Scientific Method/Characteristics of Life

Biology

Means the study of life.

Theory

A theory explains why and how a phenomenon occurs. It offers an explanation backed by evidence and experimentation. It can be changed as new data emerges. Examples: Theory of Evolution

Law

A scientific law is something that has been proven true and correct numerous times and can explain what will happen under specific conditions. Typically, laws involve math. Examples: Law of Gravity

The Scientific Method

A series of steps in which a question and/or problem is investigated by observing and experimenting.

The Steps of Scientific Method

1. Stating the problem/question, 2. doing prior research, 3. forming a hypothesis, 4. experimenting, 5.analyze your data, 6., make conclusions

Inference

A conclusion drawn from evidence about something that is happening now based on prior knowledge or experiences.

Hypothesis

A possible explanation it must be testable! A hypothesis can be set up as an “If, then” statement.

Prediction

A prediction is what you think is going to happen in the future.

What is the number of variables needed to conduct an experiment?

You must have two variables and a control group.

Control Group

A group that is NOT experiment on; left alone to see what would happen without your manipulations so that you can compare results.

Placebo

A placebo is an inactive substance or fake treatment that has no medical affect.

What is an experimental group?

This is the group that receives the independent variable or treatment.

What is an independent variable?

The manipulated variable: what is changed during the experiment.

Dependent Variable

Responding variable: what you measure during the experiment.

What are the different components of an experiment?

The independent variable, dependent variable, constants and control group and experimental group.

What is the difference between quantitive and qualitative data?

Quantitive data=numbers(quantity), Qualitative data=descriptions(quality)

Which variable goes on the X-axis and which goes on the Y-axis?

• X-axis (Horizontal): Independent Variable (what you change/manipulate)

• Y-axis (Vertical): Dependent Variable (what you measure/observe)

How do you set an appropriate scale for a graph axis?

• Find the range (highest value minus lowest value).

• Divide the range by the number of grid squares available.

• Round up to a clean, even increment (like counting by 2s, 5s, or 10s).

• Ensure data spreads out to fill at least half the page

What are the rules for writing a graph title and axis labels?

• Title Format: "The Effect of [Independent Variable] on [Dependent Variable]" (or "Dependent vs. Independent").

• Axis Labels: State the variable name and always include units in parentheses

When do you use a Bar Graph versus a Line Graph?

• Bar Graph: Used for categories or distinct groups (e.g., types of plants, different brands).

• Line Graph: Used for continuous data over time to show trends and changes (e.g., height growth over 10 days, temperature changes). [1, 2, 3]

Key (Legend)

A guide that explains what the colors, symbols, or patterns on a graph mean.

Science

A systematic way of learning about the world through observation, questioning, and experimentation.

X-Axis

The horizontal line at the bottom of a graph.

Y-Axis

The vertical line on the side of a graph.

1. Describe the scientific method as a complete, six-step process, from the initial question to the final conclusion. For each step, explain its purpose and why it is a critical part of a systematic investigation.

The scientific method is a structured, cyclical loop used to investigate the natural world.

• Step 1: Observation / Question

• Step 2: Background Research

• Step 3: Form a Hypothesis

• Step 4:Experimentation (Testing)

• Step 5: Data/Analysis

• Step 6: Conclusion

Using the scenario provided in the notes, "Does fertilizer increase the number of tomatoes on a single tomato plant?", design a complete and valid experiment. Describe your hypothesis, identify the independent and dependent variables, define your control and experimental groups, and list at least three other factors that must be kept constant between the groups to ensure accuracy.

• Hypothesis: If a tomato plant is given fertilizer, then it will produce a greater number of tomatoes because fertilizer provides essential nutrients that support fruit growth.

• Independent Variable (IV): The presence or absence of fertilizer.

• Dependent Variable (DV): The total number of tomatoes produced on a single plant.

• Experimental Group: A group of tomato plants that receive a specific, measured amount of fertilizer.

• Control Group: A group of tomato plants that receive no fertilizer (only water) to establish a baseline for comparison.

