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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.