lecture01_introductiontobiology_sv

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SCIENCE AND BIOLOGY

Lecture 1

Biology

What are we doing when we study biology?

Properties of Life

Living organisms share several basic properties

1. Order and Cellular Organization

2. Metabolism/Energy Utilization

3. Regulation and Homeostasis

Properties of Life

– 4. Growth, and development and reproduction

– 5. Heredity

– 6. Response to the environment

– 7. Evolve

Hierarchy of Life

biology is organized intoa hierarchy of levels

each higher level contains

novel properties not

present at the simpler

level of organization

Biological Science

was founded with the development of

1) CELL THEORY:



Cells

cell – highly structured compartment ….

L. Pasteur showed that cells do not arise by spontaneous generation

• Because all cells come from preexisting cells, single-celled organisms in a population are related to a single

common ancestor, and all cells in a multicellular

organism also descend from a single ancestral cell

Biological Science

2) THEORY OF EVOLUTION BY

NATURAL SELECTION:- characteristics of species change

through time….why?

- evolution occurs when heritable

variation leads to differential

reproductive success



•1858: Darwin and Wallace proposed thatall species are related by descent from a

common ancestor

• Species are related to one another, but

change over time

• Natural selection explains how this occurs

Biology is a Science

Science:

• biologists test ideas about how the natural worldworks by evaluating predictions made byhypotheses

• carefully designed experiments are an importanttool for hypothesis testing

Stages of a Scientific Investigation

The scientific process can be divided into several stages:

1. Observations

2. Generating a hypothesis

3. Prediction

4. Experimentation / Testing

5. Conclusion

Hypothesis Testing Hypothesis

(that is testable and fasifiable)

Make prediction

Consuming vitamin C reducesthe risk of catching a cold.

If vitamin C decreases the riskof catching a cold, then peoplewho take vitamin Csupplements will experiencefewer colds than peoplewho do not.

Test prediction

Conduct experiment or surveyto compare number of coldsin people who do and do nottake vitamin C supplements.

Hypothesis

- hunch or educated guess in

which researcher integrates

all knowledge

If people whotake vitamin Csuffer fewer

colds thanthose who donot. . .

If people whotake vitamin Csuffer the

same numberof colds ormore thanthose who donot. . .

Conclude thatprediction is

true

Conclude thatprediction is

false

Do not reject

the hypothesis

Reject the

hypothesis

Conductadditional

tests

Consider alternative

hypotheses



How Scientists Think

The Logic of Hypothesis Tests:

A hypothesis that fails our test is rejected and considered

disproven

A hypothesis that passes is supported, but not proven

a null hypothesis expresses no difference

Why not proven?

Experimentation

Experiments: are contrived situations

Variables: factors that can change in value under different

conditions

Independent variables: can be manipulated by the scientist

Dependent variables: not changed by the researcher

Experimentation

Controlled Experiments

Controlled experiment: tests the effect of a variable

Control: a subject who is?

Differences can be attributed to the experimental treatment

Scientific Method

1) observation: my flashlight doesn’t work

2) question:3) hypothesis:

4) experiment:5) conclusion:

Science and the Scientific Method

1. observations and measurements that …..

2. ideas/hypotheses are testable by experiments

that others …….

Science

Can science answer all questions?

limited to organisms and processes that ?

What about supernatural and religious phenomena?



Food Competition Hypothesis:

Food competition hypothesis:giraffes evolved long necks bynatural selection becausethose with long necks reachfood unavailable to others

Prediction: giraffes feed high intrees

Observe and test predictions

Simmons and Scheepers tested the:

Food Competition Hypothesis: Prediction

and Tests

prediction does not hold

true

alternative hypotheses?

Alternative Hypothesis Sexual competition

hypothesis

giraffes evolved long necks

because males with longer

necks win more fights than

shorter-necked giraffes,

thus father more offspring

Data support this hypothesis

Observation: chili peppers are hot

Ques. Why are chili peppers hot?



STUDY OF EVOLUTION

initiated scientific

study of evolution

approach toevolution based onhypotheses

Charles Darwin(1809-1882)

Darwin’s theory of evolution was based on

the following hypotheses

1) earth is very old

- organisms have been changing throughout thehistory of life

2) all organisms are descendants of a single commonancestor

Darwin’s theory of evolution was based on

the following hypotheses

3) species multiply by splitting into daughterspecies

4) evolution proceeds via gradual changes inpopulations

5) the major agent of

evolutionary change

is natural selection

Theory and Certainty

to scientists, a theory represents ………….

to the general public, a theory represents ……..

Theory and Certainty

From Hypothesis to Theory:

powerful, broad explanations of natural phenomena as a result of extensive and

reproducible observations

rests on many hypotheses that have been tested

is comprehensive and only becomes widely accepted only if supported by

extensive accumulation of evidence: indicates a high degree of certainty

however, there is no absolute truth in science

Theory of Evolution

Is a scientific theory because:

of its broad application

has been validated by continuous scientific

observations and experiments worldwide

lecture01_introductiontobiology_sv

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