Evolution Chapters 15, 16, 17

Definitions of Evolution Organic Evolution- gradual change in species over time Geologic Evolution- evolution of the earth

Fossils Trace of an organism preserved by natural processes Compare fossils with today’s species to study evolution Generally skeletons are fossilized Sedimentary rock forms layers as water deposits sediments so that the oldest layers are on the bottom and the newer layers are on the top- this gives scientists a fossil record

Fossils (continued) Scientists use C-14 and U-238 to date fossils and rocks Geologic Time Scale- Earth’s history is divided into eras Certain organisms lived in each era First organisms were prokaryotic and marine There are many missing links Many fossils are of extinct species Less than 1% of all species that ever lived exist today There are times in the geologic time scale where many species became extinct at once (dinosaurs)

Living Organisms Comparative Anatomy- study of similarities and differences among organisms Homologous Structures- parts of different organisms that have similar structures but different functions (bird wing and human hand), these organisms are close evolutionarily Analogous Structures- parts of different organisms that have a similar function but different structure (bird wing and insect wing), these organisms are not close evolutionarily

Living Organisms Homologous Structures Analogous Structures http://carrier.pbworks.com/f/homologous%20structures.jpg Analogous Structures http://open.jorum.ac.uk/xmlui/bitstream/handle/123456789/954/Items/S365_1_002i.jpg

Living Organisms (continued) Vestigial Structures- serve little or no function in today’s organism but had a purpose at some time (appendix, tailbone)

Living Organisms (continued) Embryological Similarities- if the embryos are similar, then the organisms have similar ancestors (human, chicken, pig) http://home.honolulu.hawaii.edu/~pine/book1qts/embryo-compare.jpg

Living Organisms (continued) Biochemical Similarities- if the DNA structure is similar, then similar proteins are produced and the organisms have common ancestors Family: Mustelidae New Family: Mephitidae “noxious gas”

Origins of Life Spontaneous Generation- Living things arise from nonliving matter This was a popular belief for thousands of years

Controlled Experiments- proved that Spontaneous Generation could not occur Francesco Redi- (mid-1600’s) Rotting meat in jars Disproved spontaneous generation Louis Pasteur- (mid- 1800’s) Broth in flasks Finally convinced people that spontaneous generation was wrong

Heterotroph Hypothesis The modern hypothesis of the origin of life The earth’s temperature was much higher 3.5 billion years ago Gases were in different proportions (NO oxygen!!) Organic compounds formed (protein substances) These substances formed clumps which were inside a shell of water molecules These clumps developed the ability to divide- the first heterotrophs Eventually autotrophs developed (and thrived since there was competition for nutrients) Availability of oxygen changed the earth’s conditions

Chemical Classification (4 min)

Modern Theories of Evolution- Lamarck’s Theory (1809) Law of Use and Disuse- The more an organism uses a part, the stronger it becomes The less an organism uses a part, the weaker it becomes Inheritance of Acquired Characteristics- Characteristics acquired through use and disuse can be passed on to offspring Example: Giraffes necks became elongated by stretching them to reach food http://thisoldearth.net/Images/giraffe.jpg

Modern Theories of Evolution- Lamarck’s Theory (1809) This theory was disproved by Weissman. He cut the tails off 22 generations of mice! (ouch) Out of 901offspring, not one had an abnormality

Darwin’s Theory of Evolution (1859) Darwin sailed on the HMS Beagle as the ship’s naturalist Sailed to Galapagos Islands off of the coast of Ecuador in the Pacific Ocean Darwin observed that many species existed on the islands that also existed on the mainland but were slightly different There were also differences from island to island among species http://plg.uwaterloo.ca/~migod/846/2011-Winter/Beagle.jpg http://i.dailymail.co.uk/i/pix/2008/11/11/article-1084712-026E5D5C000005DC-735_468x286.jpg

Darwin and Natural Selection (4min)

Darwin’s Theory of Evolution (continued) Overproduction- There are many more offspring produced than needed A species population remains fairly constant over time Many offspring do not reproduce Competition- Allows only a few offspring to reproduce

Darwin’s Theory of Evolution (continued) Variation- Individuals vary in characteristics (running, strength, disease resistance) Some variations allow the individual to survive (getting food, escaping a predator) Adaptations- Organisms better adapted to their environment will survive and reproduce

Darwin’s Theory of Evolution (continued) Natural Selection- The environment selects which individuals survive since those better adapted to the environment survive and reproduce These adaptations are passed on to the offspring Survival of the fittest!! Speciation- Over time, the favorable adaptations become widespread in a population and the unfavorable ones disappear When there are many changes, eventually a new species forms Geographic isolation can lead to speciation

Whales Pakicetus (53 mil) Maiacetus inuus (47.5 mil) Protocetids (25 mil) http://observationsofanerd.blogspot.com/2009/02/new-link-in-chain-of-whale-evolution.html

Rate of Evolution Gradualism- Punctuated Equilibrium- Evolution occurs slowly and continuously over time Punctuated Equilibrium- Species remains the same for thousands of years Change occurs over a short period of time

Synthetic Rate of Evolution Change in the allele frequency within a population over time Populations evolve, not individuals! Population genetics- the study of changes in the genetic make-up of populations Gene pool- The total of all alleles in a population Each allele occurs within a certain frequency (1 in a 1,000; 1 in a 1,000,000)

Sources of Variation Mutation- Genetic Recombination- Migration- Is rare for any one gene If a mutation is helpful to a species, these organisms survive and reproduce and this allele becomes more frequent Genetic Recombination- Occurs in meiosis (crossing over) and at fertilization Migration- Brings different genes together Effects small populations

Sources of Variation (continued) Genetic Drift- In a small population if some individuals have an allele that no other individuals have and they do not reproduce; those alleles are lost Hardy-Weinberg Law- shows how rapidly evolution occurs in certain large populations

Adaptation An inherited trait that improves chances of survival and reproduction Camouflage- organism blends into the environment Warning coloration- bright colors warn predators against eating the organism

Adaptations Mimicry- an organism mimics another organism’s coloration Or coconut octopus

batesian mimicry examples

Natural Selection (3 Types) Directional Selection- An extreme phenotype becomes favorable Occurs when the environment changes or a species migrates Example is the giraffe’s long neck Stabilizing Selection- The average phenotype is favorable Keeps allele frequencies constant Disruptive Selection- 2 opposite phenotypes are favorable Creates 2 subpopulations May create 2 species

Types of Speciation Isolation- Adaptive Radiation- Geographic- populations separated due to river, mountains, etc Reproductive- populations can no longer interbreed Adaptive Radiation- Organisms of a species move (radiate) into different areas and adapt into their environment which leads to new species

Convergent Evolution Unrelated species develop similar characteristics Example: insect wings and bird wings Tasmanian devil and coyotes Leads to analogous structures http://en.wikipedia.org/wiki/Tasmanian_devil http://en.wikipedia.org/wiki/Coyote

Coevolution 2 or more species evolve in response to each other Example 1: Bees and certain flowers open in the day Example 2: Bats and certain flowers open at night

Examples of Natural Selection Mosquitoes resistant to DDT Bacteria resistant to a certain antibiotic Light colored moths live in areas with light trees Dark colored moths live in areas with dark trees