Asexual Reproduction

1. Asexual Reproduction Group Members :Omar Wright Ryan Sweeney Ashley Moyabheer Ainsworth Bennett

2. What is asexual reproduction? • Asexual reproduction is a mode of reproduction by which offspring arise from a single parent, and inherit the genes of that parent only, it is reproduction which does not involve meiosis, ploidy reduction, or fertilization. • A more stringent definition is agamogenesis which refers to reproduction without the fusion of gametes. Asexual reproduction is the primary form of reproduction for single-celled organisms such as the archaea, bacteria, and protists

3. The different modes through which asexual reproduction takes place are binary fission, spore formation, vegetative reproduction and budding.

4. Advantages of asexual reproduction • 1. Large numbers of offspring are reproduced very quickly from only one parent when conditions are favourable. • 2. Large colonies can form that can out-complete other organisms for nutrients and water. • 3. Large number of organisms mean that species may survive when conditions or the number of predators change. • 4. Energy is not required to find a mate Read more:

5. Disadvantages of asexual reproduction • 1. Offspring are genetic clones. A negative mutation can make asexually produced organisms susceptible to disease and can destroy large numbers of offspring. • 2. Some methods of asexual reproduction produce offspring that are close together and compete for food and space. • 3. Unfavourable conditions such as extreme temperatures can wipe out entire colonies.

6. Vegetative Reproduction • Vegetative reproduction is a form of asexual reproduction in plants, where parts of the plant fall off and develop into new plants. Potato tubers are one example of a plant that used this form of reproduction. Since asexual reproduction doesn't require another partner, or pollen transfer it is very quick and is guaranteed. This is very good for people using potatoes in their products, because reproduction is very fast, so they can make more potatoes, and hence make more money. The main disadvantage of this form of reproduction, is that the new plants will all grow very close to each other and to the parent. This will cause a struggle for soil, nutrients and light, and will consequently cause the plants to be less healthy.

7. Fragmentation • Fragmentation is another form of asexual reproduction in plants, and is very similar to vegetative reproduction. This is when an organism is broken into 2 or more pieces, and each one grows into a new individual. For this type of reproduction the plant must have good powers of regeneration. This could be a disadvantage if the plant is in poor conditions, as it wouldn't have good powers of regeneration, and so it wouldn't be able to reproduce. On the positive side, it can produce many new individuals very quickly

8. Binary Fission • A method of asexual reproduction that is employed by most prokaryotes. In binary fission, the living cell divides into two equal, or nearly equal, parts. It begins when the DNA of the cell is replicated. Each circular strand of DNA then attaches to the plasma membrane. The cell elongates, causing the two chromosomes to separate. The plasma membrane then invaginates (grows inward) and splits the cell into two daughter cells through a process called cytokinesis.

10. Vegetative Propagation It is a process where a plant can reproduce asexually, with the use of a vegetative part of the original plant. This process can occur naturally. It can also be done manually, and is especially beneficial when one wants to create new plants from fruit or vegetable parent plant. Vegetative propagation techniques have been used with varying degrees of success, in attempts to help developing countries produce larger sources of food for the population.

11. We all are accustomed with growing new plants from seeds. No doubt, seeds are one of the most versatile means for producing new plants. However, the major drawback of seed propagation is that some species of plants either do not produce seeds or majority of the seeds are not viable. In such cases, vegetative propagation becomes very important.S

12. Advantages of Vegetative Propagation • The offspring produced are generally identical, and hence, the more beneficial characteristics can be preserved. • In this gardening process only one parent is required, unlike sexual reproduction methods like pollination. • Vegetable propagation is faster. For e.g., the bacteria can multiply every 20 minutes, which helps the organism to increase their number at a faster pace, in cases where the number of species are depleted due to certain reasons, like diseases.

13. Many plants produced are able to suffice during unfavorable conditions. This is due to the presence of organs which help in asexual reproduction like bulbs and tubers. • This process of propagation is especially beneficial to horticulturists and agriculturists, as they can raise various fruits and vegetable plants without requiring to buy seeds. • With modern techniques of tissue culture combined, one can grow virus free plants.

14. Cutting Method Of Vegetative Propagation • Propagating plants from cuttings method is also called as striking or cloning, in which a piece of plant containing at least one stem cell is placed on suitable medium like soil, potting mix or rock wool. This cutting helps to produce new roots, stems or both, and develops into a new plant.

15. Stem Cutting • Stem cuttings can be taken from the main stem or the side branches of the plant. Different types of stem cuttings are: • Herbaceous Cutting - Houseplants like chrysanthemum, rhododendron and geranium are propagated by herbaceous cutting. For this type, rooting is easy and the growth phase has nothing to do with root formation. So, you can make stem cuttings at any time, when the plant is growing actively. More on ways for propagating rhododendron. • Softwood Cutting - This cutting is made from the new stem growth of the current season and is easy to promote rooting. Deciduous shrubs like lilac, plum, rose and forsythia are propagated by softwood cuttings.

