I have covered each topic of NCERT in explaining first chapter. In this chapter very basic information on reproduction is discussed.This is helpful for Board as well as NEET students.
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2. Reproduction
1. Reproduction is a fundamental feature if living
organisms which involves the transmission of genetic
material from one generation to next ensuring the
survival of species over a longer period of time.
2. Reproduction (or breeding) is the biological
process by which new individual organisms –
"offspring" – are produced from their "parents "of
their own kind.
3. Reproduction is a fundamental feature of all
known life ; each individual organism exists as the
result of reproduction.
3. Characteristic feature of Reproduction
All mode of reproduction have some basic features:
Synthesis of RNA , proteins and other biomolecules.
Replication of DNA.
Cell division and growth of cells.
Formation of reproductive units.
Development of new individual from reproductive
units.
4. Purpose of Reproduction
CONTINUITY OF SPECIES :- Reproduction maintains
the continuity of species.
POPULATION ORGANISATION :- It maintains
population of young, adults and aged individuals of a
species.
REPLACEMENT :- It replaces individuals dying due to
ageing.
VARIATION :- It introduces variations in the organisms
. Useful variations help in adaptations and evolution.
LIFE :- Existence of life on the Earth is possible only due
to reproduction.
5. Life span
The period from birth
to natural death of an
organism is called its
life span.
Life span of an
organism may be from
few minutes to several
thousand years.
6. Life Span of Living Organism
Living Organism Life Spam
May Fly 1 Day
Butterfly 1-2 Weeks
Wheat Plant 6 Months
Crow 15 Years
Dog 25 Years
Banana Tree 25 Years
Human 100 Years
Banyan Tree 200 Years
7. Phases of Life
Life of an Organism
usually include four
Phases:-
Birth
Juvenile Phase or
Vegetative Phase
Reproductive or
Maturation Phase
Ageing or senescent
Phase.
Natural Death.
9. ASEXUAL REPRODUCTION
In this reproduction only one/Single parent is involved.
Formation and fusion of gametes doesn’t take place.
The offspring produced are genetically and morphologically
similar to parents. So , they are also known as CLONE.
In asexual reproduction only one type of cell division take
place i.e. Mitosis.
Asexual reproduction doesn't take part in evolution.
It generally takes place from the somatic part of the body of an
organism.
Example:- Euglena,Paramecium,Amoeba.
10. Fission ----------- a) Binary Fission
b) Multiple Fission
Budding ---------- a) Exogenous Budding
b) Endogenous Budding
Spore formation
Regeneration
Fragmentation
Plasmotomy
Vegetative Propagation
Tissue Culture/ Micropropagation
Cloning
Types of Asexual Reproduction.
11. Asexual reproduction takes place in various ways.
These are as follows:-
Fission:- It is the division of the parent body in to two
or more daughter individuals identical to the parents. It
is of two types:-
Binary Fission:- In this, parent organism divides in to
two halves, each half forms an independent daughter
organism. Ex- Bacteria , Protozoa.
Multiple Fission:- In this, the parent body divides in to
many daughter organisms . It occurs in Amoeba and
Plasmodium.
13. Budding
Formation of daughter individual
from a small projection , the bud
,arising on the parent body is
called Budding.
It occurs in some lower animals
such as sponges, Hydra.
On the basis of location of bud
budding may be of two types:-
Exogenous Budding :-
When the bud grows on outer surface
of the body. Ex-Hydra. The bud is
identical to the parent.
When the bud is large enough , can
break off of the parent body and
lives on its own.
Endogenous Budding :-
When the bud grows on inner surface
of the body. Ex- Sponges.
15. Spore Formation
Spores
Spores are usually thick or thin
walled haploid and unicellular
propagule which under favorable
conditions can give rise to new
organism using mitotic division.
There are several kinds of spores.
These are zoospores,
sporangiospores, conidia,
chlamydospores etc.
Sporulation refers to the
formation of spores from
vegetative cells during
unfavorable environmental
conditions.
Ex- Rhizopus.
16. Conidia Zoospores
Conidia are asexually
produced spores that are
borne externally in chains to
the cells that produce them.
A zoospore is a motile
asexual spore that uses a
flagellum for locomotion
and able to swim in water.
Penicillium
17. Regeneration
Regeneration is the formation of the whole body of an organism from a
small fragment (Morphallaxis) or the replacement of lost part
(Epimorphosis).
18. Fragmentation
Fragmentation in
multicellular organisms is
a form of
asexual reproduction i
n which an organism is
split into fragments.
Each of these fragments
develop into matured,
fully grown individuals
that are identical to their
parents.
Ex- Spirogyra, Sponges.
