Reproduction: Sexual & Asexual Methods

• Reproduction and development are essential biological processes.

Sexual Reproduction

• Requires two parents (male and female).
• Offspring are genetically different due to the mixing of genes.
• Involves fertilization, which is the fusion of gametes.

Asexual Reproduction

• Involves only one parent, without the involvement of gametes.
• Offspring are genetically identical to the parent, essentially clones.
• Does not involve fertilization; relies on methods like budding and binary fission.

Binary Fission

• A single parent cell divides into two genetically identical daughter cells.
• First the parent cell replicates its DNA, then the cell wall and cytoplasm divide, creating two daughter cells.
• Examples of organisms that reproduce this way include bacteria, amoeba, and paramecium.

Budding

• A new individual grows as an outgrowth from the body of the parent.
• A bud forms on the parent, grows into a miniature version, and then detaches to live as an independent organism.
• Examples include yeast and hydra.

Fragmentation

• An organism breaks into multiple pieces, and each piece regenerates into a complete organism.
• The parent organism breaks apart due to injury or environmental factors.
• Each fragment can develop into a new, genetically identical individual.
• Examples include flatworms and starfish.

Spore Formation

• Spores reproductive cells are produced by the parent organism, which can develop into new individuals.
• The parent organism produces spores through cell division.
• Spores are released, remain dormant for extended periods, and germinate and grow into new individuals in favorable conditions.
• Examples of organisms include ferns, mushrooms, and molds.

Vegetative Propagation

• New plants are produced from the vegetative parts roots, stems, or leaves of the parent plant.
• Methods include cutting a stem and planting it or separating a sucker (shoot growing from the base).
• The vegetative part develops roots and grows into a new, genetically identical plant.
• Examples include potatoes (tubers), strawberries (runners), and spider plants (plantlets).

Types of Union of Gametes

• Gametes are sperm and the ovum.

Isogamy

• Involves the fusion of similar gametes, which are motile and often indistinguishable in size and shape.
• Two gametes come together, and their genetic material fuses to form a zygote.

Anisogamy/Heterogamy

• Involves the fusion of dissimilar gametes
• This is a common type of gamete union where a larger, non-motile female gamete (egg or ovum) is fertilized by a smaller, motile male gamete (sperm).
• The genetic material fuses to form a zygote.

Oogamy

• Oogamy is the most common form of heterogamy.
• The male gamete (sperm) is highly motile and much smaller than the non-motile female gamete (egg).
• Oogamy is observed in animals and some plants.

Bisexual Reproduction

• An individual organism produces two types of gametes: male (sperm) and female (egg).
• This is the most common form of sexual reproduction in animals.

Hermaphroditism

• A hermaphrodite is an organism that possesses both male and female reproductive organs.
• Both male and female sex organs are functional at the same time, allowing for self-fertilization.
• Self-fertilization isn't always the case. Some hermaphrodites may have mechanisms to prevent it, favoring cross-fertilization.
• Examples of hermaphrodites include earthworms, slugs, and some fish species.

Intersex

• Human focus: Refers to a condition in humans where an individual has reproductive or sexual anatomy that doesn't fit the typical definitions of male or female.
• Chromosomes might not match external genitalia.
• Internal and external genitalia might not be obviously male or female.
• Gonads (ovaries or testes) might be mixed or underdeveloped.

Development

• Development Involves forming sex cells, zygote formation, and subsequent stages in one's life span.
• Development is terminated by death.

Life Cycle

• The series of changes in the life of an organism, including reproduction.

The Human Reproductive System

• Organs enable humans to reproduce sexually.
• The human reproductive system enables the creation of sex cells, sperm and egg, and nurtures the developing baby
• Includes the Male and Female Reproductive Systems.

The Male Reproductive System

• Includes the bladder, vas deferens, epididymis, testes, prostate, scrotum, seminal vesicle, rectum, and anus.

