Introduction to Biology The Science of Life. What is science? Science is a way of understanding the...

Introduction to BiologyThe Science of Life

What is science?

• Science is a way of understanding the world• The goals of science are to:

– Investigate and understand the natural world– Explain events in the natural world– Use those explanations to make informed

predictions

• Science is an organized way of using evidence to learn about the natural world.

• In this class, you are going to be a scientist.

Thinking like a scientist

• Scientific thinking begins with observation.• Observation is the process of gathering

information about events or processes in a careful, orderly way.

Observations

• The information gathered from observations is called data.

• Quantitative data are expressed as numbers, obtained by counting or measuring.

• Qualitative data are descriptive and involve characteristics that can’t easily be measured.

Thinking like a scientist

• Scientists use data to make inferences.• An inference is a logical interpretation based

on prior knowledge or experience. • A hypothesis is a proposed scientific

explanation for a set of observations. • Hypotheses must be testable. They can then

be confirmed or ruled out.

Testing a Hypothesis• When possible, only one

condition should be changed during an experiment. All other conditions should remain unchanged.

• Variable – the one condition that differs while other conditions remain the same

• Control – provides a standard of comparison for the one factor that varies

The Controlled Experiment• Controlled Experiment – an experiment set up in

duplicate so that all variables are the same except the one being tested.

• Independent variable – the factor that is tested• Dependent variable – the factor that changes in

response to changes in the independent variable.• Experimental group – 1 of the 2 groups tested in

a controlled experiment; the group in which the independent variable is manipulated

• Control group – all variables remain constant; used for comparison of experimental group

Designing an Experiment

• Many years ago, people wanted to know how living things came into existence. They asked:

• How do organisms come into being?• An early hypothesis was spontaneous

generation, the idea that life could come from nonliving matter.

• For example, most people thought maggots spontaneously appeared on meat.

Redi’s Experiment

• Francesco Redi, an Italian physician, in 1668 proposed that maggots came from eggs that flies laid on meat.

Redi’s Experiment

Others were inspired by Redi’s work:

Lazzaro Spallanzani, an Italian scholar performed yet another version of the experiment:

His findings? He concluded that the nonliving gravy did not produce living things. The microorganisms in the unsealed jar were offspring of microorganisms that had entered the jar through the air.

Pasteurized• Louis Pasteur, a French scientists, conclusively disproved

the hypothesis of spontaneous generation in 1864.

• Pasteur showed that all living things come from other living things.

Pasteurization•Pasteur saved the French wine industry, which was troubled by unexplained souring of wine.

•He saved the silk industry, which was endangered by a silkworm disease.

•He began to uncover the nature of infectious diseases, showing that they were the result of microorganisms.

The Scientific Method

• Make an observation• Define the problem• Form a hypothesis• Test the hypothesis• Observe and record results• Form a conclusion

Theory• In science, the word theory can only be applied

to explanations that are well-tested and supported by experimental evidence.

• Some theories supported by evidence and tests :– General Relativity / Gravity / Black Holes– Special Relativity (E=mc2)– Big Bang– Evolution– Cell Theory– Germ Theory– Atomic Theory

Studying Life• Characteristics of Living

Things:– Made up of cells– Reproduce– Based on universal genetic

code– Grow and develop– Obtain and use materials and

energy– Respond to stimuli– Maintain homeostasis– As a group, they evolve

Living things are made up of cells

• A cell is the smallest unit of an organism that can be considered alive.

• Cells can grow, respond to their environment, and reproduce.

• The cells in multicellular organisms are often specialized to perform different functions.

Living things reproduce• All organisms reproduce,

which means they produce new organisms

• Sexual reproduction – cells from two parents unite to form the first cells of new organism

• Asexual reproduction – single parent produces offspring which are identical to self

Sea anenome undergoing asexual reproduction through fission;

Living things are based on a universal genetic code

• All organisms carry the complex information they need to live, grow, and reproduce in DNA

• That information is copied and passed from parent to offspring

• This code is over 3.5 billion years old• DNA from human colon:

Living things grow and develop

• Every organism has a pattern of development

• During development, a single fertilized egg divides again and again

• As these cells divide, they undergo differentiation – cells begin to look different and perform different functions

Living things obtain and use materials and energy

• All organisms must take in materials and energy to grow and develop.