Spirogyra
19. Plasmotomy
Plasmotomy is a type of asexual
reproduction in which a
multinucleate protozoan cell
divided into two or more
multinucleate daughter-cells
without the occurrence of mitosis.
Generally, Single-celled organisms
undergo reproduction through a
process called binary fission in
which karyokinesis is followed by
cytokinesis which means that
nuclear division is followed by
cytoplasmic division but here
cytokinesis is followed by
karyokinesis.
Ex-
Opalina,Pleomyxa,Plasmodium.
20. Vegetative Reproduction
Vegetative reproduction (also
known as vegetative
propagation, vegetative
multiplication or cloning) is any
form of asexual
reproduction occurring in plants in
which a new plant grows from a
fragment of the parent plant or a
specialized vegetative structures like
roots,stems,leaves.
It is the formation of new plants from
vegetative units such as bud , tuber,
rhizomes etc.
These vegetative units are called as
vegetative propagule.
Vegetative reproduction may occur
naturally or artificially as induced by
farmers.
Bryophyllum
Stem cutting
21. STEM
1)RUNNER :-
Runners are a special
kind of hard stem that
lie along the ground
horizontally and bears
several nodes and
internodes and when
node part comes in
contact with soil, it
send new roots into the
soil.
Ex :- Dhoob grass
(Cynodon),Oxalis.
Oxalis
22. 2) Offset
An offset is a short thick
runner like the branch on
the surface of water which
produces a new plant at
its tip. The offsets grow
in all directions from the
main stem of the parent
plant.
Ex-
Water Hyacinth propagates
by offsets.
Eichhornia crassipes
23. Eichhornia crassipes (Weed)
Water hyacinth( Eichhornia crassipes) is known as the “Terror of
Bengal” because it is an exotic shrub which is fastest growing weed
found in standing water of ponds and lakes.
It floats in water with the help of spongy stem and inflated petioles
of leafs
It grows asexually by means of offsets which bear leaves and roots
in cluster at the nodes. Once it start growing, its eradication
become very difficult.
It was introduced in India for its broad and attractive leaves and
showy flowers.
As Fish is a supplement food in Bengal and Water hyacinth makes
water oxygen and solar energy deficient and results in decline in
number of fishes and because of the fish scarcity in Bengal caused
by Eichhornia, the water hyacinth is also called "Terror of Bengal”.
24. 3) Rhizome 4) Tuber
Buds in the Rhizomes of
Banana, Ginger and
Turmeric give rise to aerial
shoots which develop in to
new plants under favorable
conditions.
The eyes (buds) present in
tuber of potato give rise to
aerial shoots.
25. 5) Bulb 6) Corm
The bulb of Onion, Tulip are
modified shoots. Each bulb
has more terminal buds
which grows into new
shoots and grows into a new
bulb.
The Corm of Colocasia has
swollen bases of stem which
have buds for vegetative
propagation.
26. 7) Sucker 8) Stolon
Suckers are plant stems that
arise from buds on the base
of parent plants stems.
Ex- Banana,
Chrysynthamum
Stolon is a horizontal
branch of a plant that forms
a base for buds to develop
into identical plants.
Ex- Strawberry
28. LEAVES
In Bryophyllum
pinnatum and
kalanchoe , the leaves
have small buds on their
margins. When these
are detached from the
plant, they grow into
independent plants;
they may also start
growing into
independent plants if
the leaf touches the
soil.
29. Artificial Vegetative Propagation
Artificial methods of asexual reproduction are
frequently employed to give rise to new plants.
They include :-
Grafting
Cutting
Layering
Micropropagation.
30. 1)Grafting
Grafting has long been used to produce
novel varieties of roses, citrus species, and
other plants. In grafting, two plant species
are used: part of the stem of the desirable
plant is grafted onto a rooted plant called
the stock. The part that is grafted or
attached is called the scion. Both are cut at
an oblique angle , placed in close contact
with each other, and are then held together.
Matching up these two surfaces as closely as
possible is extremely important because
these will be holding the plant together. The
vascular systems of the two plants grow and
fuse, forming a graft. After a period of time,
the scion starts producing shoots, eventually
bearing flowers and fruits. Grafting is widely
used in viticulture (grape growing) and
the citrus industry. Scions capable of
producing a particular fruit variety are
grafted onto root stock with specific
resistance to disease.
31. 2)Cutting
Plants such as money
plant are propagated
through stem cuttings
where a portion of the
stem containing nodes
and internodes is placed
in moist soil and
allowed to root.
In some species, stems
can start producing a
root even when placed
only in water.
32. 3) Layering
Layering is a method in which a stem
attached to the plant is bent and
covered with soil. Young stems that
can be bent easily without any injury
are the preferred plant for this
method. Jasmine and
Bougainvillea (paper flower) can be
propagated this way. In some plants, a
modified form of layering known as
air layering is employed. A portion
of the bark or outermost covering of
the stem is removed and covered with
moss, which is then taped. After some
time, roots will appear; this portion
of the plant can be removed and
transplanted into a separate pot.
