Do Now• How can you visually distinguish between newly formed
cells and older cells?
REGULATING THE CELL CYCLE 5.3
Apoptosis • Means “a falling off”• Programmed cell death. • What causes it?
• When internal or external signals activate genes that help produce self destructing enzymes.
• Nucleus shrinks and breaks apart. Immune cells recognize this and “gobble up” the cell and recycle its parts.
• Fun Fact- Blood cells only live about 120 days, Colon cells only 4 days, Skin cells 2-3 weeks!
Apoptosis During Embryo Development• Example:
• A human embryo has webbed fingers/toes. The cells between the digits undergo apoptosis during later development resulting in a baby born with unwebbed fingers/toes
Uncontrolled Division• Cancer cells continue to divide and form tumors
• Benign - cells remain clustered in one area and are often easier to remove
• Malignant- some cells break away and spread through the body via bloodstream
• Tumors - cause harm because the cells in that area don’t do their specialized function
5.4 - Asexual Reproduction• Creating of identical offspring from a single parent
• Most prokaryotes reproduce through Binary fission• Very similar to mitosis• Both form two identical daughter cells BUT prokaryotes
have no nucleus and have much less DNA which forms a circular shape, not several chromosomes.
Asexual Eukaryotes• Flatworms and sea stars = fragmentation
• Many plants can reproduce asexually through stems or underground structures that are connected to the original plant (runners)
• Some organisms reproduce sexually and asexually!• Sea anemones bud or break off small pieces
asexually and also make eggs/sperm
Pros and Cons of Asexual Reproduction• Pros:
• More efficient if the environment stays the same• Doesn’t require finding a mate! Less time and energy
• Cons:• No diversity • Could all be wiped out if susceptible to a disease or environmental
condition
• https://www.youtube.com/watch?v=jk2RJm5RBEk• https://www.youtube.com/watch?v=z7I0mw4ZDJA• https://www.youtube.com/watch?v=G41EANkcMvg
• http://www.scientificamerican.com/article/asexual-lizards/
5.4 Multicellular Life• Cells -> tissues -> organs -> organ systems -> organisms
Cell differentiation• Process by which unspecialized cells develop into their
mature forms/functions • Almost each cell in your body has a full set of DNA but
only uses specific genes needed to carry out its job
Examples of Differentiated cells• Skin cells - help prevent infection and dehydration• Bone cells- for a hard matrixes that support and protect
organs• Intestinal cells- have large surface area to increase
absorption of nutrients
Stem Cells• Divide and renew themselves • Remain undifferentiated• Develop into a variety of specialized cell types• When it divides it either forms 2 stem cells or one stem
cell and one specialized cell
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