Class 10 How Do Organisms Reproduce Notes

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Class 10 How Do Organisms Reproduce Notes

CBSE Class 10 How Do Organisms Reproduce Notes

CBSE Class 10 How Do Organisms Reproduce Notes PDF

Reproduction

We all are aware of the fact that how races of species are continued .we have seen in our own families that generations form generations and so on and the race of humans or any other species continues. This is possible just due to the act of reproduction. So, in this chapter we are going to study about it in detail.

Reproduction is defined as the “ process of giving birth to young ones.”

As you can see in the picture that this adult dog gave birth to puppies and then these puppies will transform in to adult dogs and then they become parents to new puppies and so on the race continues

Sexual reproduction in plants

We come across two kinds of plants flowering and non flowering or we can say angiosperms and non angiosperms. In angiosperms the sexual reproduction occurs as they have reproductive parts and the process of reproduction is explained below:

In plant, reproductive part is flower.

Flower consists of pedicel, thalamus, sepals, petals, gynoecium (F.R.P) & androecium (M.R.P). The structure is shown below :

The gynoecium consists of ovary containing placenta and ovules ,the cylindrical style and stigma. Similarly androecium consist of filament , anther lobe enclosing pollens. The ovary contains ovules as shown in figure:

The pollen grains consist of a layer of exine and intine enclosing cytoplasm, a tube cell and 2 male nuclei.

Pollination is the transfer of pollen from the anther to the stigma of a flower. It can be self or cross pollination depending upon the type of plant.

Process of Pollination

Through any agency, pollen is deposited on the stigma of a flower. On stigma it absorbs some nutrients & swells up and due to that its exine ruptures & intine protrudes to form a long tube.

This pollen tube grows day by day & finally enters the embryo sac through micropyle & pours all its contents that is 2 male gametes and tube cell.

Seed : Under favourable conditions they develop into a fully grown plant. This zygote takes nutrition from endosperm & will develop into Embryo which will finally form a seed.

So we can define the two processes as the Fusion of male gamete with Polar Nuclei to form endosperm is called Triple Fusion and as two fertilizations are taking place, therefore, the process is called double fertilization.

Sexual reproduction in humans

Types of organisms :

Unisexual : the organisms which have only one sex in them .

Bisexual organisms : organisms which have both the sexes in them Example : earthworm

Fertilization: It is the fusion of male gamete with the female gamete. It can be internal like humans or external like aquatic organisms. Their reproductive organs are called gonads. Their gonads produces cells that actually participate in fertilization i.e. gametes.

Male reproductive system

The male reproductive system consists of the following parts:

Testes- A pair of testes descend from body into the pouch like structure called the scrotum. Their function is sperm formation facilitated by the hormone testosterone.

Scrotum – A membranous structure that encloses testes and provide 2-3o C less temperature than body temperature for spermatogenesis.

Epididymis-Their function is to store sperm temporarily.

Vas deferens- It is a duct that carries sperm.

Seminal vesicle- It is a gland that secretes seminal fluid .

Function of fluid- Their function is to provide motility med to sperms. Also they provide nutrition to the sperm.

Sperm mixed with fluid is called semen.

Female Reproductive System

Ovaries- It is a pair of ovaries which is present in the females and their function is egg production facilitated by the hormone oestrogen.

Fallopian tube- It is a tube that receives ovum.

Uterus- It is a Sac where the embryo develops.

Cervix- It is the cap of the vagina.

Vagina- The Outer exposed part of the female reproductive system is called vagina.

Fertilization :In fertilization the following events occurs:

Ovulation – It is the release of ovum from the ovary into the fallopian tube. With the ovulation, thickening of uterine wall takes place. Ovulation occurs every month in female after attaining puberty (i.e. after the age of 13).

Copulation – During intercourse, sperm of the male is injected into the female’s vaginal tract. In one secretion there are a million sperms but only one sperm is capable of fusing with the ovum. All others are degenerated.

Fertilization – The fusion of sperm & egg is called fertilization & it take place in the fallopian tube. As a result diploid zygote is formed.

Implantation– The fixing of the zygote into the uterine wall is called implantation.This takes place after few days of fertilization.

Placenta- It is the temporary formed tissue that provides nutrition to the growing embryo or developing zygote.

Gestation period– It is the period of development of zygote into full grown foetus. In humans it is of 9 month.

