Transcript Evolutionary Theory Holt Ch. 16 Glencoe Ch. 15 Evolution: Process by which species change over time. Descent with Modification.

Evolutionary Theory
Holt Ch. 16
Glencoe Ch. 15
Evolution:
Process by which species change over
time.
Descent with Modification
Charles Darwin
1809-1882
English Naturalist
HMS Beagle 1831-1836
Sailed around world
gathering specimens and
fossils and observing
geology
Route of HMS Beagle
Darwin collected fossils
Some fossils looked
like modern animals.
Some fossils were different:
Giant Ground Sloth
from Patagonia
Fossil Record = All fossils known to science
Younger fossils lie above older fossils in
undisturbed rock layers
Comparing fossils shows a gradual
change from past to present life
We keep finding new fossils, but the fossil
record will still have gaps
Layers of rock include fossils
shows history of
life over millions
of years.
Fossils support Evolution
From looking at the
fossil record, Darwin
suggested that whales
may have come from
a 4-legged land
mammal.
http://www.txtwriter.com/Backgrounders/graphics/evolution/page2a.jpg
Evolution of horse hoof
Evidence of Geologic Change
Darwin found
marine fossils high in
the mountains
How did they get
there?
Convergent plate boundaries push up mountains
Galapagos Islands
Galapagos Islands = hot spot
Islands formed by hot
magma reaching surface
of crust
Older islands (4 million
years old) are eroded and
lower.
Newer islands (7000
years) are steeper
Darwin found unique animals
Marine iguana
Many other species
that live no other
place on earth.
Galapagos Island Finches
Darwin’s Thinking…
Perhaps a few finches from the S. Am.
mainland migrated to the new islands.
http://ecuador.america-atlas.com/pictures/galapagos-islands.jpg
Darwin noticed that
the finches on
different islands were
slightly different:
Different beaks
Different diets
Over time their
descendents were
“modified” as
different groups
specialized in
eating different
foods.
http://pustakalaya.olenepal.org/wiki/images/94/9454.jpg
http://www.bio.miami.edu/~cmallery/150/evol/24x9.jpg
Each type of finch occupies a different
niche (ecological role) so competition is
reduced.
Adaptive radiation - one species diversifies
into several species, each adapted to a different
niche
Darwin didn’t invent evolution…
Jean Baptiste Lamarck (1744-1829)
Proposed a theory of
evolution in which a trait
could change due to
use or disuse
AND those changes would be
passed to offspring =
Acquired Characteristics
Lamarck’s Evolution
According to Lamarck,
this body builder’s
offspring would be
born buff.
Galapagos Tortoises
Darwin noticed that
the giant tortoises on
different islands had
different characteristic.
How would Lamarck
explain these
differences?
Galapagos tortoise
closeup!
Why are the animals different?
Each island has slightly different weather:
lower islands are barren and dry,
higher islands are wetter
So, different islands have different
vegetation, different habitat.
Tortoises with longer necks could reach
the higher vegetation in drier areas, so
they survived and reproduced, passing
their long-necked genes to their offspring.
Tortoises in wetter areas had plenty to
eat and didn’t need long necks to survive
and reproduce.
Galapagos tortoise
Natural Selection:
Individuals that have
traits better suited to
their environment
are more likely to
survive and
reproduce.
“survival of the
fittest”
http://www.uri.edu/cels/nrs/paton/spring_peeper/
sppe_camoflage2.JPG
What are the 4 steps
of natural selection?
Darwin’s steps of natural selection:
Variation –inherited variation in every
population
Overproduction – populations produce
more offspring than can possibly survive
(leads to competition for resources!)
Selection – individuals with favorable traits
leave more offspring
Adaptation – over time, favorable traits
become more common in a population
Darwin considered
More Evidence:
Artificial Selection
Population growth (Malthus)
Age of the Earth (Lyell & Hutton)
Darwin’s Artificial Selection
When breeding
livestock, humans
choose the parents
with traits they want
in the offspring.
