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?