Download asexual reproduction - Farmingdale Schools

ASEXUAL REPRODUCTION
ALL CELLS COME FROM PRE-EXISTING CELLS
* when offspring are produced from a single parent, it is called asexual
reproduction
* the offspring are identical to the parent!
By cell division, one cell divides to become two. This process is used by some
organisms, such as protozoans, to reproduce. In other, multicellular organisms, this
process is used to grow in size or to replace tissues.
* when offspring are produced from two parents, it is called sexual reproduction
* the offspring is a combination of the two parents
REMEMBER CYTOLOGY--the study of cells
the nucleus ...
watch all the basics
of mitosis
... is the control center ...
... which has the genetic material ...
... which is DNA
(deoxyribonucleic acid)
* lots of DNA when it is bunched up is called a chromosome
CHROMOSOMES = LOTS OF DNA
Chromosomes are only visible during cell division (mitosis) because they coil up. It
has one 'arm' (chromatid) until it doubles...then it has two 'arms' (chromatids)
MITOTIC CELL DIVISION
ALL CELLS ARISE FROM OTHER CELLS BY CELL DIVISION. THIS PROCESS INVOLVES BOTH:
1) MITOSIS (duplication of the nucleus)
* this is an orderly series of complex changes in the nucleus
* this involves an EXACT DUPLICATION of the complete set of chromosomes
* also makes sure that these chromosomes are separated into two equal sets
* forms 2 cells identical to the first
2) CYTOPLASMIC DIVISION (cytokinesis)
* when the cytoplasm of the parent cell divides into 2 daughter cells
* also called cytokinesis
***When the process of cell division is uncontrolled, cells keep reproducing... which
another great PBS
site, this shows how
cancer (a form of
mitosis) spreads
through the body
is called CANCER***
* Mitosis happens in all cells in humans EXCEPT eggs and sperm
made for
egents biology,
this is a must
see animation/
description of
mitosis
CELL DIVISION
the process by which the nucleus of a cell divides,
producing two nuclei with the diploid (2n--2 sets of
chromosomes) number of chromosomes
watch all the basics of mitosis
I. INTERPHASE
* in between actual divisions
* the cell grows
work with cells in different phases of mitosi
* DNA exists as chromatin (a messy plate of spaghetti)
* the DNA duplicates (replicates) so now there are briefly
4 sets (4n); normally there are just 2 (2n)--one from each
parent
* the centrioles also replicate (duplicate)
II. PROPHASE
* the DNA starts to condense and form chromosomes-the two halves of the chromosome (each chromatid) are
held together at the centromere
* the nuclear membrane that keeps the DNA (now in the
form of chromosomes) in the nucleus starts to disappear
* the centrioles start to move towards different ends (or
poles) of the cell
* the spindle apparatus (looks like a cage) forms from the
framework of the cell around the centrioles (which now
are look like stars called 'asters')
a basic
interactive
animation of
mitosis
III. METAPHASE
* the spindle apparatus is fully formed and the
fantastic interactive animation of the phase
of mitosis
chromosomes attach to it at the centromere
* the chromosomes line up in the middle of the spindle
(called the metaphase plate)
IV. ANAPHASE
* the chromosomes separate at the centromere and split
apart (chromosomes move away from each other)
* the spindle fibers shorten and pull the chromosomes to
each end (aster)
V. TELOPHASE
* the chromosomes have finished moving to the different
poles (ends) of the cell
* a new nuclear membrane starts to form around each
new COMPLETE set of chromosomes
* the DNA starts to uncoil again to form chromatin
AT THIS POINT, ONLY THE NUCLEUS HAS DIVIDED
INTO 2 IDENTICAL NUCLEI...WE STILL HAVE ONLY 1
CELL!
VI. CYTOPLASMIC DIVISION
* after the reformation of the nuclear membrane, the
cytoplasm divides
* this make 2 daughter cells that are identical to the
parent, but smaller!
CLONING
* making a duplicate of an organism or one or more of its cells by artificial means
* Dolly the sheep was cloned using nuclear transfer methods (see picture)
Mitosis and
Asexual
Reproduction
outstanding
reference to what
cloning really is;
contains a few
reat click-and-play
animations
Tim and Moby
discuss cloning.
cloning, accurately
described in this
NOVA clip
clone MIMI THE
MOUSE!; shown in
school, this is a mus
see for students and
parents to show how
nuclear transfer
(cloning) is carried
out
COMING SOON...CLONING HUMANS?
MORAL IMPLICATIONS? IS THIS RIGHT?
DIFFERENCES BETWEEN PLANT AND ANIMAL CELL DIVISION
1) in animal cells, centrioles help form the spindle; centrioles are not found in plant
cells
2a) in animal cells, cytoplasmic division occurs by the cell pinching in...
2b) in plant cells, a CELL PLATE forms between each new cell, like a cell wall
TYPES OF ASEXUAL REPRODUCTION
Mitosis and Asexual
Reproduction
* carried out by unicellular organisms, many lower animals, and
many plants
* asexual reproduction IS mitosis
* offspring are identical to the parents
* the process is usually rapid and results in a large number of
offspring
* there are several types of asexual reproduction
1) binary fission
* the equal division of nuclear material and cytoplasm resulting in 2
new organisms
* basically is simple animal cell mitosis
* carried out by paramecium, ameba, bacteria, and many algae
2) budding
A) in unicellular organisms
* similar to binary fission BUT has an unequal division of
cytoplasm; offspring is smaller than the parent
B) in multicellular organisms
* a bunch of cells form a smaller organism on the original if
conditions are favorable
* the bud develops into a fully functional organism which may or
may not detach from the parent
3) sporulation
* spores are single, specialized cells that are released from the
parent and can develop into new individuals if the conditions are
right
* occurs in molds and mushrooms
4) regeneration
A) of body parts
* new tissues can be produced to replace those lost or damaged
* occurs in such animals as lobsters, crabs, and gecko lizards
B) new organisms
* when an entire new organism is produced from part of the original
organism
* occurs in seastars and planarians (a type of simple annelid)
(as long as a ray--one of the points--has some of the center piece,
it can grow into a whole new seastar!)
5) vegetative propagation
* when new plants develop from roots, stems or leaves of the
parent organism
* many different types
A) cuttings
* a new plant grows from a piece of the parent
* ex. coleus, geraniums
B) bulbs
* bulbs bud from parent plants
* can grow into new individuals
* ex. onions, tulips
C) tubers
* stem-like structures that grow underground from the parent
* can form new individual organisms if the conditions are right
* ex. potatoes
D) runners
* stem-like structures that grow above the soil from the parent
* when it reaches a favorable spot (enough light, water...) it will
grow into a new individual
* ex. strawberries, ivy
E) grafting
* special tissues--called cambium (embryonic) tissues can be
attached to a cutting of a parent plant
* ex. seedless oranges
* can artificially grow plants with different characteristics that are
desirable!