Reproduction in humans
Reproduction is a characteristic of all living organisms. It is the process that makes more of the same kind of organism. Reproduction is essential in all species to ensure that the species does not extinct. There are two types of reproduction, Asexual and sexual reproduction. Asexual Reproduction:
Asexual means not sexual. This means that this kind of reproduction does not involve sex. Asexual reproduction is the production of genetically identical offspring from one parent. It is simply a single organism growing a new organism from itself. Asexual Reproduction in Bacteria:Bacteria are tiny single-celled organisms. They reproduce by a process called binary fission. In binary fission, one bacterium grows and exact copy of its DNA coil which carries its genetic information. Then the bacterium completely divides witch one DNA coil in the parent and one in the daughter bacterium. Each bacterium can undergo binary fission once every 20 minutes making them able to reproduce massive numbers from one parent in very little time.Asexual Reproduction in Fungi:Earlier, you’ve studied that fungi are multi-cellular organisms that grow long threads called hyphae on pieces of food. There are two types of hyphae, reproductive and feeding hyphae. Reproductive hyphae grow vertically above the food material. At the top of the hyphae, there is a spherical bag in which many spores are grown. This bag is called sporangium. Spores being produced in the sporangium are reproductive structures that can grow into another fungus. At some point, the sporangium will burst open dispersing the spores into the air. If a spore falls on an area of favorable conditions (food – water – air) it will germinate and grow into a new identical fungus.
| Asexual Reproduction in Potato Plants:
A potato plant starts as a lateral bud (seed) under the soil. In favorable conditions, a shoot grows out from the bud vertically, which then becomes the stem of the plant above the soil. Roots also grow out of the bud downwards into the soil. The bud is now a plant. The stem then grows a part of it under the soil, which is called underground stem. Swellings start to grow from the underground stem; these swellings are called tubers which are the new potatoes. Glucose formed by photosynthesis in the leaves of the above ground stem is converted into sucrose and transported down the stem to the tubers to be stored there as starch. When the tubers are fully grown the mother plant dies and the new lateral buds form on the tubers. These buds then grow into new potato plants identical to the mother plant.
Sexual reproduction is the process involving the fusion of haploid nuclei to form a diploid zygote and the production of genetically dissimilar offspring. Sexual Reproduction in Flowering Plants:
In a plant, the organs which are responsible for sexual reproduction are the flowers. The diagram below shows a typical flower. Sex cells are called gametes. The male gametes are produced inside the anther. And the female gametes are produced inside the ovules. Some flowers can produce both male and female gametes. They are calledhermaphrodite. Male gametes are inside pollen grains in the anthers.
Methods of Pollination:
Pollination is the transfer of pollen grains from the male part of a flower to the female part of a flower. There are two methods of pollination, insect pollination and wind pollination. Some flowers pollinate by insects while others pollinate by wind. Insect pollinating flowers have special attractive features like brightly colored petals, attractive scents and sugary nectar. These features’ aim is to attract insects like bees to come and collect their nectar. While an insect is collecting the nectar, its body will touch the anthers. The pollen grains of insect pollinating flowers have hooks and spikes all over them in order to stick to the bodies of the insect that touch it. When this happens, the...
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