Ground Layering
33. 4) Micropropagation
Micropropagation (also called plant tissue culture) is a method of
propagating a large number of plants from a single plant in a short time
under laboratory conditions. This method allows propagation of rare,
endangered species that may be difficult to grow under natural
conditions, are economically important, or are in demand as disease-
free plants.
To start plant tissue culture, a part of the plant such as a stem, leaf,
embryo, anther, or seed can be used. The plant material is thoroughly
sterilized using a combination of chemical treatments standardized for
that species. Under sterile conditions, the plant material is placed on a
plant tissue culture medium that contains all the minerals, vitamins,
and hormones required by the plant. The plant part often gives rise to
an undifferentiated mass, known as a callus, from which, after a period
of time, individual plantlets begin to grow. These can be separated; they
are first grown under greenhouse conditions before they are moved to
field conditions.
34. Advantages of Vegetative Propagation
It is cheaper, rapid and convenient method of growing
plants.
Plants like Banana, Grape, Pineapple, Orange, Rose,
Jasmine etc do not produce viable seeds. These are
grown only by vegetative propagation.
Desirable characters of fruits and flowers can be
maintained in plants grown by vegetative propagation.
Grafting helps in combining good traits from two
varieties in a single plant.
Good qualities of a species or variety can be maintained.
Plants grown by vegetative propagation have exact
qualities of the parent plant.
35. Disadvantages of Vegetative propagation.
It does not produce new varieties.
Plant lose physical strength and good health when
grown repeatedly.
Plants so produced are genetically alike, hence they
are susceptible to the same diseases.
Undesirable Character persist in the species
generation after generation.
36. Sexual reproduction
Sexual reproduction is a type of reproduction that
involves a complex life cycle in which a gamete (such as
a sperm or egg cell) with a single set
of chromosomes (haploid) combines with another to
produce a organism composed of cells with two sets of
chromosomes (diploid).
Sexual reproduction is termed as biparental.
Sexual reproduction involves meiosis during gamete
formation and mitosis during development of offspring
from zygote.
Offspring's are neither genetically identical to the
parents nor to each other.
37. Sexual reproduction involves formation of male and
female gametes, either by the same individual or by
the different individual of opposite sex.
In animals, the male gamete is formed by the
process of spermatogenesis while the female gamete
is formed by the process of oogenesis.
Spermatogenesis and oogenesis is collectively
known as Gametogenesis.
The process of fusion of both these gametes is
known as fertilization.
After fertilization a diploid zygote is formed which
results in to formation of a new individual organism.
38. Reproduction in flowering plants
Monocarpic Plants :-
These plants produce flowers only once in
their life. After flowering, they
produce fruits and die.
All annuals (Wheat , Rice) and biennials
(Radish, Carrot) are monocarpic.
A few perennial plants like certain species
of Bamboo and Neelakuranji are also
monocarpic.
Bamboo flowers only once in their
lifetime. This plant dies after it sets
seeds. This plant usually flowers after
50-100 yrs, produces a large number of
fruits and dies.
Strobilanthus kunthiana ( Neelakurinji) flower
once in 12 yrs. Its mass flowering
transformed large tracts of hilly areas
in Kerala, Karnataka and Tamil Nadu
(Nilgiri).
39. Polycarpic Plants
These are perennial
plants that flowers
repeatedly at
intervals every year.
Ex- Apple, Orange,
Mango etc.
A few perennial plant
bear flower
throughout the year.
Ex- China Rose.
These plants do not
die after flowering.
40. Breeding of animals
On the basis of breeding, animals are of two types:-
SEASONAL BREEDERS :- They reproduce at a particular
period of the year. Such as Frog, Lizard, most birds, deer
etc.
CONTINUOUS BREEDER :- These animals continue to
breed throughout their sexual maturity. Such as rabbit,
mice, cattle etc.
The females of placental mammals shows cyclic changes
in the activities of ovaries and accessory ducts as well as
hormones during the reproductive phase.
41. CYCLIC CHANGES DURING REPRODUCTION
In non-primate mammals like cows, sheep,
rats, deers etc., such cyclic changes during
reproduction are called Oestrus cycle.
In primates (Monkeys, apes and humans)
such cyclic changes during reproduction are
called Menstrual cycle.
42. Events in sexual reproduction
The event of sexual reproduction follow a regular
sequence.
For convenience these sequential events are grouped
into three distinct stages as follow :-
1) Pre-fertilization events/changes.
2) Fertilization.
3) Post-fertilization events/changes.
