CHARACTERISTICS OF LIVING THINGSSCIENTIFIC METHOD

MICROSCOPY

Introduction to Biology

Life

What is required for something to be considered living?

Consider the following questions… How big/complex must something be? What must it be able to do? Where must it come from? What are the essential components? How is it different from something nonliving? Is seeing believing??????

Apple debate

Is an apple living or nonliving? Why?

So, what makes something living?

1. Living things are based on a universal genetic code. All organisms store the complex information they need

to live, grow, and reproduce in a genetic code written in

a molecule called DNA! The information is copied and passed on from parent to

offspring. With a few minor variations, life’s genetic code is almost

identical in every organism on Earth.

2. Living things grow and develop. Every organism has a particular pattern of growth and

development. During development, a single fertilized egg divides

and divides again. As these cells divide, they differentiate, which

means they begin to look different from one another and perform different functions.

3. Living things respond to their environment. Organisms detect and respond to stimuli from their

environment.

A stimulus is a signal to which an organism responds.

4. Living things reproduce. All organisms reproduce, which means that they

produce new similar organisms. Most plants and animals engage in sexual reproduction.

In sexual reproduction, cells from two parents unite to form the first cell of a new organism.

Other organisms reproduce through asexual reproduction, in which a single organism produces offspring identical to itself.

5. Living things maintain a stable internal environment. Most organisms need to keep conditions inside

their bodies as constant as possible, even when external conditions change dramatically.

All living organisms expend energy to keep conditions inside their cells within certain limits.

This process is called homeostasis.

6. Living things obtain and use materials and energy. All organisms must take in materials and energy to

grow, develop, and reproduce. The combination of chemical reactions through which

an organism builds up or breaks down materials is called metabolism.

7. Taken as a group, living things evolve. Over generations, groups of organisms evolve, or

change over time. Evolutionary change links all forms of life to a

common origin more than 3.5 billion years ago. Evidence of this shared history is found in all aspects

of living and fossil organisms, from physical features to structures of proteins to sequences of information in DNA.

8. Living things are made up of cells. Organisms are composed of one or more cells- the

smallest units considered fully alive. Cells can grow, respond to their surroundings, and

reproduce. Despite their small size, cells are complex and highly

organized.

Scientific Method

1. Observing and Asking Questions2. Inferring and Forming a Hypothesis3. Designing Controlled Experiments4. Collecting and Analyzing Data5. Drawing Conclusions

Scientific Method

1. Observing and Asking Questions Observation-

What you see, touch, taste, feel, hear, etc. For example: The grass is green.

Scientific Method

2. Inferring and Forming a Hypothesis Inference-

a logical interpretation based on what scientists already know. Leads to a…

For example: The grass is green because its cells contain chlorophyll.

Hypothesis- A scientific explanation for a set of observations that can

be tested in ways that support or reject it. Typically an “if”…. “then” statement For example: If you provide the plant with nutrients, then

it will grow.

Scientific Method

3. Designing a Controlled Experiment Controlled experiment-

a hypothesis should be tested by an experiment in which only one variable is changed. All other variables should be left unchanged, or controlled.

Variable is any factor that can change (for example, temperature,

light, time, and availability of nutrients). Controlled variable

is the variable left the unchanged.

Scientific Method

3. Designing a Controlled Experiment, ctd… Independent variable

The variable that is deliberately changed For example: time, temperature, pH

Dependent variable The variable that is observed and that changes in

response to the independent variable For example: plant growth, heart rate

Scientific Method

3. Designing a Controlled Experiment, ctd…An experiment typically contains a:Control group

Exposed to the same conditions as the experimental group except for one independent variable.

Serves as a standard for comparison to the…

Experimental group The group that the independent variable is applied to.

Scientific Method

4. Collecting and Analyzing Data Quantitative data

Numbers obtained by counting or measuring Qualitative data

Descriptive and involve characteristics that cannot usually be counted.

Scientific Method

4. Collecting and Analyzing Data, ctd…

Charts and graphs are tools that help scientists organize their data.

Scientific Method

5. Drawing conclusions Use experimental data as evidence to support, refute,

or revise the hypothesis being tested, and draw a valid conclusion.

Often many experiments must be performed to fully support or reject a hypothesis.

What is a Scientific Theory?

Scientific Theory A well-tested explanation that unifies a broad range of

observations and hypotheses that enables scientists to make accurate predictions about new situations.

For example: Cell Theory, Gravitational Theory, Evolutionary Theory, etc…

The Compound Light Microscope

Antone von Leeuwenhoek assembled the first microscope that was useful for scientific research.

Compound light microscopes reflect light through a set of lenses and the specimen to magnify the specimen. Could be used to look at living or nonliving things.

The Compound Light Microscope

1. Base: Part on which the microscope rests

2. Mirror/Light source: Reflects light through objective lens into barrel of

microscope

3. Stage: Surface on which the slide is placed.

4.Arm Part by which microscope is carried

The Compound Light Microscope

5. Fine adjustment Used for fine, detailed focusing of microscope

6. Coarse adjustment Used for initial focusing of microscope; moves the

stage up and down for focusing

7. eyepiece/ocular Tube containing the ocular lens through which you

look into microscope

8. body tube Tube extending from eyepiece to objectives

The Compound Light Microscope

9. Nosepiece Revolving circular structure containing objectives

10. High power objective (10X, 40X) Objective used for focusing minute details on microscope

slide

11. Low power objective (4X) First objective used for focusing microscope slide

12. clip Used to hold slide on stage

13. diaphragm Controls amount of light that goes through stage into

objective lens.

The Compound Light Microscope

Two important characteristics that determine the quality of a light microscope:1. Magnification – an increase in the apparent size of

an object. We calculate magnification by the following:

Magnification of eyepiece x magnification of objective lens = total magnifying power

2. Resolution – the measure of clarity of an image. As the magnification increases, the resolution of the image decreases.