Biology Class 9 Notes- Chapter 6

BRYOPHYTES AND TRACHEOPHYTES

Q No.1: What are bryophytes?

Ans. The word bryophyte is derived from Latin language word (bryo = "moss" + -phyte = "plant"). It is defines as multicellular, eukaryotic chrolophyllous non-vascular plants having cell wall and zygote develops into embryo.

General Characters:

Ø  Bryophytes are simplest group of plants which are poorly adapted to life on earth, so they live in damp shady places. Therefore they are amphibians because they need water for sexual reproduction.

Ø   They have thalloid bodied which are not differentiated into true roots, stem and leaves. Instead of roots they have hair like rhizoids and pseudo-stem and leaves.

Ø  They do not have vascular bundles and carry out the transport of water and nutrients via diffusion.

QNo.2: Define heteromorphic alternation of generation in bryophytes.

Ans. Bryophytes show heteromorphic alternation of generation it means two generations called Gametophyte and Sporophyte, which are morphologically and cytologically different. In bryophytes the dominant generation is gametophyte which is haploid. The gametophyte reproduces sexually by reproducing male and female gametes. These two fuse to form zygote, which develops into embryo. Then this embryo gives rise to sporophyte which may be partially or completely dependent on gametophyte. Spores are produced in sporophyte after meiosis. Each spore germinates into gametophyte.

QNo.3: Define classification of bryophytes.

Ans. Bryophytes are classified into three groups:

1.      Hepaticae (Liverworts): For example Marchantia having dichotomously branched (divided into two equal parts), dorsiventral (two surfaces differing from each other) thalloid structure.

2.      Musci (Mosses): For example Funaria having rhizoids, pseudo-stem and leaves.

 

3.      Anthocerotae (Hornworts): For example Anthoceros having horn like capsules.

QNo.4: Write a note on Funaria.

Ans. The name Funaria is derived from Latin word “funis” meaning a rope. The plant is small about 1-3 cm long.

(a) Gametophyte: It consists of rhizoids, branched pseudo-stem and leaves. Male sex organs are called antheridia (Single antheridium) located at apex of male branch. Female organs are called archegonia (Single archegonium) at the tip of female branch.

Fertilization takes place when plant is completely in water. Zygote is formed inside the archegonium and develops into an embryo. Embryo develops into a sporophyte, which remain attached to gametophyte.

(b) Sporophyte: It consists of foot, seta and capsule. Foot is attached to gametophyte and absorbs nutrients from it. Seta lift up the capsule is air. Within capsule spores are formed after meiosis. Due to dehydration, capsule burst, open and spores are liberated. Each spore develops into a new Funaria gametophyte.

QN.5: What are tracheophytes (Vascular Plants)?

Ans. Tracheophyte (Trachea = Vessels; Phyton = Plant) have conducting or vascular tissues, (such as xylem and phloem). These tissues also give rigidity and support to plant body. Tracheophytes are believed to have originated from the green algae (Chlorophyta).

General Characters:

Ø  All tracheophytes have well developed true roots, stem and leaves. They vary is height from miniature to giant Sequoia (red wood tree).

Ø  All tracheophytes show alternation of generation is which sporophyte is dominant and totally independent. Whereas gametophyte generation may be small, inconspicuous, short lived and totally dependent on sporophyte except in Pteridophytes.

Ø  Zygote develops into embryo, which rises into a young plant.

QNo.6: Give classification of Tracheophytes.

Ans.

QNo.7: Describe some members of Pteropsida (Ferns).

Ans. (a) Pteris: It is found in wild state in some regions of Punjab and Sindh. It is common ornamental plant. The dominant generation is sporophyte.

Habit:

Ø  Sporophyte have adventitious roots.

Ø  Under-ground stem-rhizome.

Ø  Pinnate compound leaves called fronds.

Ø  Sporangia in sori found under the surface of sporophyll (Sporangia bearing leaves).

        (b) Adiantum: It grows in wild. It resembles the Pteris except the shape of leaflets, which are broad and arranged alternately. Sporophyte is dominant and is a small herb consisting of a stem, root and leaves.

Habit:

Ø  Stem: Short, thick, rhizome

Ø  Roots: Fibrous, adventitious, arise from lower side of rhizome.

Ø  Leaves: Large, pinnately compound, having rachis bearing leaflets or pinnae arranged in an alternate manner. Lower pinna is further divided into pinnules.

Ø  Sori (Single Sorus): They occur under the surface of pinnules. Each sorus consists of small pores producing bodies of sporangia.