• Controlled Variables (Constants):

  1. Amount of water given

  2. Sunlight Exposure

  3. Type of Plant/Soil

Compare and contrast the concepts of an inference, a prediction, and a hypothesis. Use the examples from the source material(look at notes on design an experiment) to illustrate the distinctions and explain how each concept relates to the initial stages of a scientific investigation.

Concept	Definition	Example / Distinction
Inference	A logical conclusion or interpretation based on prior knowledge and immediate observations.	Example: "The tomato plant leaves look yellow, so the plant is lacking nutrients." It explains a current state.
Prediction	A statement about what will happen in the future if a specific action is taken.	Example: "If I add fertilizer, the plant will grow more tomatoes." It is a simple guess of an outcome.
Hypothesis	A formal, testable statement that combines the prediction with an explanatory cause.	Example: "If fertilizer is added, then tomato production increases because nitrogen stimulates plant reproduction." It sets up the actual test.

Explain the crucial role of data analysis and conclusion-drawing in the scientific method. Explain what actions a scientist must take if their hypothesis is accepted versus if it is rejected.

Data analysis and conclusion-drawing turn raw numbers into actual science. Without this step, an experiment is just a list of random observations.

What a Scientist Must Do Next

• If the hypothesis is ACCEPTED: The scientist must repeat the experiment to ensure the results weren't a fluke, then publish the findings so others can review and replicate them.

• If the hypothesis is REJECTED: The scientist reflects on the data, revises their original idea, forms a new hypothesis, and designs a fresh experiment to test it.

You have just completed an experiment testing the effect of three different types of soil (Categories: Sandy, Clay, Loam) on the final height of bean plants (measured in cm). Outline, step-by-step, how you would create a graph to present your data. Be sure to identify the correct graph type, explain how you would label the axes and title, and describe how you would plot multiple data sets if necessary.

• Step 1: Identify Graph Type

  • Use a Bar Graph because the independent variable consists of separate categories (Sandy, Clay, Loam) rather than continuous data.

• Step 2: Set Up Axes

  • Label the horizontal X-axis as Soil Type (Independent Variable).

  • Label the vertical Y-axis as Final Height (cm) (Dependent Variable).

• Step 3: Determine Scale

  • Divide the highest plant height by the available grid squares. Count by clean increments (2s, 5s, 10s) so data fills over half the page. Space categories evenly.

• Step 4: Write Title

  • Use the standard format at the top: "The Effect of Soil Type on the Final Height of Bean Plants".

• Step 5: Plot Data

  • Draw a bar for each soil type up to its measured height. If you tested multiple seeds per soil, plot the calculated average height. If comparing multiple bean types, draw side-by-side bars and include a Key (Legend).

What are the 8 characteristics of life?

1. Metabolism

2. Reproduction

3. Cells (made up of cell(s))

4. Homeostasis

5. Evolution

6. DNA (contains DNA)

7. Development and Growth

8. Respond to stimuli

MR CHEDDR

Metabolism

All living things need to consume nutrients to obtain energy.

What is the difference between autotrophic and heterotrophic?

Autotrophic means that the organisms are producers because they are able to make their own food. Examples of this are photosynthesis. Heterotrophic means that the organisms are consumers because they need to eat in order to obtain energy.

Reproduction

The process of making the next generation of organisms and it may be a sexual or asexual process.

What is the difference between asexual and sexual reproduction?

Asexual reproduction means that offspring are genetically identical to a single parent. Sexual reproduction is when offspring have a unique combination of genetics from two parents.

Cells(made up of cells)

The basic unit structure and function of all living things.

What is the difference between unicellular and multicellular?

Multicellular organisms are composed of more than one cell. Unicellular organisms are single celled.

Homeostasis

The maintenance of a stable internal environment despite a challenging external environment. The state of stability is called dynamic equilibrium.

What does it mean to “maintain homeostasis”?

Maintaining homeostasis means keeping a stable and balanced internal environment inside a living body despite changes in the outside world.