Ex: dogs, cows,
horses, pigeons
Population growth:
Thomas Malthus pointed out that food
supplies were limited and the human
population could not keep increasing
exponentially.
Darwin applied this to all populations:
organisms must COMPETE for limited
resources!
Age of the Earth
In Darwin’s time most Europeans believed in the
biblical age of the Earth (a few thousand years).
James Hutton and Charles Lyell were geologists
who studied fossils and rock layers and suggested
that the
Earth was much older (millions of years)!
…long enough for species to evolve
gradually.
On the Origin of Species
by Means of Natural Selection
Darwin hesitated to publish his ideas
because they conflicted with popular
religious beliefs about the origin of life.
He waited until 1858 when Alfred Wallace
convinced him to go public with his book,
On the Origin of Species.
Evolution:
A change in an
inherited
characteristic of a
population over time.
Individuals DO NOT
evolve!
Adaptation:
An Inherited trait present in a population
because it helps individuals survive AND
reproduce in a given environment.
Individuals may have adaptations, but
they DO NOT CREATE adaptations
through use. (That’s Loser Lamarck!)
Now, work with the person sitting next
to you to think of a particular
organism’s adaptation. Be prepared
to explain how that adaptation might
have evolved.
Macroevolution (forming new
species) is a slowww process!
It takes many generations to
develop adaptations!!!
Microevolution is a change in
the gene frequencies of a
population.
Can happen quickly
Ex: antibiotic resistant bacterial
colonies
Speciation:
New species evolve and no longer
interbreed with the ancestor.
What is a species?
Morphological (what they look like)
Biological (reproduction)
Molecular (DNA)
Evolution is a unifying theory
Darwin brought together evidence from
geology, biogeography, ecology,
paleontology.
Today Evolutionary Theory also includes
evidence from developmental biology,
genetics, and biochemistry.
What are
homologous traits or
homologies?
Anatomy gives clues to evolutionary
relationships:
Homologous structures: traits that are similar in
2 or more species, inherited from a common
ancestor.
http://mysite.verizon.net/vzepz6a9/biorefweb/homologous_structures.jpg
Biogeography
Study of the locations of organisms around the
world.
Large, flightless birds are found in similar
habitats, different locations.
http://landresources.montana.edu/dward/images/diversity_ecology_evolution/fig_8.jpg
Embryology - study of
developing embryos
Compare the
development of
embryos of
different species.
All vertebrate
embryos have a tail
at some point in
development.
http://images.google.com/imgres?imgurl=http://nitro.biosci.arizona.edu
/courses/EEB182/Lecture02/figures/embryo.gif&imgrefurl=http://nitro.b
iosci.arizona.edu/courses/EEB182/Lecture02/lect2.html&h=301&w=55
7&sz=8&hl=en&start=1&tbnid=RPSVmqo94XabJM:&tbnh=72&tbnw=1
33&prev=
Genetics:
Compare DNA
sequences to find
hereditary
relationships.
The more similar the
genes, the more
closely related the
organisms.
http://www.nap.edu/books/11876/xhtml/images/p20013a49g31001.jpg
http://www.youtube.com/watch?v=_Y58x68OAs
U&annotation_id=annotation_454588&feature=iv
Biochemistry:
All life is built
from the same 20
amino acids.
compare
differences in
amino acids of
same protein.
Darwin’s Theory
Strengths:
Weakness:
1. Organized notes,
observations, evidence.
1. Darwin didn’t
know about genes.
2. Showed the mechanism
of change.
3. Showed that variation
was starting point of
evolution.
Cladogram – a tree-like diagram that shows
evolutionary relationships.
http://bio1903.nicerweb.com/Locked/media/ch25/25_11Cladogram.jpg
Evolutionary novelty:
a characteristic shared by one branch of the cladogram