Introduction to Evolution- Ch. 23
• Limbs evolved from fins after fish invaded dry land. -False
• Lobe-finned fish have the same bones you have in your arm. - True
How do we make sense of our place in the world?
• Religious and mythological answers to this
• Hypothesis Testing- testing to see if things are true (Aristotle)
• Natural History- Aristotle founded this
• Aristotle- 1 one to study science
The Earth’s biota changes over time- plants and animals change over time (Empedocles)
Geology: Catastrophism or Uniformitarianism?
• The Earth is very old
• Questioning of ideas happened in 1700’s
• Lyell- studied erosion of farm land and it could happen on a large scale and it was natural (Grand
• He said that it wasn’t a catastrophe that did that
• Proved that the earth was older than bible said
The Diversity of Life
• Organisms are well-suited to their habitats
• Long beaks- need to get food way down
• How did they get that way?
• Inheritance of acquired characteristics
o Jean Baptist LaMarck
o Over time animals change physically to be better and pass to offspring due to environmental
• Intelligent design- William Paley
o The bird is that way bc God designed it that way
Erasmus Darwin (Charles’ Grandfather)
• Wrote The Temple of Nature (original title- The Orgin of Society)
• Published posthumously in 1803
• Non- conformist
• Non- religious
• Mother: Susannah Wedgwood (rich on her own) • Father: Robert Darwin, FRS (leading scientific society)
• The Mount
• Childhood home- very large
• Early schooling was done by older sister Caroline
• 1824- belittled by his father at a school performance
• Age 9- attended Unitarian Minister’s School in Shrewsbury
• 1825- Age 16- Started medical school at The University of Edinburgh, bc his dad wanted him to
become a physician
• Darwin’s 1 scientific mentor: Robert Grant
o Lamarckian- believed in Lamarckian inheritance
o Marine biologist
• Hates studying medicine- watching surgery makes him ill
• Enjoys natural history and field trips
• Must go and get divinity degree (Cambridge)
o To be a gentleman naturalist you need income and leisure time
o The only career that provides both is Anglican minister.
o Enough money and time to support yourself
• Scientific Mentors at Cambridge
o Robert Sedgwick, FRS- Professor of Geology (colleague of Lyell)
o Rev. John Henslow- Professor of Botany (gets Darwin to think about diversity of plants and
• 1831- Finishes 10/178 with a degree in theology
• H.M.S Beagle with Capt. Robert FitzRoy- make charts of harbors
o Adventures beckons Darwin- wanted a scientist to go with them to write down about all that
they see- plants, animals, etc.
o Dad doesn’t want him to go
o Uncle Jos- Josiah Wedgwood II- persuades to let him go (it works)
o Last 5 years (1831-1836)- went around S. America, Africa, Australia
o Gets seasick so he read Lyell’s Principles of Geology and collects specimens and journals from
around the world
▪ Talks about ancient earth
▪ Ships back tons of specimens
• 1871- The Descent of Man and Selection in Relation to Sex (wrote this)
o Expert on barnacles
o Two Fundamental Insights from this book
o Natural Selection- explains how organisms change over time and why they are well-suited to
o All living organisms are derived from a common ancestor- explains that new species come
from pre-existing species.
