Transcript Chapter 2 part 3

Chapter 2.3
How Cells Reproduce
Cell Reproduction
 All
organisms, including you, begin
life as a single cell.
 One
cell divides into two cells, those
two cells divide into two cells.
 This
is how you have grown to your
present size.
Stretch Your Mind
 Starting
from one cell, how many
hours do you think it would take if a
cell divides every hour to make one
million cells?
 Estimate,
 Then calculate!
Regeneration
 Many
living things are able to grow
new body parts to replace damaged
or missing parts.
 This
ability to replace body parts is
called regeneration.
 Can
we regenerate?
Human Regeneration
 We
cannot grow a new arm or leg,
but when we scrape our skin or
break a bone, our bodies regenerate
the skin or bone to heal ourselves.
 The cells in your skin wear out
quickly and only live for days or
weeks.
 The nerve cells can last a lifetime.
Examples
 Lizards
can grow a new tail
 Lobsters, newts, tadpoles, and
insects can grow new legs.
 Deer shed antlers each year and regrow them.
 Plants can re-grow their roots.
Mitosis
 How
 You
does one cell become two?
must observe the nucleus of the
cell.
 Some will not look like dark circles
anymore but will have threadlike
objects.
 These are called chromosomes.
They only become visible when a cell
is about to divide.
Mitosis
 Chromosomes
contain the cell’s
genetic material, or DNA. DNA
contains the instructions for new
cells to have the characteristics of
the parents.
 Mitosis is the process of when
genetic material duplicates and
divides into two identical sets of
chromosomes.
 The two new cells are called
Daughter cells.
How rapidly do cells divide?
 Different
cells divide a different
 Bacterial
cells divide once every 20
rates.
minutes.
 Frog Embryos divide in about an
hour.
 Liver cells divide only once every 200
days.
Cells and Cancer
 Cancer
cells divide at a far greater
rate than normal cells and they
spread to other parts of the body.
 “Mitosis gone Wild”
 Cancer can be caused by the
environment or personal habits.
 Treatments are most successful in
early detection.
Review
 What
are chromosomes?
 What is mitosis?
 Give an example of regeneration?
 Why do cells of a multicellular
organism continue to reproduce even
after the organism is fully grown?
Review
 How
is a daughter cell like the
original cell from which it formed?
 How can you tell from a cell’s
appearance alone whether the cell is
undergoing mitosis?
 APPLY: What evidence do you have
that some cells in your body are
dividing?