lecture 3: studying life Flashcards
What is a biological specimen and what can it be?
Your subject/unit of study
- Can be an organism, cell population, biomolecule preparation, ecological group/population
What are some characteristics of model organisms?
- Convenient to study: small size, simple feeding
- Large number of offspring (rapid development)
- Genetics understood and controlled through breeding
- Have attributes that make them useful to study
What are the 2 approaches to studying life?
- Reductionist
- Holistic
- Need to use both
What is reductionism?
Reduces a system into components
- Starts with this first
- Easier
- But miss emergent properties and understanding of a system
What is holism?
- Tries to understand how components work together
- More informative to understand life
- Harder
What are the 2 types of biological studies?
- Discovery studies: DESCRIBES nature using INDUCTIVE reasoning
- Hypothesis testing: EXPLAINS nature using DEDUCTIVE reasoning
What are the 2 types of reasoning?
- Inductive reasoning (new discovery): Oberservation —> Generalizations —> Hypothesis
- Deductive reasoning —> Hypothesis —> Predictions —> Experiment
What is “describing nature”?
- Based on observations
- Leads to generalizations
- Leads to hypothesis testing
What are the steps in “explaining nature”?
- Ask a question: from observations
- Form a hypothesis: propose possible answers to questions; based on solid rationale
- Hypotheses lead to predictions: lead to predictions that are testable
- Testing predictions: experiments designed to test predictions made by hypotheses
What are the 2 possible results of experiment?
- POSITIVE RESULT: supports hypothesis
- NEGATIVE RESULT: falsify hypothesis
- The null (no effect) hypothesis is supported
Results cannot PROVE a hypothesis, it SUPPORTS/FALSIFIES it
Types of variables?
- Qualitative: non-numerical and descriptive
- Ranked: data listen in order of magnitude
- Quantitative: numbers, continuous/discontinuous
What is a causal experiment?
To determine whether one variable (x) has an EFFECT on another (y) to support the hypothesis
What is a controlled experiment?
Experiment conducted in an environment where only the variable to be tested has an effect on the result
- To control for unwanted variables not by eliminating them through environmental regulation,. but by CANCELLING their effect using a CONTROL TREATMENT
What is a control treatment?
Subject is treated under a condition where all variables are held constant BUT independent variable is CHANGED & set to a REFERENCE CONDITION
What does a control treatment tell you?
Allows experimenter to measure the BASELINE (initial condition) measurement of dependent variable
Why is a control treatment important?
Allow experimenter to determine whether a change observed in the experimental treatment is due to independent variable or not
What is a controlled variable?
Variable held constant between treatments (one varibale that should change is the independent variable)
What are replicates?
Multiple independent subjects (units of study) for each treatment to form a group
What do replicates tell you?
The VARIABILITY in the response of your subjects WITHIN the same treatment group (BIOLOGICAL VARIABILITY)
Why are replicates important?
Must know variability in the response WITHIN a treatment group to know wheter a DIFFERENCE BETWEEN TREATMENT GROUPS IS REAL (to know that results aren’t just caused by biological reasons)
What are the 2 reasons why replicates are important?
- Must know how variable a response is between replicates treated the same way to know if A DIFFERENCE OBSERVED FOR A SUBJECT TREATED DIFFERENTLY IS REAL (statistical test to verify)
- Larger samples = better estimates of the characteristics of the population under study
- The more replicates, the better
- Reduces sampling error
What is the difference between a scientific theory vs Hypothesis?
- Theory is:
1. Much broader
2. General
3. Supported by much greater body of evidence