Human Male Reproductive Parts and Their Functions

• Testis is where sperms are produced
• Epididymis is where sperms are temporarily stored.
• Scrotal sac/scrotum Supports the testis and epididymis.
• Vas deferens is where the sperm passes through from the testis before it joins the urethra.
• Seminal vesicle secretes fluid that forms part of the semen; secretion gives the semen its alkaline characteristic to counteract the acidity of the vaginal tract and therefore protect the sperm; the fluid also contains sugars like fructose.
• Prostate gland secretes fluid that provides alkalinity to the semen and proteolytic enzymes, citric acid, phosphatases, and lipids.
• Bulbourethral glands produce clear, viscous secretion known as pre-ejaculate that helps to lubricate the urethra for sperm to pass through, neutralizing traces of acidic urine in the urethra and helps flush out any residual urine or foreign matter.
• Urethra connects the urethra and the urinary bladder. Serves as passageway of both sperm and urine and terminates in the external urinary meatus of the penis.

The Sperm Pathway:

• Testes → Epididymis → Vas deferens → Urethra → Seminal vesicles → Ejaculatory duct → Prostate gland → Expulsion from the body .

The Female Reproductive System

• Includes the fallopian tube, ovary, uterus, cervix, and vagina.

Human Female Reproductive System:

• Endometrial lining/endometrium is The innermost lining of the uterus where the embryo implants and develop.
• Fallopian tubes are paired tubes connected to the uterus and terminate near the ovaries, where fertilization takes place.
• Ovaries are female gonads that release the oocytes during ovulation; which are caught by the fallopian tubes' fimbriae.

Ovaries

• They are two almond-shaped organs.
• Inside the ovary, follicles exist.
• Ovaries are the little sacs that hold immature egg cells (oocytes).
• Follicles have starts to mature egg cells.
• When an egg matures, it's time for ovulation.
• Follicles bursts open and releases the egg into the fallopian tube
• They are also known as oviducts which are paired tubes that are connected to the uterus and terminate near the ovaries; this is where fertilization takes place.
• The uterus is also known as the womb, where the embryo develops where the embryo develops and has thick muscular walls, blood vessels, and the endometrial lining.
• The innermost lining of the uterus is called endometrial lining/endometrium lining where the embryo implants and develop.

Human Female Reproduction

• If the sperm fertilizes the egg in the fallopian tube, it becomes a fertilized egg (zygote).
• Following fertilization, the fertilized egg travels down the fallopian tube towards the uterus.
• With fertilization, the fertilized egg will implant itself into the thick lining of the uterus.
• After implantation occurs, the fertilized egg starts dividing and growing into a baby.
• The placenta is a organ that grows in the uterus, which provides nourishment and oxygen too the baby.
• Should there be no fertilization, the egg and thickened lining of the uterus (endometrium) break down and exits the body through the vagina as a period..

The Journey of the Sperm Cell

• Testes → Epididymis → Vas deferens → Urethra → Ejaculation → Vagina → Cervix → Uterus → Oviducts

Contraception

• Includes ovulation-suppressing, barrier, chemical, surgical, and implantation-suppressing methods and others.

Contraception and its Types

• Ovulation-suppressing methods prevent the oocyte to mature
• Type of contraception taken in by women to prevent them from ovulating.
• Process that blocks any one of the following stages of reproduction in humans: release and transport of gametes, fertilization, implantation and actual completion of development of the embryo/fetus.

Barrier methods

• Condom (inserted on the male is inserted penis to prevent release of sperm into the female reproductive tract)
• Diaphragm blocks the cervix, preventing the passage of the sperm into the uterus.
• Cervical cap covers the cervix and blocks passage of the sperm into the uterus.

Chemical methods

• Spermicidal jelly or foam kills the sperm on contact; they are placed inside the vaginal canal.

Surgical Methods

• A special type of contraception prevents fertilization is involved by surgery
• Vasectomy surgical method for men; it entails cutting the vas deferens in the man
• Tubal ligation surgical method for women; it entails the cutting of the fallopian tubes of the woman.

Implantation-suppressing method

• Type of contraception that prevents the blastocyst from being implanted in the endometrium.
• Intra-uterine devise (IUD), implantation-suppressing method blocks the blastocyst from implanting into the endometrium
• Morning-after pill blocks the action of hormones that prepare the uterus to receive the embryo.

Other Methods

• Abortion is a type of contraception of the deliberate removal of the embryo/fetus before it completes gestation.
• Coitus interruptus requires the man to remove the penis before ejaculation.
• Abstinence involves a ban on physical sexual contact whether man and the woman do not engage in sexual intercourse.