6.4.1: Natural clones Flashcards
What are clones?
Genetically identical organisms or cells.
What is vegetative propogation?
Reproduction from vegetative parts of a plant- usually an over-wintering organ.
What are clones produced by?
- Asexual reproduction in which the nucleus is divided by mitosis.
- Mitosis produces two identical copies of the DNA, which are then separated into two genetically identical nuclei before the cell divides to form two genetically identical cells
Why might the cells produced by mitosis not be physically or chemically identical?
They may differentiate to form two different types of cell.
Give examples of clones formed in nature.
- Any organism that reproduces asexually will produce clones of itself.
- Single-celled yeasts reproduce by budding and bacteria reproduce by binary fission.
- Both examples involve exact replication of DNA, so the cells produced are genetically identical.
What are some advantages to reproduction by cloning?
- If the conditions for growth are good for the parent, they will also be good for the offspring.
- Cloning is relatively rapid - so the population can increase quickly to take advantage of the suitable environmental conditions.
- Reproduction can be carried out, even if there is only one parent and sexual reproduction is not possible.
What are some disadvantages to reproduction by cloning?
- The offspring may become overcrowded.
- There will be no genetic diversity (except that caused by mutation during DNA replication).
- The population shows little variation.
- Selection is not possible.
- If the environment changes to be less advantageous, the whole population is susceptible.
Why are plants able to reproduce by cloning?
- Because the differentiation of many plant cells is not as complete as that in animals.
- Many parts of a plant contain cells that retain the ability to divide and differentiate into a range of types of cell.
What does natural cloning involve?
- A process called vegatative propagation.
- This is a process of reproduction through vegetative parts of the plant, rather than through specialised reproductive structures.
What are runners (or stolens) and rhizomes?
- Horizontal stems that can form roots at certain points.
- If they grow on the surface of the ground they are called runners or stolens.
- They are called rhizomes if they are underground.
How are some rhizomes adapted?
As thickened over-wintering organs from which one or more new stems will grow in the spring.
What are suckers?
- New stems that grow from the roots of a plant.
- These may be close to the base of an older stem or could be some distance away.
- In all cases, the original horizontal branch may die, leaving the new stem as a separate individual.
What are bulbs?
- An over-wintering mechanism for many perennial monocotyledonous plants.
- Bulbs consist of an underground stem from which grow a series of fleshy leaf bases.
- There is also an apical bud, which will grow into a new plant in the spring.
- Often a bulb contains more than one apical bud and each will grow into a new plant.
What are corms?
- Often mistaken for bulbs but are solid rather than fleshy like a bulb.
- A corm is an underground stem with scaly leaves and buds.
- Corms remain in the ground over winter.
- In the spring buds grow to produce one or more new plants.
- Croci and gladioli reproduce using corms.
How does the Kalanchoe plant reproduce asexually?
- Clones grow on the leaf margins.
- The immature plants drop off the leaf and take root.
