plant reproduction --topic 4

reproduction defintion

process by which new individuals of the species is being made

reproduction is necessary for

continuity of species

simplest form of reproduction

binary fusion in yeast and bacteria (asexual)

asexual reproduction defintion

only requires one parent and no gametes are involved (eg, veggie reproduction / budding)

types of asexual reproduction

1. binary fission

2. budding

3. spore formation

4. fragmentation

5. regeneration

6. vegetative reproduction

binary fission

a single parent cell divides into two daughter cells (amoeba / bacteria)

budding

parent cell produces bud , it gets detached and develops into new individual (yeast/hydra)

spore formation

reproduces by forming spores , under favourable conditions spores develop into new individuals (fern, fungi)

fragmentation

organism with filamentous body , break into 2 or more fragments . each fragment grows into a new individual

regernation

organisms body breaks up into one or several parts. each part develops into new individual (eg. hydra, planarian )

vegetative reproduction

organisms produce new individuals by a vegetative part of the plant (potato/onion)

artificial vegetative propagation (involve in asexual reproduction)

1. cutting

2. layering

3. grafting

4. tissue culture

cutting

a part of the stem is cut and the cut end grows into new plants when placed in moist soil (rose/guava/mango)

layering

the stem of a plant is bent down until it touches the soil. the stem is then cut once it develops roots and grows into a new plant (rose/jasmine)

grafting

stem of a plant is cut and then fitted on another strong plant and covered with grafting wax (apples/oranges)

tissue culture

a collection of techniques used to maintain or grow plant cells, tissues or organs under sterile conditions on a nutrient culture medium of known composition (highest success rate , one tissue=many plants)

asexual reproduction advantages

1. involves a single parent organism + no gametes (easier)

2. all characteristics are passed on to offspring

3. genetically identical offspring produced

4. many organisms reproduce asexually ( not mammals) when conditions are favourable (eg: food / water sufficient supply)

5. able to colonise favourable environments quickly since large number of offsprings are produced

asexual reproduction disadvantages

1. lack of genetic variation (may not have genes to survive the change )and can be affected adversely by sudden changes in environment (eg: drought/diseases)

sexual reproduction definition

involves the fusion of two gametes to form a zygote during fertilisation

sexual reproduction characteristics

1. requires two organisms of the same species , one male one female

2. gametes are produced in meiosis (cell division )

3. offspring receives combination of genes from parents

4. each offspring is genetically different from parents

sexual reproduction advantages

1. offspring are genetically different from parents , able to adapt to new environments , increase survival chance of a species

sexual reproduction disadvantages

1. two parents are needed and thus require more time (slower)

2. genetically varied offspring may not always have the desired combination of genes and thus not always favourable in commercial crop production