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Welcome to Life on Earth!
Rob Lewis512.775.6940
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The Science of BiologyThemes…
and –just what is science ?
how about this biology stuff?
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The Process Of Science
• No absolute truths in science• Our understanding about nature comes from
ability to observe. • Science has levels of confidence in explanations
for natural phenomena• Assumes a rational universe
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The Process Of Science Scientists use two main approaches to
learn about nature Discovery Science – observe and describe,
then use inductive reasoning to draw general conclusions
Hypothesis-Based Science - attempt to explain observations by forming and testing hypotheses
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Scientific Theory Characteristics:
Broad in scope, generate hypotheses Supported by massive body of evidence Constantly challenged through testing of the specific,
falsifiable hypotheses they generate. Examples:
Einstein’s Theory of General Relativity Darwin’s Theory of Evolution Lemaître’s Big Bang Theory of the Universe
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Hypothesis-based Science
Hypothesis-based science involves: Observations, questions, hypotheses
as tentative answers to questions Deductions leading to predictions, and
then tests of predictions to determine if a hypothesis is falsifiable
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What is a hypothesis? A a tentative or educated guess at an answer to
a problem or question being asked. A good hypothesis makes predictions that can
be tested. Hypothesis-based science uses deductive
reasoning that flows from a general premise to a specific premise.
Important point (aspect) of this process is the deduction can be tested
One experiment can’t prove or disprove!
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Hypothesis-based Science
• Two important qualities:• A hypothesis must be testable.• A hypothesis must be falsifiable
• If a hypothesis is correct, and we test it, then a particular outcome is expected
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Scientific Method key steps: Make observations
Ask questions about the observations: How? Why? When?
Generate hypotheses; explanations of the phenomena, phrased to be testable.
Derive predictions; logical, testable outcomes of the hypotheses use deductive reasoning Predictions take the form of: If X is true, then Y
Test the predictions; determine if the predictions are supported (fail to falsify) or falsified
A hypothesis becomes credible when repeated attempts to disprove it fail…
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Flow Diagram of the Scientific Method
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Biology- What is it?
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Biology: Scientific Study Of Life 0
Is it alive? How do we know?
Lump of coal
E. colibacterium
Ebola virus
Yeast
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Biology Nature is not neatly packaged … Organisms (and their environments):
natural systems chemistry and physics apply
Biology: multidisciplinary science draws on the insights from other sciences.
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What is Life? no simple, one-sentence definition recognize life by what living things do living organisms share common features
or properties
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Properties of Life Complex levels of organization, ordered
structures Regulate internal conditions Harvest and use energy Reproduce and evolve Grow and develop Respond to environmental stimuli
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Organizational Hierarchy Life - a hierarchy
of structural levels Successive levels
show additional emergent properties
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The hierarchy of Life
Organ systems Organs Tissues Cells Organelles Molecules
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complexity
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Emergent Properties Life’s basic characteristic = a high degree of
order – fight entropy Biological organization - based on structural
level hierarchies, each builds on the level below Each step upward novel properties emerge Emergent properties come from component
interactions Emergent properties reflect importance of
structural arrangement and organization
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Reductionism Complex organization of life presents a dilemma:
cannot fully explain a higher level of organization by breaking into parts (stops functioning!)
cannot analyze complex system (organism or cell) without taking apart
Reductionism – Reducing complex systems to simpler components Balanced by objective of understanding emergent
properties.
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Unity and Diversity Biology – think of it as having two
dimensions: Vertical - covers the size scale from atoms to
the biosphere Horizontal - encompasses the diversity of life
(includes organisms throughout history of life - 4 billion years!)
size
Life diversity progress
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Life Diversity Currently -- ~ 1.5 million species
over 280,000 plants 50,000 vertebrates over 750,000 insects. Thousands added each year
Total life diversity estimates --5 million to over 30 million species
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Unity Underlying the diversity
of life is a striking unity, especially at the lower levels of organization.
universal genetic DNA language unites organisms
unity is evident in many details of eukaryotic cell structure
Fig. 1.12
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Unity and Diversity Evolution -- key to understanding biological diversity The evolutionary connections explain unity and diversity
of life Descent with modification accounts for both the unity
and diversity of life. In many cases, features shared by two species are due to their
descent from a common ancestor. Differences are due to modifications by natural selection
modifying the ancestral equipment in different environments. Evolution -- core theme of biology - a unifying thread
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TaxonomyA system for organizing, classifying & naming living
things.Primary concerns of taxonomy are classification, nomenclature, and identification.
A way to communicate…
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Old School: Five Kingdoms
•Monera(“alone”)
•Protista(“first”)
•Fungi
•Plantae
•Animalia
Bacteria
Archaea
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The five-kingdom system became the standard until molecular biology techniques were used to develop the Domain system.
Fig. 1.14 Traditional Whittaker system of classification
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Classification- some notesProkaryote vs EukaryoteLinnaean classification Kingdom phylum class order
family genus species(King Phillip Came Over For Good Spaghetti)
Taxonomy:Old school five kingdomsNew and improved three domains
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Levels of ClassificationDomainPhylum or DivisionClass OrderFamilyGenusspecies
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Domains – a new Idea!Developed after the five-kingdom systemEubacteria -true bacteria, peptidoglycanArchaea –odd bacteria that live in extreme
environments, high salt, heat, etcEukarya- have a nucleus, & organelles
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Example Classification
(Notice a kingdom is inclusive, and genus and species are less inclusive...)
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New School: Three Domains
•Bacteria–Monera
•Archaea–Monera
The Domains Bacteria & Archaea = prokaryotes
•Eukarya (eukaryotes)
–Plantae–Animalia–Fungi–Protista
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The Domain system was developed by Dr. Woese. The basis of the Domain system is the rRNA sequence information.
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NomenclatureBinomial (scientific) nomenclature Genus – Bacillus, always capitalizedspecies - subtilis, lowercaseBoth italicized or underlined
Bacillus subtilis (B. subtilis)
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IdentificationThe process of discovering and recording the
traits (physical, biochemical, genetic) of organisms, thereby, placing them in a taxonomic scheme.
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Evolution- what about it? Charles Darwin - theory of evolution
by natural selection, his book presented two important concepts:
Species evolved from ancestors, and there was modification in the process or, as Darwin stated, “descent with modification.”
Natural selection occurs as heritable variations are exposed to environmental factors that favor the reproductive success of some individuals over others.
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