Download Chapter 15 Evolution outline

ET 1
Enduring Understanding(s)
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Evolutionary evidence (embryonic, DNA biochemical) explains
similarities among organisms.
Natural selection and the changing environment are mechanism of
evolution.
Organisms change over time.
Essential Questions
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How do new species arise?
How does natural selection affect a population?
What accounts for the diversity in the world around you?
What is an adaptation?
Evolution: Evidence and Theory
I. The Fossil Record
*shows the history of life on Earth
*shows that different organisms appeared for a time and then
disappeared, which were then followed by other new
organisms
*Evolution studies the varieties and interactions of living
things across time.
A. Nature of Fossils
1) fossiltrace of a long-dead organism
*found in sedimentary rock
2) sediment (dust, sand, mud…)deposited by wind or
water
3) Sedimentary fossilsfrom hard body parts(shell,bone)
* hard mineral replaces soft tissues.
4) mold(fossil type) imprint of an organism’s shape in
rock. (limestone)
5) cast filled mold fossils (filled with minerals)
Rocklike model
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6) Robert Hookeone of the first to study fossils (used
Microscope) thought fossils are remains of plants
and animals
B. Distribution of Fossils
* Nick Stenoproposed Law of Superposition
successive layers (Stratum) of rock or soil is
deposited on top of one anotherlowest stratum
(layer) oldest…top stratum most recent
* Relative ageusing steno’s law of superpositionby
Comparing fossils in different strata one can say a
Fossil is older or younger than another fossil
*Absolute agedetermined by radioactive dating
1) Succession of forms
*Extinct
*Mass extinctions brief periodlarge numbers of
Species disappeared (or became extinct)
2) Biogeography
Study of geographic distribution of fossils and of
living organisms
Ex.) new organisms appear in areas were fossils
show similar ones already existed.
II. Theories of Evolution
*Evolutionorderly succession (process of steps) of changes
*new life forms appear to be modifications of old life forms
found in the fossil record.
A. Lamarck’s Explanation
*Proposed similar species descended from a common
ancestor.
*Acquired traitsNOT determined by genesare traits
that come about during an organisms lifeas a result of
an organisms experience or behavior (mutation)
B. The Beginning of Modern Evolutionary Thought
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*Darwin/Wallace both independently proposed
hypothesis of Natural Selection
*Natural Selection process by which organisms that are
best suited to their environment reproduce more
successfully than other organisms. so organisms
pass on favorable traits over generations favorable
trait is seen more and more in a population.
*Populationinterbreeding single-species group
*Darwin published The Origin of Species (1859)
1) Charles Darwin
***Natural selection acts on INDIVIDUALS.
***POPULATIONS evolve
C. DARWINS THEORIES
* Darwin sums up natural selection and evolution in two
theories (1. Descent w/ modification 2.modification by
natural selection)
1) Descent with Modification
*new life forms that appear in fossil record are
modified descendents from older species
*he also inferred that all species descended from
one or a few original types of organisms.
2) Modification by Natural Selection
*Environment limits the growth of populations by
increasing the rate of death or decreasing the rate
reproduction or both.
*Organisms with (within the same species) more
favorable traits will leave more offspring than
organisms with fewer beneficial traits.
*Adaptwhen genetics in a population change over
generations to allow the population to become
more suited to the environment (result is evolution)
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….(to adapt is to evolve)
*Fitness an individual organism’s contribution
(in an evolving population) to the next generation.
organism w/ high fitnesswell adapted to
environmentreproduces more successfully
*Adaptive advantagean organism with a favorable
trait
III. Evolution in Process
*continuous process
*evidence of evolutionstudy genotypic/phenotypic evidence
in modern organisms
A. EVIDENCE OF EVOLUTION
1) Homologous and Analogous Structures
*Homologous Similar features that originated in a
shared ancestor. may not be obviouspenguin
wing and alligator armcome from same
structures in embryo
*Analogoushave identical functions, and look
very similar. very different embryological
development
2) Vestigial Structures
*Vestigial featuresfeatures on an organism that
have no apparent use (useless)  (ex. Tail bone in
humans.) Evidence that the feature was
functional in some ancestor of the modern
organism.
3) Similarities in Embryology
*In the early stages of development, all vertebrate
embryos are similar, but the similarities fade
as development proceeds
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4) Similarities in Macromolecules
*Darwinmore-similar forms of organisms have a
more recent common ancestor than do less-similar
formshe did not know it but this is true at the
molecular level as well. Homologous proteins
of 2 species is proportional to the length of time
that has passed since the 2 species shared a
common ancestor.
B. PATTERNS OF EVOLUTION
1) Coevolutionwhen two or more species in close
association with each other change  (ex.preditor and
prey) (ex. Plant and animal that eats plant)
2) Convergent Evolution
*Convergent evol. appear very similar but are not
closely related (ex. Dolphin and Shark)
*Very similar in characteristics because they
share the same environment.
3) Divergent Evolution
*Divergent evol.  2 or more related populations
or species become more and more dissimilar.
why?  habitats become different
 Ex. (lions and tigers) can result in
different species.
*Adaptive radiation type of divergent evol.
many species evolve from a similar species
 (Ex. Darwin finches) why?different
Types of food in different habitats.
*Artificial selectiondivergence sped up artificially
(ex. Dogs  same species with many different
phenotypic traits