Evolution and Darwin What is evolution X A

Evolution and Darwin

What is evolution? X • A slow • A heritable change in the characteristics within a change population from one over generation to the next time • The development of new types of organisms from preexisting types of organisms over time

Evolution Primers • Isn't Evolution Just a Theory? ? ?

History of Evolution

Charles Darwin – a brief history • Born in England on February 12, 1809 • In 1831 began a 5 -year journey on the HMS Beagle as a naturalist • Observations and specimen collections led him to develop “the single best idea anyone has ever had” • “Developed a scientific theory of biological evolution that explains how modern organisms evolved over long periods of time through descent from common ancestors” • Darwin video clip

• Darwin set sail on the H. M. S. Beagle (18311836) to survey the south seas (mainly South America and the Galapagos Islands) to collect plants and animals. • On the Galapagos Islands, Darwin observed species that lived no where else in the world. • These observations led Darwin to write a book.

Darwin’s Observations 1. Species vary globally – Darwin noticed that different, yet ecologically similar, animal species inhabited separated, but ecologically similar habitats around the globe – Flightless birds (emu, ostrich, rhea) – Convergent evolution

Darwin’s Observations 2. Species vary locally – Darwin noticed that different, yet related, animal species often occupied different habitats within a local area – Tortoise, mockingbirds

Darwin’s Observations 3. Species vary over time – Darwin noticed that some fossils of extinct animals were similar to living species - fossils – preserved remains of ancient, extinct organisms Who is Charles Darwin?

Friends • Friends Evolution Montage

Ideas that Shaped Darwin’s Thinking • Lyell & Hutton – – • Concluded that Earth is extremely old and that the processes that changed Earth in the past are the same processes that operate in the present (still changing) Hutton (in 1785) – geological processes shape Earth Lyell (in 1830) – uniformitarianism – geological processes we see in action today must be the same ones that shaped Earth millions of years ago Lamarck – 1809 – – – Inheritance of Acquired Characteristics Organism could change during their lifetimes by selectively using or not using various parts of their bodies; then pass these acquired traits on to their offspring, enabling species to change over time One of the first naturalist to suggest that species are not fixed One of the first to try and explain evolution scientifically using natural processes Recognized that there is a link between an organism’s environment and it’s body structures

“The Inheritance of Acquired Characteristics” Lamarck vs Darwin • 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. -A muscle builder will pass the muscles on to his offspring…. NOT TRUE

Ideas that Shaped Darwin’s Thinking • Malthus – 1798 – English economist – Reasoned that if the human population grew unchecked, there would not be enough living space and food for everyone • Artificial Selection – Nature provides variations, but humans select those they find useful

Artificial Selection • The selective breeding of domesticated plants and animals by man. • Question: What’s the ancestor of the domesticated dog? • Answer: WOLF • This is STELLA!!!!!

Darwin’s Contribution to Science Darwin developed a scientific theory of biological evolution that explains how modern organisms evolved over long periods of time through descent of common ancestors.

Darwin and Wallace • Same conclusion about evolution as a result of similar experiences – Influenced by Lyell and Malthus – Observed plant and animal life in several parts of the world – Wallace (1858) sent Darwin a manuscript describing “natural selection” – Wallace and Darwin arrived at theory of Natural Selection independently, and presented their ideas in public together in 1858

Charles Darwin Wallace kind of gets dissed • Wrote in 1859: 1859 (11/24 – pub) • “On the Origin of Species by Means of Natural Selection” • Main points: 1. Struggle for Existence (competition) 2. Variation and Adaptation 3. Survival of the Fittest 4. Natural Selection

Struggle for Existence • Organisms produce more offspring than can survive. (OVERPRODUCTION) – Grasshoppers can lay more than 200 eggs at a time. Only a small fraction of these offspring survive to reproduce.

