Homeostasis and Feedback Loops in Biology

Homeostasis

The ability to maintain a relatively stable internal state that persists despite changes in the world outside.

Response

Any behavior of a living organism that results from a stimulus or change.

Behavioral Response

A physical response related to motor neurons that may be conscious or unconscious.

Physiological Response

An unconscious response to stimuli that tends to be internal in the body.

Feedback Loop

Feedback systems that help maintain stability as internal conditions change.

Set Point

The 'normal' level in the body of a certain condition.

Stimulus

Something that causes a change in the body; results in imbalance away from normal.

Receptor / Sensor

A biological mechanism that senses a change in the body.

Control

A biological mechanism that receives information from a sensor and directs a response.

Effector

A muscle, gland, or organ that responds to a stimulus after receiving a message from the control.

Response / Effect

The action taken by the effector to return to set point.

Negative Feedback Loops

Work to oppose the original stimulus and bring back to normal.

Positive Feedback Loops

Work to enhance the original stimulus and set a new normal.

Independent Variable

Solution

Dependent Variable

Mass of Orbeez

Constants

Time for Orbeez to Sit, Amount of Solution, Number of Orbeez, Temperature of room

Hypothesis Format

IF (solution is changed somehow), THEN (mass will change in a specific way), BECAUSE (reasoning connected to scientific ideas)

Percent Change Formula

(Final - Initial / Initial) X 100

Control Solution

The solution used as a baseline for comparison in the experiment.

Distilled Water

A solution used in the experiment to observe the effects on Orbeez.

Salt Water

A solution used in the experiment to observe the effects on Orbeez.

Onion Cells

Cells observed in different solutions during the investigation.

Blood Cells

Cells observed in different solutions during the investigation.

Isotonic Solution

A solution where the concentration of solutes is equal inside and outside the cell.

Hypertonic Solution

A solution with a higher concentration of solutes compared to the cell, causing water to flow out.

Hypotonic Solution

A solution with a lower concentration of solutes compared to the cell, causing water to flow in.

Homeostasis

The process by which living organisms maintain a stable internal environment.

Membranes

Structures that separate the internal contents of a cell from its external environment.

Data Collection

The process of recording observations and measurements during the experiment.

Observations

Notes made about the appearance and behavior of cells in different solutions.

Brainstorming

The process of generating ideas and explanations based on observations.

Investigation 1

The first part of the experiment focusing on Orbeez and their mass changes.

Investigation 2

The second part of the experiment focusing on living cells in various solutions.

Experimental Procedure

The steps outlined to conduct the experiment and gather data.

Iso / Hypo / Hypertonic

(solution compared to cell)

Salt solution

(Iso/ Hypo / Hyper -tonic) compared to the cells.

Distilled water

(Iso/ Hypo / Hyper -tonic) compared to the cells.

Swelling

Occurs when cells are placed in a hypotonic solution.

Shrinking

Occurs when cells are placed in a hypertonic solution.

Secretion

Occurs to cells in an isotonic solution.

Absorption

Occurs to cells in a hypotonic solution.

Control Solution

Distilled Water (no solutes)

Mass stayed same

Indicates isotonic conditions.

Mass increased

Indicates hypotonic conditions.

Mass decreased

Indicates hypertonic conditions.

Water flows out of cell

Occurs when solute concentration is higher outside of cell.

Water flows in and out equally

Occurs when solute concentration is equal inside and outside of cell.

Water flows in cell

Occurs when solute concentration is higher inside cell.

Illustration of tonicity

Must include an image of a 'cell' and arrow showing direction of movement of water/solvent.

Evidence

What did you observe about the orbeez when they were in each solution?

Reasoning

Why would you expect to see the results you did?

CER table

Used to analyze data on the Orbeez from Investigation 1.

What I See

From our investigation.

What it Means

From our scientific discussion of solutions.