The Theory of Evolution and Natural Selection Evolution is neither more nor less than the result of respecting the reality and consistency of the physical world over time.- Renowned Cell Biologist Kenneth Miller

1/20/2015 Warm-Up Answer the following questions in your own words: 1. What is the difference between a scientific theory and a belief? 2. Define evolution in your own words 3. Do you feel that there is an 'either /or' choice between religious beliefs and evolutionary theory - ie. that you must reject the idea of evolution because of your religious beliefs, or that you can't believe in God if you accept the evidence for evolution? Is it possible to have both a belief in God and an acceptance of the evidence supporting evolution?

But It’s Only a Theory, Right? In science, theories are statements or models that have been tested and confirmed many times. In science, the term "Theory" does not express doubt. They explain a wide variety of data and observations They can be used to make predictions They are not absolute, can be changed as new evidence is found

Observations help Explain Why do so many different animals have the same structures, the arm bones in a human are the same bones as a flipper in a whale? Why is the sequence of DNA very similar in some groups of organisms but not in others? Why do the embryos of animals look very similar at an early stage?

As the 19th century dawned, it was generally believed that species had remained unchanged since their creation However, a few doubts about the permanence of species were beginning to arise

Darwin’s Research As a boy and into adulthood, Charles Darwin had a consuming interest in nature Darwin’s father sent him to medical school, but he found medicine to be boring and quit. He enrolled at Cambridge University to be become part of the clergy of the church. o Most scientists at this time were also clergymen. After graduation, he went on a voyage around the world on a ship called the HMS Beagle.

The Voyage of the Beagle During his travels on the Beagle, Darwin was able to observe adaptations of plants and animals from many diverse environments. o Rainforests of Brazil o Grasslands of Argentina o Mountains of Peru One of the most important visits he made was to the Galápagos Islands west of South America

LE 22-5 NORTH AMERICA SOUTH AMERICA AFRICA EUROPE AUSTRALIA PACIFIC OCEAN ATLANTIC OCEAN England Cape of Good Hope Cape Horn Tierra del Fuego Galápagos Islands Darwin in 1840, after his return HMS Beagle in port Equator Tasmania New Zealand Andes

The Galapagos Islands Darwin found animals on these islands that weren’t found anywhere else in the entire world. He theorized that the animals had migrated from South America and then began developing specific adaptations to their new environment.

The Galapagos Islands Darwin also noted that the animals on the Galapagos islands were amazingly unafraid of humans. After watching a lizard that was partly buried in the sand, he wrote this: “I then walked up and pulled it by the tail; at this it was greatly astonished, and soon shuffled up to see what was the matter; and then stared me in the face, as much as to say, “What made you pull my tail?”

Darwin’s Focus on Adaptation Darwin noted many adaptations, or characteristics that enhanced the organisms chances of survival. He began to form a theory that as organisms gradually accumulated new adaptations, they would form a new species. o One of the best examples of this theory is the different species of finches on the islands. o The birds were all very similar except for their beaks.

LE 22-6 The long, sharp beak of the cactus ground finch (Geospiza scandens) helps it tear and eat cactus flowers and pulp. The large ground finch (Geospiza magnirostris) has a large beak adapted for cracking seeds that fall from plants to the ground. The green warbler finch (Certhidea olivacea) used its narrow, pointed beak to grasp insects.

In 1844, Darwin wrote an essay on the origin of species and natural selection but did not introduce his theory publicly, anticipating an uproar. o His theory suggested that new species developed over time naturally, not directly from God. In June 1858, Darwin received a manuscript from Alfred Russell Wallace, who had developed a theory of natural selection similar to Darwin’s. Darwin quickly finished his book, entitled The Origin of Species and published it the next year.

The Origin of Species The ideas of Origin of Species can be summarized with these two main points: o Evolution explains life’s unity and diversity. o Natural selection is a cause of evolution.

Descent with Modification Darwin did not call his theory “evolution”. He used the phrase descent with modification. o This means that all organisms are related. o All species came from a common ancestor. In the Darwinian view, the history of life is like a tree with branches representing each new species. o Each new species is simply a “modified” version of its ancestor.