Variations and Adaptations • There is variation in nature, and certain variations – called adaptations – increase an individual’s chance of surviving and reproducing. – Physical, physiological, and/or behavioral traits that enhance an organisms chances for surviving in its environment • Green vs. yellow color in grasshoppers is a heritable variation: green can blend into environment and avoid predators

Survival of the Fittest • Suggests that natural selection selects mainly for survival… IT DOES NOT • Selects for contribution of genes to future generations – Reproduction resulting in viable offspring – Selects for individuals that are able to produce the greatest number of offspring, that in turn, can survive and reproduce • Green grasshoppers have higher fitness and so survive and reproduce more often than yellow

Natural Selection • How Does Evolution Really Work?

Survival of the Sneakiest • Survival of the Sneakiest

• Will the grey mouse or white mouse survive more easily? • What characteristic is affecting the fitness of the mice?

• Peppered Moths: Dark Light In the year Year 1848, 5% of the population was dark colored moths while 1848 95% was light 5% colored. 95% • In the year 1895, 98% was dark colored while 2% was light 1895 98% 2% colored. • In the year 1995, 19% was 19% dark colored while 81% was light colored. • What was the reason for the changes in the number of dark and light colored moths? • In the early 1800 s, England was not so industrialized yet and pollution was still low. The trees had light colored bark so the light colored moths had a better advantage and a better survival rate than dark colored ones. • In the late 1800 s, England started to become more industrialized and factories increases. These factories caused trees to become soot coated, the bark was darker. The dark colored moths were then camouflaged and survived more than light colored ones. • Then in the mid 1900 s, the air started to become cleaner due to clean air

• http: //www. sciencenetlinks. com/interactives/evolution. html Another example of natural selection…

Darwin’s Finches – A Close Look at Darwin’s Finches When Charles Darwin traveled to the Galápagos Islands, he found a variety of species of finches. Although each species was slightly different from the others, all the species were related. None of the finch species he found were similar to finches on the mainland. When Darwin saw such extensive diversity of species in a single group of birds, he hypothesized that they all could have descended from a common ancestor. His observations of these finches helped him formulate his concept of evolution. The phylogenetic tree below shows the relationships Darwin proposed among the species of finches. The tree is based on a comparison of the anatomy, behavior, and location on the island of each finch species. Look carefully at each species, and notice the dramatic difference among the beaks. Each type of finch has a beak adapted to its diet. 1. Which Darwin’s of the ground finches above wouldradiation. be able to eat the largest, finches are anillustrated example of adaptive Adaptive radiation is the emergence many species from a common toughest nuts and seeds? Explain yourofanswer. ancestor that was introduced to various new environments. For radiation to occur, newdiagram. environments offer 2. Study theadaptive insect-eating finches shownthe in the What must can you infer about new opportunities and pose new problems of survival for the insects of the Galápagos Islands? species.

What does Darwin’s mechanism for evolution suggest about living and extinct species? ? ? • All organism descended from a common ancestor • “Descent with modification” • Homer Evolution

Evidence for Evolution • • • Biogeography Fossil Record Comparative Anatomy Developmental Biology Comparative Biochemistry How Do We Know Evolution Happens?

Biogeography – study of where organisms live now and where they and their ancestors lived in the past • Patterns in the distribution of living and fossil species tell us how modern organisms evolved from their ancestors – Closely related species differentiate in slightly different climates – Very distantly related species develop similarities in similar environments Adaptive Radiation • Evolutionary process that gives rise to new species adapted to new habitats and ways of life

The Age of the Earth and Fossils – The Age of the Earth • Earth had to be old enough for these proposed changes to occur – plenty of time for Natural Selection • Earth is ~4. 5 byo (determined by radioactive dating) – plenty of time for natural selection to take place – Fossils discovered after Darwin fill in some of the “gaps” in the fossil record – One fossil shows the evolution of whales from a landbased mammal (book figure 16 -3)

Comparing Anatomy and Embryology • Homologous Structures – Parts that are similar in structure but different in function – Humans, penguins, alligators, bats all have the same bones in their arms but they are used for different things • Similar Embryos – Embryos of different organisms are very similar and have similar structures early on – Must have similar proteins at work • Vestigial Structures – Structures that are so reduced in size or function that they are merely traces of similar organs in other species (I. e. tailbone and appendix in humans) • Analogous Structures – Parts that are similar in function but not structure – i. e. Wing of bee, bird, bat

Genetics and Molecular Biology • All organisms have DNA – Therefore similar RNA, similar genes, and similar proteins • All organisms have ATP

Evolution of Populations Ch 17 • Process of change over time • A change in the genes!!!!

