Asexual Reproduction Flashcards
Binary Fission
Occurs in prokaryotes (bacteria). Each cell splits into two daughter cells which are identical to the parent cell.
Process of Binary Fission
- Bacterial cells absorb food and grow larger, once it has reached a certain size it begins to divide
- The circular DNA replicates and the 2 new chromosomes separate.
- Two new cell membranes form down the middle of the cell.
- Cell wall material forms between the new membranes and then the two new cells split apart.
Budding
The new organism is produced as an outgrowth or bud of the parent which is later released as an independent clone of the parent.
Process of Budding (in yeast)
1.At a certain size the yeast cell’s DNA replicates then the nucleus divides by mitosis
2. A small swelling appears at the side of the yeast cell called a bud.
4. One of the daughter nuclei enters the bud and after a while the bud breaks off as a new identical cell.
NB yeast cells do not divide equally in half
Fragmentation (in filamentous algae)
A single chain of cells grows in length. Any cell in the chain can enlarge, and divide by mitosis to form 2 new identical cells and make the chain longer.
Spore Formation (in fungi)
Fungi exhaust their food supplies very quickly, so they need to produce spores (which are identical) to colonies new sources.
Spore Formation (process)
- Portions of the fungi known as Sporangiophores grow up into the air and the tip of each swells up to form a sporangium.
- Haploid nuclei move from the hyphae(body structure of the fungi) move into the sporangium and divide by mitosis.
- The sporangium is separated from the rest of the hyphae by the columella
- Cytoplasm and a cell wall forms around groups of several nuclei to form a spore.
Asexual reproduction in plants
Producing new individual plants by modification of vegetative growth rather than reproduction involving flowers. A bud grows and develops from the parent plant and at some stage becomes detached and starts to lead an independent existence.
Ginger
They have a swollen horizontal stem known as a rhizome. Leaves also grow from buds on the rhizome. These buds have meristematic tissue which grows to provide branches on the rhizome. The rhizome system can therefore spread through the soil and cover much ground. Eventually, it will fragment into several separate plants.
Asexual reproduction
The production of new organisms from a single organism without the fusion of gametes. The new offspring is a clone of its parent. Limited variation may arise as a result of mutation.
Meristems
Consists of undifferentiated cells that divide by mitosis.
Auxin
Found within the shoot tip(apex) of the plant. Stimulates growth/cell elongation by softening cell walls so they stretch when the cell absorbs water. Helps plants to grow towards the light.
Cytokinin
Found in the root tip. It stimulates cell division. Used in tissue culture to stimulate cell division.
Gibberellin
Found in roots and young love. Stimulates cell elongation and growth
Cuttings
Part of the plant is removed by cutting and placed in a suitable medium for growth. It produces adventitious roots and grows into a new plant. Rooting cam be stimulated with a special rooting hormone such as NAA.
a leaf at the point where it meets the stem
across the root
across a side shoot