LE 22-7 Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) Years ago 0 10, Millions of years ago Moeritherium Barytherium Deinotherium Mammut Platybelodon Stegodon Mammuthus Elephas maximus (Asia) Loxodonta africana (Africa) Loxodonta cyclotis (Africa)

Natural Selection and Adaptation Charles Darwin’s theory can be broken down into five different observations. o Observation #1 : For any species, population sizes would increase exponentially if all individuals that are born reproduced successfully.

Observation #2: Populations tend to be stable in size, except for seasonal fluctuations Observation #3: Resources are limited Observation #4: Members of a population vary in their characteristics; no two individuals are exactly alike

Observation #5: Much of this variation is heritable

Conclusion #1: More individuals are produced than the environment can support; o Frogs lay thousands of eggs at a time, but only about 1% survive to adulthood. Play the Roll for Survival Game!

Inference #2: Survival depends in part on inherited traits. o Individuals with traits that give them an advantage are more likely to reproduce and have offspring.

Inference #3: Individuals that reproduce the most will pass favorable characteristics to their offspring. o Over generations, these characteristics will accumulate.

Summary of Natural Selection Natural selection is differential success in reproduction from interaction between individuals that vary in heritable traits and their environment Natural selection produces an increase over time in adaptation of organisms to their environment If an environment changes over time, natural selection may result in adaptation to these new conditions

Key Points to Consider 1. Variation exists among individuals in a species. 2. Individuals will compete for resources (food, mates, and space) 3. Competition would lead to the death of some individuals while others would survive 4. Individuals that had advantageous variations are more likely to survive and reproduce. 5. Evolution is change over time This process came to be known as Natural Selection The favorable variations are called Adaptations

Evolution Heritable genetic change in populations or groups of populations over time Changes in gene pool Also includes populations diverging from one another over time  may lead to new species

Mechanisms of Evolution Genetic Drift o Population Bottlenecks o Founder Effect Gene Flow o Immigration o Emigration Mutations Mimicry Natural Selection

Genetic Drift Changes in gene pool of populations due to random chance

Genetic Drift

Genetic Drift Image Credit: UC Museum of Paleontology's Understanding Evolution

Genetic Drift Genetic drift has a bigger effect on small populations.

Bottleneck Effect Changes in gene pool of populations due to some event  drastically reduces population

Bottleneck Effect Survival is random Whether an organism survives does not depend on any characteristic (allele)

Example of Bottleneck Effect Population of plants on a mountain side An avalanche wipes out all but a patch of plants behind the shelter of a large outcrop.

Example of Bottleneck Effect Plants behind the outcrop survived only because they were out of the path of the avalanche. There was nothing about the plants’ genes that influenced survival.

Example of Bottleneck Effect Surviving population has an allele frequency different from the original population.

Bottleneck Effect

Bottleneck Effect: Cheetahs 10,000 years ago, cheetah populations worldwide crashed Due to climate change Photo Credit: Courtesy of Smithsonian National nationalzoo.si.edu

Cheetahs Only cheetahs in Africa & Eurasia survived Location, not genes  Survival Photo Credit: Kevin Walsh, 2006, Wikimedia Commons

Cheetahs Cheetahs today: Genetically identical Photo Credit: Lukas Kaffer, 2007, courtesy of Wikimedia Commons

Bottleneck Effect: Northern Elephant Seals Once numerous in the northern Pacific. 1800s: Hunted extensively for blubber Photo Credit: Michael Baird of bairdphotos.com, courtesy of Wikimedia Commons

Northern Elephant Seals Only animals in a Mexican colony survived Photo Credit: Michael Baird of bairdphotos.com, courtesy of Wikimedia Commons

Northern Elephant Seals Today: >100,000 individuals Very little genetic diversity Photo Credit: Mila Zinkova, 2008, courtesy of Wikimedia Commons

Founder Effect New population established by very small number of individuals (“founders”) By chance, founder group has a different allele mix than original population

Example of Founder Effect 200 German immigrants founded the Old Order Amish of Pennsylvania Photo credit: : Matthew Trump, 2004, Wikimedia Commons

