AIM: How do groups of cells behave when their external environment is changed? Do Now: How does the paramecium maintain water balance in freshwater ponds? HW: None Agenda: Do Now Lab #10: Diffusion and the Onion Cell (Part I)

This Week’s Agenda Week #14: 3/1-3/5 Today Lab #9: Diffusion and the Onion Cell (Part I) Tuesday Lab #9: Diffusion and the Onion Cell (Part II) Wednesday Water Level Homeostasis in Humans: Why do we get thirsty? After school TOMORROW… Tutoring

How do SINGLE-CELLED organisms maintain water level homeostasis? 70% water 90% water

Diffusion vs. Active Transport This does NOT require energy. It is like moving DOWNHILL. Active Transport This DOES require energy. It is like moving UPHILL.

Diffusion and the Egg 70% water 100% water 50% water (50% corn syrup) 70% water

Lab #9: Diffusion and the Onion Cell Problem: How do groups of cells behave when their external environment is changed? How is water homeostasis (balance) in these cells affected by this change? Materials:

Lab #9: Diffusion and the Onion Cell Plant CellAnimal Cell

Microscope Parts eyepiece arm Course adjustment knob Fine adjustment knob diaphragm stage Stage clips Low power objective lens High power objective lens Light source Revolving nosepiece Eyepiece lens Base

Creating a Wet Mount Slide Place distilled water over onion skin 1) View first under low power (4X objective lens) - use course adjustment knob first to focus the image 2) Sketch cells under low power 3) View under high power (10X objective lens) - use only the fine adjustment knob to focus the image 4) Sketch cells under high power 5) Add salt water without lifting the coverslip. 6) Sketch cells under high power after addition of salt water Addition of salt water without lifting the cover slip

LABEL THE CELL WALL AND THE CELL MEMBRANE IN EACH OF YOUR DIAGRAMS!

AIM: How do groups of cells behave when their external environment is changed? Do Now: How does the paramecium maintain water balance in freshwater ponds? HW: p. 7 - Diffusion and the Onion Cell Agenda: Do Now Lab #10: Diffusion and the Onion Cell (Part II)

Lab #9: Diffusion and the Onion Cell Problem: How do groups of cells behave when their external environment is changed? How is water homeostasis (balance) in these cells affected by this change? Materials:

Observations Low PowerHigh Power

Observations Treated with distilled water Cell wall Cell membrane Onion cell Hypothesize: What will happen to the onion cells when you add salt water to the slide?

Creating a Wet Mount Slide Place distilled water over onion skin 1) View first under low power (4X objective lens) - use course adjustment knob first to focus the image 2) Sketch cells under low power 3) View under high power (10X objective lens) - use only the fine adjustment knob to focus the image 4) Sketch cells under high power 5) Add salt water without lifting the coverslip. 6) Sketch cells under high power after addition of salt water Addition of salt water without lifting the cover slip

LABEL THE CELL WALL AND THE CELL MEMBRANE IN EACH OF YOUR DIAGRAMS!

Observations Treated with salt water Treated with distilled water Salt CANNOT diffuse through the cell membrane, water CAN. The cell membrane of Cell A shrivels up because water diffuses OUT of the cell. (from high water concentration inside the cell to low water concentration outside the cell) Cell wall Cell membrane Cell wall Cell membrane

Diffusion and the Onion Cell Treated with distilled water Distilled Water (100% water) HIGH water concentration LOW water concentration

Diffusion and the Onion Cell Treated with salt water Salt Water (95% water) LOW water concentration “Where there is SALT, WATER will follow” HIGH water concentration

Treated with salt waterTreated with distilled water

Diffusion and the Egg 70% water 100% water 50% water (50% corn syrup) 70% water

AIM: How do humans maintain water balance (homeostasis)? Do Now: What is the difference between diffusion and active transport? HW: Diffusion and the Onion Cell worksheet Agenda: Do Now/Announcements Mini-Lesson: Diffusion and the Onion cell Case Study: Why do we get thirsty? Work collection

Observations: Low PowerHigh Power Lab #9: Diffusion and the Onion Cell Problem: How do groups of cells behave when their external environment is changed?

Observations Treated with salt water Treated with distilled water Salt CANNOT diffuse through the cell membrane, water CAN. The cell membrane of Cell A shrivels up because water diffuses OUT of the cell. Cell B swells up because water diffuses INTO the cell. Cell wall Cell membrane Cell wall Cell membrane

Diffusion and the Onion Cell Treated with distilled water Distilled Water (100% water) HIGH water concentration LOW water concentration

Diffusion and the Onion Cell Treated with salt water Salt Water (95% water) LOW water concentration “Where there is SALT, WATER will follow” HIGH water concentration

Treated with salt waterTreated with distilled water

Water balance (homeostasis) in Humans How are water levels in OUR bodies affected by our environment? How do we maintain stable water levels? NEGATIVE FEEDBACK and…which body system?

Body Systems work to maintain Homeostasis

The Excretory System Maintains water balance Eliminates waste from the body The urine maker and the body’s filter Urine storage Urine’s way out! How does this system work to maintain water balance?

Example: What happens when we eat salty foods? Water Balance in Humans

Water Concentration Homeostasis in Humans Normal water level in the blood and body cells. You eat a salty meal. Salt enters the blood. Body cells shrink as water diffuses out of the cells and enters the salty blood. Water level in the cells is too low. Brain detects higher salt levels in the blood and sends signal to the kidney. The kidney allows LESS water to enter the urine. The body retains (hangs on to) more water. Also, our brain creates a feeling of thirst, causing us to drink! Water level in the blood increases. Water flows back into the body cells. What happens when we eat salty foods?