Evolution Change Over Time Evolution Definition: A change in a population of a species over time Organisms evolve to adapt better to their environment According to Evolution, all living things (organisms) on the planet are related and have a common ancestor A unicellular prokaryote (bacteria) that lived near hydrothermal vents where the temperature is near 200 degrees Fahrenheit amidst poisonous hydrogen sulfide and deadly sulfuric acid First need to talk about formation of earth: 4.6 billion years ago! How do we know this stuff: RADIOACTIVE DATING- Not relative dating- Formation of EARTH Solar system in beginning (~5 billion yrs ago) was a swirling mass of gas and dust that collapsed inward leaving some debris outside (planets) First Prokaryotes (the early cells that are still around today aka bacteria) Since no oxygen on earth before 1.7 bya, first cells must have been anaerobic-- Most likely heterotrophs that depended on organic molecules. After consuming all organic molecules, there was a need for some organisms to evolve into autotrophs These first autotrophs resembled archaebacteria (aka extremophiles) These early archaebacteria obtained their energy by chemosynthesis, which produced atmospheric O 2. First cells by endosymbiosis After almost 1 billion years of O 2 production, life exists only in the ocean. Then many of these cells began sticking together, first in colonies, then permanently attached; first multicellular organisms: early invertebrates Then after more oxygen was released by early plant forms and algae, multicellular organisms diversified rapidly (Cambrian explosion) The Scientists Lamarck Darwin 1
Jean Baptiste Lamarck Evolution occurs as structures develop through use, or disappear because of disuse, and these acquired characteristics are passed to offspring EXAMPLE: Over a Giraffe s lifetime it can stretch its neck and its offspring will be born with long necks. Who was Charles Darwin Studied Medicine Hated the sight of blood Received a BA in Theology Had 10 children Valid? Not valid? Theory of Evolution At the age of 22, Darwin was an unpaid naturalist on a naval voyage on the HMS Beagle On the trip, Darwin saw things that he thought could only be attributed to a process of gradual change Theory of Evolution In The Galapagos Islands, Darwin collected more than a dozen species of finches (13) Each had a specialized diet and way of obtaining food. These finches resembled a finch species from South America. 2
Darwin s Finches Theory of Evolution descent with modification evolution aka: change over time Returned from trip at age 27. Still left with the question: How does evolution occur? Darwin made following principles: 1. There is variation within populations 2. Overproduction: Not all young in each generation can survive, results in competition 3. Adaptations leads to some variations being favorable 4. Descent with modification: Individuals that survive and reproduce are those with favorable variations Therefore, those traits will increase in a population and the nature of the population will gradually change Natural Selection Populations change in response to their environment so they are more likely to reproduce. Selection acts on populations, species evolve Survival of the Fittest Fitness refers to the better trait in a population. Evolution happens because of natural selection Look at the next slide and try to figure out which trait is the fittest in the beetle population. Eventually what will happen to the beetle population? The population will change so much evolution will occur. 3
Adaptation Adaptations are inherited traits that increase a group s chance of survival & reproduction Variation & Species 1. Variation = differences between members of a population Example from class: 2. Species = group that can breed & produce healthy & fertile offspring This type of finch has a thick beak adaptation for cracking open seeds What is a species? LIGER = male lion + female tiger Are tigers & lions in the same species? Artificial Selection Selective breeding, humans selectively breed species for specific traits. Why or why not? How do new species form? Geographic Isolation When members of a population are separated Ex: polar, grizzly, & black bears 4
Reproductive Isolation When members of a population can t breed even though they live nearby Ex: different mating seasons or different mating calls Different Types of Evolution 1. Divergent evolution 2. Convergent evolution 3. Coevolution Divergent Evolution Isolated populations evolve independently Ex: polar & grizzly bears changed independently due to different habitats Convergent Evolution Unrelated species become more alike because they live in similar environments Ex: shark & dolphin Coevolution Species that interact closely adapt to one another Ex: flowers & hummingbirds Adaptive Radiation Evolution of many diverse species from one common ancestor Ex: Galapagos finches discovered by Darwin 5
Fossils gave the idea of species becoming extinct. After this mass extinction there was a sharp increase in the number of species. This is called Episodic Speciation Biodiversity: amount of variety of living things in an area. Between the coral reef and Antarctica, which place has higher biodiversity? 5 Lines of Evidence for Evolution Evidence for Evolution Adaptations Camouflage, Mimicry Fossils Anatomy Embryology Biochemistry DNA Evidence Structural adaptations have been observed in populations of birds, insects, and many other organisms. Example: Camouflage adaptations of mantids that live in different environments Adaptations: Camouflage Hi! Scorpion fish 6
Adaptations: Mimicry Adaptations: Mimicry monarch butterfly viceroy butterfly moth caterpillar katydid Pair Share In your own words, explain how mimicry is different from camouflage. Analyzing Fossil Evidence Fossil: a trace of a long-dead organism Biological diversity: many different fossils found showing different species or subspecies. Episodic speciation: time when a large number of species appear Mass extinction: brief periods in time where large numbers of species disappeared (Ex: dinosaurs) Fossils The fossil record provides evidence for the theory of evolution. Transitional forms link fossils to modern species. Elephant evolution based on fossils Ichthyostega (transitional fossil from fish to land animals) 2 min. video clip http://animal.discovery.com/videos/animalarmageddon-ichthyostega.html Archaeopteryx (transitional fossil from reptiles to birds) Watch first 1 min. 30 sec. video clip http://www.youtube.com/watch?v=p7ehjoy8tcw&feature=related 7
Trilobite The records for marine fossils, such as this 400 million year old trilobite, are the best tool for studying biodiversity through history because they re longer and better preserved than the records for land fossils. (image from Oxford University) Sedimentary Fossil Formation Anatomy: Homologous structures: similar in function and organisms do share common origin. Look the same Forearm bones in mammals Homologous structures Anatomy: Analogous structures: similar in function, but organisms do not share a common origin. work the same Example: Insect wings and bird wings. Anatomy: Vestigial structures: body parts that have lost their function over time and are now useless. Examples: human appendix 8
Embryology: Vertebrate embryos are similar, pointing to common origin. Embryology Developmental homology Biochemistry a.k.a. Molecular evidence Biochemistry: Similarities in DNA sequence point to a common origin. The fewer the differences, the more closely related two organisms are. Cladogram: Visual way to show how closely related species are. Pair Share Refer to the illustration. The bones labeled A are known as a) vestigial structures. b) sequential structures. c) homologous structures. d) fossil structures. 9