Transcript The Theory of Evolution

Evolution
Early Ideas
• SPONTANEOUS GENERATION
– Idea that life arose from non-living things
– Example: Flies from rotten meat
Early Ideas
• BIOGENESIS
– Life comes from life
• Example: Spiders lay eggs
Darwin’s Ideas
*History of Evolution
• The theory of evolution
existed before Darwin.
– Wallace
– Lamarck
• It was his Theory of
Natural Selection that
became widely
accepted.
*History of Evolution
• Before Darwin, it was believed that the Earth
and its organisms were young and that they
did not change.
• In 1831, Darwin began a
voyage around the world
on a ship, the H.M.S. Beagle.
History of Evolution
• Galapagos Islands
– Volcanic islands off the South American coast
• Island species varied from the mainland
species, and from island-to-island
– Example: Each island had either long or short
necked tortoises depending on the island's
vegetation
History of Evolution
• Darwin concluded that adaptation to the
environment can cause diversification,
including origin of new species.
*History of Evolution
• In 1859, Darwin
published his ideas in a
book called The Origin
of Species
• Made the argument
that organisms change
over time to better suit
their environment
Natural Selection
• NATURAL SELECTION
– Organisms that are most fit for the environment
will survive & reproduce
• Their traits will be passed on to the next generation
• Over time, population will evolve to have the trait
Natural Selection
• 4 criteria for natural selection to occur
1. Variation between organisms
2. Over-production causes competition
3. Traits are passed on (heredity)
4. Some organisms survive/reproduce more than others
Why must we meet these conditions?
Imagine this scenario:
All females genetically identical
All males genetically identical
No one female or male is “more fit” than the
other, therefore no reason to choose one
male or female over another
All matings result in the same offspring
Or this scenario…
Important Evolution Facts
• Natural selection
acts on individuals
– Individual organisms
are selected for or
against
• Populations evolve
– Not individuals!
Natural Selection
• Over time, organisms will develop
ADAPTATIONS to their environment
– Increase an organism’s FITNESS
• FITNESS – ability of an organism to survive and
reproduce
Types of Adaptation
• 3 main types of adaptations:
1. STRUCTURAL
•
Unique body structures
• thorns on roses, webbed feet
2. PHYSIOLOGICAL
•
Unique chemicals or biochemical abilities
• poisons in snakes, antibiotic resistance
3. BEHAVIORAL
•
Unique behaviors
•
bird migration, plants growing toward light
Grasping - Raptors use their large curved
claws to snatch fish from the water.
Scratching - Pheasants scratch the soil for
food & have nail-like toes.
Swimming - Ducks use their feet like
paddles.
Perching - Robins have a long back toe,
which lets them grab a perch tightly.
Running - Many fast-running birds have
three toes rather than four.
Climbing - A woodpecker's hind toes
enable it to climb without falling backward.
Types of Adaptations
• Important structural adaptations
– CAMOUFLAGE
• Blending in to the environment
– MIMICRY
• Mimicking a dangerous organism to scare predators
CAMOUFLAGE
MIMICRY
PHYSIOLOGICAL
BEHAVIORAL
Creation of New Species
• SPECIATION – organisms acquire enough
unique adaptations to become their own
species
Creation of New Species
• Different types of selection can lead to
speciation
Types of Selection
• STABILIZING
– An intermediate phenotype is favored
• Acts against individuals who deviate too far from the average
Selection for
average size
spiders
Normal
variation
Example: Human Birth Weight
Types of Selection
• DIRECTIONAL SELECTION
– Favors individuals with extreme values of a trait
• causes the population to evolve in a particular direction
Normal
variation
Selection
for longer
beaks
Example: Peppered Moth
Types of Selection
• DISRUPTIVE SELECTION
– Favors phenotypes of opposite extremes; disfavors
intermediate phenotypes
Selection for
light limpets
Normal
variation
Selection for
dark limpets
Which type of selection is it?
Early breeders were interested in
dogs with the greatest speed. They
carefully selected from a group of
hounds those who ran the fastest.
From their offspring, the
greyhound breeders again selected
those dogs who ran the fastest. By
continuing this selection for those
dogs who ran faster than most of
the hound dog population, they
gradually produced a dog who
could run up to 40 mph.
Which type of selection is it?
Suppose there is a population of rabbits, those with black fur
and those with white fur.
If this population of rabbits were put into an area that had very
dark black rocks as well as very white colored stone, what type
of selection would you expect to occur?
Which type of selection is it?
The Siberian Husky is a medium dog,
males weighing 35-60 lbs. The Siberian
Husky is well designed for working in
the snow. If the Siberian Husky had
heavier muscles, it would sink deeper
into the snow, so they would move
slower or would sink and get stuck in
the snow. Yet if the Siberian Husky had
lighter muscles, it would not be strong
enough to pull sleds and equipment,
so the dog would have little value as a
working dog.
