Ch 11
Asexual Reproduction
Single parent / No energy is expended trying to attract a mate a defend
mate from others.
Offspring have identical hereditary traits (genetic clones). / Mitosis
Basis for eukaryotic asexual reproduction.
Advantageous in constant environments, if all the clones are adapted to
the current environment.
One given about the environment; it will change in the future.
What is hard to predict, how will the environment change.
Sexual reproduction
• Sexual reproduction creates genetic diversity in a population
* This is important because the environment is constantly
changing, and organisms require genetic diversity to create
variability in case the environment changes
• The offspring of sexually reproducing parents are expected to vary at
the genetic level
(? ) Will all of these variations be successful in the current environment?
• Some will be well adapted, survive and successfully reproduce
Others might survive but have trouble reproducing
Some may not survive at all (and thus will not reproduce)
, Sexual reproduction
Gametes fuse to form a zygote
Zygote has recombined genes of two parents (one cell)
/Produces genetic variability
Meiosis: is basis of this genetic variability
Sexual reproduction
Sexual reproduction requires the use of gametes (sex cells)
Gametes fuse to create a zygote
In order for the offspring and the parents to have the same number of
chromosomes per cell
*Gametes must have half of the total amount of chromosomes as a
autosomal cell (autosomal cells are not gametes)
Most eukaryotes are diploid
Gametes must therefore be haploid
To create haploid daughter cells from a diploid mother cell, the cell divides
by meiosis
If gametes were created by mitosis, they would be diploid, and the offspring
would be tetraploid (4n) – that does not happen
Two haploid sex cells (gametes) fuse to form a single diploid zygote
Meiosis: Produces gametes
2
Asexual Reproduction
Single parent / No energy is expended trying to attract a mate a defend
mate from others.
Offspring have identical hereditary traits (genetic clones). / Mitosis
Basis for eukaryotic asexual reproduction.
Advantageous in constant environments, if all the clones are adapted to
the current environment.
One given about the environment; it will change in the future.
What is hard to predict, how will the environment change.
Sexual reproduction
• Sexual reproduction creates genetic diversity in a population
* This is important because the environment is constantly
changing, and organisms require genetic diversity to create
variability in case the environment changes
• The offspring of sexually reproducing parents are expected to vary at
the genetic level
(? ) Will all of these variations be successful in the current environment?
• Some will be well adapted, survive and successfully reproduce
Others might survive but have trouble reproducing
Some may not survive at all (and thus will not reproduce)
, Sexual reproduction
Gametes fuse to form a zygote
Zygote has recombined genes of two parents (one cell)
/Produces genetic variability
Meiosis: is basis of this genetic variability
Sexual reproduction
Sexual reproduction requires the use of gametes (sex cells)
Gametes fuse to create a zygote
In order for the offspring and the parents to have the same number of
chromosomes per cell
*Gametes must have half of the total amount of chromosomes as a
autosomal cell (autosomal cells are not gametes)
Most eukaryotes are diploid
Gametes must therefore be haploid
To create haploid daughter cells from a diploid mother cell, the cell divides
by meiosis
If gametes were created by mitosis, they would be diploid, and the offspring
would be tetraploid (4n) – that does not happen
Two haploid sex cells (gametes) fuse to form a single diploid zygote
Meiosis: Produces gametes
2
