophyte

Ans :

(i) Red Algae (Rhodophyceae) and Brown Algae (Phaeophyceae)

Feature	Red Algae	Brown Algae
Color	Reddish-brown to purple	Brownish-green
Primary Pigment	Chlorophyll a and d	Chlorophyll a and c
Stored Food	Floridean starch	Mannitol and laminarin
Cell Wall	Cellulose and agar	Cellulose and algin
Examples	Porphyra (nori), Chondrus crispus (carrageenan source)	Laminaria (kelp), Sargassum

(ii) Liverworts and Mosses

Feature	Liverworts	Mosses
Thallus Shape	Flattened, lobed	Leafy
Rhizoids	Simple, unicellular	Multicellular, filamentous
Gametangia	Embedded in the thallus	Raised on stalks
Sporophyte	Small, inconspicuous	Larger, more prominent

(iii) Homosporous and Heterosporous Pteridophytes

Feature	Homosporous Pteridophytes	Heterosporous Pteridophytes
Spore Type	Produce only one type of spore (microspore)	Produce two types of spores: microspores and megaspores
Gametophyte	Bisexual, producing both male and female gametes	Unisexual, producing either male or female gametes
Examples	Ferns like Pteris, Adiantum	Selaginella, Salvinia

10.Match the following (Column I with Column II).

Column I Column II

(a)Chlamydomonas (i)Moss

(b)Cycas (ii)Pteridophyte

(c) Selagmella (iii)Algae

(d) Sphagnum (iv)Gymnosperm

Ans :

(a) Chlamydomonas – (iii) Algae

(b) Cycas – (iv) Gymnosperm

(d) Sphagnum – (i) Moss

11. Describe the important characteristics of gymnosperms.

Ans :

Gymnosperms are a group of seed-bearing plants that are distinguished by their naked seeds. This means that their seeds are not enclosed in a fruit, unlike angiosperms. Other key characteristics include:

Woody plants: Gymnosperms are typically woody plants, such as trees and shrubs.
Cones: They produce cones, which are structures that contain the seeds.
Resin ducts: Many gymnosperms have resin ducts, which produce a sticky substance used for protection and wound healing.
Needle-like leaves: Many gymnosperms have needle-like or scale-like leaves, which help them to conserve water in dry environments.
Lack of flowers: Unlike angiosperms, gymnosperms do not produce flowers.
Wind pollination: Gymnosperms are typically wind-pollinated, meaning that their pollen is carried by the wind to reach the ovules.