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Evolutionchange over time.
The process by which modern organisms have
descended from ancient organisms.
OWL PELLETS
What can skeletal remains reveal?
Vocab pg 392 and 401
Kahoot:
Owl pellet dissection
How Do We Know?
How do we know anything about the past
if humans were not around?
By studying other planets and rocks on
earth we know that earth was molten rock
4.6 billion years ago.
Gravity pulled the densest to the center
and the crust was formed 500 million ya
Then….
The atmosphere formed because of
gravity and life would not have existed like
we know it because volcano gasses were
in the atmosphere and it was too hot.
Clues in the Rocks
Clues in the Rocks
Eventually the earth cooled and oceans
formed 500 milya
1st life clues came from 3.5 bill ya
How do we know??????
FOSSILS
FOSSILS
Most organisms decompose when dead.
99% of species that lived on earth are
extinct – only a tiny amount of those
fossilized.
Fossils ONLY form when buried in
sediment soon after death.
Most common in aquatics environments
because sediment is always moving
Law of Supposition
Types of Fossils
Trace fossils- any indirect evidence left by
an organism- example footprints, burrows,
feces
Types of Fossils
Molds and Casts
Mold is an impression of an organism
Cast is a mold filled with sediment
Types of Fossils
Replacement- original material is replaced
with mineral crystals leaving a replication
of the organism.
Types of Fossils
Petrified- empty pores fill with minerals
Types of Fossils
Amber- preserved tree sap traps and then
hardens preserves organism
Types of Fossils
Original- mummies or freezing
Why are they not everywhere?
Why don’t we see fossils everywhere?
What type of rock must they be in?
Why are there sea shells on top of
mountains?
What type of fossil would the bones of
your owl pellet likely form? Why?
How do we know???
How old a fossil is?
Dating fossils
1. Relative dating- compare to the layer of
earth they were found in
2. Radiometric dating – uses half life of
isotopes of the rock fossil was found in.
3.Carbon dating- for mummies or
unaltered living organisms
½ life- dating
Geological Time Line
Foldable
4.6 meter long where each meter
represents 1 billion years and each mm= 1
million years
Earth formed at one end – humans the
other
Geological Time Line
High lights!
Origin of Life
Oldest ideas of life was spontaneous
generation.
Redi’s meat experiment
Replace with Biogensis
Louis Pasteur- used flasks to grow
organisms
Premordial Soup Hypothesis
Simple organic molecules could be made
from inorganic compounds- Miller Uray
experiment
THEN…
Protein synthesis gave rise to genetic
code and RNA gives life its first genetic
code.
Molecules go to cells and metabolisms
evolve
ENDOSYMBIOTIC THEORY
ENDOSYMBIOTIC THEORY
How Does Evolution Occur?
We have all heard of ….
But is that what it really means?
History
Before Darwin…
Jean Baptiste Lamarck—first evolution
theory in 1809
– Nature moves toward perfection
– Thought that it happened by…
Use and disuse
Inheritance of acquired traits
Lamarck—Use and disuse
Ex. fiddler crabs’ claws gets larger with use during
lifetime
Ex. blacksmith’s biceps get larger over time
Lamarck—Inheritance of Acquired
Traits
Modification
acquired during
lifetime is passed
on to offspring
Not true!
Ideas Darwin considered…
James Hutton: (gradualism) geologic change is
continuous & slow
Sir Charles Lyell: (uniformitarianism) forces that
shape Earth are still occurring (volcanoes,
earthquakes, etc)
Result—Earth must be more than a few thousand
yrs. old
Malthus
Believed that species
have the capacity to
overproduce offspring
(only the fittest
survive)
This could lead to a
lack of food, space,
etc for human
population.
Charles Darwin- Born 1809
Credited with the Theory of Evolution
based on Natural Selection.
H.M.S. Beagle- ship’s naturalist
Did not believe that species
change at the start of the voyage.
Darwin married his first cousin
Emma Wedgwood…
Down House, Darwin’s home
Voyage of the HMS Beagle
1831-1836
Galapagos Islands-located off
coast of South America
At first he believed that the Earth was
6000 years old; species were designed for
specific habitats and appeared on Earth in
present forms
On the Galapagos Islands, he realized that
the species were like those of South
America, but not exactly.
He specifically noted the different finches,
tortoises, and iguanas
Galapagos Islands
A Galapagos Tortoise
Darwin’s finches (13 different species)
Could all have come from a single species in South
America?
Iguanas- Marine and Land
Significant findings…
Fossils resembled living organisms in same
area—why had they died and others lived?