Parturition – Expelling a fully grown baby from mother’s body is known as parturition.

Menstruation

At the age of 13 years (Puberty) ovum production starts in the females.

Usually one ova is released in fallopian tube after 28 days.

During ovulation, uterine wall thickens & blood supply in it increases.

If the ovum is not fertilized then thickened wall of uterus along with blood vessels is bled

out from vagina & is called menstruation.

It occurs 14 days after ovulation & last for 3-5 days.

After menstruation, uterine wall starts building up so that it can receive next ovum.

The cycle of menstruation is repeated after every 28 days.

Menarche: beginning of menstruation (start of 12-13 year of age)

Menopause: stoppage of menstruation (around 50 year of age )

Methods to control population

There are different means of population control as increasing population leads to increase in demand. As we all know resources available are limited therefore population control is an important concern :

Barrier method: in this devices like condoms etc. are used that prevent the sperm from meeting the ovum.

Chemical method: There are 2 types of chemical methods

Oral pills

Vaginal pills.

Oral pills- It contains hormones which obstruct ovulation

Vaginal pills- It contains spermicides that kill the sperms.

Surgical method:

In males – The vas deferens in the male is cut & ligated that prevents the sperm from coming out (vasectomy).

In females – The fallopian tube in females is cut & ligated that prevent ovulation (Tubectomy).

Sexually transmitted diseases

How do organisms Reproduce – They are sexually transmitted diseases that are transmitted due to blood contact , used syringes, sexual intercourse etc. The common sexually transmitted diseases are AIDS, Gonorrhea, Syphilis etc.

AIDS: It is caused by the virus HIV. It is a fatal disease in which the immune system of a person weakens and he becomes more prone to infection.

Asexual reproduction

There are different methods involved in asexual reproduction:

Fission: In this the parent organism splits up into two or more new organisms (Daughter cells are of two types binary fission and multiple fission:

Binary fission (when 2 daughter cells are formed) . as shown in figure:

In case of amoeba :

Firstly the cell grows in size duplicate to its genetic material . Then the genetic material divides itself into two followed by the division of cytoplasm so constriction appears finally in the nuclear material. Cytoplasm divides and gives rise to two daughter cells

Multiple fission (When many daughter cells are formed) .

For example- it is seen in the plasmodium. In the starting the cell enters the parent cell and divides repeatedly to form many daughter cells.

They remain enclosed in a protective layer called cyst during unfavourable condition and then in favourable condition cyst breaks and are then released and ready to infect other body cells .

Budding: In it there is a small outgrowth that appears from the parent plant. This outgrowth develops more to form bud. When the bud is fully formed it detaches itself from the parent plant and under favourable conditions it develops into a new organism.

Example- Hydra

Spore Formation: The parent plant produces many microscopic spores which when fullydevelop are shed off and under favourable conditions develop into new organisms.

(iv) Vegetative Reproduction: Many plants reproduce by their vegetative parts like roots, buds stem and leaves. So the formation of new individuals by vegetative parts is called vegetative reproduction.It can be natural or artificial.

Natural Vegetative Reproduction: In this portion of parent plant gets detached and this detached portion grows into a new plant. It can be through roots (sweet potato, dahlia, etc). It can be through stem(potato, banana, etc). It can be through leaves(bryophyllum, begonia)

Artificial Vegetative Propagation: The Process of artificial vegetative propagation is as follows:

Layering

Grafting

Tissue culture

Grafting :

In this the stem of parent plant is cut and called as stock. A cut part of another stem of another plant is bought and both are tied together with the help of cloth . This is then left for a few days tied together.In the meantime we see that it grows as one plant.

Layering: In this the side branch is extended and a portion of it is buried in the mud. Then it is left for a few days. In the meantime that buried portion develops roots so this side branch is cut and propagated as other plant . It grows and form a new plant

Tissue Culture: It is the development of a fully grown plant from few isolated plant cells. In this process, first the cells of any part of plant are isolated and put in to media. In media they divide to form un-organised mass of cells called the cambium.Then this cambium is transferred to the media where it is provided with all nutrients. As a result it develops roots. Then this cambium with root is shifted to a media where all necessary physical conditions are provided where it gives rise to the shoot. Finally it transforms into a seedling. Then it is shifted into a pot where it grows and form fully grown plant.