BIOLOGY Volume 3 - A Guide to General Biology - 2004

21. REPRODUCTION

21.2. Advantages and Disadvantages of Natural Asexual Reproduction

Both Selection/8.html">Asexual and sexual reproduction have distinct advantages, and both processes are observed in A wide variety of organisms. Some organisms, including humans and many animals, reproduce exclusively through sexual reproduction. For the amoeba, asexual reproduction appears to be the only method. We cannot definitively state that one of these forms of reproduction is superior to the other; both prove to be successful in their respective ecological contexts.

Advantages

During asexual reproduction, parent Cells divide to produce genetically identical daughter cells. In eukaryotes, this process occurs via mitosis. Asexual reproduction offers the following advantages:

1. Only a single parent is required. Sexual reproduction involves two individuals, which entails significant expenditures of time and energy to find a partner or, in the case of sessile organisms such as plants, requires specialized mechanisms like pollination, during which a vast number of Gametes are wasted. One solution to this problem is Hermaphroditism, where a single individual produces both male and female gametes.

2. Genetically identical offspring. If a given species is well-adapted to its environment, the genetic uniformity of the offspring can be advantageous, as successful Gene combinations are preserved intact.

3. Dispersal and distribution. Asexual reproduction frequently AIDS in the geographic spread of a species. For example, Penicillium and Mucor are common Molds that spread rapidly through asexually produced spores. Due to their negligible weight, these spores are easily carried by the wind, enabling the Fungi to colonize new food sources. Plants that produce creeping rhizomes—such as weeds growing on sand dunes or mudflats, or species like bracken and cordgrass—rapidly expand their territory using this method.

4. Rapid reproduction. Bacteria are capable of dividing every 20 min, multiplying their population size with extreme speed. The life cycles of many parasites include one or more stages of rapid asexual reproduction, which compensate for heavy mortality rates at other life stages. Classic Examples include the malaria parasite (Plasmodium), tapeworms, and the Liver fluke.

Disadvantages

1. Lack of genetic variation among offspring (the advantages of genetic variation are discussed in section 21.5).

2. When reproduction relies on spore production, many spores fail to find a suitable microenvironment for germination, meaning the energy and metabolic resources invested in their creation are wasted.

3. When a species colonizes a restricted area via clonal spread, overpopulation and the subsequent depletion of nutrients can rapidly occur.