Biology Chapter: Reproduction

Reproduction

• Reproduction is the process by which living things create offspring.
• There are two types of reproduction: sexual and asexual.
• Sexual reproduction involves two parents, with each contributing half of the genetic material (DNA).
• Asexual reproduction involves only one parent.
• Examples: Humans = sexual, bacteria = asexual.

Sexual Reproduction

• Involves two parents (male and female).
• Each parent contributes half of the genetic material (DNA) to create the offspring.
• Examples include: humans, dogs, most animals, and flowering plants.
• Gametes (sex cells) are produced by the parents.
• Male gametes are sperm cells.
• Female gametes are egg cells.
• Sperm is relatively smaller and motile.
• The ovum (egg cell) is comparatively larger.
• The union of sperm and egg is called fertilization, creating a zygote.
• Sexual reproduction involves the union of sex cells (gametes) from two parents, resulting in genetically unique offspring.
• There are two primary types of fertilization: internal and external.

External Fertilization

• Water or a moist environment is needed for the gametes to not dry out.
• Both male and female gametes are released into the same area.
• This simultaneous release is called spawning.
• This method is common in amphibians and fish.
• Advantageous for large numbers of offspring, but exposure to environmental hazards decreases the chance of the zygote's survival.
• Zygotes develop outside the parent's body.
• Frog is an example of an animal exhibiting external fertilization.

Internal Fertilization

• The egg is fertilized inside the female reproductive tract.
• This process is also known as copulation.
• This method is common in mammals, including humans.
• Advantageous since it offers protection for the zygote.
• Development of the fertilized egg (zygote) occurs within the female reproductive tract.

Fertilization

• Fertilization is the union of male and female gametes producing a diploid zygote.
• Internal fertilization occurs within the female body; external fertilization requires an aqueous environment.
• Methods of fertilization include external and internal fertilization.
• IVF (In Vitro Fertilization) is a type of fertilization where fertilization takes place outside of the female body (in a laboratory).

Egg Cells

• Egg cells, or ova, are present in the female from birth.
• They are produced in the ovaries, along with hormones that regulate the menstrual cycle.
• They contain the female genetic material.

Sperm Cells

• Sperm cells are produced in the testes (testosterone).
• The testes are located in the scrotum.
• Sperm cells have a head, body, and tail, containing genetic material and enzymes for penetrating the egg.
• Mitochondria provide energy for movement.

Advantages of Sexual Reproduction

• Produces varied offspring.
• Improves species survival in varying environments.

Disadvantages of Sexual Reproduction

• Takes more time and energy (needs two parents).

Advantages of Asexual Reproduction

• Faster method
• Needs only one parent

Disadvantages of Asexual Reproduction

• No variation, making it harder for species to survive environmental changes.

Asexual Reproduction

• Does not involve the union of gametes.
• One parent produces offspring without the involvement of another individual of the same species.
• Offspring are genetically identical (clones) to the parent.

Types of Asexual Reproduction

• Budding
• Binary Fission
• Spore Formation
• Vegetative Propagation
• Fragmentation
• Regeneration

Budding

• A new organism develops as an outgrowth or bud from the parent.
• The bud grows and eventually detaches, becoming an independent organism.
• This method is common in yeast and some animals.

Binary Fission

• The parent cell divides into two genetically identical daughter cells.
• This method is common in bacteria, and some protozoans.

Spore Formation

• Spores are specialized, microscopic cells produced by certain organisms.
• Spores can be spread to new environments by wind or water.
• They germinate into a new individual when conditions are favorable.
• Mushrooms and molds use this method.

Vegetative Propagation

• New individuals are formed from parts of a plant other than seeds.
• Common in plants and involves various methods like cuttings, layering, grafting, and tissue culture.
• Plants, in this case, are clones of the parent plant.

Fragmentation

• The parent organism breaks into fragments.
• Each fragment develops into a new individual.
• Planaria is an example of this type.

Regeneration

• The ability of an organism to replace lost or damaged body parts.
• Starfish and lizards are examples of animals that exhibit this.

Corn, Tuber, Bulb, Rhizomes

• Modified underground stems used for food storage and asexual propagation in plants.
• Examples vary, with each having particular adaptations for survival.

Artificial Vegetative Propagation

• This involves human interaction to induce vegetative propagation for commercial purposes.
• The methods include cutting, layering, grafting, and tissue culture.
  • These methods preserve desirable traits in specific plants.

In Vitro Fertilization (IVF)

• A reproductive technology where fertilization takes place outside a woman's body in a lab and then transferred back into her.

Mammal Gestation Periods (Table)

• Data on average gestation periods for various mammals.
• Demonstrates time differences based on the species.

Importance of Sexual Reproduction

• Variety for survival; offspring differ.
• Better survival chances, helps species survive changing environments.