Advantages vs. Disadvantages
Advantages in black
Disadvantages in red
Sexual Reproduction
It has the ability to create variation by mixing
the genes of different individuals
Two individuals are required
A suitable mate must be found
The entire reproduction process takes a longer
time (can be up to almost 2 year) – that’s a lot
of energy!
Thus, populations spread much less quickly
The species can therefore adapt to an
environment which (has) changes(/d)
Because of variation of genes a species will
never maintain a perfect adaptation to an
environment
A disease is less likely to wipe out a population
Asexual Reproduction
Variation can only occur by somewhat rare
random mutation
Only one individual is required to reproduce
and thus this individual can be isolated
It takes less time and energy (none) to find a
mate
It takes far less time and energy to undergo the
entire process of reproducing.
A population can very quickly spread
A species is very vulnerable to change in an
environment
A suitable (and stable) habitat can be exploited
more perfectly
A disease to which one individual is susceptible
any other individual of the same species, who
do not have a random mutation will also be
susceptible
Leading to variation
Random Assortment of chromosomes in metaphase:
When the homologous pairs of chromosomes line up along the “diameter” of the cell, the
maternal and paternal copies of each chromosome go randomly on either side of the divide.
Then when the cell splits each of the two daughter cells will have a different combination of
their grandmother’s and grandfather’s genes. And so, each of the four haploid gametes
produce will have different genes, leading to variation.
Crossing over of chromosome legs (chromatids) in metaphase:
When the chromosomes line up, because they are simply strand of DNA, it is possible that
they might become entangled and thus, when the spindle fibres begin to contract, it is
possible that a portion of the original gene will be replaced by the opposite parent’s gene,
creating a totally new gene.
Random mutations in DNA replication
When DNA is being copied it is possible that a mistake, either and omission, addition or
change to the amino acid sequence, may occur and go uncorrected producing new entirely
new genetic material.
Fertilisation
The fact that any sperm cell can attach to the egg cell to produce a zygote and no gene is
biased for or against means that we preserve existing genes and that each offspring has a
unique set of these existing genes.