Introduction to biology

BIOLOGY

Themes of biology

1. Levels of organization2. The cellular basis of life3. Genetics4. The correlation between structure and

function5. The interaction of organisms with their

environment6. Homeostasis7. Evolution, unity, and diversity8. Science as a process

1. Levels of organization

1. Levels of organization

1. Levels of organization

Emergent properties Characteristics not

present at simpler levels of organization

Holism An organism is more

than the sum of their parts

Reductionism By studying an

organisms parts, you can understand it better as a whole

2. Cellular basis of life

Cell theory All cells come from other

cells All living things made of

cells Classification of organisms

Size – single or multicellular Complexity – eukaryotic or

prokaryotic Energy use – autotroph and

heterotroph

3. Genetics

Organisms pass on genetic information to their offspring via DNA

Four different letters in DNA make organisms what they are

Billions of these letters code for an organism

4. Structure and function

The structure of things are related to their function – form fits function Anatomy and

physiology

5. Ecology

Organisms always interact with their environment Nutrient cycling Energy flow Human impact on the environment

6. Homeostasis

The ability of an organism to maintain its internal conditions

Feedback mechanisms Positive

feedback Negative

feedback

7. Evolution, unity, and diversity

Evolution Change in

frequency of alleles in a population over time

Organisms share common ancestors

Natural selection, “survival of the fittest,” drives evolution

7. Evolution, unity, and diversity Diversity is enormous

Taxonomy – scientific classification

Kingdom-phylum-class-order-family-genus-species

All organisms exhibit similarities in genetic code, cell structure, and metabolic pathways

8. Science as a process

Inductive reasoning Use specifics to

make general conclusion

Deductive reasoning Use general idea to

learn specifics

8. Science as a process

Testing hypotheses is the basis of science Propose an idea to

a problem or question

Scientific method A flexible outline

to answer questions or solve problems

Requires evidence

The effect of gestational age on birth weight

8. Science as a process

Science continually incorporates new data to gain a better understanding of the world

Science as a process and technology

Technology improves the ability to learn about many aspects of biology

EXPERIMENTAL DESIGN

Independent and dependent variables

Independent variable What the scientist

intentionally changes

Dependent variable What is measured,

or what changes in response to the independent variable

Control and experimental groups

Both relate to the independent variable

Control group What all other groups

are compared to Usually the lowest,

highest, or “normal” value

Experimental groups All of the other values

of the independent variable compared to the control group

Scientific title

Should be descriptive enough to indicate what is going on in the experiment

“The Effect of (IV) on (DV)”

Hypothesis

Must be falsifiable

More than an educated guess

Can’t be “proven,” only rejected

“If…then…”

Constants

Factors that remain consistent throughout the experiment

There should only be one independent variable in an experiment

GRAPHING

Graphs

The purpose of a graph is to help visually depict data and trends in data

There are many requirements to graph data properly

Requirements for graphing

Scientific title Axis labels Regular

intervals Variables on

correct axes Choosing the

right type of graph

The effect of work experience on income

Requirements for graphing

Variables on correct axes Independent

variable on x axis

Dependent variable on y axis

Choosing the right type of graph

Pie chart Typically

shows part, or percentage, of a whole

Choosing the right type of graph

Scatter plot and line graphs Used to look at

the relationship of one variable on another

Usually requires an independent variable that is a number

Can use a line of best fit

Choosing the right type of graph

Bar graph Typically

used when the independent variable is not a number

Choosing the right type of graph

Box and whisker graph Similar to a

scatter plot or bar graph, but shows much more detail

Choosing the right type of graph

WRITING A LAB REPORT

Using experimental design

Pre-lab

Overview

Introduction

Materials

Procedure

Data

Conclusion

Trials

The more data you can collect, the better

At a minimum, 30 trials per experimental group

CHI-SQUARED ANALYSIS

Forming a null hypothesis

Used because you don’t “prove” a hypothesis, but can reject one

If you accept your null hypothesis, you would reject your original hypothesis

An overview of Chi-squared

You try to evaluate how likely your results could be due to chance

Requires two variables: O – observed data E – expected data

Levels of significance

How sure you want to be that your results are not due to random chance

Degrees of freedom

The number of possible outcomes or selections, minus 1

Example problem

If you rolled 120 six-sided dice and you ended up with: 27 1’s 23 2’s 11 3’s 19 4’s 18 5’s 20 6’s

And you want 95% confidence… would you reject or accept your null hypothesis?

Example problem

If you rolled 120 six-sided dice and you ended up with: 27 1’s 25 2’s 11 3’s 19 4’s 18 5’s 20 6’s

And you want 95% confidence… would you reject or accept your null hypothesis?

Observed values – 27, 25, 11, 19, 18, 20

Example problem

If you rolled 120 six-sided dice and you ended up with: 27 1’s 25 2’s 11 3’s 19 4’s 18 5’s 20 6’s

And you want 95% confidence… would you reject or accept your null hypothesis?

Expected values – 120/6 = 20

Example problem

Observed values – 27, 25, 11, 19, 18, 20 Expected values – 120/6 = 20

(27-20)2+ 20

(25-20)2+ 20

(11-20)2+ 20

(19-20)2+ 20

(18-20)2+ 20

(20-20)2

20

Example problem

Observed values – 27, 25, 11, 19, 18, 20 Expected values – 120/6 = 20

49+ 20

25+ 20

81+ 20

1 + 20

4 + 20

0 20

= 160 20

= 8

Example problem

If you rolled 118 six-sided dice and you ended up with: 27 1’s 23 2’s 11 3’s 19 4’s 18 5’s 20 6’s

And you want 95% confidence… would you reject or accept your null hypothesis?

= 8