Old Order Amish One couple brought allele polydactyly  Six fingers and toes Photo credit: G. Baujat and M LeMerrer, 2007, Wikimedia Commons

Old Order Amish Inbreeding has  frequency of polydactyly Click on this link: 06/3/l_063_03.html 06/3/l_063_03.html Photo credit: gadjoboy, 2006, Wikimedia Commons

Gene Flow Movement of alleles between populations Immigration: movement of alleles into a population Emigration: movement of alleles out of population

Example of Gene Flow Transfer of pollen from one population of sunflowers into another population of sunflowers Photo Credit: Sunflower Pollen, Courtesy of Wikimedia Commons

Example of Gene Flow Male juvenile Belding’s ground squirrels emigrate from their birthing population to new populations % emigrate as juveniles. Remaining males leave by the end of their first year. Photo Credit: Courtesy of Yathin at FlickR, n/set / n/set /

Mutations Mutations can add new alleles to a population Review this BIOL 1406 concept Photo Credit for black Eastern Fox Squirrel: Jeffrey Pippen, Duke University Photo Credit for wild-type Eastern Fox Squirrel: Calibas, 2007, Wikimedia Commons

Asexual Populations Mutations are primary source of genetic variation in asexual populations Photo Credit for E. coli 0157 colonies: Centers for Disease Control, 2005, Wikimedia Commons

Natural Selection Environment determines which genes are passed onto the next generation Based on which individuals successfully survive and reproduce

Mimicry The similarity of one species to another which protects one or both species o Can be appearance, behavior, sound, scent, or location Mimicry is related to camouflage Occurs when a group of organisms, the mimics, evolve to share common perceived characteristics with another group---the models Which is deadly and which is friendly? Deadly Friendly

Natural Selection Requires: o Genetic Variation o Overproduction of Offspring o Struggle for Existence o Differential Survival and Reproduction

View video at: Photo credit: Dean E. Briggins, U.S. Fish and Wildlife Service,

Genetic Variation Organisms in the population vary in their characteristics Variations are heritable  Passed from parents to offspring

Variation in Snail Shells

Flower Variations

Natural Selection Flow Chart

How Natural Selection Works

View “Pocket Mouse and Predation” at Photo Credit: Cheryl S. Brehme, USGS at

View “Pocket Mouse Evolution” at Photo Credit: J. Harris, American Society of Mammalogy, at:

Artificial Selection Humans select which genes are passed onto the next generation Based on characteristics that humans find valuable or desirable

View “Dog Breeding” at Photo credit: papillon.cz, courtesy of Wikimedia Commons (

View “Breeding Teosinte” at Photo credit: USDA, 2005, courtesy of Wikimedia Commons

Another Example of Artificial Selection

Sexual Selection Some characteristics influence individual’s chance of mating Photo Credit: Ian Sewell, 2006, Wikimedia Commons

Sexual Selection Individual may have shorter life but will have better chances of mating and producing offspring Photo Credit: David Dennis, 2007, Wikimedia Commons

Types of Sexual Selection Mate Competition o One sex competes for access to the other sex o Other sex always “chooses” winner Mate Choice o One sex chooses mate based on characteristics of other sex

Example of Mate Competition Male bighorn sheep fight for mates Male with largest horns usually wins Photo Credit: Alan D. Wilson, naturespicsonline.com, courtesy of Wikimedia Commons

Video of Bighorn Sheep Fighting: Photo Credit: Jon Sullivan, Wikimedia Commons

Example of Mate Choice Peacocks display their tails Females choose male with showiest tail Photo credit: Aaron Logan, courtesy of Wikimedia Commons

Example of Mate Choice Large tails decrease survival of peacocks Natural selection favors small tails Photo credit: Jörg Hempel, courtesy of Wikimedia Commons

Example of Mate Choice Peacocks with small tails do not mate Mate choice favors large tails Photo credit: Jyshah, 2007, courtesy of Wikimedia Commons

View the video at: Photo credit: Myukii, courtesy of Wikimedia Commons

The End Unless otherwise specified, all images in this presentation came from: Campbell, et al Biology, 8 th ed. Pearson Benjamin Cummings.

