Sexual reproduction is the fusion of two gametes to form a zygote which develops in to a new organism Taylor (1997). Its role is to provide genetic variation needed to adapt to ever-changing environment Kent (2000). Asexual reproduction on the other hand, is reproduction by a single organism without the production of gametes Taylor (1997). It provides a much better rate of return Kent (2000). Sexual and asexual reproduction is to ensure that genetic material are transmitted from one generation to the next, ensuring that specie survive Taylor (1997).
Introduction
Sexual and asexual reproductions are suited for different environmental circumstances Solomon (2004). The process whereby a male sex cell and a female sex cell combine to form the first cell of a new individual is called sexual reproduction Alters (2000). Although sexual reproduction involves the combination of sex cells, many organisms can’t reproduce in that way and so reproduce asexually Alters (2000). Asexual reproduction can occur in all five kingdoms of life Alters (2000). Sexual and asexual reproduction both have their advantageous and disadvantageous characteristics, with respect to survival of populations and species Alters (2000).
Reproduction is the production of a new generation of individuals of the same specie Taylor (1997). Ensuring that species survives over a long period of time, depends on the transmission of genetic materials from one generation to the next Taylor (1997). In asexual reproduction, DNA simply replicates generation after generation Davis (1998). Sexual reproduction requires fertilization the fusion of two gametes to form a zygote Davis (1998). The generation of a new individual by asexual reproduction is formed without the
union of gametes Alters (2000). It is a cloning process- a method of exact replication of parental organisms Alters (2000).
Asexual reproduction requires one parent, whereas sexual reproduction usually
involves two parents Fogiel (1978). The advantage of asexual organisms
producing by one self is that it requires no mating to produce off springs,
saving resources that would otherwise be put into courtship for example, Cavendish
(2010). This advantage is probably the reason why asexual reproduction is
common among sessile animals (those that cannot move about) and those that live
in dispersal populations, where the chance of finding a mate is small Cavendish
(2010). In sexual reproduction two parents is a disadvantage because time and
energy are needed to find a mate Taylor (1997). The picture above shows star
fish being reproduced asexually by fragmentation.
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Secondly, asexual reproduction produces
genetically identical off springs Taylor (1997). The numerous off springs are
genetically identical to the original parent ensures that favorable
combinations of genes are perpetuated exactly Minkoff (2000). Sexual
reproduction produces some individual with genotypes that are well adapted to
the environment, but it also produces some individuals that are less well
adapted Solomon (2004). If the organism is well adapted to its environment, the
fact that it is genetically identical may be an advantage, as successful
combination of genes are preserved Taylor (1997). In addition, asexual
reproduction has a greater chance for its off springs to disperse and spread
Taylor (1997). More generations of off springs can be produced in a small
amount of time Minkoff (2000). Those organisms reproducing asexually can
generally do so faster and with low energy cost Minkoff (2000).To prove this
fact, bacteria can divide as often as once every 20 minutes, allowing members
to build up very rapidly Taylor (1997). The picture above shows binary fission
in bacteria. In comparison to sexual reproduction, they cannot produce at a
very fast rate. Example, human beings
takes nine months to produce a young.
Sexual reproduction is
advantageous. It produces genetic
variability (variation) among organisms of the same specie Alters (2000). When
environmental conditions change, population with genetic variability can adapt
and change to suit the environment overtime Alters (2000). In comparison to
asexual reproduction, once the environment is unstable, the chance of an entire
generation of specie to die is very high Taylor (1997). This is because asexual
reproduction produce clone, as a result, if one organism is affected by the
environment then all will be affected (unless in the case that one is mutated).
Sexual reproduction brings about and
evolutionary advantage. By mixing genetic material from both parents, variation
is encouraged Cavendish (2010).
Table showing: the comparison between asexual and sexual
reproduction.
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Asexual reproduction
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Sexual reproduction
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One parent only
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Two parents
|
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No gametes are
produced
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Gametes are produced. These are
haploid and nuclei of two gamete fuse to form diploid zygote.
|
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Depends on mitosis
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Depends on meiosis
being present at some stage in life cycle to prevent chromosome doubling in
every generation
|
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Off spring is
identical to parent
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Off springs are not identical to
parents.
|
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Commonly occur in
more plants, simple animals and microorganisms
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Occurs in almost all plants and animal specie
|
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Often result in
rapid production of large numbers of off spring
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Less rapid increase in numbers
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The greatest advantage of sexual reproduction is the genetic
variation that is favored whenever future conditions are uncertain Minkoff
(2000). The alternation and fertilization and meiosis is common to all
eukaryotic organisms and constituents the sexual life cycle Davis (1998).
Reference
·
The
Gist of Genetics: Guide to learning and review. Rowland Davis et al. 1998.
·
Biology:
understanding life, Sandra alters, 2000.
·
Advanced
biology by Michael Kent (2000) .
·
Biology
7th edition, Eldra Pearl Solomon et al., 2004.
·
The
biology problem solver: Max Fogiel research and education association, 1978.
·
Anatomy
and physiology: Marshall Cavendish Corporation 2010 .
·
Biology
Today: an issue approach: Eli C. Minkoff and Pamela J. Baker. 2000 .
·
Biological
Science 2 : Systems maintenance and change D.J Taylor et al. 1997.
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