Evolution Through Natural Selection - WHS-Rambo-Wiki

“Evolve” Means to Change Over Time
The belief that life on Earth has changed over
time is quite old
To be considered science, this belief requires
a great deal of evidence
The Development of Evolutionary Theory
Naturalists have always wondered at the
diversity of living things………
Great varieties in shape, size, and ecological role
Estimated 3 million to 20 million different living
Much of the natural world’s biodiversity has vanished
through extinction
99% of all species that ever lived are now extinct
Permian-Triassic Mass Extinction
What Killed the Dinosaurs?
Development of Evolutionary Theory
What could cause such great diversity, and
why have so many species died out?
Charles Darwin offered an explanation based on
careful observations
Who was Charles Darwin?
Development of Evolutionary Theory
Darwin Concluded:
Physical traits and behaviors enable organisms
to survive and reproduce (called Fitness )
Fitness results from adaptations
Darwin reasoned that adaptations result from
natural selection and result in evolution
Evolution is the process by which living things
change and diversify over time
Development of Evolutionary Theory
These ideas were widely challenged
until a tremendous amount of evidence
was gathered to support evolution!
Now…The Theory of Evolution is the
Cornerstone of Biology
Explore the Evolution Revolution
Scientists from many disciplines including
biology, chemistry, physics, geology, and
paleontology have contributed to the case
for evolution!
The Origin of Life
The Fossil Record
Comparative Embryology
Comparative Biochemistry
Comparative Anatomy
Isn’t Evolution Just a Theory?
The Origin of Life
Origin of the Universe
Big Bang (animation)
Early Earth
Evolution Starts Up: Chemical Evolution
Heterotroph Hypothesis: Molecules of life
arose from inorganic building blocks
The Miller-Urey Experiment
Studied Molecules Present at Time of
Early Earth
Methane, Ammonia, Carbon
Dioxide, Water Vapor
Mixed Molecules in Reaction Chamber
Sparked with Electricity to Simulate
Exposed Mixture to UV Radiation to
Simulate Cosmic Rays
Produced Basic Amino Acids and Organic
Biological Evolution
RNA as a information molecule and
Endosymbiotic Theory
Mitochondria and chloroplasts were
originally free living prokaryotic cells
Both have own DNA and ribosomes
Joined together to cooperate
The Study of the Earth and Rocks
Early Ideas About Earth:
People believed Earth was only a few
thousand years old
People believed that rocks and geological
features were shaped by catastrophic
events and rarely changed
In the 18th and 19th Century Scientists
Studied Geology in Great Detail
Over millions of years 1 original continent Pangea
drifted apart to make our modern continents
Continental drift is gradual “gradualism”
Hutton and Lyell:
Earth is Changed
by Weather and
Natural Processes
like Volcanoes
and Erosion
Takes a Very
Long Time!
These ideas refute the idea that the Earth is
only a few thousand years old
Backed up by radiometric dating
The Earth is approximately 4.6 Billion Years Old
4,600,000,000 years is a long time!
The Fossil Record
Fossils are the preserved remains of
ancient organisms
Provide information about past
Shows that many diverse organisms
lived at different times in Earth’s
The Fossil Record
Taphonomy: The Formation of Fossils
Fossils form in sedimentary rock
Dead organisms covered by sand and silt
Sediments are passed into bone by
pressure from above (fossils form in
sedimentary rock)
Determining the Age of Fossils
Relative Dating: Technique used by
scientists to determine the age of fossils
relative to fossils in other layers of rock
Different layers represent different geologic
Older fossils found in lower layers, newer
fossils found in upper layers
Cannot determine the actual age of the
Determining the Age of Fossils
Radioactive Dating: Process by which traces of
radioactive elements are analyzed to calculate the
actual age of a fossil
Many radioactive elements can be used as geologic
clocks. Each radioactive element decays at its own
nearly constant rate. Once this rate is known,
geologists can estimate the length of time over
which decay has been occurring by measuring the
amount of radioactive parent element and the
amount of stable daughter elements
Radiometric Dating
Potassium 40
Argon 40
1.25 billion
Rubidium 87
48.8 billion
Thorium 232
Lead 208
14 billion
Uranium 235
Lead 207
704 million
Uranium 238
Lead 206
4.47 billion
Carbon 14
Nitrogen 14
5730 years
Half life
The Geologic Time Scale
Based on fossil and geologic evidence
A record of the Earth’s past
Divided into Era, Period, and Epoch
Shows that life on Earth followed geologic
change on Earth
Deep Time Activity
Interactive Time Scale
Comparative Embryology
Embryos are organisms at early stages
of development
Comparative Embryology
All vertebrate embryos,
including humans, share
Eye spot
• (Evolution of the Human Eye)
Gill pouches
Shows similar genetic
Comparative Biochemistry
All life is based on organic chemistry
Carbon based compounds
All life uses same molecule as blueprint
Similar chemical processes
Bacteria, algae, and plants all do photosynthesis
Similar organisms have similar genetic code
Humans and chimpanzees share nearly identical
genes (98.4% identical gene sequences) Video
Anatomy and Comparative Anatomy
Vestigial Organs
Organs inherited but not used by modern
Present but greatly reduced in modern
Hip bone in python
Appendix in human
Tail bone (cocyx) in human
Anatomy: Homologous Structures
Similar parts of different organisms,
often quite dissimilar in purpose, that
developed from the same ancestral
body parts (Video)
Divergent evolution
Anatomy: Analogous Structures
Similar in purpose, but not inherited
from a recent common ancestor
Environment selected for trait
Wings of birds and insects
Convergent evolution
There is overwhelming evidence to
support the Theory of Evolution
Evidence comes from disciplines as
varied as biology, geology, chemistry,
physics, astronomy, and paleontology
Evolution has produced the great
beauty and diversity of life on Earth
over the last 4 billion years
Natural Selection
and Speciation
Charles Darwin
Studied Medicine and Theology
Excelled in Geology and Biology
In 1831 Darwin joined the H.M.S.