43. Pre-fertilization events
It includes all the event which are prior to fusion of gametes.
The two main pre-fertilization events are as follow:-
1) Gametogenesis :- The process of formation of male and female
gametes. Gametes are haploid (n) cells. Gametes may be :-
Homogametes or Isogametes :- The two gametes are similar in
appearance and can not be differentiated into male and female gametes.
Ex- Cladophora.
Heterogametes :- The two gametes are morphologically different and can
be distinguished in to male and female gamete. The male gamete is called
Antherozoid or Sperm and female gamete is called egg or ovum.
44. Sexuality in organisms
In Plants,
Homothallic and Monoecious :- These terms are used to describe the bisexual
condition of plant and some fungi.
Heterothallic and Dioecious :- These terms are used to describe the unisexual
condition of plant and some fungi.
Staminate:- Those flowers which bears only stamens.
Pistillate :- Those flowers which bears only pistil or carpel.
Monoecious Dioecious
Ex- Maize, Pine, Spruce Ex- Papaya, Dates, Kiwifruit
45. In Animals,
Unisexual :- Individuals of all species either male or female. Ex- cockroach.
Bisexual or Hermaphrodite :- Species which possess both male and female
reproductive organ in same body.
Ex- Earthworm, leech ,Sponge ,Tapeworm.
Several organism belonging to monera ,fungi and bryophytes have haploid plant
body but organisms belonging to pteridophyte, gymnosperms, angiosperms
and most of the animals including human being, the parental body is diploid.
In diploid organisms , specialized cells called meiocytes (gamete mother cell)
undergoes meiosis which results in the formation of haploid gamete.
Bisexual animal: EarthwormMonoecious plant: CharaDioecious Plant: Marchantia
46. 2) Gamete Transfer
In majority organisms, male gamete is motile where as
female gamete is non-motile or stationery.
Exceptions, in few fungi and lower algae both types of
gametes are motile.
A medium is required through which male gamete can
move.
In algae, bryophytes and pteridophytes water is the
medium for gamete transfer.
To compensate loss of male gametes during transport,
the number of male gametes produced is several
thousand times the number of female gamete produced.
47. Pollination
The transfer of pollen grains from the anther to the stigma is called
pollination.
Pollen grains germinate on the stigma and the pollen tube carrying
the male gametes reaches up to the ovule and discharge the gametes
near the egg.
Pollen grain showing pollen tube.
48. fertilization
This process is also called Syngamy in which fusion of two gametes
takes place and results in the formation of zygote.
Parthenogenesis :- In some organisms like rotifers, honey bees and
even some lizard and birds (turkey) the female gamete undergoes
development of new organism without fertilization. This
phenomenon is called parthenogenesis.
Rotifer
The smallest animal on the
Earth
Honey
Bee
Turkey
49. Fertilization are of two types:-
1) External fertilization :- In aquatic organisms, like algae,
fishes as well as amphibians Syngamy / fertilization takes place outside
the body of the organism in an external medium (water). Its major
disadvantage is that offsprings are extremely exposed to predators who
threats their survival up to adulthood.
Spawn
50. 2) Internal fertilization :- In many terrestrial animals like fungi and
other higher animals and majority of plants, they develop a special mechanism in
which male deposits its gamete inside the female body and Syngamy/fertilization
takes place. In this case, the male gamete is motile and has to reach to female
gamete in order to fuse with it.
Chances of survival of offsprings are more. Therefore a small number of egg is
produced.
POST FERTILIZATIONCHANGES
Events in sexual reproduction after the formation of zygote are called post
fertilization events/changes. In organisms with external fertilization the zygote is
formed outside the body while with internal fertilization the zygote is formed
inside of the body.
The development of zygote depends on type of lifecycle and environment.
In organisms like fungi and algae, zygote develops a thick coat which is resistant
to damage. It undergoes a period of rest before germination.
In organism with haplontic life cycle, zygote divides by meiosis to form haploid
spores that grow into haploid individual.
51. Embryogenesis
The process of development of embryo after the formation
of zygote is called embryogenesis.
Zygote
Cell Division (Mitosis)
Cell Differentiation
Specialised tissue
Organs
Organisms
52. On the basis of development of zygote takes place outside the body of female
parent or inside, i.e, whether they lay fertilised/ unfertilised egg or give birth to
young ones animals are categorise in to following:
Oviparous :- In oviparous animals like reptiles and birds, the
fertilised egg is covered by a hard calcareous shell are laid in a safe place
and after a period of incubation young ones are hatched out.
Viviparous :- In most of the mammals, the zygote develops in to a
young one inside the female body. After attaining a certain growth young one is
delivered out of the body of female and due to proper embryonic care and
protection the chances of survival of young one is greater.
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