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Life!

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Life! And how we try to figure it out Figure 1.2 The hierarchy of biological organization Biology Define life (good luck!). How do we know a living thing when we see one? – PowerPoint PPT presentation

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Title: Life!


1
Life!
  • And how we try to figure it out

2
Figure 1.2 The hierarchy of biological
organization
3
Biology
  • Define life (good luck!).
  • How do we know a living thing when we see one?
  • list characteristics common to ALL living
    things.

4
Characteristics 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

5
What makes Biology a science?
  • How do you know science when you see it?
  • list some characteristics of science and
    describe how scientists work.

6
Science is
  • Objective
  • Data driven
  • Experimental
  • Attempt to find the best possible naturally
    occurring explanation for a phenomenon.

7
Observations 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?

8
Where 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.

9
Abiogenesis 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!

10
Really 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).

11
An 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!

12
Francisco 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.

13
Redis Alternative
  • OBSERVATION Flies land on meat that is left
    uncovered. Later, maggots appear on the meat.
  • HYPOTHESIS Flies produce maggots.

14
Redis 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!

15
The 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?

16
Procedure
Uncovered jars
Covered jars
Several days pass
?
?
17
Results
Uncovered jars
Covered jars
Several days pass
Maggots appear
No maggots appear
18
CONCLUSION
  • Maggots form only when flies come in contact with
    meat.
  • Spontaneous generation of maggots did not
    occur.

19
Spallanzanis 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.
20
Pasteurs Experiment 1860
Broth is boiled.
21
Pasteur
Broth is boiled.
Broth is free of microorganisms for a year.
22
Pasteur
Broth is boiled.
Broth is free of microorganisms for a year.
Curved neck is removed.
23
Pasteur
Broth is boiled.
Broth is free of microorganisms for a year.
Curved neck is removed.
Broth is teeming with microorganisms.
24
Biogenesis 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.

25
But 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!
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