Download
asexual reproduction n.
Skip this Video
Loading SlideShow in 5 Seconds..
Asexual Reproduction PowerPoint Presentation
Download Presentation
Asexual Reproduction

Asexual Reproduction

544 Views Download Presentation
Download Presentation

Asexual Reproduction

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Asexual Reproduction

  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.

  3. ASEXUAL REPRODUCTION SEXUAL REPRODUCTION involves one parent only. Parent cell splits into two to produce new cells (MITOSIS). Offspring therefore identical to the parent (CLONE). Results in a lack of variation and diversity between parent and offspring and among offspring. Gametes and fertilization are NOT required. Involves two parents (male and female). Two sex cells (gametes) made by MEIOSIS fuse to form the offspring. Offspring therefore has characteristics from both parents but are not identical to the parents or one another. Results in variation and diversity between parent and offspring and among offspring. Gametes and fertilization ARE required.

  4. What is asexual reproduction? 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

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

  6. 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

  7. 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.

  8. 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.

  9. Vegetative Reproduction 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.

  10. POTATO

  11. ASEXUAL: NATURAL VEGETATIVE PROPAGATION Occurs when new plants are formed from the outgrowths of old ones. Examples are: Runners where the stems run horizontally from a plant and new plants form at nodes (strawberry, pumpkin). Bulbs are underground buds and new buds grow from the parent one (onion). Plantlets are tiny plants that grow along the margins of certain leaves. Eventually the plantlets fall off and develop into new plants (the Leaf of Life).

  12. RUNNERS

  13. BULBS

  14. PLANTLETS

  15. ASEXUAL REPRODUCTION: ARTIFICIALVEGETATIVE PROPAGATION Gardeners and farmers often use artificial means when they want to propagate more of a plant that is of good quality because the offspring will be identical to parent. These methods include: Cuttings Grafting

  16. ASEXUAL REPRODUCTION: ARTIFICIAL VEGETATIVE PROPAGATION Gardeners and farmers often use artificial means when they want to propagate more of a plant that is of good quality because the offspring will be identical to parent. These methods include: Cuttings Grafting

  17. PROPAGATION BY CUTTINGS Parts of a plant are cut off and given suitable conditions so developing their own roots and shoot and become a new plant. Examples are sugarcane, yam and hibiscus.

  18. PROPAGATION BY GRAFTING A shoot (the scion) from a young plant bearing fruits or flowers is attached to the stem of an already established root system (the stock). The new plant that grows has beneficial characteristics of both the stock and scion e.g. mango, citrus and rose-bushes.

  19. SPORE FORMATION

  20. 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.

  21. 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

  22. 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.

  23. 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.

  24. 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.

  25. 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.

  26. Stem Cutting 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.

  27. 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.

  28. 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.

  29. 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.

  30. 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.

  31. 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.

  32. Micropropagation/Tissue Culture

  33. 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.

  34. Micropropagation/Tissue Culture

  35. 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.

  36. Micropropagation/Tissue Culture

  37. ASEXUAL REPROUCTION IN ANIMALS

  38. ASEXUAL REPRODUCTION Various types of asexual reproduction are: Binary fission (animal) Budding (animal) Fragmentation and segmentation (animal) Parthenogenesis (plant, animal) Vegetative propagation (natural, plant) Vegetative propagation (artificial, plant) Sporulation (plant, fungi)

  39. ASEXUAL: BINARY FISSION Occurs is protists such as the Amoeba and in bacterial cells. The parent cell splits into two identical daughter cells by mitosis.

  40. ASEXUAL: BUDDING Occurs in protists and fungi such as yeast. The daughter cell buds or pinches off from the parent as a smaller replica (clone) then grows to mature size.

  41. ASEXUAL: FRAGMENTATION and SEGMENTATION Occurs in flatworms (fragmentation) and ringed worms (segmentation). Parent organism breaks into different fragments or segments, which form new individuals.

  42. ASEXUAL: PARTHENOGENESIS The growth and development of an embryo or seed without fertilization by a male. Occurs naturally in some lower plants, some invertebrates (e.g. water fleas, aphids) and some vertebrates (e.g. lizards, salamanders, some fish, and even turkeys). Parthenogenetic populations are typically all-female.

  43. Fragmentation Fragmentation is another form of asexual reproduction in animals. 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 organism must have good powers of regeneration.

  44. Fragmentation

  45. Fragmentation

  46. Fragmentation 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