Galapagos Islands:
– Animals resembled mainland’s, but different
– Characteristics of animals and plants
differed from island to island.
Darwin thought and thought…
He hypothesized that new species were a
result of natural selection.
Natural Selection: Nature (environment)
selects survival traits (variations)
Darwin’s book,
On the Origin of Species (1859)
Theory of Natural Selection
Variations occur in nature
There is a struggle for existencecompetition
Survival of the Fittest- organisms best
suited for their environment will survive,
reproduce and pass their traits to
offspring.
Overproduction of offspring
Artificial Selection
Plant and animal breeders who selected traits
causing variations so why would nature be
different?
Evidence for Evolution
1. Fossil Records
Older fossil records are in lower rock
layers
Derived Traits: new traits not found in
similar fossils
Ancestrial traits: primitive features that
appear in ancestors – teeth, tails
Transitional fossils- show changes in traits
Evidence for Evolution
Comparative anatomy- what do you see?
Evidence for Evolution
Embryos of related
ancestors are similar
in early stages.
– Gill slits and post
anal tail?
Evidence for Evolution
Vestigial structures: reduced form of a
structure in other organisms. Ex birds
wings, appendix and snake pelvis
Vestigial Organs
Organs that have no function now but did
have a function in ancestors.
– Ex: appendix, tailbone
Evidence for Evolution
Analogous structures: not all similar
features mean a common ancestor. Ex
the wing of a beetle and bird evolve for
different reasons.
Homologous Body Structures
Wing of a bat resembles forelimb of a
mammal, not a bird.
Wing of bird resembles forelimb of reptile.
Evidence for Evolution
Biochemical Evidence
Comparing DNA nucleotide sequences.
Evidence for Evolution
Geographic Distribution-Due to different
climate changes adaptations resulted in
differences among organisms.
How does this happen?
Adaptation
A trait shaped by natural selection which
makes a living thing better able to survive
in its surroundings
Three Types:
– Structural
– Behavioral
– Physiological
Survival of the Fittest
Fitness = reproductive success or the
number of offspring you produce that
contribute to the next environment.
Better adapted = more fit (not strongest)
Structural Adaptations
Traits that involve the physical
structure (anatomy) of an organism.
–Ex: Camoflague, mimicry, beak of a
bird, claws, etc.
Mimicry—edible comes to look like
poisonous
Camouflage—walking stick &
toad
Behavioral Adaptations
Inherited traits or actions that help an
organism survive and reproduce in a given
environment.
– Examples: birds migrating, opossum faking
death
Physiological Adaptations
Traits that involve the internal functions or
chemistry of an organism.
– Examples:
– Chemicals to digest food
– Antarctic fish with “anti-freeze” in their body.
– Venom of a snake
– Anitbiotic resistance
Mechanisms of Evolution
Natural Selection is not the only
mechanism for evolution
Population genetics – how do any
recessive genes ever show up?
Shouldn’t dominant always take over?
Evolution won’t occur unless allelic
frequencies ( how many Aa vs AA) are
acted upon by forces that cause change
Hardy-Weinberg Principle
Allele frequency remains constant in a
population (no evolution) if these factors
are present in the population:
– Random mating
– Population size very large
– No movement in or out of population
– No mutation
– No natural selection
Can determine frequencies by using
the Hardy-Weinberg equation…
2 alleles—A & a
3 combinations—AA, Aa, & aa
Let p = A and q = a
A + a = 100 percent of alleles
So…p + q = 1
Square both sides…
– p2 + 2pq + q2 = 1
– homozygous dominant + heterozygous +
homozygous recessive = all possible combinations
Practice Problem
Having long tongues is dominant in frogs.
64% of the frog population is homozygous
dominant. What percentage of the
population is heterozygous?
Practice problems
Equilibrium
If Hardy Weinberg = 1 then equilibrium
exists
This hardly happens in nature over the
extended period because of
No Genetic drift
No gene shuffling
No gene flow
No Founder effect
No mutations
No Bottle neck
No random mating
No natural selection
Evolution of Populations
Gene Pool: the combined genetic
information of a population.
Two main types of Genetic Variation:
– Mutation: a change in the DNA strand
– Gene Shuffling: during sexual rep.,
chromosomes move independently producing
millions of combinations of genes.
What is all that stuff?
Genetic Drift- change in alleles due to
chance. Some individuals by chance
leave more genes in the pool!
What is all that stuff?
Gene flow-also called migration- moves
genes from one population to another- like
pollen.
What is all that stuff?
