Transcript Evolution - flickbio

EVOLUTION
 Evolution - change over generations
 Organisms change over time – this
is a fact. How organisms have
changed throughout earth’s history
is theory.
EVIDENCE OF EVOLUTION
 Fossils
 Comparative anatomy
 Embryology
 Biochemistry
 Genetics
 Direct observation
FOSSILS
 Fossils - a trace of an organism that lived
long ago
 Fossil records- use radiometric dating or
rock layers to date fossils
 Fossil records are incomplete:
• soft tissues
• weather
 Geographic distribution of species
 Similar organisms in different areas
 Fossils of extinct organisms
COMPARATIVE ANATOMY
 Comparative anatomy- The study of
structures of different organisms
 Homologous structures - similar
structures modified between
different organisms
• The more similar the structures,
the closer the relationship
between two organisms
• Example: a bat’s wing, a horse’s
leg and a human forearm
Homologous structures
 Vestigial Organs - structures that have no
function in present organisms, but may
have been used in ancestors
 Example in animals
• pelvic bone in some snakes and whales
 Examples of vestigial organs in humans
• appendix
• wisdom teeth
• body hair
• pointed canines
A transitional fossil
EMBRYOLOGY
 Comparative embryology - the
study of embryos (early stages
of life) of different organisms
The more similar the embryos,
the more closely related two
organism are
• ex. human and pig embryos appear
very similar to each other

BIOCHEMISTRY & GENETICS
 Chemicals (like proteins, DNA,
mRNA etc) in different
organisms show similarities.
 More similar chemicals means
more closely related
 Example- Hemoglobin in
chimpanzees is very similar to
hemoglobin in humans
GENETICS
 How are offspring genetically
different from their parents? In
other words, how can evolution occur
from one generation to the next?
 Meiosis – remember, individuals can
make lots of genetically different
sex cells
 Mutations – DNA can change!
 Sex – combines two individuals’
DNA together
 DNA sequences of all living
things have many similarities
 Base sequences of DNA
• DNA of humans and
chimpanzees is 98%
identical
• DNA of humans and other
mammals is 80% identical
Hemoglobin sequences in vertebrates
DIRECT OBSERVATION
 Direct observation - evolutionary
changes are happening NOW
• Example - bacteria becoming
resistant to antibiotics
Charles Darwin in 1859, the year The
Origin of Species was published
CHARLES DARWIN
 Charles Darwin – an
Englishman credited for first
describing natural selection
• HMS Beagle – a British
survey ship on which Darwin
was a naturalist. This ship
sailed around the world in
1831.
Figure 15–1 Darwin’s Voyage
Section 15-1
 Galapagos Islands – located 600
miles west of South America. The
islands have very different
climates and thus the organisms
adapt according to the
environment.
 Giant tortoise, marine iguanas,
and finches vary from island to
island due to different
environments
Giant Tortoises of the
Galápagos Islands
Pinta
Pinta Island
Tower
Marchena
Intermediate shell
Fernandina
James
Santa Cruz
Isabela
Santa Fe
Hood Island
Floreana
Isabela Island
Dome-shaped shell
Hood
Saddle-backed shell
A Galápagos Islands tortoise
 Artificial Selection – people chose
particular species to breed
(selective breeding)
Artificial selection helped to explain
that variations in species could make
them better adapted.
 Dog breeders, farmers, gardeners
have been using artificial selection
for years.