Beagle on a trip around the world to
make maps
He was the ship’s naturalist
Darwin’s Diary
The Voyage of the Beagle: Ports of Call
Noted that populations of organisms were slightly
different from place to place
Each group was modified to their specific environment
The Galapagos Archipelago
Land Iguana
Marine Iguana
The Origin of Species Interactive Exploration
Evolution Through Natural Selection
There is variation in populations caused by
genetics (Praying Mantis Camouflage)
Many more offspring are produced than can
survive. Many die through predation or starvation
Some variations are favorable and help
organisms compete to survive and reproduce
Over time, the organisms with favorable
variations become plentiful. The ones without
favorable variations become rare or extinct
Reluctantly published On the Origin of Species in
Natural Selection modifies populations.
Some evolutionary changes are so great
that some organisms can no longer
interbreed with the original population
A new species results
An interbreeding population of organisms
that can produce healthy, fertile offspring
Reproductive Barriers and Speciation
Prezygotic: gametes never meet and fuse
Geographic isolation (allopatric speciation)
Ecological isolation
Behavioral isolation (lacewing songs)
Mechanical isolation
Seasonal isolation
Postzygotic: genetic differences manifest
Hybrid inviability
Hybrid sterility (tigons and ligers)
Patterns in Evolution
Adaptive Radiation
Development of numerous new species from a
common ancestor in diverse environments
Darwin’s Finches (Origin of Species Activity)
Punctuated Equilibrium
Evolution Produces Diversity
All living things are classified by characteristics
into 5 kingdoms of life
bacteria, unicellular prokaryotes
single celled eukaryotes
multicellular, eukaryotic, nonmotile, heterotrophs
multicellular, eukaryotic, autotrophs
Animalia: multicellular, eukaryotic, motile, heterotropohs
Linnean Taxonomy
Example: human classification
Kingdom animalia
Phylum chordata
Class mammalia
Order primate
Family hominid
Genus homo
Species sapiens
Binomial nomenclature uses genus and
species to make the scientific name
Homo sapiens
Classification activity
Human Evolution
Explore Human Evolution
View the Becoming Human broadband
As you view each segment, visit the related
exhibits to further explore this topic
Go to the Learning Center and select the
“Calculating Cousins” activity
Go to the Learning Center and select the
“Chromosome Connection” activity
Go to the Learning Center and select the
“Building Bodies” activity
The Order Primate
Characteristics of Primates
Strong hands and opposable thumbs
Free-moving shoulder joint
Forward facing eyes and stereoscopic vision
Intelligence/larger brain
Social complexity
What Characteristics do Humans Have?
All of those of primates, plus
Upright posture and bipedal
Use of tools and technology
Advanced intelligence
Complex communication and speech
The Steps to Human Evolution
Bipedal (Walking on all two’s)
Increased Brain Size
Take a look at the Human family tree
The Hominid Family
Each year new fossils are found to add
to the Hominid family tree
Most fossils of early humans are found
in Africa and lower Asia
Most well understood members include
genus Australopithecus (extinct) and
genus Homo
Solve the Riddle of the Bones
Genus Australopithecus
First human ancestor to live on the
ground and walk on two legs
As evidenced by the Laetoli footprints
Ape-like jaw
Small brain
Short stature
Found only in South and East Africa
The Australopithecines
A. anamesis
A. afarensis
A. africanus
A. robustus
A. boisei
3.2 MYA (Finding “Lucy”)
2.5 MYA
Genus Homo
More modern hominids that exhibited major
evolutionary steps
Increased brain size
Use of tools
Use of fire
Use of shelter
Language and civilization
Homo habilis “The Tool Man”
Approx. 2.5 MYA
Brain ½ size of
modern human
First to make and
use stone tools and
Homo erectus “The Upright Man”
Direct ancestor of
modern humans
Widespread in Africa
and Asia by 1 MYA
Evidence of use of
shelter and fire
Homo sapiens “The Wise Man”
Most likely evolved from H. erectus as early
as 400,000 years ago
Greatly increased brain size
Consisted of 2 groups
Cro-Magnon/modern H. sapiens
Found in Neander Valley in Germany
Fossils found throughout Europe,
Middle East, and Asia from 150,00030,000 years ago
Large bodies and brains
Evidenced painting, religion, complex
social structure
“Cave man”
Cro Magnons and Fully Modern Humans
First early modern H. sapiens appear about
130,000 years ago
Thinner bones, smaller jaws, higher skull
with little or no brow ridge, and larger brains
Cave art shows complex religion and culture
Lived alongside Neanderthal for several
thousand years, but eventually out-competed