Chapter 15 Evolution
Think About It?
What is evolution?
Why does it happen?
How does it happen?
What is evolution?Change in a population over time at genetic level mutations
MutationsChange in DNA code can affect phenotype
REVIEW: From Gene to Protein
The Darwin Dude5 year voyage on Beagle (1831-36)
Naturalist: surveyed coast of S.A.
Wrote “Origin of Species”
Collected:–Rocks–Fossils–Plants–Animals
Charles Lyell’s Principles of Geology proposed Earth was millions of years old!
The Darwin Dude
Explained marine life at high elevation in the Andes
Giant fossil versions of smaller living mammals
Earthquakes could lift rocks great distances very quickly.
Lyell:
Galapagos Island Facts
Part of Ecuador
13 main volcanic islands
Formed between 5 - 10 MYA
Darwin & Galapagos Organisms adapted to their environment
“Darwin’s Finches”– Gould (ornithologist) finches were separate species not found any where else.
Mechanism for evolution = Natural Selection
Darwin believed new species appear gradually through small changes in ancestral species.
Breeders – can promote specific traits by selecting and breeding organisms that have the most exaggerated expressions of those traits.
Known as Artificial Selection!
Artificial Selection:
If humans could change species by artificial selection, the same process could work in nature!
Given enough time this process could produce new species!
Inference:
Artificial Selection:
Noteworthy Species
Darwin’s Finches
Adaptive Morpholog
y
Why do species change?
Variations & adaptations help organisms survive
Camouflage
Camouflage
Human population, if unchecked, would eventually outgrow its food supply, leading to a competitive struggle for existence.
Darwin believed Malthus’s ideas could be applied to the natural world.–Some competitors are better equipped for survival than others!
Thomas Malthus:
Natural SelectionOrganisms with favorable traits survive & reproduce
Variation is key
Natural Selection (cont.)
Struggle for existence
Species become better fit for their environment
If not they could DIE!
Natural Selection (cont.)
4 Main Principles (pg 421):
1. Variation2. Heritability3. Overproduction4. Reproductive
Advantage
Individuals in a population differ from one another.
Example:
1. Variation:
2. Heritability:Variations are inherited from
parents.
Example: X
3. Overproduction:
Populations produce more offspring than can survive.
Example: – 48 white tiger litters produces 148 cubs
–105 of them died without reproducing 71%
4. Reproductive Advantage:
Some variations allow the organism that possesses them to have more offspring than the organism that does not possess them.
Example: White tigers have powerful jaws & teeth, very strong sense of smell, sharp eyesight, and excellent swimmers!
Types of Natural Selection
1. Stabilizing Selection: Average phenotype favored
Ex. Human baby weight
Stabilizing Selection
Types of Natural Selection
2. Directional Selection: increases “extreme” versions of traits
Ex. Peppered Moth, Darwin’s finches
Peppered Moth: Natural
Selection
Directional Selection
Types of Natural Selection
3. Disruptive Selection: splits populations into 2 groups
Both extremes favored
Ex. Marine & Land Iguanas
Disruptive Selection
V = Variation: All life forms vary genetically within a population. It is this genetic variation upon which selection works.
I = Inheritance: Genetic traits are inherited from parents and are passed on to offspring.
S = Selection: Organisms with traits that are favorable to their survival get to live and pass on their genes to the next generation.
T = Time: Evolution takes time. Evolution can happen in a few generations, but major change, such as speciation, often takes long periods of time.
Evidence of Evolution
1.Fossil Record Fossils:
preserved evidence
Found in Sedimentary rock
Provides record of species that lived long ago.
Some similar to current ones!
Some species unchanged!
Evidence of Evolution
Similar fossil forms:
Glyptodon &
Armadillos
Species unchanged:
Horseshoe Crab!
Fossil Record (cont)
A. “Soft parts” don’t fossilize
B. Specific conditions are needed to form fossils
C. Hundreds of transitional fossils found
Classes of Traits:
Two major classes of traits while studying transitional fossils:–Derived traits: newly evolved features
–Ancestral traits: more primitive features that appear in ancestor forms.
2. Homologous Structures:
Anatomically similar structures
Evidence of common evolutionary origin
Evidence of Evolution
Homologous Structures
Analogous Structures:
Can be used for same purpose and can be superficially similar in construction but are not inherited from a common ancestor.
Analogous Structures:
3.Embryology: similarities in embryos
Evidence of Evolution
Embryology: Embryo – early, pre-birth stage of an organism’s development.
Vertebrate embryos exhibit homologous structures during certain phases of development.
4.Compararative Biochemistry: Organisms have similar DNA, genes and enzymes
Evidence of Evolution
Comparative Biochemistry:
The more closely related the species are, the greater number of amino acid sequences they will share.–Ex. Chimpanzees and Humans share 96% similar sequences!
Humans & Chimpanzees:
Human genome is 96% similar to great ape species.
Pan troglodytes (species of chimp) used in study – The number of genetic differences
between humans and chimps is ten times smaller than that between mice and rats.
Pan troglodytes (common Chimp)
5. Vestigial Structures: reduced in size, no longer have function
Evidence of Evolution
Formation of new species
Become genetically different
What is Speciation?
What are Species?Group of organisms that can interbreed & produce fertile offspring
Infertile SpeciesHorse + Donkey = Mule
64 ch. + 62 ch. = sterile
Liger
http://www.youtube.com/watch?v=WdTln4QwexQ&feature=related
Species Loop Hole Not a perfect definition
Used for classification
Some different species can produce fertile offspring
Grizzly Bear & Polar Bear
“Pizzly” or “Grolar”
Rate of Speciation Gradualism: Evolution occurring at slow rate
Punctuated Equilibrium: Evolution occurring at irregular rates
Cause of Speciation
1. Geographic Barriers
Mountains, Rivers, etc.
2. Environment Changes
3. Reproductive IsolationExamples:
–mating at different times
–birds mating with others who sing a particular song.
Cause of Speciation
1.Adaptive radiation (divergent evolution)
2.Coevolution3.Convergent
evolution
Patterns of Evolution:
Relatively short period of time
1 species gives rise to many
Usually occurs after mass extinctions
1. Adaptive Radiation:
Evolution of 1 species affects the evolution of another species.
2. Coevolution:
Unrelated species evolve similar traits
Under same environmental pressures
3. Convergent Evolution: