Lecture 1

Lecture 1: Introduction and Scientific Method

Covers Chapter 1.1, 1.3, 1.4

Organization of Matter

• Elements: all matter is composed of substances called elements (ex: carbon, nitrogen, gold, silver, etc)

• Atom: the smallest unit of matter in an element (ex: an atom of carbon, nitrogen, etc)

• Molecules: two or more atoms bonded together. (ex: 1 carbon atom + 2 oxygen atoms = carbon dioxide)

• MORE ABOUT ELEMENTS, ATOMS AND MOLECULES IN THE NEXT LECTURE!

Organization of Matter

• Cell: basic unit of living organisms– Contains simple and complex ORGANIC molecules– Definition of “Organic”: a molecule that contains

carbon• Tissues: a group of similar cells• Organs: collection of tissues that serve a

common function• Organ systems (ex: CV system)• Organism/Individual

Copyright © 2011 Pearson Education, Inc.

Figure 1-1 Levels of organization of matter

Organization beyond the individual*

• Species: organisms of same type capable of interbreeding

• Population: group of organisms of same species living in a given area

• Community: collection of populations of DIFFERENT species that interact with one another

• Ecosystem: a community and its nonliving environment

• Biosphere: entire surface of Earth, including living and nonliving components

What is science?

• “Organized enterprise that gathers knowledge about the world and condenses it into testable laws and principles.”

• Biologists always want to answer questions, also known as “scientific inquiry”.

Scientific Inquiry is based on a small number of assumptions

• Natural Causality: all events can be traced to natural causes

• Natural Laws are timeless: always been that way and law applies everywhere (ex: gravity, evolution, etc)

• People are able to perceive and measure events. These perceptions/measurements provide us with reliable objective information about the natural world.

• Judgements about these events can differ as a result of cultural/religious beliefs (ex: evolution)

So how do biologists study life?

• Answer: the scientific method!• Method for making observations of specific

phenomena and searching for the order that underlies this phenomena

• Example here:

Scientific Method*

• 6 interrelated elements:– Observation– Question– Hypothesis– Prediction– Experiment or Observation– Conclusion


The car won't start.

Why won't the car start?

The car won't startbecause the batteryis dead.

Propose a newhypothesis.

IF the hypothesis is correct,THEN the car will start if thebattery is replaced.

The battery is replaced.If the car doesn’t start:If the car starts:

The dead batteryhypothesis issupported.

Observation

Question

Hypothesis

Prediction

Experiment orObservation

Conclusion

Observation & Question

• Maggots can be seen on rotting meat left out after a few days.

• It was thought that the maggots came FROM the meat. (spontaneous generation).

• However, Redi also saw flies swarming on the meat.

• Question: COULD THE FLIES BE THE SOURCE OF THE MAGGOTS?

Hypothesis & Prediction

• Hypothesis: A supposition (guess), based on observations, that is offered as an answer to the question or explanation for the observed phenomena.

• To be useful, hypothesis must lead to a prediction. Expressed as if….then.– Ex: If the maggots came from the flies, then

keeping the flies off the meat will prevent maggots.

Experiment and Observation

• Experiments require controls: situations that keep untested variables constant– Put one piece of meat in an airtight containerAND– Have one piece of meat left out (control)– All other variables are the same– (If he put one piece of meat in a container AND

put that container in a bucket of ice, then he would be changing two variables.)


Experimental variable: gauze prevents the

entry of flies

Controlled variables:time, temperature,

place

Results

Control situation Experimental situation

Place meat in each jar

Obtain identical pieces of meat and two identical jars

Flies swarm around and maggots appear

Leave the jaruncovered

Leave exposedfor several days

Flies are kept fromthe meat;

no maggots appear

Cover the jarwith gauze

Leave coveredfor several days

Experiment:

Observation: Flies swarm around meat left in the open; maggots appear on the meat.

Question: Where do maggots on the meat come from?

Hypothesis: Flies produce the maggots.

Prediction: IF the hypothesis is correct, THEN keeping the flies away from the meatwill prevent the appearance of maggots.

Conclusion: The experiment supports the hypothesis that flies are the source ofmaggots and that spontaneous generation of maggots does not occur.

Example in every day life

• Car won’t start.• Battery dead?• If battery dead, then car will start with new

battery.• Change battery (BUT DON’T CHANGE

ANYTHING ELSE – STARTER, IGNITION COIL)• Car starts…it was the battery!

Use in medicine

• Testing new drugs• Always a control and experimental group (try to get a

large, broad experimental group so results can be applied to the WHOLE population)

• But people differ in many environments (nutrition level, population density, access to clean water, etc). Best weapon against sampling error is large experimental group)

• Placebos often used (fake pills)• Experiments can also be

– Blind– Double blind

To prevent bias

Conclusion

• After experiment is done, then either – Accept hypothesis– Do not accept hypothesis (reject)

• Accepted hypotheses must be repeatable and testable by many different scientists. If it continues to be accepted, eventually may become a common scientific theory.

• If rejected, scientists may re-examine method and re-test with different parameters

Scientific Theories

• As a result of scientific method, we now have many scientific theories: a general explanation for important natural phenomena that has been EXTENSIVELY TESTED AND REPRODUCED. Scientists believe these theories to be fact.

• EX: law of gravity, atomic law, cell theory.

Cell Theory (COVERED Extensively in lecture 4)

• The cell is the basic unit of life. • Cells have elaborate structures:

– Genes: more about DNA later– Organelles: structures that perform specific

functions (obtain energy, movement, making larger molecules)

– Plasma Membrane– Nucleus


mitochondrion

cytoplasmicfluid

flagellum

vesicle

ribosomeson rough ER

centriole

intermediatefilaments(cytoskeleton)

Golgiapparatus

cytoplasm

lysosome

exocytosis ofmaterial fromthe cell

polyribosome

nuclear pore

basal body

nuclear envelope

chromatin (DNA)nucleolus

nucleus

plasmamembrane

roughendoplasmicreticulum

free ribosome

smoothendoplasmicreticulum

microtubules(cytoskeleton)

microfilaments

What else characterizes living things?*

• 1.) living things made of cells• 2.) organisms maintain homeostasis (body temp, etc.) Energy

is used to maintain homeostasis.• 3.) living things respond to stimuli• 4.) Living things acquire materials (to grow and reproduce)• 5.) Living things grow• 6.) Living things reproduce themselves• 7.) Living things have the capacity to evolve• WE HAVE TO HAVE A WAY OF CATEGORIZING ALL OF THE LIFE

FORMS ON EARTH.

Categorizing life* • 3 domains:

– Bacteria– Archaea– Eukarya

• First 2 are procaryotes (no nucleus-genetic material in cytoplasm) , made of simple, single cells (usually)

• Eukarya has bodies composed of one or more complex cells. They are eucaryotes (membrane enclosed sac containing cell’s genetic material)


BACTERIA ARCHAEA EUKARYA

animalsfungi

plants

protists

FIRST CELLS

Eukarya*

• Further divided into:• Fungi• Plants• Animalia• Protists


Tree of life

Last way to categorize life*(how organisms get energy)

• Autotrophs (Arch, bact, some protists)– Self feeding: photosynthesis– Convert inorganic carbon (CO2) to carbs, fats and

proteins (organic carbons) to be used by them or ingested by heterotrophs

• Heterotrophs(arch, bact, and eukarya)– Other feeding: need to eat other organisms to get

energy. Cannot make their own carbs, fats, proteins. More about how WE get energy in Lecture 5?6?

Autotrophs & heterotrophs

Lecture 1

Technology

Transcript of Lecture 1