The Scientific Method
- Observation
- Question
- Hypothesis
- Experiment
- Results
- Conclusions
Hypothesis
must be something you can test
Testing a Hypothesis - Experiments
- must produce measurable results that disprove or support the hypothesis
- results of experiments must be interpreted (conclusions)
- ideal experiment will yield results with only one possible interpretation
- outcomes might have multiple interpretations
- biases can influence conclusions
- good design avoid alternate interpretations or biases
Making a Good Experiment
- Limit variables- makes results easier to interpret
- Limit bias- everyone has biases
- Reproducibility - make sure it wasn’t a fluke, or due to some unconsidered variable
Limiting Variables
- variable is any factor that can be controlled, changed, or measured in an experiment
- scientists try to change just one variable per experiment
- the independent variable is what is being manipulated as a potential cause- what gets changed
- dependent variable is the response, output, or effect under investigation- what gets measured
Experimental Group
group getting treatment that is being tested
Control group
group not getting treatment- serves as baseline, and ensures validity of experiment
* may often receive a placebo instead of experiential treatment
Reproducibility & Statistical Analysis
- scientists must repeat experiments several times to ensure that findings are not due to chance alone
- other scientists should be able to reproduce findings
- data should have statistical analysis performed
Peer Review & Publication
- scientists evaluate each others work before it is published
- check for rigor, reproducibility
- conclusions reasonable based on data
- reviewers suggest additional experiments that could strengthen or weaken conclusions - self correcting- hypotheses may change
Theory
a well-sustained explanation which is comprehensive and able to explain a great many observations
Hypothesis
- no expectation of truth
- narrow in scope
- subject to immediate testing
- must be falsifiable; can be refuted by contradictory evidence
Theory
- well-substantiated and never been shown to be false
- broad in scope
- already supported by a large body of evidence
- must be falsifiable; can be refuted by contradictory evidence
The Scientific Process - Review
- scientists try to design experiments to limit variables and bias
- make conclusions based on data and info they have at the time
- as scientists gain new knowledge, they may disprove old hypothesis and generate new hypotheses
- scientific knowledge builds on itself and is self correcting
- takes a long time to build a scientific consensus
- takes a long time for an explanation for observations to become a scientific theory
What does food provide
- energy: muscle cells need energy to help us move, braincells- think, digestive system cells- use food we eat
- building blocks: bodies make new cells to replace old ones, about 330 million new cells each day, food providing building blocks for our cells and bodies
What are we made of
- water
- organic compounds- large complex molecules that have carbon as their backbone- often with hydrogen and oxygen
- inorganic compounds- other molecules, not carbon based, like salt, calcium
Organic Compounds (macromolecules)
Living organisms composed of 4 major types
1. protein
2. carbohydrates (sugars)
3. lipids (fats)
4. nucleic acids (DNA/RNA)
Carbohydrates (sugar)
- structure of our cells
- components for making other molecules
- energy storage (glucose)
- communication between cells
- large polymers made up of sugar monomers
- key structural component of plants
Lipids (fats)
- membranes of our cells
- storing excess energy (triglycerides in body fat)
- steroid hormones (testosterone and estrogen)
- hydrophobic
- not a polymer, made up of membranes called phospholipids
Proteins
- incredibly diverse molecules
- perform most of the tasks in our cells, in our bodies
- each protein has a unique shape that helps dictate its function (what other molecules it can interact with)
- proteins are made up of a sequence of smaller molecules called amino acids
- sequence of amino acids determines the shape/function of the protein
Nucleic Acids
- DNA and RNA
- hold all genetic info
- tell us how to build our bodies to function
- DNA is made up of sequences of smaller molecules called nucleotides
Vitamins & Minerals
- vitamins are small organic molecules
- minerals are inorganic molecules (salt, calcium)
- usually in small amounts in our body but are vital for life functions
What’s in our food
- macronutrients- proteins, carbs, lipids
- micronutrients- vitamins & minerals
How many amino acids do cells use
about 20 different amino acids
* sequence determines shape and function
* shapes of proteins determine what molecules they can interact with
* protein shape determines function
How many different nucleotides does DNA use
- 4 different nucleotides
- order of nucleotides in DNA determines traits of organism
