REPRODUCTION
Has been written by: Jhon Frentin
students majoring in biology at
the University of Muhammadiyah Malang
East Java, Indonesia
Why is reproduction?
One question about the
living things that no exceptions are living things will die. Life is going to
end in a way that is very diverse. An organism may be eaten, probably killed by
the parasite, may also die of hunger, or perhaps perish because of natural
events such as floods brought dead drifting, burning in lava, landslides. Only
a handful of dead organisms because of advanced age.
Therefore, it is clear
that life will eventually run out, unless the individual bar uterus being
formed. There are two possibilities: the ingredients that are not living
somehow becomes life itself; organisms or pieces may break away and become new
creatures apart. The first possibility is known as "spontaneous
generation" or " be themselves". The second possibility is known
as reproductive or breeding.
Let's review the first
possibility, is the spontaneous generation. We have seen the beginning of life
on earth. Circumstances suggested by Oparin might actually happen in the
hundreds of millions of years ago. But it is clear that condition does not
occur in our time.
Nevertheless, many
people believe that living things can arise from dead matter by way of
"spontaneous generation". For example, some people think that a fly
can occur from rotten meat; mice arise from ragged clothing; pinworms growing
of coconut pulp.
Since the seventeenth
century, when Francesco Redi (1626-1698), poet and expert knowledge of the
nature, conduct research as described in Figure 16.1, biologists no longer
believe in the spontaneous generation of organisms that big.
Source:
biografiektum.blogspot.com
Figure 16.1
Redi experiment: (A) larvae
develop in the meat is placed in a vessel. (B) another vessel covered with a
cloth, and no larvae develop in the flesh. But there is a fabric cover on the
eggs of flies and fly larvae evolved the egg.
Leeuwenhoek's discovery
of microorganisms by itself revive attention to spontaneous generation through
experiments Pasteur demonstrated that these organisms are also derived from
other similar organisms. Culture is seen as the only way for the emergence of a
new individual.
For species, breeding
is the answer to the problem of death. For individuals, the death of open
problems, and for the individual, it is not necessary breed. Therefore culture
is a living process that is somewhat different from the processes of life are
discussed in the fourth section. Breeding is not intended to defend the
individual, but for the continuity of the species.
Various breeding
All organisms have the
same basic life functions. But we have seen, that the organisms did exercise
its functions in various ways, in accordance with diverse structures. Diversity
in the structure and processes is also a characteristic of breeding. Breeding
can take place in two very different ways in their influence on the continuity
of the species, by breeding with breeding asexually or sexually.
Asexual propagation
Easier to describe the
processes of asexual propagation, rather than making the limit. But we can say
that if one or more new individuals coming from the other single individual,
then the breeding process, with a few exceptions, is asexual.
Most organisms that
reproduce asexually, can also reproduce sexually. But in sexually breeding Deuteromycota not known, and a few other
groups are rare sexual breeding. Species that primarily rely on asexual
propagation means it's close at the end of the evolution, because these
organisms have little opportunity to make changes in order to face the changes
in the environment.
Vegetative
multiplication. Cassava farmers plant cassava stems cut up into parts that have
"eyes". Eye in question is going to bud. After several days of
planting, the buds will develop into branches with leaves. This growth is done
by sucking food reserves stored in the pole pieces. Soon the roots grow from
the base of the stem, and after some
time forming new plants.
Similarly the potato
plant with tubers cut up potatoes into pieces that are large enough and have
the "eye". Bred by planting pineapple tree buds that came under his.
Everywhere sellers plants shredding branches of woody plants, planting earlier
pieces in the wet sand, and acquire new plants.
Multicellular organisms
capable to reshape the parts that date. This ability is called regeneration.
This is one aspect of the growing process is common. We have the ability to
regenerate our skin fragments were removed. In the cases discussed above, the
regeneration progressed to an extreme degree: a small, separated from one
individual can grow into a new individual who stands alone.
In plants, buds or
branches may form roots. In contrast, the roots may grow stem piece. In either
case, a new plant may ultimately formed. Many plants reproduce this way without
human assistance. Some kind of Brophyllum
forming buds at the edges of its leaves. The buds then took root, and grow into
a new plant. (Figure 16.2) on several species of buds formed after the leaves
broken from the stem, but in other species formed when the leaf buds are still
attached to the stem.
Figure 16.2
Vegetative propagation
in Bryophyllum. Small plants arising from the contours on the edge of the leaf.
Such buds are also
formed by the Agave plant. Only, here the formation is not on the edges of the
leaves, but the flowers themselves branching. In addition to the formation of
buds which later released from the trunk. Agave forming a long slender branches,
grow laterally penetrate the soil. A bit far from the mother plant this branch
appear above ground. At, the end of the branch formed leaves and roots. Thus
the newly established plants.
Breeding themselves
with a long branch is also carried by water hyacinth plants that we get a lot
of floating in the marshes or ponds. Breeding to the way we were talking about,
everything is breeding vegetatively.
There are way too
similar reproduction in animals, for example, we take the sea star (oyster
predators). First regular oyster farmers chopping the arrest of starfish and
threw it back into the water. But starfish has a large regenerating power.
Every hand that still has a piece of the center, it grows into a new starfish.
Oyster farmers had actually breed starfish.
But starfish do not
reproduce by splitting themselves in separate pieces. Actually this way is
rarely found in animals. As exceptions are some species of freshwater annelid
worms, commonly breed in a way that just broke in two parts. The face then formed
the rear, and the rear forming the front.
Cleavage. Breeding the
single-celled organisms, such as diatomaceous, many green algae and most
protists, often merely a single cell division. This division produces two
offspring, but in the process loses its parent identity. This kind of culture
is called fission. Breeding can occur by cleavage at a specific period in the
life cycle of an organism other during breeding in other ways pula.tetapi turns
out that there are always some organisms reproduce by fission.
Cleavage usually
involves the process of mitosis, but there are exceptions to Cilliata, bacteria
and blue ganggana. Previously people thought that the bacteria does not have an
organized nucleus material. With electron microscopy now people can see that at
least a structure similar to the nucleus. Investigation tentanf indirect
descendants have shown, that each bacterium has only one chromosoma. In fact,
the blue algae can not be demonstrated the existence of something resembling
the nucleus.
Germination. In some
protists, plants and animals, a puppy can grow from the body of an adult
individual. While the puppy was enlarged, formed various parts resulting in a
duplicate of the parent. Eventually these offspring may become detached from
the parent and the individual who stands alone.
Breeding with spores.
On breeding and vegetative bud formation, a new individual grows from
penjuluran a structure or tissue under normal circumstances serve as a form
nonreproduktif parent organism. Also on cleavage no special breeding structure:
one cell that always serves as an individual, splitting it. But in most
multicellular organisms (and also in some unicellular organisms), there are
tools that special breed.
The kinds of breeding
structure called (sporangium or spore box (Greek: spores = seed, angeion + =
small container). Meaning of the word is actually misleading spores. Sporangium
In many spores are formed, each consisting of a single cell with a thick wall.
If ruptured sporangium, spores are very small spores that can be carried by
wind or water to flow long distances, without damage. Due to the evaporation of
water only a few, then these spores can live long survive in dry air. If the
spores reached the place favorable, the spores had grown into a new organism. Though
spore formation does not occur in animals, but the spores are very common
plants in the world.
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