Transcript File - Schuette Science

Source: donsmaps.com
Chapter 17 and 18: Darwin’s
Theory of Evolution
Source: http://anthro.palomar.edu/evolve/evolve_2.htm
Theory of Evolution
Evolution:
Gradual process (over millions of years!)
by which modern organisms have
descended from ancient ancestors
Evolution is based on scientific facts,
observations and hypotheses
Proposed by Charles Darwin… let’s
examine his voyage and data.
Charles Darwin
English naturalist
Set sail on a 5 year cruise on the HMS
Beagle in 1831
Source: http://anthro.palomar.edu/evolve/evolve_2.htm
The Voyage
At each stop, Darwin:
Made biological and geological
observations
Collect plant and animal specimens
Collected Fossils
Darwin Observed
A great deal of biodiversity!
Vast number or plants & animals
species lived at each location
Each species seemed well adapt to its
environment
An intriguing geographic distribution of species
Today we know that there are about 1.75
million species on the planet.
This number only represents 1% of all
species that ever lived on Earth!
The Galapagos Islands:
An Important Influence on Darwin
Small group of Islands located 1000km west of South
America
The Islands had very different climates
Darwin noticed that plants and animals varied noticeably
from island to island.
• Ex:
 Land Tortoises
14 different sub-species
4- extinct
1 almost extinct
9- living
Source: www.thebestofecuador.com
Darwin found the shell shape
corresponds to the habitat
Lonesome George
Figure 15-3 Variations in Shell Shape (p. 371)
Darwin’s Thoughts
Where did all
the animals
come from?
Where did
humans
come
from?
What
about
fossils?
Has
everything
always been
here?
How old
is the
earth?
Do plants
ever
change?
What
happened
to all the
dinosaurs?
Darwin’s Proof
Evidence of Evolution
The Fossil Record
Geographical Distribution
Similarities
• Embryology
• Chemical Compounds
• Body Structures
The Fossil Record
By comparing older fossils with younger
fossils, evidence of change is clear.
Geologic Time Scale
Precambrian 4.6 bya-544 mya (life, eukaryotes)
Paleozoic 543-245 mya (cambrian explosion)
Mesozoic 245-67 mya
Triassic: Mammals/dinosaurs appear
Jurassic
Cretaceous – radiation of species (spp)
Cenozoic 66 mya to present (human era)
Radiometric vs. Relative Dating
½ Life of Elements
Decay
Depths of Strata
Geographic Distribution of
Living Species
Darwin discovered the existence of
similar but unrelated species in different
locations
Darwin later realized the similar animals
were products of different lines of
evolutionary descent.
Similarities in Early
Development
Let’s examine embryos
In the late 1900’s many thought, embryos
looked the same
While that’s not exactly the case
• Similar genes are at work in early development
• As they grow the become more dissimilar
• Differences caused by genes that have
changed due to evolution
Similarities in Early Development
Similarities in Body Structure
Embryos develop limbs that are structurally similar
Evolutionary changes altered the structure and
appearance based on their FUNCTION
Why? They’re adapted to allow organisms to survive
in their environment
These structures are called Homologous
Contrasting idea: Analogous Structures (suggest
species evolution converged due to similar
environments)
Homologous Structures
Analagous Structures
Vestigial Organs
Organs that have no or little purpose.
Evolution has lead to adaptations that suit
particular organisms
Similarities in Chemical
Compounds
All organisms use DNA and/or RNA
Many organisms have similar proteins
The more closely related two species
are, the more their chemical properties
resemble each other.
Darwin’s ideas were heavily
influenced the ideas of the
time
Early Explanations of Change
James Hutton (1726-1797)
Thought that geological changes were the
result of gradual change over a long period
of time
Earth is 4.6 billion years old!
Significant:
• many at and before his time
believed the earth was only
a few thousand years old.
Early Explanations of Change
Charles Lyell (1797-1875)
Developed the theory of
uniformitarianism
“the present is key to the past”
The current geologic processes have shaped
the earth’s topography.
Geologic processes take a long time! (millions
of years!)
Early Explanations of Change
Jean Baptiste Lamarck (1744-1829)
Proposed a theory of evolution based on selective
use or disuse of traits
• All organisms have a tendency toward perfection
 Organisms are continually changing and acquiring features
that help them
• Use and Disuse
 Organisms can alter the size/shape of a particular
appendage by using it in a new way
Inheritance of Acquired Traits
 modifications could be passed on to offspring
 giraffes who developed longer necks from stretching could
pass these long necks onto their offspring
Early Explanations of Change
Jean Baptiste Lamarck (1744-1829)
Lamarck did not know how traits were
acquired and passed on.
His hypothesis had many flaws.
His ideas helped ideas about adaptation
paved the way for Darwin’s theory
Early Explanations of Change
Thomas Malthus (1766-1834)
Was an economist
Notice babies were being born faster than
people were dying.
Figured, sooner or later living space and
food supplies would be in short supply
Events such as famine, war and disease
would limit population growth
Darwin would later apply this idea to plants
and animals
Darwin Presents His Case
Darwin reflected on his findings for
many years after returning home.
He wrote about his theories in, On the
Origin of Species.
Published in 1859
23 years after the voyage of the Beagle
http://www.pbs.org/wgbh/evolution/educators/teachstud
s/svideos.html
Inherited Variation vs.
Artificial Selection
Variations:
Different forms of alleles for a trait
Inherited Variations
Traits passed on from parent to offspring
Artificial Selection (ex. dog breeding)
Humans select useful variations from naturally
occurring traits
Selective breeding practices
Evolution by Natural
Selection
The Struggle for Existence
Darwin thought nature used an “artificial selection
process”
Members of each species compete for resources
Natural Selection
Processes in nature that over time results in only
the survival of the fittest species
Results in changes of inheritable characteristics of
a population.
Changes increase a species’ fitness in its
environment
Survival of the Fittest
Fitness
Ability of an individual to survive and
reproduce.
Fitness is a result of adaptations
Adaptation
Physical and behavioral traits that allow an
organism to survive in its environment
Darwin Concluded:
Over long periods of time, natural selection
produces organisms that have different
Structures
Niches
Habitats
Species descended with modifications from a
common ancestor.
Implies all living things are related to one another
This principle is known as common descent
Darwin’s Finches
Similarities can be explained
with Darwin’s theory:
Living organisms evolved with gradual
modification of earlier forms of an
ancestor with common descent.
Let’s Look at an Example…
In pre-industrial England, there was a
species of moth called the
Peppered Moth (Biston betularia)
Almost all peppered moths were gray with
dark flecks
Rarely were they black
The Peppered Moth
The peppered moth tend to rest
on tree trunks during the day
The gray moth were well
camouflaged on the gray tree
trunks
Black moths stand out and are
easy targets for birds.
The Peppered Moth
Now, turn to England
during Industrial Times…
Pollution from the factories
turned tree trunks black
with soot.
Now, the black moths were
camouflaged on the trees.
The Peppered Moth
The black moths had a
better chance of survival
They had a higher fitness
After many moth
generations, almost all the
months in industrial areas
were black
The Peppered Moth
Black coloration is an adaptation to
an environment with black tree
trunks
In an industrial environment, black
moths survive to reproduce better
than gray moths.
Therefore, their genes are passed
on to future generations