Reproduction: Asexual vs. Sexual

• Reproduction is a biological process where organisms produce new individuals similar to themselves.
• The importance of reproduction lies in continuing generations and introducing variation.
• Variation helps organisms adapt to changing environments, provides stability to species, and supports evolution.
• DNA copying during reproduction leads to errors, which cause variation.
• There are two types of reproduction: asexual and sexual.

Asexual Reproduction

• Requires only a single parent.
• Does not involve the formation of gametes (sex cells).
• Produces individuals that are genetically identical to the parent.
• It is a rapid multiplication process.

Sexual Reproduction

• Requires two parents.
• Involves the formation and fusion of gametes (sex cells).
• Introduces genetic variation in offspring.
• Slower process compared to asexual reproduction.

Fission

• Fission is a type of asexual reproduction where a parent cell divides into two or more daughter cells.
• Binary fission involves the division of a parent cell into two daughter cells.
• Multiple fission involves the division of a parent cell into many daughter cells.
• Amoeba undergoes irregular binary fission (can split from anywhere).
• Euglena undergoes longitudinal binary fission (splits lengthwise).
• Paramecium undergoes transverse binary fission (splits horizontally).
• Plasmodium reproduces through multiple fission.

Fragmentation

• Fragmentation occurs when an organism breaks into fragments, and each fragment develops into a new individual.
• Spirogyra is an organism that reproduces through fragmentation.
• As Spirogyra matures, it breaks into fragments, each growing into a new organism.

Regeneration

• Regeneration is the ability of an organism to regrow lost or damaged parts.
• Hydra can regenerate new organisms from cut pieces.
• Planaria can also regenerate, with each cut piece forming a new Planaria.

Budding

• Budding involves the formation of a bud on the parent organism, which eventually detaches and becomes a new individual.
• Hydra reproduces through budding
• A bud forms on the Hydra
• The bud detaches to form a new Hydra.
• Yeast cells reproduce through budding as well
• A bud forms on a cell
• Many buds can form on an initial bud
• All separate to create new yeast

Spore Formation

• Involves the formation of spores, which are small, reproductive units that can develop into new organisms.
• Happens in organisms like Rhizopus
• Rhizopus are bread molds
• Rhizopus contains Sporangia, which contain spores
• Once spores spread they reproduce rapidly
• Is the fastest process

Vegetative Propagation

• Vegetative propagation involves the reproduction of plants through their vegetative parts such as stems, roots, and leaves.
• Two types of vegetative propagation exist
• Natural
• Artificial

Natural Vegetative Propagation

• Natural vegetative propagation occurs through:
• Underground stems (e.g., potato).
• Leaves (e.g., Bryophyllum, where new plants grow on the leaves).
• Roots (e.g., sweet potato).

Artificial Vegetative Propagation

• Artificial vegetative propagation:
• Cutting: Cutting a piece of a plant stem and planting it to grow a new plant (e.g., rose).
• Layering: Bending a plant stem and covering it with soil to encourage root formation, then separating it as a new plant.
• Grafting: Joining parts of two plants to grow as one, such as attaching an apple tree scion onto a mango tree stock.
• The bottom portion is known as the stock
• The top portion is known as the scion

Benefits of Vegetative Propagation

• Quick and cheap method.
• Disease-free plants can be produced.
• Desired traits of plants can be selected and maintained.
• Genetically identical plants can be produced.
• Almost 100% survival rate for new plants.

Tissue Culture

• Involves growing plants from a small piece of plant tissue in a laboratory setting.

Sexual Reproduction in Plants

• Plants have both sexual and asexual reproduction methods.
• Plant parts include petals, and sepals.

Plant Anatomy

• Petals:
• Colored leaves of the plant
• Give plant color
• Sepals: Protect the flower when it is a bud

Stamen

• The stamen is the male reproductive part of a flower.
• The stamen includes the filament and anther.
• The anther contains pollen grains.
• Pollen grains contain male gametes (sex cells).

Pistil

• The pistil is the female reproductive part of a flower.
• Includes Stigma, Style, and Ovary.
• The stigma is sticky
• The ovary contains ovules, which contain female gametes.

Pollination

• Pollen grains from the anther are transferred to the stigma during pollination.
• The pollen grain creates a tube (pollen tube) to reach the ovule and transfer the male gamete.
• The male and female gametes fuse in the ovule, resulting in fertilization.
• The fertilization creates a zygote.

Plant Types

• Bisexual plants have both male (stamen) and female (pistil) parts in the same flower.
• Unisexual plants have either male or female parts in separate flowers.

Pollination Types

• In self-pollination, pollen is transferred from the anther to the stigma of the same flower.
• In cross-pollination, pollen is transferred between different flowers.
• Agents of pollination include wind, birds, etc.

Post Fertilization

• After fertilization, the ovary becomes the fruit, and the ovule becomes the seed.

Seed Parts

• Seed has three parts:
• Seed coat (protection).
• Embryo.
• Plumule which is new future shoot
• Radicle which is the future root
• Cotyledon (food storage).

Sexual Reproduction in Humans

• Puberty is the period when humans begin to sexually produce.
• The changes happen in women and men.

Male Reproductive System

• Consists of many key structures.
• The scrotum is a muscular sac containing the testes.
• Testes produce sperm cells and testosterone.
• The temperature is regulated because it is outside the body
• Vas deferens carries sperm from the testes to the urethra.
• Located behind the bladder
• Is a muscular tube
• Seminal vesicles and prostate gland add fluids to the sperm.
• The mixture of fluids and sperm is called semen.
• The urethra carries semen out of the body through the penis.
• The outer placement of the scrotum regulates sperm production by maintaining a lower temperature than the body.

Female Reproductive System

• The vagina leads to the cervix, which separates the vagina from the uterus.
• The uterus has a thickened wall called the endometrium in anticipation of pregnancy.
• Fallopian tubes connect the ovaries to the uterus.
• Ovaries release an ovum (egg cell).
• Fertilization occurs in the fallopian tube.
• The zygote implants in the uterus

Implantation

• Attachment of the growing embryo to the endometrium in the uterus.

Placenta

• Placenta is a lifeline connected to the baby.
• Specialised tissue facilitating exchange of nutrients and waste between the mother and the embryo.
• Nutrients are absorbed by mother's blood
• Supplied to the baby.

Menstrual Cycle

• Each month, the female ovary releases an egg
• The uterus prepares by thickening its walls
• It either receives the sperm cell, or menstruation occurs
• If fertilization does not occur, the uterine wall breaks down and is expelled from the vagina as blood and mucus
• This breakdown is the menstrual cycle.

Reproductive Health

• Focus on population control and preventing sexually transmitted diseases (STDs).
• Two types of STDs exist
• Bacterial
• Gonorrhea
• Syphilis
• Viral
• AIDS
• Warts

Contraceptive Devices

• Used for population control
• Mechanical Method: Condoms prevent fertilization.
• Chemical Method: Pills prevent egg formation, but have side effects.
• Intrauterine Contraceptive Device (IUCD).
• Also known as a copper T
• Surgically inserted into the vagina
• Blocks the sperm cell from connecting
• Surgical Method.
• Vasectomy (male): cutting and tying the vas deferens to prevent sperm from leaving the body.
• Tubectomy (female): cutting and tying the fallopian tubes to prevent egg transport.