Entrance MCQs Bioinformatics Concepts

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Online Notes on Chapter=8 ( How do Organisms Reproduce) Part 2

How do Organisms ReproduceThis is Online Notes on Chapter=8 (How do Organisms Reproduce)  Part 2 for preparation of CBSE BOARD Examination, NTSE etc.




Sexual Reproduction:


When reproduction takes place as a result of the fusion of male and female
gametes is called sexual reproduction.
Fusion of gametes is called fertilization which results in variation.


Sexual Reproduction in Plants:


• Flowers are the reproductive organs of plants.
• A typical flower consists of four main whorls namely sepals, petals,
stamen and pistil.


Types of Flowers:



• Bisexual flower : Both male and female reproductive parts are present.
E.g., Hibiscus, mustard.

• Unisexual flower : Either male or female reproductive part is present.
E.g., Papaya, watermelon.

Structure of Flower :


Structure of Flower


Process of Seed Formation:


• Pollen grains, produced in the anther, are transferred to the stigma of
same flower (self pollination) or stigma of another flower (cross
pollination) through agents like air, water or animals.

• Pollen grains germinate and form pollen tubes which pass through style
to reach upto the ovules present in ovary.

• The fusion of male and female gametes is called fertilization. Zygote is
produced inside the ovary.

• Zygote divides to form embryo. Ovule develops thick coat and changes
into seed gradually.

• Ovary changes into fruit and other parts of flower fall off.
Germination of pollen on stigma


• The seed germinates to form a plant under suitable conditions such as air,
moisture etc.


Reproduction in Human Beings:


• Humans use sexual mode of reproduction.

• Sexual maturation : The period of life when production of germ cells
i.e., ova (female) and sperm (male) start in the body. This period of

sexual maturation is called puberty.




Changes at Puberty:


(a) Common in male and female

• Thick hair growth in armpits and genital area.
• Skin becomes oily, may result in pimples.

(b) In girls

• Breast size begin to increase.
• Girls begin to menstruate.

(c) In boys

• Thick hair growth on face.
• Voice begin to crack.

These changes signals that sexual maturity is taking place.


Male Reproductive System:



(a) Testes : A pair of testes are located inside scrotum which is present
outside the abdominal cavity. Scrotum has a relatively lower temperature needed
for the production of sperms.
• Male germ cell i.e., sperms are formed here.
• Testes release male sex hormone (testosterone). Its function is :

(i) Regulate production of sperms.
(ii) Bring changes at puberty.

(b) Vas deferens : It passes sperms from testes upto urethera.

(c) Urethera : It is a common passage for both sperms and urine. Its outer
covering is called penis.

(d) Associated glands : Seminal vesicles and prostate gland add their
secretion to the sperms. This fluid provide nourishment to sperms and make their
transport easy.

Sperm alongwith secretion of glands form semen.
Human − male reproductive system



Female Reproductive System:


(a) Ovary : A pair of ovary is located in both sides of abdomen.

• Female germ cells i.e., eggs are produced here.
• At the time of birth of a girl, thousands of immature eggs are present
in the ovary.
• At the onset of puberty, some of these eggs start maturing.
• One egg is produced every month by one of the ovaries.

(b) Oviduct or Fallopian tube:

• Receives the egg produced by the ovary and transfer it to the uterus.
• Fertilisation i.e., fusion of gametes takes place here.

(c) Uterus : It is a bag-like structure where development of the baby takes
place.

• Uterus opens into vagina through cervix.
Human − female reproductive system



When egg is fertilised :


• The fertilized egg called zygote is planted in uterus and develops into an
embryo.

• The embryo gets nutrition from the mother’s blood with the help of a
special tissue called placenta. It provides a large surface area for the
exchange of glucose, oxygen and waste material.

• The time period from fertilization upto the birth of the baby is called
gestation period. It is about 9 months.


When egg is not fertilised :


• The uterus prepares itself every month to receive fertilized egg.

• The lining of the uterus becomes thick and spongy, required to support
the embryo.

• When fertilisation had not taken place, this lining is not needed any
longer.

• This lining breaks and comes out through vagina as blood and mucus.
This cycle takes around 28 days every month and called menstruation.

Reproductive Health:

Reproductive health means a total well-being in all aspects of reproduction
i.e., physical, emotional, social and behavioural.

Sexually Transmitted Diseases (STDs):

• Many diseases can be sexually transmitted such as :
Bacterial : Gonorrhoea and syphilis.

Viral : Warts and HIV-AIDS
• Use of condom prevents these infections to some extent.

Contraception:

It is the avoidance of pregnancy, can be achieved by preventing the
fertilisation of ova.


Methods of contraception:



(a) Physical barrier:


• To prevent union of egg and sperm.
• Use of condoms, cervical caps and diaphragm.

(b) Chemical methods:

• Use of oral pills
• These change hormonal balance of body so that eggs are not released.
• May have side effects.


(c) Intrauterine contraceptive device (IUCD):


• Copper-T or loop is placed in uterus to prevent pregnancy

(d) Surgical methods:


• In males the vas deferens is blocked to prevent sperm transfer called
vasectomy.

• In females, the fallopian tube is blocked to prevent egg transfer called
tubectomy.

Female Foeticide:


• The practice of killing a female child inside the womb is called female
foeticide.

• For a healthy society, a balanced sex ratio is needed that can be achieved
by educating people to avoid malpractices like female foeticide and
prenatal sex determination.

• Prenatal sex determination is a legal offence in our country so as to
maintain a balanced sex ratio.