Females can produce offspring without a mate
since they can produce eggs that require no
Asexual reproduction occurs when food is
plentiful, while sexual reproduction is triggered
during times of environmental stress.
Advantages and disadvantages?
You are made of about 100
trillion cells and they all come
from a single fertilized egg.
Red blood cells die and are
replaced at a rate of one million
Why does a cell divide?
To replace old cells
For the organism to grow
Cells can’t keep on growing, they need to stay
small because diffusion is efficient on short
distance only. Do p. 85 in Biology 11
Time interval between nuclear divisions.
During this phase, a cell increases in mass,
roughly doubles the cytoplasmic components,
and duplicates its chromosomes.
What does DNA looks like?
Duplication of DNA
How is replication done?
Action again but with clarifications!
Mitose: Prophase http://img.sparknote
Pro-: prior to
The chromosomes condense, becoming
shorter and thicker.
The centrioles move to opposite poles of the
cell and spindle fibres start to form.
Centrioles and spindle fibres = spindle
Spindle fibres attach to the centromeres of the
The nuclear membrane starts to dissolve.
Examples of prophase
Meta- : occurring later than
Chromosomes composed of sister chromatids
move toward the equatorial plate.
Ana- : upward, backward, again
The centromeres divide and the sister
chromatids, now referred to as chromosomes,
move to opposite poles of the cell.
An image of a new lung cell stained with
fluorescent dyes undergoing mitosis, specifically
during late anaphase. The material stained green
are the mitotic spindles and the material stained
light blue are the chromosomes. The cellular
membrane is invisible during this photo.
Telo- : end
Chromosomes reach opposite poles of cell and
begin to lengthen.
Spindle fibres dissolve
And nuclear membrane forms around each
mass of chromatin.
Cytoplasm begins to divide
In an animal cell, a furrow develops, pinching
off the cell into two parts.
In plant cells, the separation is accomplished
by a cell plate that forms between the two
chromatin masses. The cell plate will develop
into a new cell wall
Did you know?
Telomeres are caps at the ends of chromosomes that
prevent the chromosomes from sticking together.
It is thought that telomeres might play a role in the age
of a cell.
Scientists have determined that telomeres are shaved
down each time a cell divides. The length of the
chromosomes of a 70-year-old human is much shorter
than that of a child.
Scientists think it is the short length of chromosomes
that is the signal to the cell that division can no longer
What do you understand?
Do p. 90 questions # 1 – 11 but not #4
Do the Instructional Master 3.2E, Number the
phases and write the names underneath.
Do the crossword puzzle
Go online to look at mitosis in onion root tips
and count the different phases to figure out the
length of the phases
Do a real onion root tips lab