SUPPORT MATERIAL

Chapter-1

Clone : A group of organism derived from a single individual and hence morphologically and genetically similar.

Embryogenesis : The process of development of embryo from zygote.

Juvenile Phase : It is the period of growth before maturity when sex organs are not functional.

Meiocytes : These are specialized cells of diploid organisms which undergo meiosis.

Pericarp : It is the protective covering of fruit, may be divided into epicarp, mesocarp and endocarp.

Parthenogenesis : Development of an egg into an embryo without fertilisation.

Gamete Transfer

1. In Algae, Bryophytes and Pteridophytes : The male and female gametes are flagellated and motile, need a medium (water) to reach the egg.

2. In seed Plants : Pollen grains are transferred to stigma of flower of same species by various agents.

3. In animals :

(a) By Copulation . e.g., Reptiles, Birds and Mammals.

(b) By External medium . e.g., Fishes and Amphibians.

Sporulation :- During unfavorable conditions organisms like Amoeba surrounded by resistant coat (three layered - hard covering ) or cyst. This is called encystation . Within cyst a number of spores are formed . On returning favourable conditions, the cyst burt and spores are liberated and gradually grows into adults. This process is known as sporulation.

Fragmentation : It is a type of asexual reproduction where an organism splits into fragments. There fragments develops into fully grown individual. eg. spirogyra, fungi and some annelids.

Regeneration: It is a process of renewal, restoration and growth. It can occur at the level of the cell tissue and organ . It is common in Hydra , Planaria and echinoderms .ŸIn human, liver has power of regeneration, if it is partially damaged.ŸDuring danger a lizard discard a part of tail which can regenerate latter.

CHAPTER 2

SEXUAL REPRODUCTION IN FLOWERING PLANTS

Autogamy : When pollen grains of a flower are transferred from anther to stigma of the same flower.

Coleorhiza : Aprotective sheath of radicle in monocot seed.

Endothecium : A fibrous layer in the anther next to epidermis.

Geitonogamy : Self pollination between flowers of the same plant.

Micropyle : Asmall pore in the ovule through which the pollen tube enters.

Nucellus : Multicellular tissue in the centre of ovule where embryo sac is present.

Tapetum : Inner most layer of cells in pollen sac which provide nutrition to developing pollen grains

Viability of Seed : Ability of seed to retain the power of germination.

1. Microsporangium (Pollen sac) : Outermost layer = Epidermis

Second layer = Endothecium

Middle layer = 2 - 4 layers of cells

Innermost layer = Tapetum [Nourishes the developing pollen grains(Microspores)]

2. Microsporogenesis : Process of formation of microspores from a pollen mother cell.

Megasporangium (Ovule) :

ŸThe ovule is a small structure attached to the placenta by means of a stalk called funicle.

ŸThe point of attachment of the body of the ovule to the funicle is known as hilum. The main body of the ovule is composed of paranchymatous cells known as nucellus.

ŸEach ovule has one or two protective integument, which encircle the ovule except at the tip having small opening called micropyle.

ŸOpposite to micropylar end, is chalaza. Generally a single embryosac or female gametophyte located in

nucellus.

ŸCells of nucellus have abundant reserve food material and provide nourishment to the developing embryo.

 Female gametophyte (Embryo sac) : In a majority of flowering plant one of the megaspore is functional while other three degenerate.

The functional megaspore develops in embryo sac.

The nucleus of the functional megaspore (n) undergoes three successive mitotic cell division which results the formation of eight nucleate stage of embryo sac (free nuclear division).The cell wall formation starts at eight nuclear stages. Three cells are grouped together at micropylar end to form the egg apparatus.(2 synergids + 1 egg cell).

Dicot Embryo : A typical dicot embryo consist of an embryonal axis and two cotyledons.The portion of embryonal axis above the level of cotyledons is the epicotyle which terminates with the plumule or stem tip.

The portion below the level of cotyledons is hypocotyl that terminates at its lower end in the radicle or root tip.

Monocot Embryo : Monocot (Rice, Maize etc.) has one cotyledon called Scutellum.The embryonal axis has the radicle and root cap enclosed by a sheath called Coleorrhiza.

The upper end (epicotyle) has plumule which is covered by hollow folder sturcture, the coleoptile.

Apomixis : Apomixis is a form of asexual reproduction that mimics sexual reproduction where seed are formed without fertilisation.

Polyembryony : Occurance of more than one embryo in a seed. e.g. Orange, lemon, onion, mango, ground nut.

Reasons of polyembryony : More than one egg may be formed in the embryo sac.More than one embryo sac may be formed in an ovule.