Solved Exercise, Bio-11, Ch-09


(i) The sporophyte is _______ and _______ generation and the gametophyte is _______ and ______. (less conspicuous & dependent / more conspicuous & dominant)

(ii) The motile asexual reproductive cells are characteristics of _______ and are called _______. (bryophytes, antherozoids)

(jiii) The sexual reproduction is said to be oogamous or heterogamous if the two fusing gametes are ________. (morphologically different)

(iv) In the stem of Monocotyledons, the bundles are ________ while in the stem of Dicotyledons they are ________. (scattered, in ring)

(v) The double fertilization is the characteristic feature of _______. (angiosperms)

(vi) Stem roots and leaves are the _________ parts and flowers, fruits and seeds are the ________ parts of the plant. (vegetative, reproductive)

(vii) ________ is the phenomenon of the production of two kinds of spores in the plants. (heterospory)

(viii) The naked-seeded plants are included in the group _______. (gymnosperm)


(i) (a) How are ferns better adapted to life on land than liverworts and mosses?

Ferns are better adapted to land than liverworts and mosses due to vascular tissues, true roots, stems, and leaves, allowing for efficient nutrient transport and structural complexity. Additionally, ferns have a more effective spore dispersal system and a larger, complex life cycle.

Mature liverwort and moss gametophyte are nutritionally self-supporting because they contain photosynthetic tissue to synthesize their own food.

Adiantum or maiden-hair fern grows along moist walls and water courses. When its spores are dispersed from sporangia, lying in the underside of leaf margins, they mostly fall on wet or moist soil. So, their chances of survival and development are far more than the wind-dispersed spores which may not get moist environment to grow. That’s why, wind-dispersed spores are always produced in large number because emost of them are gone wasted.

Megaspores are larger than microspores because they contain stored food for the development of zygote.

Angiosperms revolutionized seed plants with features like:

  • Enclosed seeds: Offering protection and dispersal advantages.
  • Flowers: Attracting pollinators and aiding efficient reproduction.
  • Double fertilization: Leading to nutrient-rich endosperm for developing embryos.
  • Diverse adaptations: Thriving in various environments and dominating land ecosystems.

Consult text book for descriptive question.

(iv) What is the importance of the following?

(i) Seed.

(ii) Double fertilization.

(iii) Heterospory.

Importance of Seed:

Seeds empower seed plants to thrive and diversify across the globe because of the following benefits:

(1) Reproduction: Efficient means to create new individuals, enabling survival and spread.

(2) Dispersal: Travel away from parent, reducing competition and finding new niches.

(3) Protection: Hard coats shield embryo from harsh environments, allowing dormancy.

(4) Nutrition: Stored food provides initial energy for seedling growth.

Importance of Double fertilization:

Double fertilization in flowering plants is crucial for both seed and fruit development. One sperm cell fertilizes the egg to form the embryo (2n), while the other combines with two polar nuclei to produce endosperm (3n). Endosperm serves as a nutrient-rich tissue for the developing embryo, ensuring successful seed germination and early seedling growth. This unique reproductive strategy enhances the reproductive success and fitness of flowering plants.

Importance of Heterospory:

Heterospory in plants is important as it involves the production of two distinct types of spores, microspores, and megaspores. This adaptation contributes to sexual reproduction by giving rise to male and female gametophytes, promoting genetic diversity. Heterospory is a key evolutionary development that enhances the adaptability and reproductive success of certain plant groups, including seed plants like gymnosperms and angiosperms.

(i)Fem sporophyteinvolves vegetative parts of plants.
(ii)The moss plantis the first cell of sporophyte.
(iii)The gameteis the last cell of gametophyte.
(iv)The sporesare asexual reproductive cells.
(v)Vegetative reproductionare haploid cells.
(vi)The oosporeis gametophytic generation.
(vii)The gameteis a diploid generation.
(viii)The spore mother cellis the first cell of gametophytes.
(ix)The sporewith naked seeds.
(x)Gymnosperms are the plantsdivides by reduction division to form haploid spores.
(i)Fem sporophytedivides by reduction division to form haploid spores.
(ii)The moss plantis gametophytic generation.
(iii)The gameteis the last cell of gametophyte.
(iv)The sporesare asexual reproductive cells.
(v)Vegetative reproductioninvolves vegetative parts of plants.
(vi)The oosporeis the first cell of sporophyte.
(vii)The gametesare haploid cells.
(viii)The spore mother cellis a diploid generation.
(ix)The sporeis the first cell of gametophytes.
(x)Gymnosperms are the plantswith naked seeds.


(i) All bryophytes (mosses, liverworts, hornworts) share certain characteristics. These are:

(a)   Reproductive cells in protective chambers and a waxy cuticle                

(b)   A waxy cuticle, true leaves, and reproductive cells in protective chambers

(c)   Vascular tissues, true leaves and a waxy cuticle

(d)   Reproductive cells in protective chambers and vascular tissues

(e)   Vascular tissues and a waxy cuticle

EXPLANATION: Gametes in bryophytes are produced and protected by the special multicellular organs called antheridia and archegonia. The Presence of cuticle on leaves reduces the loss of water by evaporation.

(ii) A heterosporous plant is one that: 

(a)   Produces a gametophyte that bears both sex organs

(b)   Produces microspores and megaspores in separate sporangia, giving rise to separate male and female gametophytes

(c)   Is a seedless vascular plant

(d)   Produces two kinds of spores, one asexually by mitosis and one type by meiosis.