Mutations- random mutation mostly cause
death but some are beneficial
Pepperd moth lab
What is all that stuff?
Random mating- mating is not random.
Mates choose carefully – example
peacock
What is all that stuff?
Bottle neck- example of genetic drift where
population declines to extremely low
numbers then rebounds
Example of Bottle neck
An example of a bottleneck
Northern elephant seals have reduced genetic
variation probably because of a population
bottleneck humans inflicted on them in the
1890s. Hunting reduced their population size to
as few as 20 individuals at the end of the 19th
century. Their population has since rebounded
to over 30,000 — but their genes still carry the
marks of this bottleneck: they have much less
genetic variation than a population of southern
elephant seals that was not so intensely hunted.
Northern Elephant Seals
What is all that stuff?
Founder effect- Small sample settles in a
location completely separate from others –
the random alleles now become the norm.
For example, the Afrikaner population of Dutch settlers in South
Africa is descended mainly from a few colonists. Today, the
Afrikaner population has an unusually high frequency of the gene
that causes Huntington's disease, because those original Dutch
colonists just happened to carry that gene with unusually high
frequency. This effect is easy to recognize in genetic diseases, but
of course, the frequencies of all sorts of genes are affected by
founder events.
Afrikaner
What is all that stuff?
Gene shuffling-crossing over!
Genes are shuffled to create variation
Three Types of Natural Selection
1. Stabilizing Selection
2. Disruptive Selection
3. Directional Selection
Stabilizing Selection
Genetic diversity decreases as the
population becomes stable.
Disruptive Selection
Directional Selection
Natural selection favors one phenotype
and the allele frequency shifts in one
direction.
Speciation
Forming a new species
This can happen because of species isolation:
– Reproductive: organisms can’t interbreed and
have separate gene pools
– Behavioral: different courtship rituals.
– Geographic: separated by barrier (river,
canyon)
– Temporal: reproduce at different times
(seasons)
Allopatric speciationgeographical
Physical barrier divides 2 populations long
enough that they will not be able to
reproduce.
Allopatric Example
Sympatric Speciation
Species evolve into new species with NO
physical barrier- side by side
200 years ago, the ancestors of apple maggot flies laid their eggs
only on hawthorns — but today, these flies lay eggs on hawthorns
(which are native to America) and domestic apples (which were
introduced to America by immigrants and bred). Females generally
choose to lay their eggs on the type of fruit they grew up in, and
males tend to look for mates on the type of fruit they grew up in. So
hawthorn flies generally end up mating with other hawthorn flies and
apple flies generally end up mating with other apple flies. This
means that gene flow between parts of the population that mate on
different types of fruit is reduced.
Sympatric example
Patterns of Evolution
Divergent evolution – aka Adaptive
radiation
Co evolution- ex mutualism
Co evolution arms race
Convergent evoution
Divergent Evolution
The process of two or more related species
becoming more and more dissimilar.
– Ex: Red fox and the kit fox. Red fox lives in mixed
farmlands and forests, where its red color helps it
blend in with surrounding trees. The kit fox lives on
the plains and in the deserts, where its sandy color
helps conceal it from prey and predators. Kit fox has
large ears as an adaptation to its desert environment.
Similarities in structure indicate that the red fox and
the kit fox had a common ancestor. As they adapted
to different environments, the appearance of the two
species diverged.
Kit Fox vs Red Fox
Co - evolution
Mutualism- as one species evolves
another does as well
Some Central AmericanAcacia species
have hollow thorns and pores at the bases
of their leaves that secrete nectar.These
hollow thorns are the exclusive nest-site of
some species of ant that drink the nectar.
But the ants are not just taking advantage
of the plant — they also defend their
acacia plant against herbivores.
Co evolution arms race
Predator / prey systems- a predator has
an adaptation that prey have to overcome.
They do and then the predator has to
evolve a new trait to fight back.
Molluscs, such as Murex snails, have
evolved thick shells /spines to avoid being
eaten by animals like crabs and fish.
These predators have evolved powerful
claws and jaws -compensate for the snails’
thick shells and spines.
Can you relate?
How does antibiotic resistance relate to
this?
Convergent Evolution
Two different species with different
ancestors evolve to display similar
physical features.
– Ex: Different anteaters found in Australia,
Africa, and America. Though not closely
related, they all evolved the "tools" necessary
to live on an ant diet: a long, sticky tongue,
few teeth, and large salivary glands.
Micro and Macro Evolution
Micro-evolution- changes in allele
frequency within a species
Macro-evolution- new species, new forms
replacing old as revealed in the fossil
record