The Science of Biology

What is Science?

The Scientific Method

Tools Used in Science

What is Biology?

What is Science?

• An organized way of using evidence to learn about the natural world

• Body of knowledge that scientists have built up

Steps used in science…

• Observation – using one or more of the senses to gather information

• Inference – a logical interpretation based on prior knowledge and experience

• Data – information gathered from observations– Quantitative –

involve numbers– Qualitative – involve

characteristics that cannot be easily measured or counted, such as color or texture

Observation vs. Inference

Statement Observation Inference

Object A is round and orange.

Object A is a basketball.

Object C is round and black and white.

Object C is larger than Object B.

Object B is smooth.

Object B is a table-tennis ball.

Each object is used in a different sport.

X

X

X

X

X

X

X X

Scientific Method

• 1. Stating the Problem – based on observations, identify a problem to be solved

Scientific Method cont.

• 2. Forming a Hypothesis – a possible explanation for a set of observations or an answer to a scientific question– Prior knowledge– Logical inferences– Imaginative guesses

Scientific Method cont.

• 3. Setting up a Controlled Experiment – an experiment in which only one variable is changed at a time– Manipulated variable (independent) – the

variable that is changed by the scientist– Responding variable (dependent) – the

variable that changes in response to the manipulated variable

– If an experiment cannot be done, field studies will be done

Spontaneous Generation Experiment

OBSERVATIONS: Flies land on meat that is left uncovered. Later, maggots appear on the meat.

HYPOTHESIS: Flies produce maggots.PROCEDURE

Controlled Variables:jars, type of meat,location, temperature,time

Manipulated Variables:gauze covering thatkeeps flies away from meat

Uncovered jars Covered jars

Several days pass

Maggots appear No maggots appearResponding Variable: whether maggots appear

CONCLUSION: Maggots form only when flies come in contact with meat. Spontaneous generation of maggots did not occur.

Another Spontaneous Generation Experiment

Gravy is boiled. Flask isopen.

Gravy is teeming with microorganisms.

Gravy is boiled. Flask issealed.

Gravy is free of microorganisms.

Another Spontaneous Generation Experiment

Broth is boiled. Broth is free ofmicroorganismsfor a year.

Curved neckis removed.

Broth is teeming with microorganisms.

Scientific Method cont.

• 4. Record and Analyze Results – keep written records of observations or data– Notebooks, journals, drawings, computer

Scientific Method cont.

• 5. Drawing a Conclusion – determine whether the hypothesis is supported or refuted

Yes

No

Then what?

• Publish study in a scientific journal

• Other scientists review the procedures and may perform their own experiments to verify the results

• If the hypothesis is continually supported it may become a theory

****No theory is considered absolute truth!!!!!

Tools used in Science…

• Microscopes– Three kinds: compound light microscope,

transmission electron microscope, and scanning electron microscope

– Magnification – determined by multiplying the eyepiece times the objective

– Resolution – ability to distinguish between two objects

Compound Light Microscope

• Light passes through the object

• Magnification up to 1000 times

• Resolution up to 500 nanometers

Compound Light Microscope

Compound Light Microscope

Transmission Electron Microscope (TEM)

• Passes a beam of electrons through the object

• Focused by magnets• Only dead cells can be

viewed• Cells must be embedded

in plastic and sliced thin• Much greater

magnification & resolution (.2nm)

Transmission Electron Microscope

Scanning Electron Microscope (SEM)

• Beam of electrons sweeps over and bounces off of object

• Produces a 3-D image• Less magnification

than TEM• Possible for living

cells

Scanning Electron Microscope

Metric System or System Internationale (SI)

• Reasons scientists use the metric system:– Based on the

number 10– Easy to convert– Universally

understood

Metric Units

• Length – meter (m)

• Mass – gram (g)

• Volume (liquid) – liter (L)

• Time – second (s)

• Temperature – Celsius (°C) or Kelvin (K)

Metric Prefixes

Deca da 10

Hecto h 100

Kilo k1000

Deci d1/10

Centi c1/100

Milli m 1/1000

Nano n1/billionth

Micro 1/millionth

METERGRAMLITER

SECOND

King Henry Died By Drinking Chocolate Milk

Monday Night

What is Biology?

• Bios – life or living things

• -ology – study of

• Study of life or living things

Characteristics of Living Things

• Living things are made of cells– Cells are the smallest

units of an organism that can be considered alive

– Unicellular – one-celled

– Multicellular – many-celled

Characteristics of Living Things

• Living things reproduce– Production of new organisms

Characteristics of Living Things

• Living things are based on a universal genetic code (DNA)

Characteristics of Living Things

• Living things grow and develop– Growth – an

increase in size– Development –

changes that occur as an organism grows

Characteristics of Living Things

• Living things obtain and use materials and energy– Producers – make

their own food– Consumers – eat

other living things

Characteristics of Living Things

• Living things respond to their environment– Temperature

• Ex. Birds fly south for the winter– Light

• Ex. Plants grow towards the sunlight if placed in a window

Characteristics of Living Things

• Living things maintain a stable internal environment– Homeostasis – keep internal conditions

relatively stable– What does your body do when you are cold?

• shivers

– What does your body do when you are hot?• sweats

Characteristics of Living Things

• As a group, living things change over time– Evolution – change over time– Ex. The brain cavity of human skulls is larger,

our jaws are smaller, on average we are taller

Characteristics of Living Things

• Living things…– Are made of cells– Reproduce– Are based on a universal genetic code– Grow and develop– Obtain and use materials and energy– Respond to their environment– Maintain a stable internal environment– Change over time

Levels of Organization

• Molecules-chemical components which are the building blocks of organelles

• Organelles-perform certain organ-like tasks within cells.

• Cell-smallest unit of life • Tissue-group of specialized cells• Organ-all tissues which work together as one• Organ System-all organs which perform common

functions

Levels of Organization

• Organism – an individual living thing– A cow

• Population – group of organisms– A herd of cows

• Community – populations that live together– A herd of cows, the grass, and flies

• Ecosystem – community & non-living factors– The cows, grass, flies, rocks, and streams

• Biosphere – contains all ecosystems– The entire Earth