Chapter 1Characteristics of Life

I. What is Biology?

1. The scientific study of life.

A. Life = Organisms1. OrganismOrganism- an individual living thing.a. can have one cell or many

cells.

Many cells. One cell.

E. coli

B. When is something alive?

1. Made of cells.

a. cellscells- small, self-contained units that are the building blocks of living things.

Blood cells Macrophage & E. coli Nerve cells

2. Can obtain and use energy.a. ex: eating, absorption,

makes own food

B. MetabolismMetabolism- combination of chemical reactions through which an organism builds up or breaks down materials as it carries out its life processes.

3. Can grow and develop

4. Responds to its environment.

a. shivering, squinting at the sun, jerking your hand

away from a hot stove.

b. Plants turn toward the sun, drop leaves in the fall.

5. Able to reproduce.

6. Are Based on a Universal Genetic Code.

7. Maintain a stable Internal Environment (HomeostasisHomeostasis)

8. As a group, living things Change over time.

C. How do we organize life?

1. Levels of Organization

a. Molecular level

b. Cellular level

c. tissue

d. organ

e. organ system

f. organism

g. populationpopulation-group of the same species in an area.

h. communitycommunity-Group of different species in an area

1. SpeciesSpecies- When two organisms can mate and reproduce fertile offspring.

i. EcosystemEcosystem-living and Nonliving things in an Area.

J. BiosphereBiosphere- The part of the Earth that contains all the Ecosystems.

D. How do we study life?

1. Scientific Method

a. Make observations and state the problem.b. Form a hypothesis (educated guess) and make a prediction (a testable statement; if…then statement

c. Design an experiment and test it

e. Form conclusions

d. Analyze the data.

f. Retest/Make new hypothesesg. Share the results

2. A good experiment always has:

a. controlled setupcontrolled setup-all factors are kept the same except one.

b. a variablea variable- one factor that is different; the one you are testing.

http://www.cleanvideosearch.com/media/action/yt/watch?v=KZaCy5Z87FA

**always repeat experiments to ensure

valid resultsLet’s take a look at an Let’s take a look at an

experiment and see if we can’t experiment and see if we can’t locate each step of the scientific locate each step of the scientific

method…method…

**When repeated experiments consistently confirm a hypothesis, it

becomes a theorytheory.

3. What’s the difference between a fact, law, and

theory?

a. FactFact- an observation that has been repeatedly confirmed.

1. Ex: The sky is blue

b. LawLaw- general description of how something behaves under certain circumstances.

1. Ex: IF I throw a ball in the air on Earth, THEN it will fall.

c. TheoryTheory- logical explanation that explains a broad range of observations.

1. Ex: Not all living things are the same as they were a million years ago because things change over time.

II. Classic Experiments

A. Case History # 1: Spontaneous Generation vs. Biogenesis

1. Spontaneous Spontaneous generationgeneration- process where life begins from nonliving things.

2. BiogenesisBiogenesis- life comes from life.

3. Francesco Redi (1668)

a. wondered if maggots on meat came from ethers (spirits) or from flies. What do you think?What do you think?

How would you test How would you test that?that?

b. Redi left an open container out with meat in it.

What do you think What do you think happened?happened?

c. it had maggots in it and flies buzzing around.

d. Then he left a container out with meat in it, but with a lid.

What do you think happened?What do you think happened?

e. No maggots

Is this enough proof that the Is this enough proof that the maggots came from the flies?maggots came from the flies?

Why/Why not?Why/Why not?

**Redi still wasn’t convinced. What if there wasn’t enough airflow for the ethers to get into the jar with the lid?

How do you think Redi How do you think Redi should change his should change his experiment so that ethers experiment so that ethers could enter the jars, but could enter the jars, but flies couldn’t?flies couldn’t?

f. Finally Redi left a jar with meat out covered in cheesecloth.

What do you think What do you think happened?happened?

g. There were maggots on the cheesecloth, but not in the jars!!

Do you think this proves Do you think this proves biogenesis? Why/Why not?biogenesis? Why/Why not?

B. Case History #2: Spontaneous Generation vs. Biogenesis. . .

continued. 1. Louis Pasteur (1862)

2. hypothesis= dust in air carried microorganisms.

a. Filled two flasks with broth (food for bacteria)

-one had a curved neck and one had a straight neck.

What do you think What do you think happened?happened?

b. straight neck had bacteria in it after 1 Day.c. curved neck didn’t even after 1 YEAR 1 YEAR !

d. He decided to tip the broth into the neck, then back into the flask.

What do you think happened?What do you think happened?

e. Broth was cloudy with bacteria after one day one day !

What do you think What do you think happened in this happened in this

experiment?experiment?

Does this prove Does this prove biogenesis?biogenesis?

Let’s ReviewWhat are the 8 characteristics of

life?What are the levels of organization?What are the steps of the

scientific method?Explain the experiments we talked about and how they followed the

scientific method.

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