Cell Division
Cell Division
Cell Division
Sexual
Asexual Reproduction
Making of new cells by mitosis
Offspring are exact replica of parent
Only one parent
Occurs in:
Unicellular organisms as a means of
reproduction
Lower plants and animals as a means of
reproduction
Most somatic cells of multi-cellular
organisms
Asexual Reproduction
Advantages
Simple
Fast
Low energy output
Large number of offspring
Daughter cells are identical to parent
cells
Asexual Reproduction
Disadvantages
No variation among offspring
Sexual Reproduction
Making of new gametes by meiosis
Involves the combining of gametes
from 2 different parents
Gametes fuse to form a zygote
(fertilized egg)
Chromosome number in gametes is
1N to ensure constant chromosome
number on future generations.
Sexual Reproduction
Advantages
Variation among offspring
Sexual Reproduction
Disadvantages
More complicated
Must find mate
High energy cost
Fewer offspring (generally)
The Cell Cycle
The life of a eukaryotic cell is
diagramed as a cell cycle
A repeating sequence of growth and
division
5 phases
The Cell Cycle
Interphase : 3 phases
G1 Phase:
S Phase :
G2 Phase:
The Cell Cycle
Mitosis - NUCLEAR DIVISION -4
phases
Prophase:
Centrioles
Spindle fibers
Nucleolus
Nuclear membrane
The Cell Cycle
Metaphase
Fibers push chromosomes to line up
along the equator of the cell
The Cell Cycle
Anaphase
Fibers shorten and pull chromatids apart
to opposite sides of the cell.
The Cell Cycle
Telophase
Spindle fibers
Chromatids
Nuclear membrane
nucleolus
The Cell Cycle
Cytokinesis: CYTOPLASM DIVISION
Not a phase of mitosis
Cytoplasm and organelles separate
Usually begins in early anaphase
Cytoplasm pinches in
In plant cells, a new cell wall is formed
between the 2 new cells – cell plate