Reproduction
- Asexual Reproduction: This type of reproduction does not involve the formation or fusion of gametes.
- Sexual Reproduction: This type of reproduction involves the formation and fusion of gametes.
Asexual Reproduction
- Major Type: Occurs predominantly under favorable conditions.
Modes of Asexual Reproduction in Plants and Animals
- Fission:
- Found in unicellular organisms.
- The cell divides equally, e.g., Amoeba.
- Fragmentation:
- The body breaks into parts, each of which can generate a whole new body, e.g., Spirogyra, bryophytes.
- Regeneration:
- Any body part can form new parts, e.g., Hydra.
- Budding:
- A bud forms on the body and grows into a full organism, e.g., Hydra, yeast.
- Vegetative Propagation:
- Vegetative parts like roots, stems, and leaves develop new identical plants (clones), e.g., sugarcane, rose.
- Can be carried out artificially by grafting, cutting, layering, and micropropagation (tissue culture). This can be practiced year-round.
- Spore Formation:
- Spores, condensed protoplasmic bodies containing genetic material, separate from the main body and germinate into new organisms, e.g., algae and fungi.
Question for Reproduction in Plants and Animals (Humans)
Try yourself:
Which mode of asexual reproduction involves the separation of condensed protoplasmic bodies?Explanation
- Spore formation involves the separation of condensed protoplasmic bodies that contain genetic material and germinate into new organisms. This mode of asexual reproduction is commonly seen in algae and fungi.
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Sexual Reproduction
- Adverse Conditions: Often occurs in adverse conditions among lower organisms, while many higher plants and animals have adapted it as their main mode of reproduction.
- Gametes: Critical for sexual reproduction, they are formed in reproductive organs and protect genetic and protoplasmic material, transmitting it to a suitable place for fusion and formation of a new organism.
Sexual Reproduction in Plants (Angiosperms)
- Growth Phases: After germination, plants go through vegetative and reproductive phases, influenced by hormones like auxin, gibberellin, and abscisic acid.
- Flower: The reproductive organ of plants. Flowers with both male and female reproductive organs are bisexual, while those with only one type are unisexual.
- Male Organ: Androecium
- Female Organ: Gynoecium
Pollination Agents:
- Wind: Anemophily
- Water: Hydrophily
- Insects: Entomophily
- Birds: Ornithophily
- Bats: Chiropterophily
- Snails: Malacophily
- Ants: Myrmecophily
The fate of various parts of flower is given below :
Sexual Reproduction in Humans
In humans only sexual mode of reproduction is found. Males and females are different from each other externally as well as internally. Male reproductive system forms sperms (male gamete) while female reproductive system forms egg (female gamete)
Comparison between secondary sexual character of man and woman is given below:
Male Reproductive System:
- Function: Produces sperm.
- Spermatogenesis: Formation of sperm occurs in the testes, which are located outside the body in the scrotum because sperm formation requires lower temperatures.
- Sperm Pathway: Sperm are delivered through the vas deferens to the urethra, which serves as a common pathway for urine and sperm.
- Accessory Glands: Includes the prostate gland and seminal vesicles, which aid in reproduction. Sperm, after being formed in the seminal vesicle, are collected in the epididymis via the rete testis.
Sperm Pathway: Seminal vesicle → Rete testis → Vasa efferentia → Epididymis → Urethra
Female Reproductive System
The female reproductive system is responsible for producing eggs. Egg production occurs in the ovaries. When a girl is born, her ovaries contain thousands of immature eggs, which begin to mature after puberty, forming primary, secondary, and eventually tertiary follicles. The tertiary follicles transform into mature Graafian follicles in response to certain hormones, following a periodic cycle known as menstruation (approximately 28 days in humans). The egg travels from the ovary to the uterus via the oviduct, where fertilization with sperm occurs to form a zygote. The zygote then moves to the uterus and develops into a new baby.
Fertilization leads to the formation of a zygote, which undergoes cleavage and soon reaches the three-layered stage called gastrula. The fate of the cells in these three primary germ layers is as follows:
Reproductive Health
Reproductive health refers to a state of physical, mental, and social well-being in all matters related to the reproductive system at all stages of life. Men and women should have access to safe, effective, affordable, and acceptable methods of family planning and appropriate health-care services to safely navigate pregnancy and childbirth.
Contraceptive Methods:
- Barrier Methods: Prevent sperm from entering the uterus and reaching the egg. These include male and female condoms, diaphragms, cervical caps, contraceptive sponges, and Lea’s shields. They are generally less effective but have fewer side effects than hormonal methods or IUDs.
- IUD (Intrauterine Device): A small plastic device containing copper or hormones inserted into the uterus by a medical professional. It changes cervical mucus to decrease fertilization probability and alters the uterine lining to prevent implantation.
- Abstinence: Voluntary refraining from sexual activity. It is the only 100% effective method to prevent pregnancy and sexually transmitted diseases (STDs).
- Withdrawal: Involves removing the erect penis from the vagina prior to ejaculation.
- Sterilization: Surgical closing of reproductive tubes. Female sterilization (tubal ligation or tubectomy) closes the Fallopian tubes, while male sterilization (vasectomy) closes the sperm-carrying tubes.
- Birth Control Pills: Daily hormone medications prescribed by a doctor containing manufactured forms of estrogen and/or progesterone.
- Amniocentesis: A medical procedure used in prenatal diagnosis to detect chromosomal abnormalities and fetal infections. A small amount of amniotic fluid, containing fetal tissues, is extracted and the fetal DNA is examined for genetic abnormalities.
Question for Reproduction in Plants and Animals (Humans)
Try yourself:
Which contraceptive method involves the insertion of a small plastic device containing copper or hormones into the uterus?Explanation
- Barrier methods prevent sperm from entering the uterus.
- Abstinence involves refraining from sexual activity.
- IUD is a small plastic device inserted into the uterus.
- Birth control pills are daily hormone medications.
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Sexually Transmitted Diseases (STDs)
Sexually Transmitted Diseases (STDs) or Sexually Transmitted Infections (STIs) are infections that can be transmitted from one person to another through sexual contact. Some STIs can also be transmitted during childbirth, through intravenous needles, or breastfeeding.
- The World Health Organization (WHO) estimates that over one million new cases of curable, sexually-transmitted bacterial infections occur worldwide every day.
- Adolescents and young adults (ages 15-24) are at the highest risk for acquiring an STD. If left untreated, STDs can have severe consequences, especially for women.
- It is crucial to seek STD testing if you suspect you may have contracted a sexually transmitted infection.
- In India, the prevalence of sexually transmitted diseases is quite high, with AIDS being a significant concern.
- Recognizing the need to strengthen the STD control program, especially in the context of the recently launched AIDS control program, efforts are being made to expand the National STD Control Programme at the community level through existing private health care services.
The most common STDs include:
- Chlamydia
- Gonorrhea
- Syphilis
- Genital herpes
- Human papillomavirus (HPV)
- Hepatitis B
- Trichomoniasis
- Bacterial vaginosis
- Scabies
- Crabs