Title: Life!
1Life!
- And how we try to figure it out
2Figure 1.2 The hierarchy of biological
organization
3Biology
- Define life (good luck!).
- How do we know a living thing when we see one?
- list characteristics common to ALL living
things.
4Characteristics of all living things
- 1. Made Up of Cells - Organization
- 2. Reproduction
- 3. Based on DNA
- 4. Growth and Development
- 5. Need for Energy
- 6. Response to Environmental Stimuli
- 7. Homeostasis
- 8. Evolution
5What makes Biology a science?
- How do you know science when you see it?
- list some characteristics of science and
describe how scientists work.
6Science is
- Objective
- Data driven
- Experimental
- Attempt to find the best possible naturally
occurring explanation for a phenomenon.
7Observations are objective
- Observe the familiar actions and describe them.
No talking! - Compare notes with others how objective were
your observations? - What happens when new observations dont fit with
the old? - How did observations lead to hypotheses on life?
8Where does life come from?
- At least by Aristotles time, people were
concerned with this. - Prevailing theory Spontaneous generation or
Abiogenesis - Life comes from non-living things.
- Based on everyday observations
- Aristotle described an active principle that
was responsible.
9Abiogenesis examples
- Salamanders and frogs come from river mud.
- Mice come from wheat that has been exposed to
sweat. - Humans???
- pregnancy and birth were understood, sexual
intercourse was important, but sperm and eggs
didnt play a role!
10Really small life?
- Microscopes allowed observation of
micro-organisms, but these were thought to come
from plants or mud mixed with water (van
Leeuwenhoek, mid 1600s). - Bacteria in meat broth were formed from the meat
(Needham, 1745).
11An alternative view Biogenesis
- By the mid 17th century some individuals
questioned abiogenesis. - Their observations suggested all living things
were produced by other living things - Biogenesis
- A test of biogenesis/abiogenesis was needed!
12Francisco Redi
- 1668 An Italian physician decided to test the
common knowledge that maggots came from rotting
meat. - Without refrigeration or concern about covering
food, maggots tended to appear on meat within a
few days. Therefore, the meat produced the
maggots.
13Redis Alternative
- OBSERVATION Flies land on meat that is left
uncovered. Later, maggots appear on the meat. - HYPOTHESIS Flies produce maggots.
14Redis Experimental Design
- If flies are kept away from meat by a covering,
no maggots should appear. - Compare to meat stored in the usual way
(uncovered) which should develop maggots. - Keep every other factor the same!
15The variables
- Independent variable
- covering over jar or not
- Controls fly access to meat
- Controlled Variables
- jars, type of meat, location, temperature, time
- Dependent variable
- maggots?
16Procedure
Uncovered jars
Covered jars
Several days pass
?
?
17Results
Uncovered jars
Covered jars
Several days pass
Maggots appear
No maggots appear
18CONCLUSION
- Maggots form only when flies come in contact with
meat. - Spontaneous generation of maggots did not
occur.
19Spallanzanis Experiment 1765
Figure 1-10 Spallanzanis Experiment
Gravy is boiled.
Flask is open.
Gravy is teeming with microorganisms.
Flask is sealed.
Gravy is free of microorganisms.
Gravy is boiled.
20Pasteurs Experiment 1860
Broth is boiled.
21Pasteur
Broth is boiled.
Broth is free of microorganisms for a year.
22Pasteur
Broth is boiled.
Broth is free of microorganisms for a year.
Curved neck is removed.
23Pasteur
Broth is boiled.
Broth is free of microorganisms for a year.
Curved neck is removed.
Broth is teeming with microorganisms.
24Biogenesis wins!
- Pasteurs experiments finally won general support
for the biological origins of living things. - Pasteur also introduced methods of food
preservation (Pasteurization!) that dramatically
increased the shelf life of foods.
25But wait! Theres more!
- Where did the FIRST living thing come from???
- Where did the universe come from???
- Lets start with nonliving things and how they
affect living things. - Abiotic vs Biotic factors!