Unit 4A Homeostasis & Portfolio

Standards

HS-LS1-3: Plan and conduct an investigation to provide evidence that feedback mechanisms maintain homeostasis.

[Clarification Statement: Examples of investigations could include heart rate response to exercise, stomate response to moisture and temperature, and root development in response to water levels.]

[Assessment Boundary: Assessment does not include the cellular processes involved in the feedback mechanism.]

Objectives:

● Conduct an investigation that provides evidence of

a feedback mechanism that maintains homeostasis.

● Identify evidence that will show how feedback

mechanisms help an organism maintain homeostasis.

Homeostasis

A state of internal balance maintained by living organisms

https://youtu.be/Iz0Q9nTZCw4

Responding to Stimuli

●The external environment is in a
constant state of change, but living
things need to maintain stable internal conditions so they can perform basic bodily functions.

●All living things have systems that allow
their body to maintain homeostasis.

●These systems respond to an environmental stimuli.

●A stimulus is an action or process that causes change.

Multiple Choice

How an organism reacts to internal or external stimuli...

• geotropism

• homeostasis

• response

• photosynthesis

Multiple Choice

the body's ability to regulate its inner environment in response to changes in the outside environment is called...

• phototropism

• homeostasis

• response

• warm

My body is TOO HOT!

●For example, the human body has an internal temperature of approximately 37oC.

●This temperature is needed for the
stability of enzymes, which may catalyze
many important chemical reactions in our body.

●When the temperature in the environment rises, our skin (integumentary body system) starts to sweat

●This sweat releases excess heat, which
helps the body maintain a stable internal temperature.

My body is TOO COLD

●When it is really cold outside, the
skeletal muscles of the human body start to shiver.

●These muscles involuntarily make
small, fast, repeated contractions,
which generate heat.

●This helps heat up the body in cold
weather.

Multiple Choice

An example of an external stimulus would be...

• You want a drink of water

• You are hungry

• You feel nauseated

• You get cold when you walk outside

Multiple Choice

An example of an internal stimuli would be...

• A rabbit sees a fox is about to attack

• A rabbit is hungry

• A rabbit hears a shotgun go off

Feedback Mechanism

• Homeostasis depends on
  feedback mechanisms.

• A feedback mechanism is a
  system that responds positively or negatively to a stimulus.

Negative Feedback Mechanism

●Negative feedback mechanism
reverses the effect of the stimuli.

●For example, when the internal body
temperature gets too high, the body
triggers a negative feedback
mechanism to cool the body.

●When the internal body temperature
gets too cold, the body uses a different negative feedback mechanism to warm the body up.

Positive Feedback Mechanism

●A positive feedback mechanism is a
system that moves in the direction of a stimulus.

●For example, when the skin is cut, the
body secretes chemicals that stimulate platelets to form a clot at the wound site.

●A positive feedback mechanism
continues this clot formation until the
wound is sealed.

Multiple Choice

When you get cut, your skin cells release hormones that signal platelets to come and stop the bleeding. Platelets then release more hormones that signal even more platelets to help stop bleeding. The hormone signals continue until the cut is closed.

• Positive Feedback Response
• Negative Feedback Loop 

Multiple Choice

What is another word that can be used to describe "homeostasis"?

• STABLE
• EQUAL
• COMPLETE
• CORRECT

Examples

●Insulin is a hormone that helps
to control glucose levels in the
blood.

●The graph below compares
glucose concentration in the
blood to insulin concentration.
Use this information and what
you’ve learned about
homeostasis.

●Is insulin part of a negative or
positive feedback mechanism in the body? Why?

Example

●Diabetes is a condition in which a
person’s body does not produce
enough insulin or cannot use
insulin effectively.

●Give an example of how diabetes
can affect the natural feedback
mechanism in the body.

Multiple Choice

When glucose levels in the blood rise, your brain sends a signal to your pancreas. The pancreas releases insulin, which opens channels in cell membranes to allow glucose to enter the cell, lowering blood sugar levels. 

• Positive Feedback Response
• Negative Feedback Loop 

This graph shows a person’s air exchange
before, during, and after exercise. Use the graph and what you have learned about homeostasis to answer the question.