What is a dynamic equilibrium?

The regulation of the internal environment like body systems to maintain stability is called dynamic equilibrium.

Evolution

This means the change of the genetic makeup in a population over long periods of time. Specific traits in the population helps adaption to the environment.

What is a common ancestor?

A common ancestor is an ancestral species or population from which two or more different descendant species or lineages evolved.

DNA

DNA stands deoxyribonucleic acid which is genetic material that is passed from parent to offspring. The DNA stores genetic information needed to grow, reproduce, and perform life-sustaining cell activities.

How do living things grow and develop?

They do this by following specific instructions coded for by their genes.

What is the difference between growth and development?

Growth is the process of getting bigger(increase in material and structures). Development is the process of changes that occur in an organisms’ life cycle from embryonic state to maturity(puberty, metamorphism).

Response to Stimuli

A response to stimuli in biology is any change in the state, activity, behavior, or growth of an organism or cell resulting from an internal or external signal.

What is the difference between stimulus and response?

The stimulus is the signal that an organism responds to(using your senses). The response it the reaction or change in action that is brought on by a stimulus.

Eukaryotic Cell

These are cells that do have a nucleus. Most eukaryotes reproduce by sexual reproduction. (human cells are eukaryotic cells)

Gene

A gene is the basic physical and functional unit of heredity made up of DNA.

Genome

A genome is the complete set of genetic material (DNA, or RNA in some viruses) found in an organism.

Prokaryotic Cell

These are cells that do not have a nucleus but they still have DNA. They reproduce asexually. They were the first organisms to evolve and were Earth’s sole inhabitants for 1.5 billion years.

The acronym MR. CHEDDR provides a framework for identifying life. Select four of these characteristics and explain in detail how they collectively distinguish a living organism, such as a sunflower, from a complex non-living object, such as a robot.

• Cells: Sunflowers are made of living, self-healing organic cells. Robots are built from dead, inorganic parts like metal and plastic.

• Metabolism: Sunflowers make their own fuel via photosynthesis to grow their bodies. Robots use external power but cannot chemically build themselves.

• Homeostasis: Sunflowers automatically balance internal needs (like opening leaf pores to manage water). Robots rely on rigid, pre-set computer code to cool down.

• DNA / Heredity: Sunflowers pass down a biological blueprint to their seeds. Robots run on human software that cannot mutate or reproduce naturally.

Discuss the central role of DNA as the "universal genetic code." Explain how genes and the genome function to pass information between generations and direct the processes of growth, development, and metabolism.

• Universal Code: All life uses the exact same four chemical bases (A, T, C, G) to store data, allowing any cell to read the genetic language.

• Passing Info: The genome is the complete instruction manual. It is copied and passed down during reproduction to keep genetic continuity.

• Directing Life: Genes are short segments of DNA that serve as specific recipes for proteins. These proteins act as the cellular workers that control growth and energy use.

Compare and contrast the two forms of reproduction: asexual and sexual. Describe the genetic outcome for the offspring in each process and connect these methods to the types of cells (prokaryotic vs. eukaryotic) that primarily use them.

• Asexual Reproduction: Requires only one parent and creates identical clones. It is the primary method for simple prokaryotes (like bacteria) via binary fission.

• Sexual Reproduction: Requires two parents mixing gametes to create genetically unique offspring. It is the main method for complex eukaryotes (plants and animals).

Argue for the statement that "Evolutionary change has linked all forms of life to a common origin." Incorporate the concepts of heritable traits, adaptation, and the phylogenetic tree in your response.

• The Argument: All life shares the same chemical toolkit (DNA and ATP), proving we all share one ancient ancestor.

• Heritable Traits: Parents pass down physical and behavioral traits to their offspring through DNA code.

• Adaptation: Natural selection keeps the traits that best fit the environment, turning them into standard adaptations over time.

• Phylogenetic Tree: These changing traits cause lineages to split. This history is mapped on the "Tree of Life," where tracing any two species backward leads to a single shared root.