(e)   Reproduces only sexually

EXPLANATION: Primitive vascular land plants produced one kind of spores, a condition called homospory. All groups of land plants up to pteridophytes are homosporous. During the early phase of evolution, some plant groups started producing two different types of spores, the smaller ones called microspores and the larger ones known as megaspores. The microspores produced inside microsporangia germinate to form male gametophyte or the microgametophyte, whereas the megaspores germinated to form female gametophyte or megagametophyte.

(iii) The male gametophyte of an angiosperm is the:

(a)   Anther

(b)   Embryo sac

(c)   Microspore

(d)   Germinated pollen grain

(e)   Ovule

EXPLANATION: The microspores in angiosperms are produced within anther by meiosis. After pollination, the pollen grain is transferred to the stigma. Here, it germinates to form a pollen tube. The nucleus of the microspore divides by mitotic divisions to form two male gametes and the tube nucleus. At this stage of development, the pollen grain is called male gametophyte.

(iv) Important terrestrial adaptations that evolved exclusively in seed plants include all of the following except:

(a)   Pollination by wind or animal instead of fertilization by swimming sperm

(b)   Transport of water through vascular tissues

(c)   Retention of the gametophyte plant within the sporophyte

(d)   Dispersal of new plants by seeds

(e)   Protection and nourishment of the embryo within the seed

EXPLANATION: Vascular tissue was evolved long before the evolution of seed producing plants. Vascular tissue is present in earlier vascular plants such as Psilopsida, Lycopsida, Shenopsida and Pteropsida. While, true seed producing plants evolved later such as Gymnosperms and Angiosperms.


Alternation of Generations in Plants: “The phenomenon of alternation of gametophyte and sporophyte in the life history of a plant is called alternation of generation.” The gametophyte or haploid stage begins with spores and ends at gametes, whereas the sporophyte stage begins with oospore and ends at spore mother cell.

Sporophyte Generation: The sporophyte generation is the diploid, multicellular phase in the life cycle of plants and algae. It produces spores through meiosis, which develop into the haploid gametophyte generation.

Gametophyte Generation: The gametophyte generation is the haploid, multicellular phase in the life cycle of plants and algae. It produces gametes through mitosis, and fertilization of gametes leads to the formation of the diploidsporophyte generation.

Comparison between Plants and Animals:

The sporophyte generation in plants is comparable to the adult animal because both have some general similarities:

Diploid: Both are the dominant, multicellular generation with 2 sets of chromosomes (2n).

Independent: Both are independent organisms capable of growth, metabolism, and interaction with the environment.

Reproductive: Both produce specialized gametes (haploid, 1n) for sexual reproduction.

Seed: A seed is a mature, fertilized ovule containing a plant embryo, stored nutrients, and a protective seed coat.

Importance of Seed: Seeds are crucial for terrestrial life as they provide a means of protected embryonic development, nutrient storage, and dispersal. This adaptation allows plants to survive in diverse environments, enhance reproductive success, and colonize new areas efficiently.

Consult textbook page 140 — 141.

Consult textbook page 146 — 148.

Difference between flowering plants & the rest of the seed plants:

Flowering plants (angiosperms) differ from the rest of the seed plants (gymnosperms) primarily in their reproductive structures. Angiosperms produce seeds enclosed within fruits, which develop from ovaries. In contrast, gymnosperms have seeds exposed on the surfaces of cones or other structures. The presence of flowers and fruits is a distinctive feature of angiosperms, setting them apart from gymnosperms in terms of reproductive adaptations.

What is the stigma?

The stigma is the receptive tip of the female reproductive organ (pistil) in a flower. It is often sticky or feathery to capture pollen grains during pollination. The stigma plays a crucial role in the fertilization process by receiving pollen grains and facilitating their germination to initiate the growth of pollen tubes, ultimately leading to fertilization of the ovules within the ovary.

Is fertilization in angiosperms direct or indirect?

Fertilization in angiosperms is indirect. The process involves the formation of a pollen tube, which grows from the pollen grain to the ovule, facilitating the transfer of sperm cells to the ovule for fertilization.

From what tissue does angiosperm fruit develop?

The angiosperm fruit typically develops from the ovary tissue of the flower. After fertilization, the ovary undergoes changes and transforms into the fruit, which protects and helps disperse the seeds.

The two classes of angiosperms are:

  1. Monocotyledonae (monocots)
  2. Dicotyledonae (dicots)

Structural Differences:

  1. Number of Cotyledons: Monocots have one cotyledon in their seeds, while dicots have two cotyledons.
  2. Leaf Venation: Monocots typically have parallel venation in their leaves, while dicots have reticulate (net-like) venation.
  3. Floral Parts: The number of floral parts (petals, sepals, stamens) in multiples of three characterizes monocots, while dicots usually have floral parts in multiples of four or five.
  4. Vascular Tissue Arrangement: Monocots have vascular bundles scattered throughout the stem, whereas dicots often have a ring arrangement.

Origin of Monocots and Dicots: Monocots and dicots both belong to the angiosperms, and they diverged from a common ancestor. Monocots are not derived from dicots or vice versa; rather, they represent two distinct lineages within the flowering plants.

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