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Cell Division!3.1: Cell division occurs in all organisms
Do Now!! What happens when you get cut? Explain in your own words what
happens when you are cut and the healing process.
Objectives To identify various reasons for cell
division To define chromosomes and identify
their importance To relate surface area : volume ratio to
reasons for cell division
Cellular Division Cell division occurs in all
organisms: Performs different functions
Unicellular organisms (ex: bacteria):Binary fission: division into 2
identical cells (clone)
Multicellular organisms (ex: US!):Mitosis
Binary fission
Mitosis
Cellular division videos Binary fission:
https://www.youtube.com/watch?v=Th4v_Q1iHfY
Mitosis: https://www.youtube.com/watch?v=
AhgRhXl7w_g
Cell division is involved in growth, development and repair
1. All organisms start as a single cell:a) Growth: limited by surface area (needs high
ratio of surface area to volume)
b) Cells are limited in size: Nutrients in and wastes out through membrane If cell grows too big, not enough material can cross
membrane fast enough So the cell divides!
Worksheet!!
Do Now!! What is the surface area to volume ratio of a
cube with a 3 cm length? Would this be ideal for the cell? Explain why
or why not.
Objectives To discuss how cell division is involved
with development and repair. To identify the steps of mitosis.
Cell division is involved in growth, development and repair (cont.)
c) Development:o Makes specialized cells- cells
modified for particular functions
o Ex: blood cell, nerve cells, muscle cells
Cell division is involved in growth, development and repair (cont.)
d) Repair:o Heals cuts and any woundso Cells divide and fill up space to close the
woundo As cells age and die, they need to be replaced.
DNA – DeoxyriboNucleic Acid
A chemical that contains information for an organism’s growth and functions: Has directions for how
to make proteins!
Double helix like a twisted ladder
Eukaryotes: located in nucleus
Chromosome Structure DNA coils around histones (proteins) to form
nucleosomes This coils to form chromatin fibers The chromatin fibers supercoil to form chromosomes
that are visible in the metaphase stage of mitosis.
We have 46 total chromosomes= 23 pairs
Question Even when you are done growing and
development appears to stop, is cell division still occurring?
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