CBSE Class 10 Science Notes Chapter 8 - How Do Organisms Reproduce?

Reproduction is one of the important processes by which every living organism makes a copy like itself. It is the means of multiplication and perpetuation of the species. In reproduction a lot of energy goes waste to produce new individuals but it is essential for the survival of a species or for the continuity of life on the earth, because the older individuals of each species undergo senescence and die.

1.0Asexual Reproduction

Asexual reproduction involves a single parent and results in offspring that are genetically identical to the parent. This method is common in simpler organisms. There are several types of asexual reproduction:

Mode of asexual reproduction

Advantages of asexual reproduction:

• It is the only method of reproduction in most unicellular organisms. 
• The parental properties are preserved. 
• It is a rapid method as it does not require any sexual maturation, production of gametes, transfer of gametes and their fusion.

2.0Sexual Reproduction

• Sexual reproduction involves the union of two individuals, typically a male and a female, to create offspring. 
• Unlike asexual reproduction, which requires only one parent and produces identical offspring, sexual reproduction involves genetic contributions from both parents, resulting in greater diversity among offspring.
• Sexual reproduction involves following steps 
• Formation of gametes (by meiotic cell division)
• Fusion of gametes (Formation of zygote)
• Development of zygote to new individuals.

Sexual Reproduction in Flowering Plants

• In flowering plants, sexual reproduction occurs in the flowers, which contain the reproductive organs. 
• A flower can be unisexual (having only stamens or pistils) or bisexual (having both). 
• The stamen is the male part, producing pollen grains, while the pistil is the female part, consisting of the ovary, style, and stigma.

• Pollination is the transfer of pollen from the stamen to the stigma. 
• This can happen through self-pollination (within the same flower) or cross-pollination (between flowers), facilitated by agents like wind, water, or animals.

• Once pollen reaches the stigma, it travels through the style to the ovary, where fertilization occurs. 
• The fertilized egg develops into a zygote, which then forms an embryo within the ovule. This ovule matures into a seed, and the ovary develops into a fruit. 
• The seed, containing the embryo, will germinate under suitable conditions, growing into a new plant.

Reproduction in Human Beings

Human reproduction is a sexual process that involves the union of male and female gametes to create offspring. This process is closely linked to the physical and hormonal changes that occur during puberty.

Male Reproductive System

• In males, sperm production occurs in the testes, which are located outside the abdominal cavity to maintain a lower temperature essential for sperm production. 
• The sperm travel through the vas deferens and mix with fluids from the prostate and seminal vesicles, forming semen. 
• The penis delivers the sperm to the female reproductive system during intercourse.

Female Reproductive System

• In females, eggs are produced in the ovaries. 
• Each month, an egg is released and travels through the fallopian tube to the uterus. 
• If fertilization occurs, the fertilized egg (zygote) implants in the uterine lining, developing into an embryo and eventually a fetus. 
• The placenta, which forms in the uterus, facilitates nutrient and waste exchange between the mother and the developing baby.

Menstruation

• If the egg is not fertilized, it disintegrates and is expelled along with the uterine lining in a process called menstruation. 
• This cycle occurs roughly every month and lasts between two to eight days.

3.0Reproductive Health

• Sexual maturity does not necessarily mean readiness for sexual activity or parenthood. Various pressures from peers, family, or society can influence decisions about sex and reproduction. 
•  It is important to consider the health implications and responsibilities associated with sexual activity.

Contraception and Disease Prevention

To prevent unwanted pregnancies and sexually transmitted infections (STIs), several contraceptive methods are available. These include:

• Mechanical Barriers: Condoms prevent sperm from reaching the egg and reduce STI transmission.
• Hormonal Methods:  Birth control pills and patches alter hormonal balances to prevent ovulation.
• Intrauterine Devices (IUDs):  Devices placed in the uterus to prevent pregnancy.
• Surgical Methods:  Procedures like vasectomy and tubal ligation block sperm or eggs from meeting.