"nothing in biology makes sense except in the light of evolution” Photo by “davemee” flickr creative commons "nothing in biology makes sense except in the light of evolution” ~Theodosius Dobzhansky (1900-1975)

Which of these applies to scientific theory? A. Theories include observations B. Theories are hunches scientists have C. Theories can include personal beliefs or opinions D. Theories have been tested many times E. Theories are incomplete, temporary ideas F. A theory never changes G. Theories are inferred explanations, strongly supported by evidence H. A scientific law has been proven and a theory has not. I. Theories are used to make predictions J. Laws are more important to science than theories Answers A, D, G, I best describe scientific theories

In science, theories are statements or models that have been tested and confirmed many times. I will read a paragraph and you take what you want from it.

They explain a wide variety of data and observations 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

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?

Photo courtesy of Swamibu, Flickr Creative Commons

Charles Darwin developed the THEORY OF EVOLUTION BY NATURAL SELECTION  which explained how organisms changed over time  (ADAPTED)

Lamarke's Theory of Acquired Characteristics Some thought that you would gain or lose features if you overused or didn't use them,  PROVEN TO BE WRONG! Example: 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. Photo courtesy of ucumari, creative commons, flickr

Darwin’s views were influenced by fossils, the relics or impressions of organisms from the past, mineralized in sedimentary rocks. Sedimentary rocks form when mud and sand settle to the bottom of seas, lakes, and marshes. New layers of sediment cover older ones, creating layers of rock called strata. Fossils within layers show that a succession of organisms have populated Earth throughout time. Fig. 22.4 Fig. 22.2

Darwin was a naturalist (what we today call biologists) He traveled the world and made observations and sketches of many species His most famous travels were aboard the H.M.S. Beagle where he traveled to the Galapagos Islands

Marine Iguana, photo courtesy of mtchm, flickr creative commons Blue-footed booby, photo courtesy of stirwise, flickr creative commons

Finch, photo courtesy of stirwise, flickr, creative commons Giant tortoise, photo courtesy of Planetgordon, flickr creative commons

Darwin noted that there existed many finches on the islands, but while they had similarities, each was adapted to eating a particular type of island food He concluded that the finches all came from one ancestral species and evolved into many new species Cactus finch, photo courtesy of zrim, flickr creative commons

He proposed the “Theory of Evolution by Natural Selection” Darwin published this work to explain the variety of species that exist on the planet He proposed the “Theory of Evolution by Natural Selection” Natural selection provided a mechanism for evolutionary change in populations.

1. Variation exists among individuals in a species. 2 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. This process came to be known as Natural Selection The favorable variations are called Adaptations Photo courtesy of digitalART2, flickr creative commons

Natural selection acts on the phenotype, or the observable characteristics of an organism, such that individuals with favorable phenotypes are more likely to survive and reproduce than those with less favorable phenotypes. The phenotype's genetic basis, the genotype associated with the favorable phenotype, will increase in frequency over the following generations. Over time, this process may result in adaptations that specialize organisms for particular ecological niches and may eventually result in the emergence of new species.

Darwin’s main ideas can be summarized in three points. Natural selection is differential success in reproduction (unequal ability of individuals to survive and reproduce). Natural selection occurs through an interaction between the environment and the variability inherent among the individual organisms making up a population. The product of natural selection is the adaptation of populations of organisms to their environment.

While natural selection involves interactions between individual organisms and their environment, it is populations, not individuals that evolve. Populations are defined as a group of interbreeding individuals of a single species that share a common geographic area.

Say in a species of blob… Say in a species of blob….there exists blobs of all shapes and sizes (variation) Blobs eat the little purple organisms that live underground and on the surface.

During a particularly hot year, food became less abundant (competition), blobs that had the ability to dig into the soil to get food had a better chance of survival. Many blobs died that year…….

The ones that survived mated and passed their genes to the next generation. (reproduction)

The next generation had move blobs with the pointed noses The next generation had move blobs with the pointed noses. That is NATURAL SELECTION. Variation Competition Survival Reproduction

Evolution is when organisms change over time Evolution is when organisms change over time. So, modern organisms descended from ancient ones

Evidence supporting evolution Fossil record shows change over time Anatomical record comparing body structures homology & vestigial structures embryology & development Molecular record comparing protein & DNA sequences Artificial selection human caused evolution

Fossil Evidence Shows numbers extinct animals Shows similarities between extinct animals and animals that are alive today The earth’s layers show a time scale of species and when they appeared on earth (and when they died out)

Dinosaurs have always fascinated us, movies such as Jurassic Park capitalize on that fascination. How do we know what dinosaurs looked like? We create a picture based on the bones we find (fossils) and use modern reptiles to guess at their texture and skin color.

