All living things share a common ancestor. We can draw a Tree of Life to show how every species is related. Evolution is the process by which one species gives rise to another and the Tree of Life grows

The theory of Evolution deals with how evolution happens. Our understanding of this process is always changing. Evolution is also a fact as there is a huge amount of indisputable evidence for its occurrence.

  Most influential contributor to thoughts about evolution  The Origin of Species  1859  Presented evidence for changes in species through Natural Selection  Galapagos Islands

 One of the first scientists to recognize that living things have changed over time  Species were descended from other species  Also realized that organisms had adapted to their environment  By selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime

The idea that organism’s alter their body by using it in new ways

 Believe acquired traits could be inherited  If an organism’s body was altered, it would pass that trait to its offspring  Example?

 5 year round-the-world voyage  at age 22  H.M.S. Beagle  Ship’s naturalist  At beginning of trip - believed species were immutable  Collected and examined the species that inhabited the regions the ship visited  Fossils, coral,plants, animals

 Volcanic islands mya  Isolated, west of Ecuador  All inhabitants are descended from species that arrived on islands from elsewhere

 Finches  Tortoises  Iguanas  Blue-footed Booby

 13 species of finches  Share many morphological features  Differ in several ways  Beak size  Beak shape  Food eaten  Evolved from a single species  He attempted to correlate variations in their traits with environmental challenges

Long neck Flared shell Short neck Domed shell DRY ISLANDS WET ISLANDS

Land Iguana Terrestrial vegetation Marine Iguana Algae eater

 The characteristics of many animals and plants varied noticeably among the different islands of the Galapagos

Darwin’s Evolutionary Ways of Thinking

 Darwin publishes Origin Of Species  Prompted after Wallace publishes essay  Words/phrases we are introduced to  Artificial selection  Struggle for existence  Fitness  Adaptation  Survival of the fittest

 Nature provides variation, humans select variation that they found useful  Livestock

 Members of the same species compete  What are they competing for?

 What Darwin called the ability of an individual to survive and reproduce  Fitness is a result of adaptation  Adaptation  any inherited characteristic that increases an organism’s chance of survival

 Individuals with characteristics that are better suited to their environment – adaptations that enable their fitness – survive and reproduce most successfully

 Over time, natural selection results in changes in the inherited characteristics of a population.  These changes increase a species’ fitness in its environment

 Principle proposed by Darwin  Over long periods of time, natural selection produces organisms that have different structures, establish different niches, or occupy different habitats  RESULT  species today look different from their ancestors

 All species, living and extinct, are derived from a common ancestor  A single “tree of life” links all living things!

 Darwin argued living things have been evolving on Earth for millions of years  Evidence for this process can be found: ▪ Fossil record ▪ Geographical distribution of living species ▪ Homologous structures of living organisms ▪ Similarities in embryology

 Fossils  remains of ancient life  Darwin compared fossils from older rock layers to those in younger rock layers to document the change of life on Earth

dinosaurshumansbacteriaorigins en.wikipedia.org/wiki/Image:Eopraptor_sketch5.png © World Health Org. © NASA complex cells The fossil record shows a sequence from simple bacteria to more complicated organisms through time and provides the most compelling evidence for evolution.

 Species living on different geographical areas had each descended from different ancestors  However, because of similar ecological conditions they were exposed to similar pressures of natural selection  similar features

 Structures that have different mature forms in different organisms, but develop from the same embryonic tissue.

 Organs of many species are so reduced in size that they are just traces of homologous organs in other species  Examples: miniature legs, tails

 Appendix  Wisdom Teeth  Tailbone  Particular Ear Muscles  VNO  Plica semilunaris

 Embryology of many animals with backbones are very similar  WHAT DOES THIS MEAN?  Certain embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates At one point… you looked like this. Thought you should know…

 Individuals organisms differ, and some of this variation is heritable  Organisms compete for resources  Each organism has different advantages/disadvantages  organisms best suited survive and pass their traits to offspring  Species today are descended with modification from ancestral species; common ancestor, single tree of life

Evolution of Populations

 When Darwin developed this theory of evolution he had no idea how heredity worked  This left him unable to explain:  Source of variation  How inheritable traits are passed through generations

 Evolutionary biologists connect Mendel and Darwin’s work in the 1930s  Gene pool: consists of all genes, including all the different alleles, that are present in a population  Typically contain traits with two or more alleles

Similar to a deck of cards – no matter how many times you shuffle, same cards (alleles) are always there.

