Download Asexual and Sexual Reproduction

Asexual and Sexual Reproduction
Mitosis Have you ever been stuck in a crowded parking lot? It
is probably crowded because there are a lot of parking spaces and
few exits. Cells let materials exit and enter through the cell membrane. If a cell is really big, materials cannot enter and leave quickly.
Cells must remain small to survive. When they grow too large, cells
divide.
Cell division starts with mitosis. Mitosis is the division of the
cell’s nucleus. The nucleus contains DNA, the material that stores
information about an organism’s growth and development. Before
mitosis begins, the DNA is copied. During mitosis, DNA winds up
tightly. The cell divides the DNA. One complete set of DNA is at
one side of the cell. The other set of DNA is at the opposite side. The
cell membrane then splits apart, forming two cells. Each cell gets
one full set of DNA. The new cells are the same as the original cell.
Asexual reproduction Species survive because parents
pass traits to their offspring. Organisms can reproduce by asexual
reproduction. In asexual reproduction, only one parent makes
offspring. The parent makes a copy of itself through mitosis. All
offspring have the same DNA as the parent.
Many species use asexual reproduction. Bacteria reproduce
asexually. They go through mitosis once to make two cells from
the original cell. Hydra reproduce asexually, too. They grow a baby
hydra on their side. When the new hydra grows big enough, it falls
off and starts a life of its own. In both examples, offspring have
exactly the same DNA as the parent and the same characteristics.
Many other organisms reproduce asexually. For example, strawberries, starfish, and tulips can reproduce asexually.
Sexual reproduction In sexual reproduction, sex cells
from two parents join. The female parent makes an egg cell. The
male parent makes a sperm cell. Each sex cell has half the usual
amount of DNA. When the egg and sperm join, the resulting offspring have unique combinations of DNA. The DNA is a mixture
from both parents. Because of this, offspring have a unique combination of traits.
Good and Bad Asexual reproduction has many good points.
It can be completed quickly. It does not use up much of the parent’s
energy. A parent can have lots of offspring in a short time. Asexual
reproduction requires one parent. The species can grow even if only
one organism is present. Asexual reproduction makes offspring that
are exact copies of the parent. Offspring will survive in environments where the parent survives.
Environments change over time. Offspring of asexual reproduction are all the same. Sometimes they are not adapted to new conditions. If conditions change too much, the parents and offspring may
die.
Sexual reproduction takes more energy and time. It requires two
parents of opposite sexes. This can be a problem if there are few
organisms in an area.
Sexual reproduction has one big advantage. Offspring have a
unique combination of DNA. Every new offspring has a different
set of traits. Some individuals are better suited to one environment.
Other organisms are better suited to a different environment. If
conditions change, some members of the species are likely to do
well in the new situation.