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MITOSIS & ASEXUAL REPRODUCTION
 Reproduction – NOT essential to survival of an individual,
BUT is essential to survival of the _______________
 2 Types of Reproduction
a) Asexual – only ____ parent  NO fusion of _______________ (sex cells)
b) Sexual – involves ____ parents  Fusion of gametes occurs to produce a
new individual
ASEXUAL REPRODUCTION
 Asexual reproduction is an example of ______ _______________
 Cell division has 2 parts
a) _______________ = the dividing of a _______________ to form ____
daughter nuclei (nuclear division)
 Involves separation of the hereditary material (______)
b) _______________ = the division of the _______________ into 2 parts
 _______________ = the period “_______________” cell divisions
 The ________ replicates at this time
--- The 2 identical strands of DNA are called _______________ chromatids
 The sister chromatids are held together at the _______________
MITOSIS is made up of 4 stages:
1) _______________
 Chromatin _______________ and becomes visible as distinct rods
--- These rods are called _______________
 The 2 pairs of _______________ begin to separate
--- But, the centrioles remain connected to each other by fine protein threads
called _______________ _______________ (made up of microtubules)
 The _______________ disappears
 The _______________ membrane disappears
2) _______________
 The 2 centrioles have moved toward opposite __________ (ends) of the cell
 Sister chromatids line up along the _______________ (equator) of the cell
 The microtubules of some _______________ fibers attach to the
_______________ of various sister chromatids
3) _______________
 All the _______________ divide
 The _______________ chromatids are PULLED,
by the spindle fibers, toward opposite poles
--- Each doubled chromosome is therefore split into ____ chromosomes
 Cytokinesis begins – the ______ _______________ begins to pinch inward
4) _______________
 The chromosomes uncoil & elongate, forming _______________
 Spindle fibers disappear
 A new _______________ membrane forms around each set of chromosomes
 The _______________ reappears
 Cytokinesis is complete, resulting in 2 _______________ ____________
(each of which is IDENTICAL to the original parent cell)
Cell Division in PLANTS
 Plant cells lack _______________, BUT spindle fibers do form
 Plant cells have rigid ________ ________ and therefore cannot
“pinch in half” like animal cells do
--- Instead, a ________ __________ forms
between the 2 daughter cells
 Results of Mitosis
a) The chromosome number is retained from generation to generation
--- This is due to __________________ of the DNA
b) Each daughter cell receives an exact _______________ of the chromosomes
present in the _______________ cell
 Cancer = _______________ cell division
Methods of Asexual Reproduction
1) Binary Fission – when a one-celled organism undergoes
cell division to form ____ one-celled organisms
 The 2 _______________ cells are exactly the same as the parent cell
Ex. Bacteria, protozoa, algae
Ex. Amoeba  Nucleus & cytoplasm divide _______________
2) Budding – a new individual develops as an _______________ of an older one
 The nucleus divides evenly (like in binary fission), BUT the
_______________ does not  Buds are therefore much _______________
Ex. Yeast (also reproduces sexually)
Ex. Hydra (also reproduces sexually)
3) Sporulation – ____________ = asexually-formed cells with a protective outer
covering to prevent _______________ out
Ex. Fungi, algae, protozoa
Ex. Bread mold (also reproduces sexually)
4) Regeneration = growing back of _______________ parts
 Invertebrates have more ______________________ (unspecialized) cells
than vertebrates do  They have a greater ability to regenerate
Ex. Planaria, starfish, hydra, earthworm, snails, slugs
5) __________________ __________________ (Reproduction)
 Plants have 3 major vegetative structures that can give rise
to a new plant  ROOTS, STEMS & LEAVES
 A _______________ is a sexual reproductive structure that produces seeds
 Vegetative propagation = growth of a new plant from the root, stem, or leaf
of a plant (via _______________ reproduction)
 2 Types
a) _______________ Vegetative Propagation
 Bulbs, Tubers & Runners
b) _______________ Vegetative Propagation
 Cutting & Grafting
Advantages of Vegetative Propagation
