Transcript reproduction - GLENEAGLESBIOLOGY

By Dr Adrian Mascia
(Ph.D Biology, Education. M,
2009, teacher of the year
TYPES OF REPRODUCTION
Reproduction: The creation of a new generation of single cells, single
celled organisms or multi-cellular organisms. The production of new
organisms will always begin with the division of a single cell.
A–sexual:
Reproduction without the assistance of another organism
Sexual:
Requires two organisms of the same species to combine gametes to form a
zygote
A-SEXUAL REPRODUCTION
There are several methods of A-sexual reproduction
1.
2.
3.
4.
5.
Fission
Spore formation
Budding
Fragmentation
Vegetative reproduction
A-sexual reproduction is very rapid, however does not
provide genetic diversity, this can put at species at risk
of extinction should conditions change
Fission
• Fission involves the replication of
chromosomal DNA
• Once replication occurs, the DNA strands
are attached at opposing ends of a cell
membrane, and cell division occurs (giving
rise to 2 identical cells)
• This is a very rapid process (exponential)
• E.G Amoeba
Spore Formation
• Spores are hardy, self
contained capsules containing
DNA
• Spores are generally mass
produced, and are very
effective as they will only leave
their dormant state when
conditions become suitable
(increasing chance of survial)
• E.G ferns, mosses, some
prokaryotes and protists
Budding
• Budding involves the
development of a new
organism from the out
growth of a parent
organism.
• The new organism may
detach at some point
and become a stand
alone organism
• E.G Hydra, some flat
worms, yeast cells
Fragmentation
• Some organisms such as
sponges have the ability to
fragment as well as reconstruct themselves
• A sponge can be broken
into many pieces, forming
many new organisms
• Can also reform a new
organism from fragments
Vegetative Propagation
• There are some species
of plants from which you
can regrow a clone of the
original plant by planting
cuttings
• This process also allows
for a process called
grafting, where two
different plant cuttings
(root and shoot) can be
combined to produce a
new plant
SEXUAL REPRODUCTION
• Basic process of Meiosis (two gamete
cells fusing to form a zygote)
• Creates genetic diversity (essential for the
survival of a species)
• Not as fast as A-sexual reproduction
Sexual reproduction in Uni Cellular
organisms
• Common misunderstanding that single celled organisms
reproduce only A-sexually
• If this were the case we would not see the amazing
diversity of single celled organisms
• Several protozoan have the ability to produce gametes
• Generally one gamete is larger and sedentary and one is
smaller and mobile (much like in humans)
• Paramecium does not involve gamete production, rather
an exchange of genetic material whilst lined up along
side one another. This process is called CONJUGATION