Part 1:
Asexual vs. Sexual Reproduction
I. Asexual Reproduction
 Form of reproduction where only one parent is
involved.
 Also reproduction without the fusion of gametes
(sperm and egg)
 Primary form of reproduction for single-celled
organisms such the bacteria, and protists. Many
plants, fungi, and even some animals reproduce
asexually as well.
II. Types of Asexual
Reproduction:
1. Binary Fission: used by bacteria
2. Fragmentation/Regeneration: used by organisms such
as Fungi, Moss, Sea Stars, Planaria
3. Budding: used by organisms such as yeast and hydra
Binary Fission
 Asexual
 Cell splits and replicated
DNA goes with each part
 Prokaryotes, Bacteria
 + Fast and easy
 - Everybody has the same
DNA
Fragmentation/ regeneration
 Asexual
 Body of parent
breaks and
produces offspring
 Fungi, moss, sea
stars, planarian
 + Easy
 - Parent broken,
same DNA
Fragmentation/
regeneration
Moss
Budding
 Asexual
 Offspring grows out
of parent
 Yeast, hydras
 + Fast, somewhat
easy
 - Same DNA
III. Asexual Advantages
1. Need one individual to reproduce; can
conserve energy
2. No genetic change “good” if environment
is stable
3. All individuals are producing offspring
4. More efficient passing genes, “faster”
IV. Asexual Disadvantages
1. No recombination of genes
2. An asexual population tends to be
genetically static
 Mutant alleles
 Beneficial alleles
V. Sexual Reproduction:
A. Processes that pass a combination of
genetic material to offspring, resulting in
diversity.
B. The main two processes are:
 meiosis (involving the halving of the number
of chromosomes)
 fertilization (involving the fusion of two
gametes and the restoration of the original
number of chromosomes.
VI. Advantages of Sexual
Reproduction
1. Offspring are genetically unique from:
• A. Crossing over
• B. Independent assortment
• C. Random fusion of gametes
2. Favorable when the environment is not stable
3. Slower rate of reproduction but faster adaptation/evolution
4. Lower extinction rates
5. Fast removal of bad mutations or can put two beneficial
mutations together
6. Better adaptation to host-parasite arms race.
7. Offspring are dispersed widely to end
up in different places from their parents
VII. Disadvantages of
Sexual Reproduction
1. Need two parents “must expend energy” to
find, identify (court), and copulate with
mate
2. Genetic recombination is counter productive
if conditions are stable
Part 2
Mitosis
Why Cell Division?
A. Necessary for the growth of organisms.
B.
Necessary for every cell in organism to have the genetic
instructions to survive.
C.
Genetic instructions passed through DNA in
chromosomes.
The Cell Cycle:
A. Cell division occurs during the cell cycle
B. It is the repeating set of events that make up the
life cycle of a cell.
C. Divided into two phases:
1.
2.
Interphase: time between cell divisions
Cell Division: consists of two stages
a. Mitosis: division of nucleus.
b. Cytokinesis: division of cytoplasm of the
cell.
Stages of Interphase:
1. G1 Phase: cell growth.
2. S Phase: DNA replication.
3. G2 Phase: growth and prep
***G0 Phase: used by some cells to exit cell cycle
Stages of Cell Division in Eukaryotes:
1) Prophase
2) Metaphase
3) Anaphase
4) Telophase
Events of Prophase:
1) DNA coils into
chromosomes.
2) Nucleolus
disappears; nuclear
membrane
disappear.
3) Centrioles appear
and migrate to
opposite sides of
cell.
4) Spindle fibers form
Events of Metaphase:
1) Chromosomes
migrate to the
center of the
dividing cell. Held
in place by the
spindle fibers.
Events of Anaphase:
1) Sister Chromatids pulled
apart by fibers.
2) Chromatids pulled toward
centrioles.
3) Now have individual
chromosomes at opposite
ends of cell.
Events of Telophase and Cytokinesis:
1)
Spindle fibers disassemble.
2)
Nuclear membranes form
around chromosomes at each
end.
3)
Chromosomes uncoil.
4)
Nucleolus forms in each new
nucleus.
5)
CYTOKINESIS occurs.
6)
Cell membrane pinches inward
(forms cleavage furrow) until
two cells form.
Stages of Cell Division in Prokaryotes:
A. Process called Binary Fission.
1.
Chromosome makes copy of itself.
2. Cell grows until it is twice its normal size.
3.
Cell wall forms between two chromosomes, and splits
into two new cells.
Multicellular Organization:
Levels of Organization:
1)
Tissue: groups of CELLS carrying out specific function
(EX. epithelial).
2)
Organ: groups of TISSUES performing specific function
(EX. stomach).
3)
Organ system: group of ORGANS performing
specific function (EX. digestive system).
*** SEE FIGURE 4-18 (p. 88)
I. Meiosis:
A. Meiosis is a reduction division, which means dividing
cells begin as diploid (2n) and divide by mitosis into
four haploid (1n) cells.
B. Meiosis involves two mitosis divisions.
C. The first cell division is called Meiosis I and the
second cell division is called Meiosis II.
D. Cells preparing for meiosis first undergo G1, S, and
G2 phases of Interphase.
II. Steps of Meiosis I:
1)
Prophase I: Same as prophase in mitosis, but Synapsis
(the pairing of tetrads- does not occur in mitosis) and
CROSSING-OVER occurs (does not occur in mitosis).
2) Metaphase I: Tetrads line up randomly along the equator
of the cell.
3) Anaphase I: Each homologous chromosome moves to
opposite pole of cell (called Independent Assortment).
4) Telophase I: Chromosomes reach opposite sides of cell,
cytokinesis begin. Result is two new cells that contain a
haploid number of chromosomes.
III. Steps of Meiosis II:
1)
Prophase II: Spindle fibers form in each cell from
Meiosis I.
2) Metaphase II: Chromosomes move to the equator of the
daughter cells.
3) Anaphase II: Chromatids separate and move towards
the poles of the cell.
4) Telophase II: Nuclear membrane and nucleolus
reappears in each of four new cells; each cell contains
half of the original cell’s number of chromosomes.