Food becomes scarce. Key Low mortality, high fitness High mortality, low fitness Directional Selection

Key Percentage of Population Birth Weight Selection against both extremes keep curve narrow and in same place. Low mortality, high fitness High mortality, low fitness Stabilizing Selection

Disruptive Selection Largest and smallest seeds become more common. Number of Birds in Population Beak Size Population splits into two subgroups specializing in different seeds. Beak Size Number of Birds in Population Key Low mortality, high fitness High mortality, low fitness

Evolution of Populations

 Natural selection is not the only source of evolutionary change. In small populations, an allele can become more or less common by chance  Genetic drift: random change in allele frequency that occurs in small populations So, genetic drift and natural selection both involve changes in allele frequencies

1. Founder Effect 2. Bottleneck Effect 1. Founder Effect 2. Bottleneck Effect

 Allele frequencies change due to migration of a small subgroup of a population

Sample of Original Population Founding Population A Founding Population B Descendants Beetles on Hawaiian islands Founder Effect : Beetles on Hawaiian islands

Major change in allele frequencies when population decreases dramatically due to catastrophe

♦ Hunted to near extinction ♦ Population decreased to 20 individuals in 1800’s ♦ Those 20 repopulated so today’s population is roughly 30,000 ♦ No genetic variation in 24 genes

Original population Catastrophe Surviving population

The formation of new biological species, usually by the division of a single species into two or more genetically distinct one.

 Kaibab Squirrel Abert Squirrel

Two populations are capable of interbreeding but do not interbreed because they have different ‘courtship rituals’ or other lifestyle habits that differ

 Eastern and Western Meadowlark populations overlap in the middle of the US

 Male birds sing a mating song that females like  East and West have different songs  Females only respond to their subspecies song.

Populations reproduce at different times

Mates in: Mates in: April July

Geographic, Behavioral, and Temporal Isolation are all believed to lead to speciation.

Convergent Evolution Process by which unrelated organisms come to resemble one another Convergent Evolution Process by which unrelated organisms come to resemble one another

Pattern of long, stable periods interrupted by brief periods of rapid change  Why would rapid change occur?  Isolation  Migration  Extinction Pattern of long, stable periods interrupted by brief periods of rapid change  Why would rapid change occur?  Isolation  Migration  Extinction

 Anna Marie, Brandon - Baltra (South Seymour) Island  Hunter, Shalom - Española (Hood) Island  Joshua, Lindsey - Fernandina (Narborough) Island  Gabe, Matt - Floreana (Charles or Santa María) Island  Kerrington, Tiana - Genovesa (Tower) Island  Aurora, Shannon - Pinzón (Duncan) Island  Kyle, Taylor - San Cristóbal (Chatham) Island  Alastair, Tenko - Santa Cruz (Indefatigable) Island  Erin, Abby - Santiago (San Salvador, James) Island  Diego, Curtis - Pinta (Abingdon) Island  Susan, Ethan - Santa Fé (Barrington) Island

 Justin, John, Robert - Isabela (Albemarle) Island  Jordan, Colton, Lauren - Santa Cruz (Indefatigable) Island  Avelyn, Daniel, Freeman - Española (Hood) Island  Clarissa, Christina, Blake - Genovesa (Tower) Island  Stella, Grant, Ben Hagan - Santiago (San Salvador, James) Island  Bruce, Ryan, Griggs - Fernandina (Narborough) Island  Jokima, Madison, Penny - San Cristóbal (Chatham) Island  Fahim, Ronnie, Hanna - Pinta (Abingdon) Island  Edgar, Olivia, Julien - Marchena (Bindloe) Island  Drew, Shayna, Dove - Pinzón (Duncan) Island