Transcript Asexual Reproduction

Asexual Reproduction
Mitosis
Mitosis so far……
• Mitosis is responsible for growth and
repair
– Growth from zygote to baby
– The growth of a baby and repair (replacing
damaged or lost cell)over its lifetime also
occurs through the process of mitosis.
.
2N
2N
N
(sperm)
Division
enabling
growth of
embryo is by
MITOSIS
2NN
(Ovum)
(Zygote)
2N
Mitosis is ALSO a mechanism of
reproduction
• Reproduction means to produce and new
organism from an existing organism/s
Asexual Reproduction
What is Asexual Reproduction?
•All living things need to reproduce themselves to continue
their species; they do this sexually, asexually, or use a
combination of both
•Asexual reproduction involves individual, or part of an
individual reproducing on its own
•In asexual reproduction, the offspring are exactly the same
as its parents, that is, they have an identical genetic makeup
and are known as clones
•There are several ways organisms can reproduce asexually
• Each method uses a process called Mitosis to produce new
cells and thus new organisms
• Let review mitosis
Mitosis
•In eukaryotic cells mitosis is the process of nuclear division
by which ONE parent cell produces TWO identical daughter
cells
•Mitosis is a part of the cell Cycle of eukaryotic cells
Which of the following cells are eukaryotic?
Ecoli bacteria, tubule cell of the human kidney, a human
white blood cell, a palisade cell from the leaf of a fern, a
yeast cell, streptococcus bacterium, a cell from the leg of an
insect
1. The Cell Cycle
Mitosis
Interphase
•The Mitosis
section of the cell
cycle can also be
divided up into a
few sections, this
time into 4
sections ……………
1. The Cell Cycle
Telophase
Anaphase
Metaphase
Prophase
Mitosis
Cytokinesis
Mitosis
Chromosomes
are pulled to
the equator
Mitosis
Mitosis
Mitosis
Metaphase
Chromosomes
align at the equator
Mitosis
Early Anaphase
Chromatids pull
separate ]
Mitosis
Mid Anaphase
Single stranded
chromosomes moving to
opposite poles of the cell
Mitosis
Late Anaphase
Single stranded
chromosomes moving to
opposite poles of the cell
Mitosis
Mitosis
Telophase
Mitosis
Mitosis
Mitosis
Asexual
Reproduction
strategies in plants
Cuttings
• Parts of stems of plants are removed and
provided with good growing conditions.
• Cells simply begin to divide by mitosis and
to differentiate into other tissues like roots,
eventually producing a whole new plan
Cuttings
Example: Many plant reproduce in this way
eg. Geraniums
Horizontal Stems
• Runners: running horizontally over the
ground and from this stem whole new plants
can develop
• Rhizomes: running horizontally under the
ground and new shoots pop up and develop
into new plants.
Horizontal Stems
Runner eg. strawberry
Rhizome e.g Bracken Fern
Tubers
• Swollen end of rhizome (stem tuber). Buds,
then shoots develop which grow into a new
plant.
• swollen root (root tuber). Shoots develop
which grow into a new plant
Tubers
Potato
tubers=
stem
tubers
Dahlia
tubers=
Root
tubers
Bulbs
• Modified stem enclosed by fleshy scale like
leaves. Cells divide by Mitosis and
differentiate into shoots and roots which
develop into a new plant.
Bulbs
Spores
• Reproductive structures formed through
mitosis. These are dispersed and germinate,
developing into a new plant.
Spores
Bracken Fern
Asexual Reproduction in
Fungi
Spore Formation
•Fungi such as mushrooms
produce single cells called
spores(by mitosis) which are
released into the
environment to propagate
A cloud of spores being released
Asexual Reproduction
Fungi
•This occurs when a new
organism is formed from an
outgrowth from the original
parent
Budding
Budding
scar
•When the outgrowth is
large enough it frees itself
from the parent
•Examples include; yeast
cells and some types of
worms
Yeast cell in
the process
of budding
Asexual Reproduction
Regeneration
•Occurs when the
organism breaks into 2
or more pieces
•A whole new organism
is produced from each
piece
•Examples include;
sponges and some
types of worms
•Eg. Planarians(pictured
right)
•starfish
Fragmentation/
Regeneration
Asexual Reproduction
Budding
•a new organism grows on
another one
•new organism remains
attached as it grows
•usually separates from the
parent organism when it is
mature
Asexual Reproduction
•Protists and fungi
•One cell simply divides into
two
Examples
•Paramecium
•amoeba
Binary Fission
Asexual Reproduction
•When an individual is
produced from an
unfertilized egg
Parthenogenisis
•Examples includes bees;
the queen lays eggs that
will produce females if
fertilized and males, or
drones, if not fertilized
•This is asexual but a rare
case of offspring not being
clones of the parent.
e.g. Some
lizard species
QUEEN
DRONE
meiosis mitosis
WORKER
DRONE
QUEEN
Asexual Reproduction
Binary Fission
In Prokaryotes
Copy the following table into
your workbook
Asexual Reproduction
In comparison to sexual reproduction….
Advantages
Disadvantages
•Organism doesn’t need to invest
time and energy in a partner
•No opportunity for genetic
variation by mixing of genes
•Organism doesn’t have to travel
to propagate its species
•Little genetic change within a
species gene pool means little
chance of species improvement
and evolution
•Less chance of harmful genetic
mutation
•Less chance of anything going
wrong as it is a simpler process
•Maintains desirable traits
•Organisms can reproduce faster
•Lack of genetic change is
particularly harmful to species
when environmental condition
change and organism can’t
adapt