aim: how do groups of cells behave when their external environment is changed? do now: how does the...
TRANSCRIPT
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 AgendaWeek #14: 3/1-3/5
TodayLab #9: Diffusion and the Onion Cell (Part I)
TuesdayLab #9: Diffusion and the Onion Cell (Part II)
WednesdayWater 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 Cell Animal Cell
Microscope Parts
eyepiece
arm
Course adjustment knob
Fine adjustment knobdiaphragm
stage
Stage clips
Low power objective lens
High 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 Power High Power
Observations
Treated with distilled water
Cell wallCell 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 water Treated 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 Power High 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 water Treated 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?