Golden
Doodle
Cockapoo
Himilayan
Cocker spaniel
and poodle
Golden retriever
and poodle
Persian and
Siamese
Tangelo = madarin
orange and
grapefruit
Broccoliflower = broccoli
and cauliflower
Artificial selection: diverse vegetables
derived from wild mustard
NATURAL SELECTION:
The survival of the fittest
 Darwin wondered why there were so
many different species of finches on
the Galapagos Islands. He proposed
the concept of natural selection.
 Natural Selection - the best adapted
individuals in a population survive and
reproduce offspring that are also well
adapted
 The least adapted produce fewer
offspring and are less likely to
survive.
 Among the various traits that exist,
certain ones may benefit a population
 The environment typically does not
cause the variation!
• Examples
• Virus from outer space – kills blueeyed people (but does not change a
person’s eyes to blue)
• Spadefoot toad – must bury itself in
the ground and mate quickly when it
comes to the surface, therefore, it
has a loud croak and long toes!
TYPES OF SELECTION
 Directional Selection – when
individuals at one end of the curve
have higher fitness than individuals in
the middle.
 Example: birds with larger beaks
are better able to survive food
shortages than those with small and
medium beaks
Figure 16–6: Graph of
Directional Selection
Key
Directional Selection
Low mortality,
high fitness
Food becomes scarce.
High mortality,
low fitness
 Stabilizing Selection - when
individuals at middle of the
curve have higher fitness
than individuals at the ends.
 Example – average-sized
babies are most likely to
survive compared to really
big and really small babies
Figure 16–7: Graph of Stabilizing
Selection
Stabilizing Selection
Key
Low mortality,
high fitness
High mortality,
low fitness
Birth Weight
Selection
against both
extremes keep
curve narrow
and in same
place.
 Disruptive selection - when
individuals at both ends of the
curve have higher fitness
than individuals in the middle.
 Example: due to small and
large seeds, birds with small
and large beaks are most fit
compared to birds with
medium beaks
Figure 16–8: Graph of
Disruptive Selection
Disruptive Selection
Low mortality,
high fitness
High mortality,
low fitness
Population splits
into two subgroups
specializing in
different seeds.
Beak Size
Number of Birds
in Population
Key
Number of Birds
in Population
Largest and smallest seeds become more common.
Beak Size
Disruptive selection in a finch population
Types of selection
Some vocab…
 Gene Pool - the entire collection
of genes among a population
 Population - All organisms within
a breeding group (same species)
 Gene Frequency - The number of
times an allele appears in a gene
pool
Figure 16–2: Relative Frequencies
of Alleles
Sample
Population
48%
heterozygous
black
16%
homozygous
black
36%
homozygous
brown
Frequency of
Alleles
allele for
brown fur
allele for
black fur
 Changes in gene frequency
mean that the population has
evolved.
 An entire population evolves,
not an individual!
 A specific gene may be
“selected” for by the
environment.
GENETIC DRIFT
 Genetic Drift - rapid changes in gene
frequency of a small, isolated
population
 Example: in small populations, a
recessive allele can become much
more common
 In the Amish population, certain
genetic disorders are more common
than in the general population.
Genetic Drift
Sample of
Original Population
Founding Population A
Founding Population B
Descendants
Genetic Drift
Sample of
Original Population
Descendants
Founding Population A
Founding Population B
OCEANIC ANGLER FISH
Sexual dimorphism
The deep sea angler shows a very strange sexual
dimorphism. The male is very small and attaches itself to the
body of the female. The teeth and the jaw recedes and the
blood circulating of the two animals become one. The male
spends the rest of his life attached to the female.
ADAPTATIONS
 Adaptations - physical traits
of a living organism that help
it to survive in its
environment
 Adaptations evolve by
chance!
TYPES OF ADAPTATIONS
 Structural – physical parts
• Ex. woodpecker’s tongue, anglerfish,
anteater’s snout, hummingbird’s beak
 Physiological – chemicals made by
organism
• Ex. poison venom of a snake, ink of a
squid
 Behavioral
 Ex. migration of birds, mating dances
Buffalo Bill Dam on the
Shoshoni River at Cody,
Wyoming and those dots
are bighorns WALKING
ACROSS IT.
TYPES OF EVOLUTION
 Convergent Evolution – when species that are
not closely related evolve similar traits (two
species look like they are closely related and
they are not)
• Example: dolphins (mammals) and sharks
(fish)
 Divergent Evolution – one species evolves into
two or more species with different
characteristics
 Example: lions and tigers evolved from a
common ancestor
Liger
Speciation
 Speciation –evolution of two different
species from one common ancestor.
 What keeps two species apart so that they
evolve differently?
 Isolating Mechanisms – keep groups apart
 Geographic Isolation – geologic changes
occur that isolate individuals of a
population
– Ex. Squirrels separated by Grand
Canyon and Darwin’s finches separated
by being on different islands
Squirrels in the Grand Canyon
Figure 15–14: Geographic Distribution
of Living Species
Beaver
NORTH
AMERICA
Muskrat
Muskrat
Beaver and
Muskrat
Coypu
Capybara
Capybara
SOUTH
AMERICA
Coypu
Coypu and
Capybara



Genetic Isolation – genes don’t mix right
– Donkeys and horses make mules, but
mules are sterile.
Temporal isolation – timings off
– Different species of skunks that mate
at different times of the year.
Behavioral isolation – behaviors don’t
match
– Certain species of lightning bugs use
different blinking patterns to attract
mates.
A male bower bird
builds a “bower” to
attract mates.
 Blue footed boobies doing their
mating dance
 Birds of Paradise doing their mating
dance
 Many different mating scenarios
THEORY OF ORIGIN OF
LIFE
 Theory - a major hypothesis that
has withstood the test of time
• Based on observations and
evidence
• The closest to a complete
explanation that science can
offer
• 40 second evolution
• Homer Simpson Evolution
ORIGINAL ATMOSPHERE
 Hydrogen cyanide, carbon dioxide,
carbon monoxide, nitrogen,
hydrogen sulfide, and water
 No oxygen gas
FIRST ORGANISMS
 Prokaryotes [bacteria] - first cells;
have genetic material (RNA or DNA);
starting 3.5 bya
 First prokaryotes were heterotrophs
(eat food)
 Later, some became autotrophs (make
own food)
 Chemosynthesis - using energy from
chemicals to make food

