1. Organization of Life &
Homeostasis
Ms. Day/ AP Biology

2. Multicellular Organisms
Cells in multicellular organisms often specialize (take on different shapes & functions)

3. Cell Specialization = DIFFERENTIATION

4. Cell Differentiation Do all cells look alike? NO!!!
Do all cells have the same functions?
Cell Differentiation
Process by which unspecialized cells (stem cells) develop into different cell forms and functions

5. How Do Cells Specialize Their Functions?
Cells in multicellular organisms become specialized by turning ON or OFF different genes different parts of their DNA

6. Levels of Organization
How are living things organized?
Chemical
Cells
Tissues
Organs
Systems
Organism

7. Organism Organization
Chemical
Atoms, molecules, compounds
Cell
Basic unit of living things
Tissue
Similar cells doing specific function
Organ
Similar tissues performing specific task
Organ System
Organs working together
Organism
All systems working together

8. Four Basic Types of Tissues
groups of cells similar in structure and perform common or related functions
Epithelial Tissue
Skin, lining of organs
Connective Tissue
Blood, bones, cartilage
Muscle Tissue
Smooth, striated, cardiac
Nervous Tissue
Nerves and fibers

10. What is Homeostasis? Process that occurs in ALL living things
All organ systems work together to achieve homeostasis
Definition:
The ability of an organism to maintain its internal environment despite changes to its internal or external environment

11. Negative Feedback It ensures that small changes don’t become too large
Process that activates body to RESTORE conditions to their ORIGINAL STATE
Counteract further change in the same direction
STOPS THE CHANGE!
It ensures that small changes don’t become too large
MAINTAINS HOMEOSTASIS
EX: Thermoregulation, Blood sugar levels, Blood Calcium level, O2/CO2 levels in blood

12. Positive Feedback Allows for small changes to become too large
Process that activates body to AMPLIFIES original change
CONTINUES more change in the same direction
INCREASES the change!
Allows for small changes to become too large
DOES NOT MAINTAINS HOMEOSTASIS
EX: Uterine contractions, Lactation, blood clotting

13. Homeostasis Control Systems
3 components:
Receptor
Control Center
Effector
detects a change in organism’s internal environment, such as a change in temperature
control center
Processes information it receives from receptor and directs appropriate response by the effector
Receptor
Control Center
Effector
Normal balance
Change in balance

14. Homeostasis Example: household thermostat
Receptor- Thermometer
Detects decrease in temperature
Control Center- Thermostat switches on furnace
Regulator- Furnace
Thermostat detects temperature increases over “normal”
Furnace turns off
Whole control system is called a negative feedback system

15. Sweat (liquid) turns to gas  requires HEAT
Negative Feedback
Example #1: Thermoregulation in body
What happens when you are too hot?
Sweat (liquid) turns to gas  requires HEAT
Heat comes from your body/skin  skin cools down

16. Negative Feedback Example #1: Regulating Blood Sugar (Glucose) Levels

18. Negative Feedback Example #2: Regulating Calcium Levels in Blood
Why do you need calcium?
Carries messages in body
Muscle contractions
Nervous system homeostasis
Bone/teeth formation
Helps blood clotting

19. CO2 levels rise pH of blood decreases
Negative Feedback Example #3:Regulating Oxygen and Carbon Dioxide Levels in Blood
O2 / CO2 level returns to normal
Holding breath,
CO2 levels rise pH of blood decreases
Control system forces exhale, inhale

20. Positive Feedback Example #1: Uterine Contractions
During childbirth…
Baby’s head PUSHES against sensors near opening of uterus
Oxytocin (hormone) released  stimulates uterine contractions
More contractions  more oxytocin
ONLY STOPS when pushing STOPS

21. Positive Feedback Example #2: Lactation (making milk)
Suckling by baby stimulates brain to release hormone (prolactin)
Prolactin makes milk
More suckling by offspring (baby)  more milk production

22. Positive Feedback Example #3: Blood Clotting
Damaged blood vessel stimulates release of clotting factors  Platelets build up at injured site
More chemicals released  more platelets
Platelets continue to pile up and until clot is formed
Finally, growth hormones stimulate cell division
platelets
fibrin
white blood cell
red blood cell
blood vessel
clot

23. Animation of Blood Glucose Regulation