Sexual and Asexual
Reproduction
• Now we are going to discuss how cells
reproduce to make new cells and keep us
alive and how humans and plants make
gametes (sex cells) for sexual
reproduction.
• We will also talk about the reproductive
systems of males and females and
fertilization and development of humans.
• Then we will talk about heredity and how
our genes are expressed to make us who
we are.
Organisms can reproduce offspring in
one of two ways:
1. Asexual reproduction – requires no
fertilization, there is only one parent
- occurs mainly in bacteria, fungi, plants,
protists, lower plants and animals.
- reproduction is quick and often
produces a large number of offspring
-Several types of asexual reproduction:
binary fission, budding, spore formation,
regeneration, and vegetative propagation
2. Sexual reproduction – The production of
offspring from the union of two sex cells,
one from each parent
- the genetic makeup of the offspring is
different from that of either parent
- requires fertilization – the union of male
and female sex cells
Something to think about
Daphnia
- reproduce parthenogenetically in the spring to end of the
summer
- Young are small copies of the adult. Mature females are
able to produce a new young about every ten days under
ideal conditions.
- The reproduction process continues while the
environmental conditions are good. When winter
approaches or in drought conditions or at times of other
harsh environmental conditions, production of new
female generations cease and parthenogenic males are
produced.
- Males can fertilize the female eggs. The eggs are
protected from harsh environmental conditions until the
more favourable times, such as spring, when the
reproductive cycle is able to take place once again.
Daphnia
• We will return to sexual and asexual
reproduction after we discuss how cells
make new cells and how cells make sex
cells.