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Transcript
Evolutionchange over time. The process by which modern organisms have descended from ancient organisms. OWL PELLETS What can skeletal remains reveal? Vocab pg 392 and 401 Kahoot: Owl pellet dissection How Do We Know? How do we know anything about the past if humans were not around? By studying other planets and rocks on earth we know that earth was molten rock 4.6 billion years ago. Gravity pulled the densest to the center and the crust was formed 500 million ya Then…. The atmosphere formed because of gravity and life would not have existed like we know it because volcano gasses were in the atmosphere and it was too hot. Clues in the Rocks Clues in the Rocks Eventually the earth cooled and oceans formed 500 milya 1st life clues came from 3.5 bill ya How do we know?????? FOSSILS FOSSILS Most organisms decompose when dead. 99% of species that lived on earth are extinct – only a tiny amount of those fossilized. Fossils ONLY form when buried in sediment soon after death. Most common in aquatics environments because sediment is always moving Law of Supposition Types of Fossils Trace fossils- any indirect evidence left by an organism- example footprints, burrows, feces Types of Fossils Molds and Casts Mold is an impression of an organism Cast is a mold filled with sediment Types of Fossils Replacement- original material is replaced with mineral crystals leaving a replication of the organism. Types of Fossils Petrified- empty pores fill with minerals Types of Fossils Amber- preserved tree sap traps and then hardens preserves organism Types of Fossils Original- mummies or freezing Why are they not everywhere? Why don’t we see fossils everywhere? What type of rock must they be in? Why are there sea shells on top of mountains? What type of fossil would the bones of your owl pellet likely form? Why? How do we know??? How old a fossil is? Dating fossils 1. Relative dating- compare to the layer of earth they were found in 2. Radiometric dating – uses half life of isotopes of the rock fossil was found in. 3.Carbon dating- for mummies or unaltered living organisms ½ life- dating Geological Time Line Foldable 4.6 meter long where each meter represents 1 billion years and each mm= 1 million years Earth formed at one end – humans the other Geological Time Line High lights! Origin of Life Oldest ideas of life was spontaneous generation. Redi’s meat experiment Replace with Biogensis Louis Pasteur- used flasks to grow organisms Premordial Soup Hypothesis Simple organic molecules could be made from inorganic compounds- Miller Uray experiment THEN… Protein synthesis gave rise to genetic code and RNA gives life its first genetic code. Molecules go to cells and metabolisms evolve ENDOSYMBIOTIC THEORY ENDOSYMBIOTIC THEORY How Does Evolution Occur? We have all heard of …. But is that what it really means? History Before Darwin… Jean Baptiste Lamarck—first evolution theory in 1809 – Nature moves toward perfection – Thought that it happened by… Use and disuse Inheritance of acquired traits Lamarck—Use and disuse Ex. fiddler crabs’ claws gets larger with use during lifetime Ex. blacksmith’s biceps get larger over time Lamarck—Inheritance of Acquired Traits Modification acquired during lifetime is passed on to offspring Not true! Ideas Darwin considered… James Hutton: (gradualism) geologic change is continuous & slow Sir Charles Lyell: (uniformitarianism) forces that shape Earth are still occurring (volcanoes, earthquakes, etc) Result—Earth must be more than a few thousand yrs. old Malthus Believed that species have the capacity to overproduce offspring (only the fittest survive) This could lead to a lack of food, space, etc for human population. Charles Darwin- Born 1809 Credited with the Theory of Evolution based on Natural Selection. H.M.S. Beagle- ship’s naturalist Did not believe that species change at the start of the voyage. Darwin married his first cousin Emma Wedgwood… Down House, Darwin’s home Voyage of the HMS Beagle 1831-1836 Galapagos Islands-located off coast of South America At first he believed that the Earth was 6000 years old; species were designed for specific habitats and appeared on Earth in present forms On the Galapagos Islands, he realized that the species were like those of South America, but not exactly. He specifically noted the different finches, tortoises, and iguanas Galapagos Islands A Galapagos Tortoise Darwin’s finches (13 different species) Could all have come from a single species in South America? Iguanas- Marine and Land Significant findings… Fossils resembled living organisms in same area—why had they died and others lived? Galapagos Islands: – Animals resembled mainland’s, but different – Characteristics of animals and plants differed from island to island. Darwin thought and thought… He hypothesized that new