Photosynthesis - using CO2 and light
to make food
• Cyanobacteria put oxygen into
atmosphere.
• Oxygen drove some life forms to
extinction, while other life forms
evolved new ways to use oxygen
(aerobic respiration).
• Oxygen formed ozone layershielded earth from harmful UV
and allowed an explosion of life
(2.7 bya)
A painting of early Earth showing
volcanic activity and photosynthetic
prokaryotes in dense mats
Other big steps…
 Eukaryotes (cells with nuclei) about 2.2 bya
 Plants and animals begin in water
 Multicellular organisms and sexual
reproduction in plants and animals (aquatic
life)
 Increased genetic diversity
 Plants and later animals colonize land around
4.5 mya.
 First dinosaurs and then first
mammals (245 mya)
 Dinosaurs go extinct around 65 mya
and this allows for evolution of larger
mammals.
 Extinctions are often followed by
explosions of new life forms!
 Remember your eras: Precambrium.
Paleozoic, Mesozoic, and Cenozoic.
HUMAN EVOLUTION
 Did man come from Monkey?
 NO!
 Humans and monkeys evolved from a
common ancestor that lived
approximately 65 million years ago and
was a tree dweller (roughly the size of
a cat). This was not a monkey like the
monkeys today.
Figure 32–16: Human and
Gorilla Skeletons
Comparing Human and Gorilla Skeletons
Modern Human
Modern Gorilla
Modern Human
Modern Gorilla
Skull atop
S-shaped spine
Skull atop
C-shaped spine
Spinal cord exits
at bottom of skull
Spinal cord exits
near back of skull
Arms shorter than
legs; hands do not
touch ground
during walking
Arms longer than
legs; hands touch
ground during
walking
Pelvis is bowlshaped
Pelvis is long
and narrow
Thigh bones angled
inward, directly
below body
Thigh bones angled
away from pelvis
Evolution of Primates
 Anthropoids developed into 3
groups:
 New World Monkeys – includes
squirrel and spider monkeys; have
prehensile tail (can coil around
branches) and lived in trees;
found in central and S. America
Old World Monkeys –
include giant apes, baboons,
and macaques; do not have
prehensile tail, but spend a
lot of time in trees; found in
Africa and Asia
 Hominoids (great apes) –
include orangutans, gorillas,
chimpanzees, and humans

HOMINIDS
 Hominid family includes modern humans
and several distinctly different extinct
species
 Bipedal – two-foot locomotion
 Freed hands to use tools
 Opposable thumb – allowed hand to
grasp objects and tools
 Increased brain size
 Family that walks on all four
Comparison of Skulls of Human
Ancestors
Large brow
ridge
Large nose
Large canine
teeth
Face protrudes
forward
Australopithecus afarensis
Weak brow
ridge
Homo erectus
Large
brain
case
Round, high
skull
Inflated
cheeks
Large
nose
Even teeth
Strong chin
Neanderthal
Cro-Magnon
Human Evolution Shockwave video
Modern Homo sapiens
Australopithecus afarensis
 Very small brain capacity
 ~3.9-3.0 million years ago (mya)
 “Lucy”
 Bipedal apes that spent some
time in trees
 Short (Lucy is 1m)
Homo habilis
 “Handy man”
 ~2.5 mya
 Increased brain size
 Began to make and use tools
 1.3 meters tall (4 feet tall)
Homo erectus
 “Upright man”
 ~ 1.8 mya - 250,000 years ago
 Taller
 Larger brain capacity
(comparable to modern humans)
 Built fires
 Migrated out of Africa into China
and Asia
Homo sapiens (“wise man”)
 Homo sapiens neanderthalis
 Neanderthals
 Overlapped in existence with
modern humans
 Heavier brow ridge
 Slightly larger brain capacity
than modern human
 Lived ~200,000 – 30,000 years
ago
 Homo sapiens sapiens





First arose in Africa around
100,000 years ago.
Lived with Neanderthals for
~50,000 years.
Tools, art, and buried dead with
rituals
One group became Cro-Magnon (in
Europe) ~40,000 years ago.
We are Homo sapiens sapiens