Animal Cell

Sexual and asexual

reproduction

Among living organisms, there are two types of reproduction-asexual and sexual.

Each type of reproduction has advantages and disadvantages.

Sexual Reproduction

Two parent cells join together to form offspring that are different from the parents.

These parent cells are called sex cells and are different from ordinary body cells.

Human body cells have 46 (or 23 pairs of) chromosomes.

Sex cells have only 23 chromosomes, half of the usual number.

Sexual Reproduction

Information contained on chromosomes determines many of our traits.

Eye color

Hair color

Blood type

Sex chromosomes determine gender.

In humans, females carry two X chromosomes.

Males have one X chromosome and one Y chromosome.

Sexual Reproduction

The result: the offspring will carry half of each parent’s traits. Each time offspring are formed, a new combination of traits is passed.

So, sexual reproduction produces offspring that have a different combination of traits than their parents and their siblings.

Sexual reproduction can occur:

Pollination is a process in which pollen is transferred to the female reproductive organs of seed plants, thereby enabling fertilization and reproduction through growth of the pollen tube and eventual release of sperm.

Sexual Reproduction

Advantage- variation among offspring allows for adaptations and natural selection to occur.

Disadvantage- organisms must find a mate in order to reproduce.

Asexual Reproduction

In asexual reproduction, a new organism (sometimes more than 1) is produced from only one organism.

New organisms have the exact same DNA as the parent.

This type of reproduction has several different processes that it could perform.

Organisms can asexually reproduce by:

Budding- new organism grows from the parent.

Examples- prickly pear cactus and potatoes.

https://www.youtube.com/watch?v=wfbhwq95Duc

Budding

https://www.youtube.com/watch?v=DY9DNWcqxI4

Binary Fission

https://www.youtube.com/watch?v=f7cXeWxxfD4

Regeneration

Organisms can asexually reproduce by:

Binary Fission-

single celled bacteria without a nucleus copies its genetic material and divides to form an exact copy of itself.

Organisms can asexually reproduce by:

Regeneration- some organisms can grow an entirely new organism from a broken piece (sea stars for example).

Organisms can asexually reproduce by:

Fragmentation: cloning in which an organism is split into fragments. Each of these fragments develop into mature, fully grown individuals that are clones of the original organism.

Asexual Reproduction

Advantage- no need to find a mate!

Disadvantage- offspring are exact copies of their parents, so organisms don’t change much over generations. Doesn’t allow for adaptations and natural selection.