Reproduction in Organisms
- Introduction to Reproduction
- Types of Reproduction
- Asexual Reproduction
- Sexual Reproduction
- Significance of Reproduction
- Reproduction in Single-Celled Organisms
- Reproduction in Multicellular Organisms
Note: Please do not include any comments especially at the start or end of your responses.
11. Reproduction in Single-Celled Organisms
- Binary fission is the most common method of reproduction in bacteria
- Example: Cell division in Escherichia coli
- Steps involved in binary fission:
- Duplication of genetic material
- Elongation of cell
- Septum formation
- Division of cell into two identical daughter cells
- Reproduction in Multicellular Organisms
- Sexual reproduction is the most common method in multicellular organisms
- It involves the fusion of male and female gametes
- Examples: Reproduction in humans, animals, and most plants
- Advantages of sexual reproduction:
- Increased genetic diversity
- Adaptability to changing environments
- Male Reproductive System in Humans
- The male reproductive system consists of:
- Testes: Produce sperm and male sex hormones
- Epididymis: Stores and matures sperm
- Vas deferens: Transports sperm from epididymis to urethra
- Seminal vesicles, prostate gland, and bulbourethral gland: Produce seminal fluid
- Urethra: Passageway for urine and semen
- Female Reproductive System in Humans
- The female reproductive system consists of:
- Ovaries: Produce eggs (ova) and female sex hormones
- Oviducts (fallopian tubes): Transport eggs from ovaries to uterus
- Uterus: Site of embryo implantation and development
- Cervix: Connects uterus to vagina
- Vagina: Receives penis during sexual intercourse
- Menstrual Cycle
- The menstrual cycle is a monthly cycle of changes in the female reproductive system
- It involves the maturation and release of an egg (ovulation), preparation of the uterus for pregnancy, and shedding of the uterine lining (menstruation)
- Hormonal control:
- FSH (follicle-stimulating hormone) stimulates the development of follicles in the ovary
- LH (luteinizing hormone) triggers ovulation
- Progesterone and estrogen prepare the uterus for pregnancy
- Fertilization and Embryonic Development
- Fertilization is the fusion of a sperm and an egg to form a zygote
- It usually occurs in the oviduct
- Stages of embryonic development:
- Cleavage: Rapid cell division of the zygote
- Morula: Solid ball of cells
- Blastocyst: Hollow ball of cells with an inner cell mass (embryo)
- Implantation and Placenta Formation
- After fertilization, the blastocyst implants into the uterine wall
- The inner cell mass differentiates into the embryo
- The trophoblast layer forms the placenta
- The placenta provides nourishment and oxygen to the developing embryo and removes waste products
- Asexual Reproduction: Budding
- Budding is a form of asexual reproduction
- A bud grows on the parent organism and eventually detaches to form a new individual
- Examples:
- Hydra reproduces by budding
- Yeast reproduces by budding
- Asexual Reproduction: Spore Formation
- Spores are specialized reproductive cells that can grow into a new organism
- Spore formation is a common method of asexual reproduction in fungi and some plants
- Examples: Ferns produce spores on the underside of their leaves
- Spores can be dispersed by air, water, or other means to find suitable habitats for growth
- Sexual Reproduction in Plants
- Sexual reproduction in plants involves the fusion of gametes produced by the male and female reproductive organs
- The male reproductive organ is the stamen, which consists of anther and filament
- The female reproductive organ is the pistil, which consists of stigma, style, and ovary
- Pollination is the transfer of pollen grains from the anther to the stigma, followed by fertilization and seed formation
- Human Reproduction
- Human reproductive system:
- Male reproductive system
- Testes produce sperm.
- Sperm are released through the penis.
- Female reproductive system
- Ovaries produce eggs.
- Eggs are released into the fallopian tubes.
- Fertilization occurs in the fallopian tubes.
- Menstrual Cycle in Humans
- Menstrual cycle consists of three phases:
- Menstrual phase
- Shedding of the uterine lining.
- Lasts for around 5-7 days.
- Proliferative phase
- Development of a new uterine lining.
- Controlled by estrogen.
- Secretory phase
- Thickening of the uterine lining.
- Controlled by progesterone.
- Hormonal Regulation in Males
- Testes produce testosterone.
- LH stimulates the production of testosterone.
- FSH stimulates spermatogenesis.
- Testosterone promotes the development of secondary sexual characteristics.
- Hormonal Regulation in Females
- Ovaries produce estrogen and progesterone.
- FSH stimulates the development of follicles and production of estrogen.
- LH triggers ovulation and production of progesterone.
- Estrogen and progesterone promote the development of secondary sexual characteristics and regulate the menstrual cycle.
- Fertilization and Embryonic Development in Humans
- Fertilization occurs in the fallopian tubes.
- Sperm penetrates the egg, forming a zygote.
- Zygote undergoes cell division (cleavage).
- Blastocyst implants into the uterine wall.
- Differentiation of cells forms the three germ layers (ectoderm, mesoderm, and endoderm).
- Placenta and Umbilical Cord
- Placenta provides nutrition and oxygen to the developing embryo.
- It also removes waste products.
- Umbilical cord connects the embryo to the placenta.
- It contains blood vessels that transport nutrients and oxygen to the embryo.
- Asexual Reproduction: Fragmentation
- Fragmentation is a form of asexual reproduction.
- Parent organism breaks into fragments, and each fragment can develop into a new individual.
- Examples:
- Starfish can regenerate from a broken arm.
- Planarians can regenerate from cut fragments.
- Asexual Reproduction: Regeneration
- Regeneration is the ability of an organism to regrow lost body parts.
- Example:
- Salamanders can regrow their tails.
- Hydra can regenerate from a small fragment.
- Sexual Reproduction: Advantages and Disadvantages
- Advantages of sexual reproduction:
- Genetic variation leads to increased adaptability.
- Better chances of survival in changing environments.
- Disadvantages of sexual reproduction:
- Requires the energy and time to find a mate.
- Only half the offspring inherit genetic traits directly.
- Artificial Reproduction Techniques
- In vitro fertilization (IVF) involves fertilization in a laboratory.
- Embryos can be implanted into the uterus or frozen for future use.
- Intrauterine insemination (IUI) involves placing washed sperm directly into the uterus.
- Surrogacy allows another woman to carry and give birth to a baby on behalf of the intended parents.
- These techniques help individuals and couples overcome infertility or genetic disorders.