Cell Division
•When do cells divide?•How do cells divide?•What is Meiosis?•How do Chromosomes combine and form new chromosomes?
Cell Size
• All living organism have same size cells
• The size of the animal does not affect the size of the cell
• Mouse cell size = elephant cell size
Eukaryotic Cell Size
• Cell membrane determines cell size• Why? Allows nutrients to enter or
exit• Larger cells require a larger cell
membrane
Volume
• The amount of space occupied by a three-dimensional object or region of space, expressed in cubic units.
Ratio
• Ratio • The comparison between 2 numbers
How do you write a ratio of 4 to 8?• 4:8• 4/8• Surface Area : Volume
Bigger is Not Better
• Cells need to remain small to survive• Larger cells have a small SA : V ratio• Makes it difficult to transport
materials into or out of the cell
• Nucleus controls the cells size
Cell Division
• Cells divide when they reach their maximum size
• Cell division = one cell split and becomes
2 cells
Growth
• Cells divide to increase the size of the organism
• Differentiation: cells develop specialized shapes and functions
• Ex. Nerve cells, heart cells, intestine cells, intestine cell
• Each cell has a unique function
Repair
• Repairs tissue• Mending of skin, blood vessels, and
bone• Regeneration of old skin cells
• Regeneration: ability to replace a missing body part, like a starfish or worm
Reproduction• Asexual reproduction: one parent
produces an offspring• Offspring is genetically IDENTICAL
to parent
• Sexual Reproduction: 2 parents produce an offspring
• Offspring has a combination of genetic material
Sexual Reproduction
• Gamete = reproductive cell; sperm or egg
• Two gametes fuse to form a zygote
Gametes
zygote
Zygote
• Divides millions x • Becomes an individual• Humans, some plants, animals
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