species were a result of natural selection. Natural Selection: Nature (environment) selects survival traits (variations) Darwin’s book, On the Origin of Species (1859) Theory of Natural Selection Variations occur in nature There is a struggle for existencecompetition Survival of the Fittest- organisms best suited for their environment will survive, reproduce and pass their traits to offspring. Overproduction of offspring Artificial Selection Plant and animal breeders who selected traits causing variations so why would nature be different? Evidence for Evolution 1. Fossil Records Older fossil records are in lower rock layers Derived Traits: new traits not found in similar fossils Ancestrial traits: primitive features that appear in ancestors – teeth, tails Transitional fossils- show changes in traits Evidence for Evolution Comparative anatomy- what do you see? Evidence for Evolution Embryos of related ancestors are similar in early stages. – Gill slits and post anal tail? Evidence for Evolution Vestigial structures: reduced form of a structure in other organisms. Ex birds wings, appendix and snake pelvis Vestigial Organs Organs that have no function now but did have a function in ancestors. – Ex: appendix, tailbone Evidence for Evolution Analogous structures: not all similar features mean a common ancestor. Ex the wing of a beetle and bird evolve for different reasons. Homologous Body Structures Wing of a bat resembles forelimb of a mammal, not a bird. Wing of bird resembles forelimb of reptile. Evidence for Evolution Biochemical Evidence Comparing DNA nucleotide sequences. Evidence for Evolution Geographic Distribution-Due to different climate changes adaptations resulted in differences among organisms. How does this happen? Adaptation A trait shaped by natural selection which makes a living thing better able to survive in its surroundings Three Types: – Structural – Behavioral – Physiological Survival of the Fittest Fitness = reproductive success or the number of offspring you produce that contribute to the next environment. Better adapted = more fit (not strongest) Structural Adaptations Traits that involve the physical structure (anatomy) of an organism. –Ex: Camoflague, mimicry, beak of a bird, claws, etc. Mimicry—edible comes to look like poisonous Camouflage—walking stick & toad Behavioral Adaptations Inherited traits or actions that help an organism survive and reproduce in a given environment. – Examples: birds migrating, opossum faking death Physiological Adaptations Traits that involve the internal functions or chemistry of an organism. – Examples: – Chemicals to digest food – Antarctic fish with “anti-freeze” in their body. – Venom of a snake – Anitbiotic resistance Mechanisms of Evolution Natural Selection is not the only mechanism for evolution Population genetics – how do any recessive genes ever show up? Shouldn’t dominant always take over? Evolution won’t occur unless allelic frequencies ( how many Aa vs AA) are acted upon by forces that cause change Hardy-Weinberg Principle Allele frequency remains constant in a population (no evolution) if these factors are present in the population: – Random mating – Population size very large – No movement in or out of population – No mutation – No natural selection Can determine frequencies by using the Hardy-Weinberg equation… 2 alleles—A & a 3 combinations—AA, Aa, & aa Let p = A and q = a A + a = 100 percent of alleles So…p + q = 1 Square both sides… – p2 + 2pq + q2 = 1 – homozygous dominant + heterozygous + homozygous recessive = all possible combinations Practice Problem Having long tongues is dominant in frogs. 64% of the frog population is homozygous dominant. What percentage of the population is heterozygous? Practice problems Equilibrium If Hardy Weinberg = 1 then equilibrium exists This hardly happens in nature over the extended period because of No Genetic drift No gene shuffling No gene flow No Founder effect No mutations No Bottle neck No random mating No natural selection Evolution of Populations Gene Pool: the combined genetic information of a population. Two main types of Genetic Variation: – Mutation: a change in the DNA strand – Gene Shuffling: during sexual rep., chromosomes move independently producing millions of combinations of genes. What is all that stuff? Genetic Drift- change in alleles due to chance. Some individuals by chance leave more genes in the pool! What is all that stuff? Gene flow-also called migration- moves genes from one population to another- like pollen. What is all that stuff? Mutations- random mutation mostly cause death but some are beneficial Pepperd moth lab What is all that stuff? Random mating- mating is not random. Mates choose carefully – example peacock What is all that stuff? Bottle neck- example of genetic drift where population declines to extremely low numbers then rebounds Example