Microevolution
• How can you tell if a population is evolving?
– Measure the allele frequency from one
generation to the next
What could be causing the population to change?
50% white : 50% black
100% black
50% BB : 50% bb
100% bb
Microevolution
• GENE POOL
– All the alleles available in a
population
– Large gene pool = high
genetic diversity
• Increased fitness levels
• More likely to survive
environmental changes
Microevolution
• GENETIC EQULIBRIUM
– allele frequencies stay the same from generation
to generation
– population is NOT evolving
50% white : 50% black
50% white : 50% black
50% BB : 50% bb
50% BB : 50% bb
Microevolution
• 4 factors that cause microevolution:
1.
2.
3.
4.
Gene flow
Random
Genetic drift
Mutation
Natural selection Non - random
Microevolution
• GENE FLOW
– Movement of genes into and out of population
through immigration and emigration
Microevolution
• GENETIC DRIFT
– Random event wipes out organisms with a
particular trait
• Leaves behind a changed population
• Ex. All green bugs killed in earthquake; all brown left
Microevolution
• MUTATIONS
– Changes in DNA cause changes in adaptations
• Genes code for adaptations
– Random mutations produce new adaptations
Macroevolution
• Speciation leads to
MACROEVOLUTION
– Evolution of new
species
– SPECIES
• Organisms that can
interbreed and
reproduce
Macroevolution
• ISOLATION can lead to macroevolution
– Inability to mate
• 2 types of isolation
1.GEOGRAPHIC
2.REPRODUCTIVE
Macroevolution
• GEOGRAPHIC ISOLATION
– Two populations are separated physically and
can’t interbreed
• Ex. Distance, barrier
– Leads to creation of new species
Macroevolution
• REPRODUCTIVE ISOLATION
– Organisms are separated by reproductive
barriers
– Not separated geographically
• Ex. Different mating dances
– Different mating seasons
– Mechanical isolation (“Parts don’t fit”)
What is the Evidence for Evolution?
• Fossil Record
• Biogeography
• Comparative
Anatomy
All provide
evidence
ancestry
• Comparative Embryology
• Comparative Biochemistry
of common
Fossils
• Fossils may show ancestors of current species
– Demonstrates common ancestry and change over
time
– TRANSITIONAL FOSSILS
• Show traits of two groups of organisms; links them
together
– Ex. Birds & Reptiles
Biogeography
• Unrelated species have
similar traits due to
similar environments
– Ex. Marsupials & Placentals
• Fossils not evenly
distributed around the
world due to
CONTINENTAL DRIFT
Comparative Anatomy
• Organisms share a common body plan
– From a common ancestor
– HOMOLOGOUS STRUCTURES
• Same structures (bones), different function
– Ex. Human arm & dog leg
» Bird wing & bat wing
– ANALGOUS STRUCTURES
• Same function, different structure
– NO link to common ancestry
» Ex. Bird wing and bug wing
Comparative Anatomy
• VESTIGIAL STRUCTURE
– Found in present day organisms but has no purpose
– Functional in ancestor
• Ex. Hip bone in whale
– Tailbone
– Wisdom teeth
Comparative Embryology
• Early embryos of all vertebrates are very similar
– Early development reflects common ancestor
Pharyngeal
pouches
Pharyngeal
pouches
Tail
Tail
Fish
Reptile
Bird
Mammal
Comparative Biochemistry
• All living things use the same basic biological
molecules for similar functions
– DNA, ATP, amino acids, etc.
– Similar molecules have similar biochemical structures
Modes of Selection
Hunting The Peppered Moth
• Pretend you are a bird that preys on peppered
moths
• Your hunting ground is the side of a tree full of
peppered moths
• You will be given 1 second to make your choice of
quadrant
• When a slide comes up, you will decide what
quadrant to hunt in
• Here are the quadrants…
READY?
Hunting The Peppered Moth
•
•
•
•
Which quadrant did you hunt in?
Why did you choose this quadrant?
How many moths were in this quadrant?
How many moths were on the tree?
• Prepare to hunt again…
• Ready?
Hunting The Peppered Moth
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•
•
•
Which quadrant did you hunt in?
Why did you choose this quadrant?
How many moths were in this quadrant?
How many moths were on the tree?
• Prepare to hunt again…
• Ready?
Hunting The Peppered Moth
• Let’s take a closer look at the first slide
• How many moths were in your quadrant?
• How many moths are on the tree?
Hunting The Peppered Moth
• Did you choose the 3rd quadrant?
• Did you notice the black moths?
• This is how the peppered moth evolved in
Manchester England
• Now let’s take a look at how the moths
changed slowly over time once the trees
were polluted
Evolution of the Peppered Moth
Peppered Moth Simulation
• Notice how the white moths were the first to
be eaten due to their lack of environmental
fitness
• Eventually all the white moths were gone
and the dark moths prevailed