QNo.8: What are Gymnosperms? Define some of its members.

Ans. (Gymnos = Naked; Sperma = Seeds) have naked ovules produced in cones. Ovules develop into naked seeds as fruit is absent due to absence of ovaries.

PINUS:

                Pinus plant is 40 to 50 meters high and up to 2 meters thick. It has well developed root, stem and leaves and reproductive bodies called cones. It has naked seeds as fruit around it does not develop.

Habit:

Ø  ROOTS: Tap roots, lateral roots are longer than primary roots.

Ø  STEM: Divided into long-shoots and dwarf-shoots.

Ø  LEAVES: Two types of leaves; 1) Foliage (needle): so called because of their shape. They are green therefore perform photosynthesis. Found at the tip of dwarf branches. 2) Scale Leaves: They are sessile, thin and brownish. They are present at main axis as well as both types of branches (Long-shoot and dwarf-shoot).

Ø  CONES: Cones are unisexual and called male and female cones.

QNo.9: Define structures of cones of pinus.

Ans. a) MALE CONE: They arise as cluster near the end of long-shoots. They are maximum 2cm in length. Each cone has a central axis or torus. This axis/torus has 60 to 100 small scales call microsporophylls. Each microsporophyll has a sac like microsporangium, which produce microspores, which develop into winged pollen grain and are liberated in the air.

b) FEMALE CONE: They develop singly in the place of dwarf-shoot. They are up to 20 cm in length and up to 10 cm in width. Each female cone has an elongated axis (thalamus) on which large number of paired megasporophylls are present, which have megasporangium or ovule. Each ovule produce 4 megaspores. Out of 4, one will survive and become gametophyte.

QNo10: Define gametophyte of pinus.

Ans. a) MALE GAMETOPHYTE: Each microspore after pollination is transferred to female cone and undergoes a period of rest in pollen-chamber inside megasporangium. During next season microspore germinates to form reduced male gametophyte. It consists of prothalial cell, elongated pollen-tube having tube cell, stalk cell and two sperms.

            b) FEMALE GAMETOPHYTE: Each megaspore develops into a female gametophyte within megasporangium. Each gametophyte has two archegonia each having single ovum/egg.

Qno.11: Define fertilization and formation of seed in pinus.

Ans. One of the gamete fuses with ovum to form oospore and becomes diploid. It develops into embryo. Whole megasporangium develops into seed. Pinus seed has seed coat, endosperm and an embryo with an axis to which 6 to 10 cotyledons are attached. Two ends of the axis have plumule and radicle. Pinus seed has epigeal germination.

QNo.12: What are angiosperms?

Ans. Angiosperms (Angio = covered; sperma = seed) are flowering tracheophytes having ovules enclosed in ovary therefore they produce seeds within fruit. Angiosperms are divided into two major groups: 1) monocotyledons (having one seed laef) and 2) dicotyledons (having two seed leaves).

PARTS OF ANGIOSPERMIC PLANT: The body of angiospermic plant may be divided into two parts:

1) VEGETATIVE PARTS: are those which do not directly take part in sexual reproduction e.g.: Root, stem, branches and leaves.

2) REPRODUCTIVE PARTS: these are sex organs with directly take part in sexual reproduction e.g. flower, fruit and seed.

QNo.13: Differentiate between dicot and monocot plants.

Dicot Plant	Monocot Plant
Ø  Plant produce two cotyledons (seed leaves)	Ø  Plant produce one cotyledon (Seed leaf)
Ø  Roots: Branched, tap root	Ø  Roots: Adventitious
Ø  Stem: Branched	Ø  Unbranched
Ø  Leaves: Small, reticulate venation	Ø  Leaves: Large, parallel venation

QNo.14: Define importance of vascular plants.

Ans.

Ø  Many angiosperms are source of food e.g. wheat, rice, maize, pulses etc.

Ø  Many vegetables come from vascular plants such as. Potato, cauliflower, radish, carrot, bean, ladyfinger, tomato, onion etc.

Ø  Many ingredients of our food come from vascular plants e.g. mustard oil, coconut, sugar etc.

Ø  Many plants are used as fodder e.g. grass, sorghum (جوئر), burseem, juntar (ڌاڻا) etc.

Ø  Many fruits come from vascular plants e.g. apple, mango, apricot, banana, citrus etc.

Ø  Timber is obtained from pinus, deodar, cedrus, sheesham, kikkar etc.

Ø  Many of them are used in making cloth e.g. cotton, jute etc.

Ø  Many are used as ornamental plants e.g. rose, jasmine, shoe flower, glory of night etc.