biology chapter 1. biology scientific study of life lays the foundation for asking basic questions...
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Biology
Chapter 1
Biology
Scientific study of life
Lays the foundation for asking basic questions about life
and the natural world
Why Study Biology?
• To learn how organisms are constructed, how they function, where they live, and what they do
• To help develop, modify, and refine ideas about life
Molecules of Life
• All things are made up of the same units of matter
• Living things are made up of a certain subset of molecules:– Nucleic acids– Proteins– Carbohydrates– Lipids
DNA (deoxyribonucleic acid)
• Signature molecule of life
• Molecule of inheritance
• Directs assembly of amino acids
DNA and Inheritance
• Inheritance– Acquisition of traits by way of
transmission of DNA from parent to offspring
• Reproduction – Mechanism by which an organism
produces offspring – Governed by instructions in DNA
Nothing Lives without Energy
Energy = Capacity to do work
Metabolism = Reactions by which cells acquire and use energy to
grow, survive, and reproduce
Sensing and Responding
• Organisms sense changes in their
environment and make responses to
them
• Receptors detect specific forms of
energy (stimuli)
• Allows maintenance of homeostasis
Levels of Organization
Cell
Multicelled Organism
Population
Community
Ecosystem
Biosphere
Interdependencies among Organisms
ProducersMake their own food
ConsumersDepend on energy stored in
tissues of producers
DecomposersBreak down remains and wastes
Decomposers
Decomposers break down dead organisms and wastes and release the nutrients they contain into the soil, where they are again available to the roots of plants (producers).
In this way, decomposers play an important role in recycling nutrients and getting rid of waste.
Energy Flow
• Usually starts with energy from sun
• Transfer from one organism to
another
• Energy flows in one direction
• Eventually, all energy flows back to
the environment
Producers
Consumers, Decomposers
NUTRIENT CYCLING
ONE-WAY FLOW OF ENERGY
In time, all energy flows back to the environment.
ENERGY FROM SUN
Unity of Life
All organisms:
– Are composed of the same substances
– Engage in metabolism
– Sense and respond to the environment
– Have the capacity to reproduce based
on instructions in DNA
Diversity of Life
• Millions of living species
• Millions more now extinct
• Classification schemes attempt to
organize diversity
Scientific Names
• Devised by Carolus Linnaeus
• First name is genus (plural, genera)
– Homo sapiens - genus is Homo
• Second name is species within genus
Eubacteria(Bacteria)
Archaebacteria(Archaea)
Eukaryota(Eukaryotes)
3 Domains
Origin of life
EubacteriaArchaebacteria
Eukaryotes
Protistans Plants Fungi Animals
6 Kingdoms
• Single cells
• No nucleus or
organelles
• Smaller, less
complex
Prokaryotic Organisms
Eukaryotic Organisms
• Single- or multi-celled
• Nucleus and other
organelles
• Larger, more complex
Mutation: Source of Variation
• Mutation = change in structure of DNA
• Basis for the variation in heritable traits
• Most are harmful
Adaptive Trait
A trait that gives the individual an advantage in survival or reproduction,
under a given set of circumstances
Evolution
• Genetically based change in a line of descent over time
• Population changes, not individuals
Antibiotic Resistance
• Antibiotics are used to kill bacteria
• Mutations for antibiotic resistance exist or arise
• Antibiotic-resistant bacteria survive and reproduce better than nonresistant
• Over time, proportion of antibiotic-resistant bacteria increases
Scientific Method
• Observe phenomenon
• Develop hypotheses
• Make predictions
• Devise test of predictions
• Carry out test and analyze results
Role of Experiments
• Used to study a phenomenon under known conditions
• Allows you to predict what will happen if a hypothesis is not wrong
• Can never prove a hypothesis 100% correct
Experimental Design
• Control group
– A standard for comparison
– Identical to experimental group except for
variable being studied
• Sampling error
– Nonrepresentative sample skews results
– Minimize by using large samples
Scientific Theory
• A hypothesis that has been tested for its predictive power many times and has not yet been found incorrect
• Has wide-ranging explanatory power– Darwin’s theory of evolution by natural
selection
Biological Therapy Experiments
Can we use viruses that attack bacteria (bacteriophages) to fight infections?
Experiment 1
• Hypothesis - Bacteriophages can protect mice against infectious bacteria
• Prediction - Mice injected with bacteriophages will not die as a result of bacterial injection
Experiment 1 - Test
• Experimental group
Inject with bacteria and bacteriophage
• Control group
Inject with bacteria and
saline
Experiment 1 - Results & Conclusion
• Experimental group
All mice lived
• Control group
All mice died
• Conclusion - Bacteriophage injections
protect mice against bacterial infections
Experiment 2
• Prediction - Bacteriophage injections will be more effective treatment than single dose of the antibiotic streptomycin
• Test - Mice injected with bacteria, then with saline, streptomycin, or bacteriophage
Experiment 2 - Results
• With 2nd injection:
– Bacteriophage - 11 of 12 mice lived
– 60 mg/gm streptomycin - 5 of 12 lived
– 100 mg/gm streptomycin - 3 of 12 lived
– Saline - all mice died
• Conclusion - Bacteriophage treatment can be
as good or better than antibiotic
Minimizing Variables
• All mice were same age and sex, reared under same conditions
• Each mouse in each test group received exact same treatment
• All mice in control group received same amount of saline
• Variable tested was antibiotic treatment versus bacteriophage treatment
Limits of Science
• Scientific approach cannot provide answers to subjective questions
• Cannot provide moral, aesthetic, or philosophical standards
Scientists Raise Questions
The external world, not internal
conviction, must be the testing ground
for scientific beliefs