The “Fog-Basking” Beetle The “Fog-Basking” Beetle is a species that only lives in the deserts of southwestern Africa. This beetle has an unusual behavior – it stands on its head. o This allows the beetle to collect water from the fog that passes by on its body. o The water then runs down into its mouth.

This is a behavioral adaptation, a specific action that increases its chances of survival. Most of the beetle’s other characteristics are the same as every other beetle on Earth. o Hard shell o Six legs o Two pairs of wings How did this new species of beetle evolve? What is its relationship with other beetles?

Evolution Evolution is the theory that every species that exists on Earth is a descendent of an ancient ancestor. o If you were to trace the history of any two species back far enough, they should eventually intersect. All species have a common ancestor.

Vegetable Evolution Many of the green vegetables we eat came from the same original ancestor, and were bred for different characteristics. This is an example of artificial selection, because these breeds were created by human action.

Evolution and Creationism Before the theory of evolution was proposed, most of the world believed in some form of creationism, where all species were created by a supernatural being. This belief was held very strongly up through the mid-1800s.

Fossils, Cuvier, and Catastrophism The study of fossils helped to lay the groundwork for the development of the theory of evolution. Fossils are remains or traces of organisms from the past, usually found in layers of rock. Each layer of rock is called a stratum. o The stratum on the surface contains younger fossils. o The stratum deep below the surface contains older fossils.

Grand Canyon

Cuvier and Paleontology Paleontology, the study of fossils, was largely developed by French scientist Georges Cuvier Cuvier made two observations from studying fossils: o Younger fossils were much more similar to living species than older fossils. o Between each layer of rock, some species disappeared, while other new ones appeared.

Cuvier and Paleontology Cuvier had observed two phenomena: o Speciation, or the emergence of a new living species. o Extinction, or the complete disappearance of a species. His theory to explain this, called catastrophism, stated that each boundary line between strata represented a natural disaster that wiped out some of the species. Example: A great flood

Theories of Gradualism Other scientists believed in gradualism. o This is the idea that profound change can take place through the cumulative effect of slow but continuous processes.

Geologists Hutton and Lyell theorized that changes in Earth’s surface can result from slow continuous actions still operating today. o For example, valleys can be formed by rivers flowing through them and eroding the soil over time. This view strongly influenced Charles Darwin o If slow, continuous changes occur in the Earth, they can also occur with life.

Lamarck’s Theory Lamarck hypothesized that can evolve new traits based on their actions and lifestyle. According to his theory, the giraffe developed its long neck by stretching it to eat from trees. o This is called an acquired trait because it developed over a single lifetime.

LE A flower mantid in Malaysia A stick mantid in Africa

Modern Application of Darwin’s Theory Darwin’s theory of evolution continues to be tested by how effectively it can account for additional observations and experimental outcomes.

Case Study: Predation in Guppy Populations The population of wild guppies were studied in two situations: o In pools containing pike-cichlids, which hunt and eat guppies intensely. o In pools containing killifish, which do not hunt the guppies as often.

LE 22-12a Predator: Killifish; preys mainly on small guppies Guppies: Larger at sexual maturity than those in “pike-cichlid pools” Experimental transplant of guppies Predator: Pike-cichlid; preys mainly on large guppies Guppies: Smaller at sexual maturity than those in “killifish pools” Pools with killifish but no guppies prior to transplant

LE 22-12b Control population: Guppies from pools with pike-cichlids as predators Experimental population: Guppies transplanted to pools with killifish as predators 92.3 Females Age of guppies at maturity (days) Males Females Mass of guppies at maturity (mg) Males – Guppies living with the pike-cichlid predators matured much more quickly. – This is an adaptation that increased their chances of reproducing before being eaten.

The Evolution of Drug- Resistant HIV Many drugs have been developed to treat HIV, but the viruses evolve resistance very quickly. One example is a drug called Epivir, or 3TC. o This drug stops HIV from infecting healthy cells. Initially, the drug works very well. However, over time, viruses that develop resistance to the drug survive and reproduce much more and pass that trait along. o After about a month, nearly 100% of the patient’s viruses are resistant.

LE Patient No. 3 Patient No. 2 Patient No Weeks Percent of HIV resistant to 3TC