9B - Sexual Reproduction and its Significances

What is Sexual Reproduction?

A mechanism through which a new individual is developed from a diploid zygote
as a result of the fusion of two haploid gametes (the sperm and the egg)
which are produced by two individuals (the males and the female parents respectively)

What is the structure of female gametes?

The egg is large,
And non motile

What is structure of male gametes?

The sperm is generally much smaller
and motile.

What forms the zygote?

Fusion of the female and male gamete forms the zygote

How are growth and gamete formation linked from a zygote?

A zygote grows into an organism by mitosis, and that organism later produces gametes by meiosis.

What is the form of reproduction for most organisms?

For the most animals, reproduction is mainly or entirely sexual

Where and how gametes are formed?

Gametes in animals are formed by meiosis
in special organs called gonads

Characteristic of gametes

Each gamete is haploid, unicellular reproductive cell

What is the function of gametes?

Reproductive cells called gametes (eggs and sperms) are the
vehicle that transmits genes from one generation to the next.

What is a bisexual organism?

I'm bisexual organisms (Hermaphrodite), one individual has both female and male reproductive structures and therefore is able to produce both male and female gametes by the same individual

Example for bisexual organism

Earthworms

What is a unisexual organisms (dioecious)?

One individual bears either male or female reproductive structures.
Therefore production of male or female gametes occurs in separate organisms (eg: Humans)

What is Fertilization in Sexual Reproduction?

Union of egg and sperm (gametes) for fusion of their nuclei
to produce diploid zygote is called Fertilization

What are 2 types of fertilization?

internal and external

What is External Fertilization?

the female releases eggs, while the male releases sperm into the external environment
and fertilization occurs in the water

Where does external fertilization occur?

Occurs in aquatic environment

Why moist habitat almost always required for external fertilization?

To prevent the gametes from drying out
To allow the sperm to swim toward the eggs

Which organisms show external fertilization?

Many invertebrates, amphibians, most bony fish

What is Internal Fertilization?

It is an adaptation that enables sperm to reach an egg even when the environment is dry

How does Internal Fertilization occur?

Sperms are deposited in or near the female reproductive tract
and fertilization occurs within the female reproductive tract (eg: insects, reptiles, mammals)

What are the adaptations seen in organisms for internal fertilization?

1. Male copulatory organ deliver sperm
2. Female reproductive tract often has receptacles for storage and delivery of sperm to mature eggs

Advantages seen in Internal Fertilization

1. Often provides greater protection to the embryos
2. Many animals show parental care
3. Internally fertilized eggs of birds and other reptiles possess shells and internal membranes that protect against water loss and physical damage
4. Production of fewer gametes than external fertilization but results in the survival of a higher fraction of zygotes

Compared to asexual reproduction a significance of sexual reproduction is

Results in the production of a unique off spring by combining genetic materials from two parents

What

Meiotic recombination during sexual reproduction during sexual reproduction helps produce varied genotypes.

Advantages arose due to unique gene combinations formed during sexual reproduction

1. Can enhance reproductive success and survival of a species in changing environment
2. Beneficial gene combinations arising through recombination may speed up adaptation.
3. Shuffling of genes might allow a population to clear sets of harmful genes more readily

Which would enhance the survival of the species