 NO _______________ (unlike with plants grown from seeds)
 ____________  It’s faster to graft than to start from a seed
 Formation of _______________ fruit
MEIOSIS & SEXUAL REPRODUCTION
MEIOSIS
 Occurs ONLY in the _______________ (sex glands) to produce
_______________ (egg & sperm)
--- Male gonads = _______________
--- Female gonads = _______________
 Known as “reduction division” because each gamete produced by meiosis
has _______________ the normal # of chromosomes
--- Therefore, in sexually reproducing organisms, meiosis followed by
__________________ maintains the _______________ number
 In HUMANS there are 46 chromosomes (called the _____ or diploid #)
--- All ____________ cells have the diploid # of chromosomes
 The haploid # (____) is found ONLY in egg & sperm cells (gametes)
 Meiosis involves ____ CELL DIVISIONS:
The following example is a cell with 6 chromosomes (3 chromosome pairs)
1. Primary sex cell of ovary or testis (2n = 6 in this case)
 Replication of each chromosome occurs  Each
chromosome is _______________ (2 chromatids)
2. The doubled chromosomes line up at the center (equator)
in _______________ _______________  Each
chromosome of a homologous pair has similar genetic
content (DNA)
 There are ____ chromatids for each type of
chromosome  This is called a _______________
 During the FIRST cell division, homologous pairs
_______________ & are pulled toward opposite poles
3. ____ cells result from the 1st division
 Each chromosome is still connected to its sister
chromatid
4. EACH cell in Step 3 undergoes a SECOND cell division
 The _______________ chromatids now separate &
move toward opposite poles
 Each of the resulting 4 cells has the
_______________ (n) number of chromosomes
MITOSIS produces cells with the normal _______________ # of chromosomes
(2n) WHILE MEIOSIS produces cells with the ______________ # (n)
 Remember, meiosis only occurs in the _______________ to produce gametes
The disadvantage of ASEXUAL reproduction is that there is _____ variation
SEXUAL reproduction, however, relies on genetic contributions from __________
parents (instead of just one)
 There is also variation in the gametes produced by each parent since
“_______________ _______________” can occur during Meiosis I
 Variation allows a population, as a whole, to __________________ to a
changing environment  What is this called???
2 Types of Sexual Reproduction
 __________________ = the _______________ of genetic material (DNA)
between 2 different _______________ types of the same species
Ex. Paramecium, spirogyra, bacteria
 __________________ = egg + sperm  _______________
--- Fertilization occurs when the _______________ of an egg & sperm fuse,
producing a zygote (= a single _______________ cell)
--- Millions of sperm are attracted to an egg, but only ____ can fertilize it
2 Types of Fertilization
a) External = gametes fuse _______________ the body of the female
 Occurs in many _______________ animals (fish, amphibians)
 Since the eggs have less chance of being fertilized, ____________
are produced
b) Internal = gametes fuse _______________ the moist reproductive
tract of the female
 Occurs in most ____________ animals (reptiles, birds , mammals)
 FEWER eggs are produced because they are well _____________
& have a greater chance of being fertilized
 Most animals have separate sexes (male & female), however…
--- ____________________ = organisms that have both _______________
& _______________
--- Usually do NOT self-fertilize
Ex. Hydra, earthworm, snails
 ____________________ = the development of an egg
_______________ fertilization by sperm
Ex. Insects (bees, wasps, ants, aphids), some lizards & snakes
The queen honeybee lays both fertilized & unfertilized eggs  The
fertilized ones become _______________ & the unfertilized ones become
______________
 ____________________ = the production of gametes (by _____________)
 ____________________ = production of sperm in the _______________
 Cytoplasmic division is _______________ & each primary sperm cell
produces ____ sperm cells, ALL of which are functional
 ____________________ = production of eggs in the _______________
 Cytoplasmic division is _______________
 Each primary egg cell produces 1 functional egg & ____
nonfunctional ____________ bodies (smaller)  Disintegrate
 Human females are born with ALL the primary egg cells they will
ever have