Evidence for Common Ancestry: Homology
• Biochemistry: ATP, enzymes, membranes, genes
o All organisms use DNA and RNA as their genetic info storage center
o How all organisms get energy: chemistry is all of the same • Molecular Genetics: info processing, DNA sequencing
• Structural and developmental homologies
o Same structure and same origin for organisms that aren’t related
o Human and turtles have same structural homology- they have a common ancestor and they
• Bird wings and bat wings are homologous structures. - true
• Bat wings and insect wings are homologous structures. – false (analogous- only same function)
• Genetic Homology (comparing amino acids)
o Defect in p53 protein- cancer
o Monkeys are the closest to us
o Humans and chimpanzee- closest out of monkey family
• Embryonic Development
o Dolphin embryos grow a hind limb but that is reabsorbed
o Related to mammals
Evidence: Biogeography and Convergence
• Anatomical- long snouts let them eat ants
• Convergence- same environment and same characteristics
• Biochemical- use antifreeze proteins to survive frigid waters
• Selection makes unrelated animals look alike
o Why Evolution is True- Coyne
• Humans and gorillas cannot interbreed. - true
• Humans and gorillas are separate species. - true
a. They are related
b. Look up interbreeding in book
• Even though chimpanzees are very close to us- they have made many adaptations like walking on all
• But humans are the ones here and now telling the story- not chimpanzees
The Theory of Evolution: Tenets
• Individuals of a population of organisms show variation in a variety of characters
o Characters are inherited from parents
• Offspring inherit traits from parents
• Some individuals do not survive and reproduce
o Not random
o Survival of the fittest
• Survival is not determined by chance
• Phenotypic variation in a population of land snails
o Same species but have different colors and sizes
• Traits are inherited- they are all related
o Dogs inherit things from wolves
• Darwin studied artificial selection in farm animals, pets, and crop plants
o Cows, Dogs and pigeons- what he studied on
• Artificial selection in corn o You can change oil content by selective breeding
o Selective breeding- done by humans for their gain (artificial breeding)
o 4-fold increase
• Not everybody makes it
o Essay on the Principle of Population
o Wrote by Thomas Malthus
o Organism born but a lot don’t survive to reproduce
o If everybody survived, the world would be overrun with organisms
• Evolution = descent with modification
o Horses- changes in leg bones (they have gotten longer)
• Tons of evidence that supports this theory by natural selection (Darwin’s theory)
• It is the fundamental organizing idea of Biology
• It tells us how we fit into the panoply of species, living and extinct
Natural Selection- Ch.24
• Sorting occurs on phenotype- what you see is where natural selection occurs
o Variation- diff. traits in a population
o Inheritance- pass to offspring
o Differential reproductive success- brighter beetles are bitter and predators learn to avoid
them. The bright beetles aren’t eaten as often so they survive and produce more offspring
compared to dull-colored beetles
▪ Results in natural selection—the proportions of the diff. variants in the beetle
population change over time
• Phenotype depends on both genotype and environment
o Depending on where a certain plant is grown, it can have variance, even though they all have
the same genotype
• Bulldog, greyhound, and dachshund
• Humans have selected for particular traits that they want
A Case Study
• Oilfield mouse- diff. colors on the backs of the mices
• Variation in coat color
• Inheritance: genetics of coat color
o Depends on the signaling protein for dark or light coat color
o If you produce ASP(protein) it will outcompete the MSH (hormone) for the receptor—
resulting in light color
• Random mutations result in variation
o Mc1R mutation- prevents MSH binding-- light
o Agouti mutation- increases ASP expression-- light
• Fitness consequences- survival of the fittest (best color)
o Owls capture more light mice in dark grounds, and light mice on lighter grounds o Small differences in fitness can result in large changes in allele frequencies over time
o Assume a population of 10,000 animals. Some have an allele that results in 1% more
o The frequency doubles every 70 generations; by 3,000 generations, the frequency would be
Constraints on Natural Selection
• Overcoming constraints
o Owls have a greater range of binocular vision compared to ostriches- the ostriches have to
▪ Good depth perception- owl
▪ Can see behind itself and bad depth perception- ostriches
o Optimal vision would be binocular vision all around your head—but that isn’t possible
o Spider---have many eyes that go around head
o Owl- have special vertebrates so they can move their heads all around
• Selection cannot overcome physical limits
o Long thin legs=speed---optimal
o Why are there no large land animals with thin legs? - physically these cannot happen, your
legs support your body so they can’t be too thin and long
▪ As body mass increases, femur length increases
o Is is possible to have a land animal with long, very thin legs?
▪ Yes, only if mass is very small
▪ Granddaddy long legs have thin and long legs because its body mass is very small
Pushing the limits of selection
• Barbaro won Kentucky Derby, shattered leg in 20 places- euthanized
o The horse had optimal characteristics to be the greatest, but human forces prevent the
success sometime. The horse in this example had to be euthanized and so it can’t reproduce
and we were the ones that hurt the natural selection of that animal.
