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.
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