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The Theory of Evolution - Explaining how organisms change ov

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Sean Holder

on 22 October 2015

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Transcript of The Theory of Evolution - Explaining how organisms change ov

The Theory of Evolution - Explaining how organisms change over time
Addressing the Misconceptions:
Biological Evolution...
1. is NOT just a theory
2. Is NOT concerned with the origin of life
3. Is NOT just concerned with the origin of humans
4. was NOT discovered or first explained by Charles Darwin
5. is NOT the same thing as natural selection
6. is NOT something that happened only in the past
7. is NOT something that happens to individuals
8. is NOT an accidental or random process
9. does NOT have any evidence against it
10. does NOT conflict with any religion

Other Misconceptions
Organisms are always getting better
Natural selection gives organisms what they ‘need.’
Evolution will create a "perfect" creature
Evolution - Creating the Idea...
Darwin vs. was right, one was wrong...
So what exactly is evolution?
Evolution- change in population over time
Better Definition = Descent with Modification
A trait has be passed from parents to offspring
Evolution can only happen to populations
The Big Picture
Lamarck- organisms change due to the pressures of their environment, traits are acquired
He proposed that by using or not using its body parts, an individual tends to develop certain characteristics, which it passes on to its offspring.
What's going
on here?
A giraffe acquired its long neck because its ancestor stretched higher and higher into the trees to reach leaves, and that the animal’s increasingly lengthened neck was passed on to its offspring.
Natural Selection happens because of inheritable variations
Overtime, natural selection results in changes in the inherited characteristics of a population.
These changes increase a species fitness (survival rate).
Natural Selection- organisms with traits best suited to the environment survive
have more offspring
Charles Darwin traveled the world on the HMS Beagle
He was a naturalist, who noticed patterns of living things
Published his book,
"The Origins of Species" describing evolution through
natural selection
Coined it survival of the "fittest"
Being Biologically Fit = being able to have successful sex or producing viable offspring
Fitness = determined by reproductive success
Not necessarily bigger, faster, stronger
Fitness is not determined by one trait but by the totality of traits in the organism
Certain phenotypes are more successful
Particular environments “select” certain phenotypes
Peppered Moth Case Study
Why do we call blending in with nature?
Natural Selection Facts & The Meanings
Fact 1: Over-reproduction occurs in nature
Fact 2: Populations do not increase exponentially
Fact 3: There are limited natural resources (food, shelter)
Fact 4: Variation exists in populations
Fact 5: Much of the variation is heritable
Fact 4 was physically observed. Darwin’s weakness was the 5th fact
Inference 1:
struggle for survival ensues
Inference 2:
Organisms with the best variations survive the struggle for life
Inference 3:
Unequal survival of organisms with different variations leads to favorable variations accumulating over time
Examples of Natural Selection
Environmental plays a huge role on selective pressure.
Organisms adapt to their environment
These adaptation can lead to vestigial organs
A vestigial organ/bone is a part of the body that
still exists, but doesn't serve a function
Natural Selection - Summary
Organisms are locked into historical constraints
Adaptations are often compromises as with seals that need to swim and walk
Not all evolution is adaptive
Organisms can’t get a trait just because they “need” it.
Evidence for Evolution
1. Fossils
2. Comparative anatomy
3. Comparative embryology
4. Biochemistry
5. Genetic evidence
6. Direct evidence

Fossils = mold or cast of organism left
in rock, fossilized bone and teeth
life becomes more complex over time
record is incomplete
Relative dating-
layers in rock bed used to date organisms
Deeper is older, shallow is younger
What can fossils tell us?
when organisms lived
Radioisotope dating
what organisms looked like
similarities and differences in organisms
Comparative Anatomy-the study of the structures of different organisms
Homologous parts modified structures among different groups of descendants
analogous parts- structures in organisms that have no common origin but serve the same function
Vestigial Organs-organs having no functions in the living organism
Comparative Embryology the study of developing plants and animals
Below is the pictures of embryos for a fish, human, rabbit, tortoise, and chicken. Can you guess which one is each type of organism?
1 2 3 4 5
comparison of DNA and proteins in the body
Example: comparison of hemoglobin (blood protein) in human, chimp, and dog. Human and chimp hemoglobin more alike than dog
Genetic Evidence
Mutations- mistakes in the genetic code
Causes changes in populations over time
Direct Evidence
Rapid Evolution
Strains of bacteria becoming resistant to antibiotics
Weeds and pesticides
Insects and pesticide
Antibiotic resistance occurs when bacteria change in some way that reduces or eliminates the effectiveness of drugs, chemicals, or other agents designed to cure or prevent infections. The bacteria survive and continue to multiply causing more harm.
Adaptation- change in a species that makes it better suited to its environment
Fur inside the ears to protect inner ear from sand
A hump to store nutrition during long trips or when food or water is scarce
Large feet for standing in the sand
Calluses on the the knees to protect from abrasion
Changes in structure or anatomy
Example: bird’s beak or claws
Mimicry- a harmless species resembles a harmful one, predators learn to avoid both species
Camouflage- species features blend in with the environment
Changes in chemical makeup
Examples: digestion enzymes, snake venom, octopus ink
Responses to the environment
Example: bird migration and bear
Mechanisms for Evolution
Species- group of organisms that can interbreed AND produce viable offspring
Populations evolve NOT individuals
Gene pool- all the alleles for a trait in the population
Over time gene pools shift to traits that are best suited to the environment
Allelic frequency- the percent of any specific gene in a population
Genetic Equilibrium- when the percentage of alleles in a population remains stable over time
Selection Types
1. stabilizing – favors average individual
2. directional – favors one extreme variation
3. disruptive – favors both extremes of variation
Stabilizing selection – acts against extreme phenotypes and favors intermediate
Directional Selection – shifts the overall makeup of the population by favoring variants at one extreme of the distribution
Disruptive Selection – favors variants at both ends of the distribution.
Spontaneous generation- non-living materials can produce life, life could be created out of nothing, from the air

Biogenesis- living organisms only come from other living organisms
Earth approximately 4.6 billion years old
Beginning- earth’s atmosphere Hot, gases like CO2 and nitrogen, little O2
Gases helped to create the atmosphere
3.5 to 4 billion years ago
Organic Molecules 
Protocells 
Prokaryotic cells (heterotrophs) 
First simple autotrophs/producer 
Eukaryotic cells 
Multicellular organisms
Origin of Life on Earth
Origin of a Species
Speciation – formation of a new species, members of similar populations no longer interbreed
Geographic Isolation
Physical barrier divides population
River, canyon, mtn. splits group
Adaptive Radiation
one ancestral species evolves into a number of species to exploit a number of habitats.
Divergent Evolution
Divergent evolution- one species evolves into two species with different characteristics (get more and more different from each other)
Convergent Evolution
Convergent evolution – distant or unrelated species evolve similar characteristics to take advantage of similar environments Example: fish and dolphin
How we show this using a phylogenetic tree
Case Study - Grand Canyon Squirrels
Behavioral Isolation
Change in behaviors
Ex. frog calls, mating displays
Temporal Isolation
Change in when organisms emerge or become reproductively active
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