Characteristics of Life
What is the basic unit of all living things?
A cell
Is this an observation or inference? “The flower has five purple petals.”
Observation
What does the Q in QEP stand for?
Question
Which variable does the scientist intentionally change: independent or dependent?
Independent Variable (IV)
What do we call the conditions that scientists KEEP THE SAME during an investigation?
Constants
A person sweats when they get too hot. What characteristic of life does this demonstrate?
Maintaining homeostasis
Is this qualitative or quantitative? “The radish plant is 7.5 cm tall.”
Quantitative
What do all three letters in QEP stand for?
Question – Evidence – Process
A scientist changes the amount of water and measures plant height. What is the DV?
Plant height
What is the purpose of a control group/baseline?
It provides a baseline/comparison for the experimental condition(s).
A plant bends toward sunlight coming through a window. What characteristic of life is being demonstrated?
Responding to stimuli
A student says, “The plant probably isn't getting enough water.” Is this an observation or inference?
Inference
Which is the better scientific question: “Are plants cool?” OR “How does the amount of water affect radish plant height?”
“How does the amount of water affect radish plant height?”
Complete our memory rules: IV = ______. DV = ______.
IV = I CHANGE IT. DV = DATA I MEASURE.
A student tests different amounts of water on radish plants. Name three constants they should keep the same.
Any 3 reasonable answers: type of seed, soil, amount of soil, container, planting depth, light, temperature, measurement method, etc.
Name four characteristics of life.
Any 4: made of cells, obtain/use energy, grow/develop, reproduce, respond to stimuli, maintain homeostasis, contain genetic material, populations evolve
A student observes that a plant has three yellow leaves and is 6 cm tall. Identify one qualitative observation and one quantitative observation.
Qualitative: leaves are yellow. Quantitative: plant is 6 cm tall / has 3 leaves.
A student wants to know whether fertilizer affects plant growth. What evidence could they collect to answer the question?
Measurements of plant growth, such as plant height in centimeters.
A scientist investigates whether water temperature affects how quickly a sugar cube dissolves. Identify the IV and DV.
IV = water temperature. DV = how quickly/time it takes the sugar cube to dissolve.
What is the difference between sample size and repeated measurements?
Sample size = number of subjects/organisms. Repeated measurements = measuring the same thing multiple times during the investigation.
A seed does not appear to move or grow while it is dormant. Explain why it can still be considered living.
It still has cells/genetic material and carries out life processes; something does not have to show every characteristic at every moment to be living.
A scientist makes an inference, but new evidence does not support it. What should the scientist do, and why?
Consider revising the inference because scientific explanations should be based on the available evidence.
Create a testable scientific question using amount of sunlight and radish plant height.
“How does the amount of sunlight affect radish plant height?”
A scientist investigates whether the amount of fertilizer affects radish plant height. Write a complete IF–THEN–BECAUSE hypothesis.
Example: IF the amount of fertilizer increases, THEN radish plant height will increase, BECAUSE fertilizer provides nutrients that plants need for growth. Accept other scientifically reasonable predictions/reasoning.
Two students test fertilizer. Student A uses 1 plant per condition and measures only once. Student B uses 5 plants per condition and measures their height every 3 days. Whose investigation should provide stronger evidence, and why?
Student B. The larger sample size and repeated measurements provide more evidence and make the results less dependent on one plant or one measurement.