Chapter 1 – The Science of Biology

The goal of science is to investigate and understand nature, to explain events in nature, and to use those explanations to make useful predictions.

Science – an organized way of using evidence to learn about the natural world

1-1 What is Science?

What Science Is and Is Not

Observation – involves using one or more of the senses – Which are?

Observation

sighthearingtouchsmelltaste

Data – information gathered from observation.

Two types of observation – Quantitative – involves numbers. Examples?

Qualitative – involves characteristics that cannot be easily measured or counted. Examples?

Observation

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

Hypothesis – a possible explanation for a set of observations or an answer to scientific questions.

*It can be useful ONLY if it can be tested.

Inference

5 Steps 1) Stating the Problem– Identify a problem to

solve.

2) Forming a Hypothesis- Example – Life can arise from not living matter or spontaneous generation. (Maggots appear on meat)

Hypothesis formulated by Francesco Redi in 1600s – Flies produce maggots.

1-2 Designing an Experiment

3) Setting Up a Controlled Experiment- Factors that can be changed in an experiment are called variables. Examples:

temperature, light, time

*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.

Why? If multiple variables are changed, one would not be able to tell which variable is responsible for the observed results

Manipulated variable – the variable that is purposely changed. (independent v.)

Responding variable – the variable that changes as a result of the manipulated variable. (dependent v.)

Types of variables

4) Recording and Analyzing Results

5) Drawing a Conclusion Hypothesis accepted or rejected?

If accepted, the test can repeated again for validity. If rejected, the experiment can be altered.

To make results more valid:(1)– Repeat the experiment(2)- Increase sample size

Experiments can be retested (like Redi’s) and/or improved with further investigation.

Examples – Needham, Spallazani, and Pasteur

In 1700s, microorganisms were discovered by Anton van Leeuwenhoek.

Publishing and Repeating Investigations

Needham and Spallazani’s Work

Filled with microorganisms

Both scientists proved existing organisms are produced only by existing organisms.

Pasteur proved that spontaneous generation was incorrect; he said that all living things come from other living things.

His work was different than Needham and Spallazani’s because he involved air.

Pasteur’s Work (1800s)

Tube cut – microorganisms present

Tube uncut – microorganisms not present.

An experiment was finally revised over a 200 year period.

Theory – applies to well-tested explanation that unifies a broad range of observation.

- starts off initially as hypothesis but then becomes so well supported.

How a Theory Develops

Characteristics of Living things1) Living things are made up of units called cells.

Cell – collection of living matter enclosed by a barrier that separates the cell from its surroundings.

Two types of organisms – multicellular and unicellular

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2) Living things reproduce.

Two types of reproduction:

sexual reproduction – involves two different parents (multicellular organisms)

asexual reproduction – involves only one parent(unicellular organisms)

3) Living things are based on a universal genetic code.

DNA - the genetic code that determines the inherited traits of every organism on Earth

4) Living things grow and develop.

5) Living things obtain and use materials and energy.

Metabolism – combination of chemical reactions in which an organism builds up or breaks down materials as it carries out its life processes

- Energy needed to live

6) Living things respond to their environment.

Organisms live in constantly changing environments.

7) Living things maintain a stable internal environment.

Homeostasis – process by which organisms keep their internal conditions relatively stable (breathing) - if disrupted in major way, organisms will not survive

8) Living things evolve, or change over time.

Branches of Biology The many levels at which life can be studied include molecules, cells, organisms, populations of a single organism, communities of populations living in the same area, and the biosphere.

Most scientists use the metric system when collecting data and performing experiments.

Metric system – decimal system of measurement whose units are based on certain physical standards

scaled on multiples of 10.

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Microscopes –devices that produce magnified images of structures that are too small to see with the unaided eye.

Microscopes

Light microscopes produce magnified images by focusing visible light rays. Electron microscopes produce magnified images by focusing beams of electrons.

Cell Culture – group of cells that develop from a single original cell.

Purpose – To test cell responses under controlled conditions and to study interactions between cells.

Laboratory Techniques

Cell fractionation – a technique in which cell parts (organelles) can be separated.