Reproduction
How Do Organisms Reproduce Class 10 Notes
Formation of new life from preexisting life is called Reproduction .
It is essential for : -
→ Replacement of dead organisms.
→ continuation of life on earth .
Mainly there are two types of reproduction -
Asexual and Sexual -
DNA (Deoxyribonucleic Acid) :
-The individuals produced by reproduction are similar to each other and their
parents .
This similarity occurs because of DNA .
Importance of DNA copying :
→ Maintenance of body design.
→Transfer of traits.
→ Variation are introduced at the time of DNA copying.
Importance of variation :
Variation ensures species can survive during unfavorable conditions. .
If there were a population of bacteria living in temperature water ,And the temp.
rises suddenly . Most of the bacteria would die but few variants resistant to
heat would survive and grow further.
ASEXUAL REPRODUCTION -
When offspring is produced by single parent with or without the involvement.
Modes of A sexual Reproduction :
1 . Fission
2. Fragmentation
3.Regeneration
4 .Budding
5. vegetative propagation
6 .Spore formation
1. Fission -
A unicellular organism ,like bacteria splits into 2 or more organisms .
Generally , It is of two types -Binary and multiple fission.
Binary fission : In Binary fission, organisms split into 2 new organism under specific conditions.
Binary Fission In Amoeba -
At first the nucleus divides into two. It is followed by division of cytoplasm Then finally splitting of parent cell into two daughter cell occurs.
Multiple fission :
The parent organism divides into many identical daughter organisms at the same time.
multiple fission can be seen in organisms, Such as Plasmodium (malarial parasite)
2.Fragmentation -
The breaking up of body of a simple multicellular organism into two or more pieces on maturing , each subsequently to form a new organism is called fragmentation.
For Example - Algae (spirogyra) : These organisms on maturation breakup into two or more small fragments or pieces . Each fragment subsequently grows to form a complete new organism.
3. Regeneration -
The process of getting back a full organism from its body part is called regeneration .
Question -Why a complex multi-organism cannot give rise to a complete individual from their cuHed body part ?
Ans : Regeneration can be used only in those organism whose body is relatively simple when compared to organisation of its tissue or cell.
But in complex multicellular organism , cell combine to make up tissue , tissue to organ , organ to organ system and finally organ system into organism . This is the reason that complex multi-organisms cannot form by culted part.
4. Budding -
In budding , small parts of body of parent organism grow out as "bud " which then detach and form a new organism. eg: Hydra , yeast.
Example - Hydra
Hydrae: Hydra is a simple multicellular organism , it reproduce asexually by process of budding using its regenerative cells .
First a small bud is formed on one side of its body by simple miotic division.
This bud then grows and forms mouth and tentacles .
Finally the new hydra.
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| How Do Organisms Reproduce Class 10 Notes |
5. Vegetative Propagation -
In vegetative propagation, new plant are obtained from part of old plant , without help of reproductive part.
Vegetative propapayathen usually involve the growth and development of one bud present on old part of plant to form a new plant .
Example - Bud of potato, bulb of onions, leaf buds of Boyophylum , roots of Dahlia.
This is Natural propagation .
Artificial propagation of plant :
A process of growing many plant from one plant by man-made method is called artificial propagation .
Common method of artificial propagation are -
Cutting : A small part of plant is removed by cutting it with a sharp knife, this is called cutting .eg sugarcane, bananas ,cactus etc.
Layering : A part (generally branch) of plant is bend toward ground leaving its growing tip rest is covered by soil . eg Jasmine, lemon ele .
Grafting : A method in which stem of 2 plant' lone with root and other without root) are joined and are allowed to grow as a single plant -
eg.-Apple , pear etc.
Advantages of Artificial propagation of plants :
° New plant will be exactly same as parent plant with any desired character of parent .
° Plants grown by this process need less attention .
° Many plants can be grown by same parent .
TISSUE CULTURE :
The production of new plant from a small piece of under plant suitable tissue (or medium cells) is removed known from as
tissue an growing culture. plant , which is grown
° Its Advantages a :
- very fast technique of growing plant .
- plants produced are disease -free .
- Number of plant produce in few and week of time and takes less space for growth.
Spore formation -
In spore formation , the parent plant produce hundred of microscopic reproductive unit called spores. When the spore case of the plant burst , then the spore spread to air, where these air- borne spore land on soil and under favorable condition they germinate into new plants.
Sexual Reproduction -
Sexual reproduction takes place by combination of 2 special reproductive ' cells called 'sex cells ' , they are also called 'gametes ' or germ cell '.
They are Two Types Of Sex Cell -
- Male sex cell female sex cell.
- Male gamete female gamete.
- Male germ cell female germ cell .
The ' fusion between male gamete and female gamete led to formation of zygote' cell which then develop to a new organism .
Sexual Reproduction in flowering plant -
The plant in which sex organ are carried by flower , and the seed is enclosed within fruit are called Angiosperms flowering plants . They bear the reproductive parts within the flower and their seeds are enclosed in a fruit .
Most plants have both male and female reproductive organs in the same flower and are known as bisexual flowers . While others have either male or female reproductive parts in a flower known as uni-sexual flowers .
Stamen:
It is the male reproduction part of the flower . A single flower may have number of stamens in it.
Anther :
It is a bi-lobed structure containing two pollen sacs present at tip of stamen . These produce pollen grains that are yellowish in color.
carpel :
It is the female reproductive part , which is present in the center of the flower B .
It comprises of mainly three parts :
Stigma :
It is the terminal part of carpel which may be sticky . It helps in receiving the pollen grains during pollination .
Style :
It is the middle elongated part of carpel . It helps in the attachment of stigma to the ovary .
Ovary :
swollen bottom part of carpel . It contains ovules having an egg cell female gamet.
Pollination :
Transfer of pollen grains from the anther of the stamen to the stigma of a flower is termed as pollination .
Self pollination :
pollen from the stamen of a flower is transferred to the stigma of same flower.
Cross pollination :
pollen from the stamen of a flower is transferred to the stigma of different flower .
Fertilization :
Pollination is followed by fertilization in plants . It is the process of fusion of male germ cells with the female gametes .
It gives rise to a zygote . As soon as the pollen lands on suitable stigma ,
it reaches the female germ cells in ovary .
This occurs via pollen tube . The pollen tube grows out of the pollen grains g travels through the style and finally reaches the ovary .
After fertilization,the zygote divides many times and forms an embryo within the ovule.
This ovule then develops a tough coat and gets converted into a seed .
The ovary rapidly grows and ripens as fruit . The seed contains the future embryo that develops into a seedling under suitable conditions .
This process is called germination.
Sexual Reproduction in Human Beings :
PUBERTY :
The age at which 'sex hormones ' are produced and a boy or a girl becomes sexually mature is called age of puberty .
Age of puberty for boys → 13 - 14 yrs
For girls → 10 - 12 yrs
Testis produce male sex hormone Testosterone and ovaries produce 2 sex hormone oestrogen and progesterone .
In both boys and girls, certain changes take place during this reproductive phase .These changes are the signals of sexual maturation.
Common changes in both:
- Growing of thick darker hair in new parts of the body such as armpits and the genital area between thighs.
- Thinner hair on arms and legs , as well as on face .
- The skin frequently becomes oily and begins to develop pimples.
Changes In Girls -
- Changes Breast in size girls begins : to increase .
- Darkening Start of menstruation of the nipple.
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