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.