• Chemical reactions through which an organism builds up or breaks down materials is called its metabolism.

• Some organisms obtain nutrients from other organisms while others obtain nutrients from air, water, and soil. All are interdependent.

Living things respond to their environment

• Organisms detect and respond to stimuli in their environment.

• A stimulus is a signal to which an organism responds.

Living things maintain a stable internal environment

• Organisms need to keep conditions inside their bodies as constant as possible.

• This process is called homeostasis

Taken as a group, living things evolve

• The traits individual organisms inherit from their parents do not usually change.

• Over many generations, given groups of organism typically evolve – change over time.

Evolution

• Evolution explains the inherited similarities as well as the diversity of life.

• Evolution is the unifying theme of biology.• All forms of life are related because we all

trace our ancestry back to a common origin more than 3.5 billion years ago.

• Evidence of this common ancestor is found in all aspects of living and fossil organisms from physical features to protein sequences.

Levels of Organization• Living things may be studied on many different levels. • The largest and most complex level is the biosphere.• The smallest level is the molecules that make up living

things.• Some of the levels at which life can be studied include:

– molecules– cells– organisms– populations of a single kind of organism– communities of different organisms in an area– the biosphere

Levels of Organization• Biosphere = The part of Earth that contains all

ecosystems

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Levels of Organization• Ecosystem = Community and its nonliving

surroundings

Hawk, snake, bison, prairie dog, grass, stream, rocks, air

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Levels of Organization• Community = Populations that live together in

a defined area

Hawk, snake, bison, prairie dog, grass

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Levels of Organization

• Population = Group of organisms of one type that live in the same area

Bison herd

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Levels of Organization

• Organism = Individual living thing

Bison

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Levels of Organization

• Groups of Cells = Tissues, organs, and organ systems

Nervous tissue Brain Nervous system

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Levels of Organization

• Cells = Smallest functional unit of life

Nerve cell

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Levels of Organization

• Molecules = Groups of atoms; smallest unit of most chemical compounds

Water DNA

Levels of Organization

Metric System

• Universal system of measurement and symbols used by scientists worldwide

• SI is a decimal system, based on tens, multiples of ten, and fractions of ten

Prefixes in SI

• Kilo – 1000• Hecta – 100• Deka – 10• Meter (unit) – 1• Deci – 0.1• Centi – 0.01• Milli – 0.001• Micro – 0.000001• Nano – 0.000000001

Tools of the Trade

• Early biologists were limited in their studies because important life details were too small.

• Anton VanLeewenhouk began extensive use of microscope. Found microscopic animals in pond water

Lab Techniques

• Cell fractionation – separate cell parts to study specific parts.– Parts added to liquid and inserted in centrifuge to

spin tube, with dense parts (participate) settling at bottom

Lab Techniques

• Variety of techniques to study cells• Cells are able to reproduce so that a group of cells,

a cell culture, develops from the single, original cell.– Used to test cell responses in controlled conditions,

interactions between cells

Microscopes• A microscope is any tool which allows the

magnification of an object• Simple – a tool which magnifies using only one

lens• Compound – tool which magnifies using two

lenses, one mounted on each end of the tube• Light – compound microscope which uses

ordinary visible light to illuminate the image of the specimen

• Electron – More powerful than light microscope. Can only be used to view dead organisms.

Parts of a Microscope

• Eyepiece – lens at the top of the tube, closest to eye

• Tube – cylinder with lenses on either end, focuses light up to the eyepiece

• Objectives – lenses at the bottom of the tube closest to the object

• Nosepiece – holds and rotates objectives

Parts of a Micrscope

• Adjustments – focus image by changing distances between objectives and specimen

• Stage – platform where specimen is placed

• Stage clips – hold specimen in place

• Diaphragm – controls light amount

• Base and arm – supports