1. Fossil record Layers of rock contain fossils new layers cover older ones creates a record over time fossils show a series of organisms have lived on Earth over a long period of time

Fossils tell a story…

Primate Fossils Australopithecus Homo erectus Homo sapien

Relative vs. Absolute Dating

Fossil

2. Anatomical record Animals with different structures on the surface But when you look under the skin… It tells an evolutionary story of common ancestors

Homologous structures Structures that come from the same origin homo- = same -logous = information Forelimbs of human, cats, whales, & bats same structure on the inside same development in embryo different functions on the outside evidence of common ancestor

Homologous structures – these are parts of the body that are similar, but have different functions ex. The flippers of whales, and the wings of birds All forelimbs of vertebrates have the same pattern of bones • Common ancestry

Homologous Structures

modifies homologous structures Adaptive Radiation - Modifies homologous structures

Morphology

But don’t be fooled by these… Analogous structures look similar on the outside same function different structure & development on the inside different origin no evolutionary relationship How is a bird like a bug? Solving a similar problem with a similar solution

In your notes…. In one sentence, write your answer to the following question….. What is the difference between homologous and analogous structures?

Vestigial Organs – these are organs or parts that seem to have no function Whales have pelvic bones that do not attach to legs

Because they used to walk on land! Vestigial organs Hind leg bones on whale fossils Why would whales have pelvis & leg bones if they were always sea creatures? Because they used to walk on land!

3. Molecular record Comparing DNA & protein structure everyone uses the same genetic code! DNA 10 20 30 40 50 60 70 80 90 100 110 120 Lamprey Frog Bird Dog Macaque Human 32 8 45 67 125 compare common genes compare common proteins number of amino acids different from human hemoglobin

Biochemistry and DNA When comparing the DNA of one species to another, more similarities are found in species that are more closely related. Lion photo credit: ucumari Tiger photo credit: digitalART2

DNA

Embryological Development Embryos of different species develop in almost identical ways. Human fetus at 8 weeks

Embryology

Convergent Evolution These animals have evolved similar adaptations for obtaining food because they occupy similar niches. What can you infer about their phylogeny from their geographic locations?

Punctuated Equilibrium “instead of a slow, continuous movement, evolution tends to be characterized by long periods of virtual standstill ("equilibrium"), "punctuated" by episodes of very fast development of new forms” The "punctuated equilibrium" theory of Niles Eldredge and Stephen Jay Gould was proposed as a criticism of the traditional Darwinian theory of evolution…what is it called?

Convergent Evolution Species exposed to the same selective pressure in different parts of the world tend to develop the same adaptations Even though they may be completely unrelated e.g. the placental wolf and the marsupial thylacine or Tasmanian wolf Thylacine Thylacinus cynocephalus Wolf Canis lupus © 2008 Paul Billiet ODWS

Convergent evolution led to mimicry Why do these pairs look so similar? Monarch male = poisonous Viceroy male = edible moth bee fly bee

Divergent Evolution Populations of a species that are separated and evolve under different selective pressures develop different adaptations as they diverge They are usually geographically separated so that there is a barrier to the mixing of genes © 2008 Paul Billiet ODWS

Direct observation of species change Bacteria become resistant to antibiotics Wolves were bred over many generations to become dogs (artificial selection) • and then bred further to create a variety of breeds

3. Micro Evolution: Natural selection in action: the evolution of insecticide-resistance •New insecticides are effective, killing 99% of the insects. The few survivors resist the chemical attack. Only these resistant individuals reproduce, passing on their resistance. In each generation the percentage of insecticide-resistant individuals increases. In general, natural selection operates not to create variation, but to edit existing variation. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Fig. 22.12 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

For patients treated with the drug 3TC, which interferes with genome replication in HIV, 3TC- resistant strains become 100% of the population of HIV in just a few weeks. Fig. 22.13 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Endosymbiotic Theory