What is the goal of science?

1. Investigate and understand the natural world.

2. Explain the natural world.3. Predict events in the natural

world.

Science is a way of knowing.

What does that mean?

Biology is the study of living things.

Bio: LivingAbio: Non-living

Thinking like a scientist.

Thinking like a scientist

• Observation

• Data– Quantitative – Qualitative

• Inference

Scientific MethodPage 8

• Asking a question• Research• Forming a hypothesis• Setting up a controlled environment

only one variable is changed at a time• Recording and analyzing the results• Drawing a conclusion• Repeating the investigation

The hypothesis of spontaneous generation

• Aristotle – Developed the theory of Spontaneous Generation (Abiogenesis) which states that:living things come from non-living thingsie. Flies came from a dead cow

Frogs come from mudMice come from dirty rags

Fransesco Redipage 11

In 1668, Fransesco Redi, an Italian physician attempted to disprove the theory of

Spontaneous Generation.

Controlled Experiment

Whenever possible, a hypothesis should be tested by an experiment in which only one variable is changed at a time. All other variables should be kept unchanged or controlled.

The variable that is deliberately changed is called the manipulated variable.

Look at Redi’s experiment and figure out what his hypothesis was and which was the

manipulated variable.

Redi’s Experiment

John Needham

• Mid 1700s

• British

• Needham tried to prove that spontaneous generation could occur in the right circumstances. (He disagreed with Redi.)

John Needham’s Experiment

He boiled broth, claiming to have killed all of he “animalcules” in it. After a few days, he used a newly developed microscope to have a look and saw many of the little animals.

What was wrong with his experiment?

Lazzaro Spallanzani

• Italian

• Felt that Redi was right and that Needham’s experiment had failed because he did not boil the broth long enough or did not have a tight enough stopper.

• He boiled 2 containers of gravy, sealed one and left the other open.

Spallanzani• After a few days:

- the open container was teeming with microorganisms and was cloudy.- the sealed container remained free of organisms.

• Conclusion:The broth did not produce living things. The microorganisms in the open container were the offspring of microorganisms that had entered through the air.

Louis Pasteur

• 1864

• French

• Designed a flask that would disprove spontaneous generation once and for all.

Pasteur

“Theory” Page 13

In science, a theory is a well-tested explanation that unifies a broad range of observations.

What’s the difference between a theory and a hypothesis?

Studying Life

• Page 15

• Biology uses the scientific method to study living things.

Living things share the following characteristics:

• Made up of units called cells• Reproduce• Are based on a universal genetic code• Grow (life span) and develop (life cycle)• Obtain and use materials and energy• Respond to their environment (stimulus/response)• Maintain a stable internal environment

(homeostasis)• As a group, change over time (evolve)

Life is Cellular

• Without the instruments that made them visible, cells remained out of sight and unknown.

• The microscope changed all that!

Microscope

Mid-1600s:- Anton van

Leeuwenhoek - Holland - Single lens microscope

to examine pond water- What did he see?

• Robert Hooke England 1665

• Compound microscope (2 lenses) to examine a thin slice of cork.

• “Cells”

Cell theory

• Soon different observations about cells were being made by scientists all over.

1. Matthias Scheiden, German botanist: all plants are made of cells

2. Theodor Schwann, German biologist: all animals are made of cells.

3. Rudolf Virchow, German physician: new cells are produced only from the division of existing cells.

In the mid-1800s these observations were combined to form the cell theory, a

fundamental concept of biology.

Cell theory states:

• All living things are composed of cells.

• Cells are the basic units of structure and function in all living things.

• New cells are produced from existing cells.

Cells

There are two categories of cells:

1. Prokaryotic

2. Eukaryotic

Complete the handout on the two cells.

Prokaryotic cells: (from the Greek meaning before nuclei)

1. lack a membrane-bound nucleus

• genetic information is in the cytoplasm.

Prokaryotic cells (prokaryotes):

2. Are bacteria3. Are smaller than eukaryotes (usually)4. Contain fewer organelles5. Do not contain organelles that have their

own membranes

Eukaryotic cells (from the Greek meaning truly nuclear)

1. All living things except bacteria.2. Have a membrane-bound nucleus where DNA (deoxyribonucleic acid) is stored.

3. Usually bigger than prokaryotes

4. Have more organelles, including some that have their own membranes

5. Are often specialized (i.e. skin cells, liver cells, heart cells)

The main difference between eukaryotic and prokaryotic cells is that eukaryotic cells have a

nucleus with a membrane around it (a membrane-bound nucleus) that holds almost all of the cell’s DNA and prokaryotic cells don’t have a nucleus. Their DNA floats around in the cytosol

(the liquidy stuff).

Eukaryotic cells (cheek cells)

Organelles

• An organelle (which means “little organ”) is a specialized structure with a specific function within the cell.

• All living material within the cell is called protoplasm