• Thoroughbred horses have thinner and long legs- but there is only so much they can handle
• In humans, the person that wins are whoever pushed themselves to almost to their limit
Criticism of Darwin’s Theory
• How do complex traits evolve?
o How did human ear evolve? - very complex
• Why do organisms have traits with no biological function?
o Why do some birds still have wings, if they don’t always use them?
• As selection eliminates unfit alleles, why doesn’t variation disappear?
o Intelligent design and attacks on evolution
Evolution of the Molluscan eye
• Lens evolves
• As it grows and needs to see- it has to evolve to form an iris and retina • It starts as just a simple layer of photoreceptor cells
• An existing trait is later adopted to serve a new function
o Feathers- some dinosaurs had them, used for gliding flight (to keep warm)
o Now feathers on birds are used to fly
• Birds use feathers for flying- true
• Birds and dinosaurs have a common ancestor- true
o Aren’t related
Traits Lacking Biological Function
• Nictitating membrane
• Plica semilunaris
o They are the equivalent to each other
o We don’t need this extra membrane bc we close our eyes
o We still have them bc the evolution of the eye comes with this baggage or structure
Vestigial Limbs in Reptiles
• Vestigial- formation of something smaller from something bigger
• They inform relationships and evolutionary history
o The hind limbs were lost- but rudiments were still left behind and after time there was a loss
of vestigial hind limb
▪ Evolution of snakes
The Power of the Evolutionary Theory
• We can use the evolutionary theory to predict where vestigial structures should be
o You look to see if they are related to an organism that has that structure that it now doesn’t
1.Natural selection sorts phenotypic differences among the individuals in a population.
2.Natural selection results in changes in the characteristics of a population over time.
3.Adaptations are inherited traits that increases the reproductive success of individuals.
4.Natural selection cannot overcome physical laws.
5.Natural selection is random; it does not “plan ahead”.
Evolution isn’t just cause by catastrophes or big events but rather by biological forces of these animals as they
interact with each other in their environments.
• The movie about the newt and the snake. Both of them evolved to affect the other.
Video- Just know the big concept from the video
Bacteria and other microorganisms can reproduce way quicker than humans can. They have been ruling over
us for many years. They are our only “prey”. Penicillin was the 1 antibiotic and was used in WWII.
Russian prisons- everyone has TB, every time they cough they expel the contagious germ. • They were given antibiotics and they got better, but the bacteria that was left were the ones that had
resistance to the antibiotic. When it came back, the old antibiotic wouldn’t cure it because the
bacteria that was left had reproduced, so them and their offspring have resistance to the antibiotics.
• They have 2 ndline drugs but not enough for everyone.
• They use prisons because it is the hub of the spread of TB. Once released, they are left out to the
world and can give off their TB to the rest of the world.
• All of the strains that are being made right now in Russia- will come and get us eventually.
• Drug-resisting microbes is the biggest issue we face. The more drugs you throw at microbes the more
• This evolutionary process doesn’t always have to be bad. We need to use evolution to benefit us.
Cholera in Peru
• Over 10,000 people died
• Spread through contaminated water
Cholera in Latin America
• They had a clean water system so over time, the microbes got less toxic and most people, if they got
Cholera, wouldn’t even know they had it.
Cheetahs (wild cats)
• Mirror images of evolutionary processes with humans. We went through similar things.
• We get HIV and felines get FIV.
• 1 million years ago- ancestors of cheetahs were infected with FIV
o The ones that survived had the resistance to FIV (mutations)
• There must be some humans that have mutations for HIV???
o The mutations make it to where there is little to no receptors that will allow the microbe to
• Peoples DNA and the DNA of the microbes have evidence of epidemics from since the beginning. They
tell a story.
• Connection of two organisms working together to benefit one another in an unconscious way
• There are two kinds of ants and one kind gets the leaves and bring it to the smaller ants for them to
chew it up so that fungus can come and kill the toxins on the leaf and they can convert the mulch to
food and sugar. The leaves need it for food and the fungus need the leaves to “live”.
o The ants have a waxy secretion (tangled strands of bacteria) that is actually alive and is t