1.

How does the function of the respiratory system relate to this graph?

2.

How does this graph provide evidence of a feedback mechanism in the body?

3.

Based on the evidence from the graph, do you think the change in breathing rate is a positive or a negative feedback
mechanism? Explain your reasoning.

Multiple Choice

Maintaining body temperature is an example of a:

• negative feedback loop
• positive feedback loop

1.

Explain the function of the circulatory system.

2.

Explain how exercise affects your circulatory
system. How does this provide evidence of a feedback mechanism?

Multiple Choice

The process of childbirth is an example of:

• negative feedback loop
• positive feedback loop

Investigation

●Scientists can investigate feedback mechanism by changing the conditions in the environment and observing how systems respond.

●For example, when a person
exercises, their muscles need more oxygen to produce energy.

●The body needs to get rid of the
excess carbon dioxide produced by cellular respiration in the muscle
tissue

●This triggers a feedback mechanism in the body that increases the
respiration rate.

Multiple Choice

The two types of feedback systems that help organisms maintain homeostasis are:

• positive and negative 
• receptor and effector
• static and dynamic
• minor and major

Multiple Choice

Failure to maintain homeostasis could result in:

• lack of internal balance
• eventual death
• difficulty carrying on metabolism 
• all three

Scientific Method

1.

Make an observation

2.

Gather backgroundinformation

3.

Create a hypothesis

4.

Create a prediction

5.

Identify variables

6.

Perform an investigation

7.

Analyze the result

8.

Draw a conclusion

Multiple Choice

Homeostasis in the human body is often maintained by a: 

• neutral feedback loop 
• solar feedback loop
• positive feedback loop
• negative feedback loop

Variables

●

Independent - Variable that
changes

●

Dependent- Variable that is observed to determine if it changes in response to the independent variable

●

Control- stays the same

Graphing Variables

Multiple Choice

The information you collect in an experiment in order to answer a question is called

• Charts

• Graphs

• Data

• Hypotheses

Multiple Choice

This type of variable is what you DON'T change in a lab

• Control

• Independent

• Dependent

Multiple Choice

A variable that is unchanged throughout the experiment is the:

• Controlled Variable

• Experimental Variable

• Independent Variable

• Dependent Variable

Multiple Choice

The independent Variable is found on the:

• X Axis

• Y Axis

Multiple Choice

The dependent Variable is found on the:

• X Axis

• Y Axis

Multiple Choice

The independent Variable is:

• What you keep the same in the experiment

• What you change in an experiment

• What you measure in an experiment

Multiple Choice

Jack is doing an experiment to see which shoes help him run the fastest. What will his independent variable be?

• The shoes he wears

• The track he runs on

• The time of day he runs

Multiple Choice

Sally is doing an experiment to see which brand of sunscreen works best. What is not a controlled variable for this experiment?

• The time of day she is in the sun

• The amount of time she is in the sun

• The amount of sunscreen she uses.

• The brand of sunscreen.

Multiple Choice

The variable that is being tested, counted or measured and is responding to the independent variable is known as:

• Control

• Independent Variable

• Constant

• Dependent Variable

Multiple Choice

Which brand of paper towel will absorb the most liquid? What is the dependent variable?

• brand of paper towel

• amount of water absorbed

Multiple Choice

Zach wants to know if the amount of time he spends on social media has an effect on his grades. What is the independent variable?

• Time on social media

• His grades

Multiple Choice

Maddie wants to determine if the weight of the dog determines the number of puppies in a litter. What is the dependent variable?

• type of dog

• number of puppies

Multiple Choice

Beth wants to know if increasing her exercise will decrease the time it takes her to run a mile. What is the independent variable?

• Distance

• amount of exercise

Multiple Choice

Brad sets up an experiment to see how the mass of a ball affects the distance it rolls off a ramp.  Identify the independent variable.

• distance traveled by the ball

• mass of the ball

• height of the ramp

• weight of the ball

Multiple Choice

Mrs. Alber wants to see how different surfaces affect how high a tennis ball can bounce. What is the independent variable?

• the different surfaces

• how high they bounce