17. Semi-Hardwood Cutting - Broad-leaved evergreens like azalea, camellia, olive, citrus and holly are propagated by semi-hardwood cutting. This method refers to cutting made from the stem growth of the current season, when the stem is not completely mature or hard. • Hardwood Cutting - Over here, the hard stem of the previous year is used for propagation. Hardwood cutting is taken at a specific time of the year, particularly during winter when the plant is inactive or dormant. Deciduous and narrow-leaved evergreens like privet, honeysuckle, quince, grape, cypress etc. are propagated by the hardwood cutting method.

18. Leaf Cuttings • Leaf cuttings can be made anytime from the plant. A healthy and disease free leaf is cut smoothly from the plant, which is then used for generating a new plant. Unlike stem cuttings that require only rooting, both shoot development and root formation are necessary in case of leaf cuttings. Not all plants can be propagated by means of leaf cutting. Rather we can say propagation by leaf cutting is successful for a few plants like houseleek, rex begonia and sansevieria.

19. Root Cutting • Plant propagation by root cuttings is also limited to a few species of herbaceous plants, shrubs and bushes and trees. Examples of plants that can be propagated by this method include raspberry, blueberry, globe thistle and acanthus. First, healthy roots of specific size (approximately the diameter of a pencil) are exposed and cut in sections of about 1 ½ - 3 inch in length. In order to avoid confusion while placing the root cutting in growth medium, the first top cutting should be made flat and the bottom cutting should be diagonal.

20. Micropropagation/Tissue Culture • This method is practiced to multiply a stock plant at a rapid rate, to produce a large number of progeny plants using the modern plant culture methods. Plant tissue culture encompasses culturing of plant parts on an artificial medium. The plant parts can be a single cell, tissue or an organ. It is also referred to as micropropagation. Plant tissue culture was practically implemented for the first time by Haberlandt, a German scientist, in 1902. Later in 1934, Gautheret found successful results on in-vitro culture of plants.

21. The basic key used in plant tissue culture is the totipotency of plant cells, meaning that each plant cell has the potential to regenerate into a complete plant. With this characteristic, plant tissue culture is used to produce genetically identical plants (clones) in the absence of fertilization, pollination or seeds. In plant tissue culture, plants or explants such as pieces of leave, stem or root is cultured in a specific plant medium, which contains essential plant nutrients and hormones. Other plant growth factors like light and temperature are maintained and regulated by using artificial conditions. All the procedures of plant tissue culture are conducted under sterile (aseptic) conditions. The explants then develop stem, roots and leaves. The generated plantlets are hardened before planting in outdoor conditions.

22. Genetic Consequences of Asexual Reproduction • A consequence of asexual reproduction, which may have both benefits and costs, is that offspring are typically genetically similar to their parent, with as broad a range as that individual receives from one parent. • The lack of genetic recombination results in fewer genetic alternatives than with sexual reproduction.

23. Genetic Consequences of Asexual Reproduction Cont`d • Many forms of asexual reproduction, for example budding or fragmentation, produce an exact replica of the parent. This genetic similarity may be beneficial if the genotype is well-suited to a stable environment, but disadvantageous if the environment is changing.

24. Genetic Consequences of Asexual Reproduction Cont`d • For example, if a new predator or pathogen appears and a genotype is particularly defenseless against it, an asexual lineage is more likely to be completely wiped out by it. In contrast, a lineage that reproduces sexually has a higher probability of having more members survive due to the genetic recombination that produces a novel genotype in each individual.

25. Genetic Consequences of Asexual Reproduction Cont`d • Similar arguments apply to changes in the physical environment. From an evolutionary standpoint, one could thus argue that asexual reproduction is inferior because it stifles the potential for change. However, there is also a significantly reduced chance of mutation or other complications that can result from the mixing of genes.

26. Videos of Asexual Reproduction • http://www.youtube.com/watch?v=tWfgpHKP0_4&feature=related • http://www.youtube.com/watch?v=9moBpphvzOI&feature=related • http://www.youtube.com/watch?v=drcnTg7ZCoc

32. Questions & Answers • Question:   What is asexual reproduction?

33. Answer:    Asexual reproduction involves only one parent and the offspring is genetically similar to the parent.

34. Question:   Name the types of reproduction that produces genetically identical offspring?

35. Answer:    Asexual reproduction is the type of reproduction that produces genetically identical offspring.

36. Question:   What are the different types of asexual reproduction?

37. Answer:    The different types of asexual reproduction are binary fission, budding, fragmentation, spore formation and vegetative propagation.

38. Question:   What is binary fission?

39. Answer:    When the parent cell divides into two cells that are almost identical, it is called binary fission.

41. Which diagram above represents binary fission?