Population Genetics • The science of genetic change in population. • Population – all the members of a species that occupy a particular area at the same time • Gene Pool – all the genes in all the members of a population

Genes and Variation • Genetics Joins Evolutionary Theory – Variation is the raw material for natural selection – Gene pool – consists of all the genes, including all the different alleles for each gene, that are present in a population – Relative frequency – the number of times that the allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur – Therefore – evolution is any change in the relative frequency of alleles in the gene pool of a population over time • 3 Sources of Genetic Variation – Mutations – Genetic Recombination in Sexual Reproduction (Ind assortment and crossing over) – Lateral Gene Transfer (conjugation) • Single-Gene (2 pheno) vs. Polygenic Traits (many pheno/bell curve) ***Natural Selection acts directly on PHENOTYPES not actual alleles*** some phenotypes are better suited to an environment than others and they will survive, reproduce and pass on their genes.

Evolution as Genetic Change in Populations How Natural Selection Works – 3 Types Stabilizing Selection ·Individuals with the average form of a trait have the highest fitness ·Represents the optimum for most traits ·Results in a similar morphology between most members of the species Directional Selection ·Individuals that display a more extreme form of a trait have greater fitness than individuals with an average form of the trait ·A shift in one direction ·Peppered moth Disruptive Selection ·Individuals with either extreme variation of a trait have greater fitness than individuals with the average form of the trait ·A shift in both direction, away from the center ·Shell color (dark rocks and light sand)

Genetic Drift • Random changes in the frequency of a gene in the absence of natural selection occurs because of CHANCE • Occurs efficiently in small populations because small changes affect more members • Two examples: a. Bottleneck effect b. Founder effect

Genetic Drift

a. Bottleneck Effect • Genetic drift (reduction of alleles in a population) resulting from a disaster that drastically reduces population size – Examples: 1. 2. Earthquakes Volcano’s

b. Founder Effect • Genetic drift resulting from the colonization of a new location by a small number of individuals. • Results in random change of the gene pool. • Example: 1. Islands (first Darwin finch)

Hardy-Weinberg Principle • Genetic Equilibrium – situation in which allele frequencies in the gene pool of a population remain constant • The concept that the shuffling of genes that occurs during sexual reproduction, by itself, cannot change the overall genetic makeup of a population. • Shows mathematically and theoretically that there are situations where evolution DOES NOT OCCUR – Seldom achieved in nature

Hardy-Weinberg Principle • This principle will be maintained in nature only if ALL five of the following conditions are met: 1. Very large population 2. Isolation from other populations (no immigration, no emigration) 3. No net mutations 4. Random mating 5. No natural selection Hardy-Weinberg Principle

Species • A group of populations whose individuals have the potential to interbreed and produce viable offspring.

Speciation • The evolution of new species. Species that occupy an otherwise unoccupied niche face no competition, they will therefore have a 100% success rate

Reproductive Isolation • Any mechanism that impedes two species from producing fertile and/or viable hybrid offspring -factor necessary for the formation of a new species • Barriers: 1. Geographic (rivers, mountains) 2. Behavorial - differences in courtship behavior 3. Temporal - fertile periods (time)

Interpretations of Speciation • Two theories: 1. Gradualist Model (Neo-Darwinian): Slow changes in species overtime. 2. Punctuated Equilibrium: Evolution occurs in spurts of relatively rapid change.

