Hypothesis

Hypothesis and research are the backbone of science. A hypothesis that is well-stated, founded in truth, and that can withstand extensive and repeated research and experimentation can lead to new discoveries and breakthroughs.

A hypothesis is a steppingstone to proving a theory. It’s an idea or a proposal based on limited evidence.

The idea or proposal must be proven through facts, direct testing and evidence.

A concept or statement must be tested to be proven credible. This serves as a starting point for further investigation to prove the hypothesis by applying the scientific method

What is a hypothesis?

A hypothesis is an educated guess or a testable statement about how or why something happens in nature, based on observations and existing knowledge.

An educated guess means a prediction or idea you come up with after thinking aniut what you already know, what you’ve observed, and any research or evidence you have- instead of just guessing randomly.

Key Parts of an educated guess:

It’s informed- based on facts, observations, or prior knowledge.

it’s logical- makes sense given the evidence you have.

it’s testable- you can check if it’s right or wrong through an experiment.

Example in everyday life

• Random guess: "I think it will rain tomorrow because I just feel like it."

• Educated guess: "I think it will rain tomorrow because the sky is cloudy, the humidity is high, and the weather forecast predicts a storm." Example in biology

• Random guess: "Plants grow faster when you sing to them."

• Educated guess: "If plants get more sunlight, they will grow faster — because photosynthesis needs light, and more light could mean more food for the plant."

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THE SCIENTIFIC METHOD

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2. Direct statement examples

• A hypothesis is a clear, testable statement that predicts what you think will happen in an experiment, based on what you already know.

3. Accessible Examples of a direct statement Hypothesis in Biology a)

Plants given more sunlight will grow taller than plants with less sunlight.

b)

Sugar added to yeast will increase the amount of carbon dioxide the yeast produces.

c)

Higher water temperatures cause fish to breathe faster.

4. Biology-Specific Examples of a Hypothesis (AP Bio-level)

a)

Increasing an enzyme's temperature beyond its optimal range decreases its. activity.

b)

c)

Closing a plant's stomata reduces its rate of transpiration.

Exposure to pesticides increases survival and reproduction in beetles with natural resistance.

SCIENTIFIC METHOD

5. Difference Between a Hypothests and guarstor

Hypothesis

Based on observations, research, and prior knowledge

Can be tested with experiments

Guess

Based on no evidence or research

May not be testable

Written in a clear, specific way

Example: If soil pH decreases, then plant growth will slow down.

Often vague or random

Example: I think plants might grow differently.

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Bad Hypotheses Examples

Hypothesis

Why It's Bad

Plants like music.

Too vague - "like" isn't measurable; doesn't state what kind of music or how to measure "liking."

If the moon is full, then students get more homework.

Not biologically relevant - no biological mechanism connects moon phases and homework.

Frogs are cool animals.

Not testable — "cool" is an opinion, not a measurable scientific variable.

If you water plants, they grow.

Too obvious and overly general - doesn't specify how much water, what type of plants, or the growth measurement.

I think bacteria hate soap.

Uses casual language & opinion — "hate" is not measurable; needs precise terms like "growth rate decreases."

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Hypothesis

If bean plants receive 6 hours of sunlight per day, then they will grow taller than plants receiving 3 hours.

If the pH of a solution decreases below 6, then enzyme X activity will decrease.

If a population of bacteria is exposed to higher temperatures, then their reproduction rate will slow.

Why It's Good

Testable & measurable - specifies variable (sunlight hours and measurable outcome (height).

If Daphnia are exposed to caffeine, then their heart rate will increase.

If yeast is given more glucose, then it will produce more carbon dioxide during fermentation.

Based on prior knowledge — pH affects enzyme structure; clear variables and outcome.

Biologically relevant - linked to temperature effects on enzymes and cell processes; measurable as reproduction rate.

Specific & testable - identifies cause (caffeine) and effect (heart rate); measurable with equipment.

Grounded in biology - uses knowledge of cellular respiration; measurable by CO, output.

What Is a

Hypothesis?

• A hypothesis offers a tentative explanation to questions generated by observations and leads to one or more predictions about the way a biological system will behave.

• A hypothesis is like "stereotyping":

- For example, We know that tomatoes are fruits, that many fruits produce ethylene, and that ethylene promotes fruit ripening.

- If tomatoes produce ethylene, then placing them in a container that traps ethylene will cause the tomatoes to ripen faster.

• This process illustrates how hypotheses can guide experimental design, allowing scientists to test their predictions against real-world outcomes.