of Bottle neck An example of a bottleneck Northern elephant seals have reduced genetic variation probably because of a population bottleneck humans inflicted on them in the 1890s. Hunting reduced their population size to as few as 20 individuals at the end of the 19th century. Their population has since rebounded to over 30,000 — but their genes still carry the marks of this bottleneck: they have much less genetic variation than a population of southern elephant seals that was not so intensely hunted. Northern Elephant Seals What is all that stuff? Founder effect- Small sample settles in a location completely separate from others – the random alleles now become the norm. For example, the Afrikaner population of Dutch settlers in South Africa is descended mainly from a few colonists. Today, the Afrikaner population has an unusually high frequency of the gene that causes Huntington's disease, because those original Dutch colonists just happened to carry that gene with unusually high frequency. This effect is easy to recognize in genetic diseases, but of course, the frequencies of all sorts of genes are affected by founder events. Afrikaner What is all that stuff? Gene shuffling-crossing over! Genes are shuffled to create variation Three Types of Natural Selection 1. Stabilizing Selection 2. Disruptive Selection 3. Directional Selection Stabilizing Selection Genetic diversity decreases as the population becomes stable. Disruptive Selection Directional Selection Natural selection favors one phenotype and the allele frequency shifts in one direction. Speciation Forming a new species This can happen because of species isolation: – Reproductive: organisms can’t interbreed and have separate gene pools – Behavioral: different courtship rituals. – Geographic: separated by barrier (river, canyon) – Temporal: reproduce at different times (seasons) Allopatric speciationgeographical Physical barrier divides 2 populations long enough that they will not be able to reproduce. Allopatric Example Sympatric Speciation Species evolve into new species with NO physical barrier- side by side 200 years ago, the ancestors of apple maggot flies laid their eggs only on hawthorns — but today, these flies lay eggs on hawthorns (which are native to America) and domestic apples (which were introduced to America by immigrants and bred). Females generally choose to lay their eggs on the type of fruit they grew up in, and males tend to look for mates on the type of fruit they grew up in. So hawthorn flies generally end up mating with other hawthorn flies and apple flies generally end up mating with other apple flies. This means that gene flow between parts of the population that mate on different types of fruit is reduced. Sympatric example Patterns of Evolution Divergent evolution – aka Adaptive radiation Co evolution- ex mutualism Co evolution arms race Convergent evoution Divergent Evolution The process of two or more related species becoming more and more dissimilar. – Ex: Red fox and the kit fox. Red fox lives in mixed farmlands and forests, where its red color helps it blend in with surrounding trees. The kit fox lives on the plains and in the deserts, where its sandy color helps conceal it from prey and predators. Kit fox has large ears as an adaptation to its desert environment. Similarities in structure indicate that the red fox and the kit fox had a common ancestor. As they adapted to different environments, the appearance of the two species diverged. Kit Fox vs Red Fox Co - evolution Mutualism- as one species evolves another does as well Some Central AmericanAcacia species have hollow thorns and pores at the bases of their leaves that secrete nectar.These hollow thorns are the exclusive nest-site of some species of ant that drink the nectar. But the ants are not just taking advantage of the plant — they also defend their acacia plant against herbivores. Co evolution arms race Predator / prey systems- a predator has an adaptation that prey have to overcome. They do and then the predator has to evolve a new trait to fight back. Molluscs, such as Murex snails, have evolved thick shells /spines to avoid being eaten by animals like crabs and fish. These predators have evolved powerful claws and jaws -compensate for the snails’ thick shells and spines. Can you relate? How does antibiotic resistance relate to this? Convergent Evolution Two different species with different ancestors evolve to display similar physical features. – Ex: Different anteaters found in Australia, Africa, and America. Though not closely related, they all evolved the "tools" necessary to live on an ant diet: a long, sticky tongue, few teeth, and large salivary glands. Micro and Macro Evolution Micro-evolution- changes in allele frequency within a species Macro-evolution- new species, new forms replacing old as revealed in the fossil record