Macroevolution • The origin of taxonomic groups higher than the species level

Adaptive Radiation aka Divergent Evolution • Emergence of numerous species from a common ancestor introduced to new and diverse environments. • Example: Darwin’s Finches

Darwin’s Finches an example of Adaptive Radiation

Convergent Evolution • Species from different evolutionary branches may come to resemble one another if they live in very similar environments. • Example: 1. Ostrich (Africa) and Emu (Australia). 2. Sidewinder (Mojave Desert) and Horned Viper (Middle East Desert) 3. Shark and Dolphin

Coevolution • Evolutionary change, change in which one species act as a selective force on a second species, inducing adaptations that in turn act as selective force on the first species. • Example: 1. Acacia ants and acacia trees 2. Humming birds and plants with flowers with long tubes

The Age of the Earth and Fossils – Fossils • Trace the evolution of modern species from ancient/extinct ancestors Radiometric Dating • Relative dating vs. – When unstable nuclei release particles or • Absolute dating radiant energy until the – nuclei becomes stable Half-life = The length of time it takes for one -half of a sample to decay to stable form

The Earth is born…

Date Event 4. 6 bya Earth was born 4 bya Cooling of Earth, 1 st solid rocks formed on earth’s surface 4 -3. 8 bya Volcanic activity & meteorites release gases that produce earth’s atmosphere Contained H 2 O vapor, CO 2, H 2, NH 3, CH 4 It did NOT contain oxygen 3. 8 bya Cooling continues, water appears, beginning of oceans Earth cool enough for liquid to stay on the ground 3. 5 bya Age of first prokaryotic microfossils Heterotrophic – obtained nutrients from organic “soup” Anaerobic – able to live in oxygen-free environment 3. 4 bya Appearance of 1 st autotrophs Organic soup begins to run out Photosynthesis begins – using H 2 S instead of water 2. 2 bya Introduction of oxygen into the atmosphere More modern form of photosynthesis appeared Used H 2 O instead of H 2 S Caused earth to cool as they converted CO 2 Led to aerobic respiration Ozone layer protection 1. 6 -1. 1 bya 1 st eukaryotic cells evolved Nucleus contains DNA, have membrane bound organelles, etc. Increased the speed of evolution Increased genetic variation 1700 s Spontaneous Generation (abiogenesis) – idea that life comes from non-life Disproven through Redi, Spallanzani, & Pastuer 1953 Miller & Urey mix methane, water, ammonia, and hydrogen with energy (sun & lightning) Primordial Soup Amino acids & other organic compounds are produced as by-products Provide glimpse at how molecules (proteins) may 1 st have formed on the Earth Sexual reproduction evolved Multicellular organisms arose Additional Info

The Age of the Earth and Fossils – The Age of the Earth • Earth had to be old enough for these proposed changes to occur • Earth is ~4. 5 byo (determined by radioactive dating) History of Earth (24 hours) 12: 00 am – Earth is formed 5: 00 am – Prokaryotes appear 4: 00 pm – Eukaryotes appear 10: 00 pm – Invasion of land 11: 59: 30 pm – Humans appear

Miller/Urey Experiment and Primordial Soup • Oparin and Haldane: hypothesized that the early atmosphere was composed of: ammonia (NH 3), hydrogen gas (H 2), water vapor (H 20), and compounds made of carbon and hydrogen, like methane (CH 4). They thought that at high temperatures, simple organic compounds (like amino acids) could form. When earth cooled, and lakes and oceans formed, theses simple compounds could be found in the water and enter complex chemical reactions fueled by lightning and ultraviolet radiation resulting in macromolecules essential to life like proteins. • Miller and Urey: 1953 set up an apparatus to test Oparin’s hypotheses. Their experiment produced a variety of organic compounds, including amino acids

Endosymbiotic. Theory • What is theory of endosymbiosis? Theory that large prokaryotic, unicellular organisms engulfed (ate) smaller prokaryotic, unicellular organisms. Engulfed prokaryotes eventually gave rise to modern mitochondria and chloroplasts. • What evidence supports the hypothesis that mitochondria and chloroplasts were once free living prokaryotic cells? Replicate independently and replicate like prokaryotes (binary fission), have their own DNA and their own ribosomes (also similar to DNA and ribosomes of prokaryotes)