Transcript Evolution by Natural Selection

Evolution by Natural Selection
http://home.comcast.net/~fsteiger/cartoon2.gif
10/2/06
ES 100: Environmental Ecology
A few more logistics…
• From Eric Zimmerman: if you are a double major in ES
and EEMB, you may not need to take this class.
• Field Trip (Wed. before Thanksgiving)
• Will take about 2 hours (8-9:50).
• Transportation provided, but self-guided field exploration
• You can do it BEFORE-hand, on your own, if you prefer
• Midterm #2 (aka Final Exam)
• Add codes: I actually have them now, come see me.
• Section assignment this week: check course website!
Recap of Intro. Lecture
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Definition of ecology
Ecology vs. Environmentalism
Reductionism vs. Systems Thinking
Scientific Method: Case study of Lake Apopka
Alligators
– Hypotheses must be testable
– A hypothesis can be disproved, yielding support for the
‘alternative’ hypothesis.
– A theory is the highest level of scientific understanding
Organization within Ecology
Ecosystem Ecology
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Community Ecology
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Population Ecology
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Physiological Ecology
The Classification of Living Things
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primata
Family: Hominidae
Genus: Homo
Species: Sapiens
Roots of Ecology
• Carl von Linné (mid 1700’s)
• classification of living things
• Alexander von Humboldt (early 1800’s)
• botanical geography
• Charles Darwin and Alfred Wallace 1850
• animal geography
• theory of evolution by natural selection
• Ernst Haeckel 1866
• coined the term “ecology”
• Edward Suess 1875
• “biosphere” as the condition that promotes life: it includes plants, animals,
and non-living things
• Arthur Tansley 1935
• “ecosystem” concept: interaction between living and non-living entities in
the biosphere
Theory of Evolution by Natural Selection
• Natural selection is the mechanism that explains evolution
• Natural Selection: scale = individual
• Evolution: scale = many generations
Temporal Scale
Theory of Evolution by Natural Selection
• Natural selection is the mechanism that explains evolution
• Natural Selection: scale = individual
• Evolution: scale = many generations
• Darwin’s observations:
• Organisms produce more young than can survive.
• All species exhibit genetic variability (from mutation and
random combination of parent’s genes).
• Individuals with traits most suited to environment most
likely to survive.
• Only survivors contribute to the gene pool.
• Theory: Lineages with most appropriate biological
programming (genes) for current environmental conditions will
leave the most descendants.
Bush, page 7:
“Sickle-cell anemia, Down’s syndrome, and
color blindness are heritable, and each
would reduce an individual’s chance of
survival in a wild human population”
When is Mutant Sickle-cell Gene
Desirable?
www.sicklecelldisease-il.org/.../ what/how.html
Natural Selection and Physical
Appearance
Optimal Foraging Theory
• Organisms that ‘forage’ most efficiently will be
more likely to reproduce (improve fitness)
– Thus, natural selection favors optimal foraging.
– Cost/benefit analysis
• What is foraging?
police.ucsb.edu/ crime_prevent.html
• What do plants and animals forage for?
Experimental Evidence for
Optimal Foraging
Would ‘field’ observation match experimental results?
Natural Selection and
Biochemical Traits
Testing Hypotheses:
Observation vs. Experimentation
• Observation:
• See patterns in the field
• Strength:
grounded in reality
• Weakness:
mechanistically weak
• Experimentation:
Manipulate system by
creating experiments
• Strength: control
variables
• Weakness: not realistic
Natural Selection and Behavior
Are Human’s Exempt from
Natural Selection?
SWEATY T-SHIRT EXPERIMENT:
http://www.pbs.org/wgbh/evolution/library/01/6/l_016_08.html
Defining ‘evolution’
Scientific Definitions:
• All the changes that have transformed life on earth from its
earliest beginnings to the diversity that characterizes it today
–Neil Campbell
• The origination of species of animals and plants
–O.E.D.
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Common Usage:
• A process of continuous change from a lower, simpler, or worse
to a higher, more complex, or better state
–Merriam-Webster’s Dictionary
From a scientific point of view, evolution is just how new
species come about
Humans as an Evolutionary Endpoint?
Theory of Evolution: Criticisms
• Microevolution is generally accepted, but
macroevolution is hotly debated
– How does evolution add information to a genome to
create progressively more complicated organisms?
– How is evolution able to bring about drastic changes so
quickly?
– How could the first living cell arise spontaneously to
get evolution started?
Pakicetus
Ambulocetus
Basilosaurus
Humpback
Section this Week
Internet assignment for section this week:
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Visit course website
Follow “Evolutionary Feast” link
Prepare (typed) assignment and bring to section
Bring food to section (can bring a form of the
fruit/vegetable- chocolate instead of cocoa beans)