Cell Division, Asexual and Sexual Reproduction: Key Differences

Plant Cell

Plant cells have centrioles but not centrosomes. They are organizers of microtubules and in organisms they take their first area near the nucleus at the start of mitosis. They use achromatic spindle fibers that align the chromosomes, and the first plate-forming fibers appear later in the cell. Plant cells have a rigid cell wall, so the plasma membrane is not pinched in a "strangulation" the way animal cells are.

Animal Cell

Animal cells have centrioles that act as spindle organizers at the end of cell duplication, and they disappear. The plasma membrane forms a cleavage furrow (the "equatorial groove") along which the cell is divided, forming two cells, each identical to the original.

Asexual Reproduction

In asexual reproduction, the new individual comes from a fragment of a progenitor or from a single cell, without sexual processes.

Features

• It is carried out very rapidly and produces large numbers of descendants. This makes the probability of morphological variability increase.
• Only one parent is required; gametes and mating partners are not necessary.
• It does not involve differentiated cells.
• It is a form of cloning, that is, new individuals are disperse-able in any geographical location.

Disadvantages

• Organisms are simpler and less differentiated.
• Minor protection and little variability in the gene pool of descendants.
• There is no recombination of hereditary characters, so all new individuals are similar to each other and to the original.

Types

• Vegetative reproduction
• Binary fission (bacteria)
• Budding (yeast)
• Multiple division (sporozoans)
• Fragmentation in animals: longitudinal and transverse
• Strobilation (medusae)
• Plants: rhizomes (potato) and runners (polyembryony)

Sexual Reproduction

In sexual reproduction, the new individual is the result of the fusion of specialized cells, or gametes, formed through a special process of cell division (meiosis).

Features

• Exchange of genetic material occurs when reproduction is accompanied by sexuality.
• In most viviparous animals, zygotes are protected by the formation and development within the mother's body.
• The body of a constant size ensures renewal of gene combinations, which are inherited.
• Heritage from the merger of genetic material from two progenitors produces recombination of genes, causing great variability.
• It contributes to the evolution of species and their adaptation to the environment.

Disadvantages

• Reproduction is very slow.
• Fewer adult descendants are produced.
• Lower ease of dispersal.
• High energy cost.
• Competition among members of a population.