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