Use asexual website mouse to move the cursor over the text and graphics in the section below. Biology at a variety of levels. Before a cell divides, its nucleus divides.
Each chromosome is copied, and each nucleus receives the same genetic material: genes, made of DNA. As each cell divides into two, the resulting “daughter” cells are therefore exact copies of one another. Only one type of cell is involved, with no input from another individual. Because no new genetic material is introduced, there is no variation in the resulting offspring. There are many examples of asexual reproduction in plants, e. These easily become detached and grow. These resulting plantlets and plants are genetically identical and will grow to look alike, provided that they are raised in the same environment.
This is often linked with surviving adverse weather conditions and keeping food reserves for the plant in order to grow again the next season. Man often uses these reserves for himself. Strawberry plants produce new plantlets by asexual reproduction. Bananas are fruits which do not contain seeds.
Banana trees are propagated from small buds called offsets at the base of the plant. One potato will grow into a plant which then stores starch in several tubers. These are organs of perennation which will survive through the winter and then grow into new plants. But how do you propagate apple trees?
Asexual reproduction is much less common in animals, but it is often seen in simpler animals e. In animal lifecycles, asexual reproduction sometimes alternates with sexual reproduction. These are different combinations of male and female gametes undergoing fertilisation and nuclear fusion. I have made these look like sperm and egg cells which are usual in the animal kingdom, but the equivalents in flowering plants are pollen and ovules. In real life the nuclei themselves are not coloured – I just used that to represent their different genetic components. This zygote then divides again and again using the normal process of cell division, producing cells containing genes which are exact copies of the original. So each cell of the embryo, and the adult organism into which it develops, contains cells which are genetically identical.
This is found in many forms of invertebrates, e. Most flowering plants are hermaphrodite. Hermaphroditism enables all individuals to be producing offspring, and encounters between pairs of organisms to be productive. There are often mechanisms to prevent hermaphrodite organisms fertilising themselves, such as different timings of the various processes, and chemical incompatibility mechanisms. When self-fertilisation occurs the result is not the same as asexual reproduction – the offspring being genetically identical to the parent. These are found in wetter places.
However there are cases of simple organisms where two very similar sized cells fuse, then after nuclear fusion meiosis occurs – and there is the suggestion that sex itself can be seen as the result of evolution. In easy times, female aphids choose to clone themselves rather than mate. Howlers are laughable mistakes – 27 pages! You can rely on us! The likely answers may surprise you. Information, has been its principal champion.