Download Evolution Evidence

Science:
How Do We Know What We
Know?
Science: How Do We Know What
We Know?
• Scientific Explanations require
credible evidence.
– Accuracy
– Repeatability
– Authority or fame noes NOT
establish credibility
– Must relate to the issue in question
Science: How Do We Know What
We Know?
• Scientific Explanations require
soundness of reasoning
– Start with accurate assumptions
– Guided by credible evidence
– Built with logical connections
– Explanations have predictive
power
• Causal relationships
(If..then...because…)
• Competing explanations not as
predictive
Science: How Do We Know What
We Know?
• Science is embedded in cultural history
– Technology available?
– Societal views?
• Is it important?
Assumptions of Science
• A. THE WORLD IS REAL
– In other words, the physical universe exists
apart from our sensory perception of it.
Assumptions of Science
• B. HUMANS CAN ACCURATELY PERCEIVE
AND UNDERSTAND the physical universe.
– In other words, we can learn correctly how the
natural world works and operates.
Assumptions of Science
• C. NATURAL PROCESSES are
SUFFICIENT to explain or account for
natural phenomena or events.
– In other words, scientists must explain the
natural in terms of the natural, not
“supernatural” or “magic”.
Assumptions of Science
• D. Scientists ASSUME THAT NATURE
"OPERATES" UNIFORMLY in both space
and time
– (unless we have evidence to the contrary)
Hypothesis, Theory and Law
• Fact An observation that has been repeatedly confirmed.
For example:23 pairs of chromosomes in human cells.
• Hypothesis
– An idea that CAN BE TESTED and verified or falsified.
• If sugar concentration is
increased then yeast
will reproduce faster
because sugar is a needed
food source.
• If the angle on the top of a
wing is increased then the
plane can carry more weight because
more lift will be created .
Hypothesis, Theory and Law
• Law
– A description of a natural phenomenon or
principle that invariably holds true under
specific conditions. Does NOT explain why.
In other words, WHAT stuff does, not WHY it
does it.
Objects attract each other
directly proportional to
– Law of Gravitation their mass
– Boyles Gas Law
For gasses at a given
temperature, pressure and
volume are inversely
proportional
Hypothesis, Theory and Law
• Theory
– a well-substantiated, overarching
EXPLANATION of some aspect of the natural
world: incorporates facts, laws, inferences, and
tested hypotheses.
• Internally consistent and compatible with the evidence
• Firmly grounded in and based upon evidence
• Tested against a wide range of phenomena
• Demonstrably effective in problem-solving
Gravitational
Atomic
Cell Theory Evolution
Theory
Theory
What is a Scientific Theory?
Descent with Modification
• Darwin’s 5 observations
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1- Exponential fertility
2- Stable population size
3- Limited resources
4- Individuals vary
5- Heritable variation
Descent with Modification
•
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Darwin’s 3 Inferences:
1- Struggle for existence
2- Non-random survival
3- Natural selection
(differential success in
reproduction)
Natural Selection
.
•
There is variation in traits.
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There is differential reproduction.
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There is heredity.
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End result:
•
If you have variation, differential reproduction, and
heredity, you will have evolution by natural selection as
an outcome. It is as simple as that.
Adaptation
• An adaptation is a feature that is common in a
population because it provides improved survival and
are produced by natural selection.
• Mimicry of leaves by insects is an adaptation for evading
predators. This example is a katydid from Costa Rica.
• The creosote bush is a desert-dwelling plant that
produces toxins that prevent other plants from growing
nearby, thus reducing competition for nutrients and
water.
• Echolocation in bats is an adaptation for
catching insects.
What is Meant by Evolution?
Evolution: A series of gradual or rapid changes, some
regular, some random, that account for the present form
and function of phenomena both living and nonliving.
• Science attempts to discover mechanisms.
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Evolution of universe (Big Bang)
Evolution of Galaxies
Evolution of Stars
Evolution of Solar systems
Evolution of the Earth System (water, landforms, atmosphere)
Evolution of Living systems
Evolution of Scientific ideas
How Do We Know That Evolution
Has Occurred?
Fossils as Evidence
What can fossils tell us?
http://people.uncw.edu/dockal/gly312/fossils/fossils.htm
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Fossils as age indicators
Fossils as environmental indicators
Fossils as indicators of Earth movements
Fossils as indicators of ancient geography
Fossils as evidence for the evolution of life
– Evolution of feathers in dinosaurs
Evolution evidence: The Fossil Record
• Succession of forms
over time
• Vertebrate descent
• Need for fossils?
Evolution Evidence: Comparative Anatomy
• Homologous structures
– (homology: similarity in
structure]
• Implies descent from a
common ancestor
• Vestigial organs
• Ex: whale/snake hindlimbs;
• appendix
• wings on flightless birds
• Tailbones when no tails
If organisms are closely related,
even if they look very different
outside, how should their bones
look inside?
If organisms are NOT closely related,
even if they look similar outside, how
should their bones look inside?
Evolution evidence: Comparative
Anatomy
• Analogous Structures
– Convergent Evolution
• Serve same purpose but
evolved separately
Evolution evidence:
Comparative Embryology
• Pharyngeal pouches,
• ‘tails’ as embryos,
• Tooth buds in birds
Evolution evidence: Molecular Biology
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Similarities in DNA,
Similarities in Proteins,
Similarities in Genes
Similarities in Gene products
COMMON GENETIC CODE
Evolution Evidence: Evolution at
work today
• Evolution of antibiotic resistant bacteria
If I understand evolutionary
theory…
…what can I
understand
?
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Modern medicine
AIDS, Influenza
History of humans
Impact of
environmental
changes
How Do We Know That Evolution
Has Occurred?
1.
2.
3.
4.
The fossil record of change in earlier
species
The chemical and anatomical
similarities of related life forms
the geographic distribution of related
species
the recorded genetic changes in living
organisms over many generations