Asexual reproduction:
fission
Fission in amebas
Key words
clone
cyst
fission
mitosis
pseudopodium
Fully grown ameba
pseudopodia
Two types of fission
Fission is the splitting of a parent cell
into a number of daughter cells. In
binary fission two cells are produced.
In multiple fission many more
daughters are produced.
● The daughters produced by fission are
genetically identical to the parent, i.e.
they are clones.
●
nucleus
Multiple fission
Binary fission
Ameba
withdraws its
pseudopodia,
and its nucleus
divides by
mitosis.
Ameba
withdraws its
pseudopodia.
Ameba
secretes
a cyst wall.
Binary fission
In Amoeba proteus (ameba), binary
fission begins when the pseudopodia
(false feet) are withdrawn to make a
slightly more spherical shape.
● The nucleus divides by mitosis to
produce two identical nuclei. These
move to opposite ends of the cell.
● The ameba constricts around the
middle and forms two daughter cells.
●
Multiple fission
Daughter
nuclei separate,
and cytoplasm
constricts.
●
Ameba
divides many
times by
mitosis.
In multiple fission the ameba
withdraws its pseudopodia to form a
more spherical shape as in binary
fission but then secretes a wall around
the cell to form a cyst.
● The cyst can survive harsher
conditions than the normal ameba
cell.
● Inside the cyst the ameba divides
multiple times by mitosis to produce
many small daughter cells. These
daughters are released when the cyst
wall breaks.
Under favorable conditions the cyst
ruptures, releasing daughter amebas.
© Diagram Visual Information Ltd.
Daughter
amebas