Principles of Evolution Chapter 10

Early Ideas About Evolution Carolus Linnaeus Botanist Classification of organisms (Taxonomy) Still used today Developed the species idea Species-organisms so related that can interbreed Common belief at the time was that organisms were fixed and never changed He thought that some organisms might be hybirds

Early Ideas About Evolution Georges Louis Leclerc de Buffon Proposed species shared ancestors Felt Earth was older than 6000 years Comparative anatomy – similar structures in related species Will discuss comparative anatomy later

Early Ideas About Evolution Erasmus Darwin Darwin’s grandfather All living things from a common ancestor Gave rise to his grandson’s theory

Early Ideas About Evolution Lamarck’s Evolution Hypotheses Living things have changed over time—and that all species were descended from other species. Organisms change to adapt to their environment Lemarck then proposed that through selective use or disuse of organs, organisms acquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over time this process led to change in a species

Early Ideas About Evolution Tendency Toward Perfection All organisms strive to be complex and perfect This leads to constant change This change is a response to the environment and a desire to be perfect

Early Ideas About Evolution Use and Disuse Organisms could alter the size or shape of an organ - Use it or lose it If you don’t use the structure it will go away If you use it continually, it will get larger

Early Ideas About Evolution Inheritance of Acquired Traits Animals can change their body If they do they can pass on the new trait Ex. – Giraffes and long necks

Early Ideas About Evolution Evaluating Lamarck’s Hypotheses Many of Lamarck’s ideas were incorrect Lemarck made the mistake of thinking that an organism’s behavior influenced the inheritance of traits by offspring. Traits are inheritted regardless of the behavior However, Lemarck at least tried and was the first to come up with a hypothesis about evolution and realize that animals adapt and change

Early Ideas About Evolution Georges Cuvier Species can’t change, but the can go extinct Fossils – preserved remains of living things Catastrophism Natural disasters shape Earth Cause species to become extinct Fossils in deeper layers of strata are much different than those close to the surface Said that new species in rock layers was due to the species moving to a new area after each catastrophic event

Early Ideas About Evolution Hutton and Geological Change Gradualism - geological forces shape the earth Layers of rock form very slowly These layers are shaped by natural forces Due to the slow nature of the forces, he concluded Earth is very old Natural forces may be the pushing up of rocks lower in the earth or are pushed up by the sea floor to become mountain ranges Natural forces also then mold and shape these structures – rain, heat, cold, wind – all of which operate very slowly – gradualism

Early Ideas About Evolution Lyell’s Principles of Geology Uniformitarianism To understand the past, you have to look in the “now” Earth process Volcanoes Earthquakes Erosion Look at current occurences because these are what shaped the earth and are still doing so This information became extremely useful to Darwin If the earth could change, could life forms It must have taken an extremely long time for life forms to change, and therefore the earth must be very old Uniformitarinism – the idea of looking at the past to understand what is going on now; the same geological processes operated in the past at the same rate the operate today

Darwin’s Observations Biodiversity – The variety of living things in life Evolution – change over time

15-1 Life’s Diversity Voyage of the Beagle Charles Darwin The Beagle was British Naval ship Charles Darwin The father of evolution 1831 – Darwin sets sail

Darwin’s Observations As a member of H.M.S. Beagle Darwin collected animal and plant specimens These specimens were later used to create the theory of evolution

Darwin’s Observations Variation – difference in physical traits He found 68 different species of beetles in one day in a Brazilian forest! Found variations when traveling from place to place Variations are different between members of a group and the members they arose from Darwin began to realize that there was an incredible amount of diversity in the world, far different from his native country

Darwin’s Observations Patterns of Diversity Types of animals in similar places Ways that animals reproduce Ways that animals survive Adaptation – feature that makes an organism better suited to its environment While visiting Argentina and Australia, he noted that there were very different species even though both areas were essentially very much the same. Darwin seemed to be amazed not only that the animals survived, but they had become extremely adept at producing offspring that were suited for a particular area.

Darwin’s Observations Living Organisms and Fossils Darwin found Glyptodon Rationalized that extinct animals looked much like existing animals Living animals were only a part of the puzzle. Some of the fossils resembled some of the organisms he had seen alive – glyptodon looked like an armadillo

Darwin’s Observations The Galapagos Islands A group of islands northwest of South America Darwin spent a lot of time collecting there: Iguanas Birds Tortoises The islands although close in proximity, did have some differences. The smallest, lowest islands were hot and dry and nearly barren. The higher islands had greater rainfall and a different assortment of plants and animals

Darwin’s Observations

Darwin’s Observations The Journey Home Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galapagos. According to this hypothesis, these separate species would have evolved from an original South American ancestor species after becoming isolated from one another. The tortoise shells could be used to predict which island they came from Darwin also saw many brown birds looking for seeds: he noted these birds had different beaks

Theory of Natural Selection Inherited Variation and Artificial Selection Variation within domesticated species species Breeders select characteristics they want Pigeons Heritable For variations to be bred for characteristic must be able to be passed on Humans help push the variation along – by choosing the cow that produces the most milk, and plants that produce the greatest fruit. BUT this variation is due to variations in the genes What does this have to do with Darwin – if humans could make this happen in such a short amount of time, you should be able to get big changes in species over a longer period of time.

Theory of Natural Selection Survival of the Fittest – individuals that can survive and reproduce This is also called Natural Selection Fitness is the ability of an organisms to survive and reproduce in its specific environment Fitness is the result of adaptations to the environment Success is determined by the inheritance of the adaptations that will make you survive and reproduce

Theory of Natural Selection Population Growth Malthus - 1798 A population can not grow forever Food Space He reasoned that the only thing to keep growth in check was disease, famine, and war Darwin thought that this reasoning applied even more to animals and plants – they produce far greater amounts of offspring than humans If all the offspring survived, surely the would overtake the world Very few offspring survive and those that do, only a few live to see reproductive age – plants and animals

Theory of Natural Selection Evolution Struggle for Existence Members of one species compete with each others (populations) for resources Food Living Space Predators that are the fastest or are adept hunters will be more successful

Theory of Natural Selection The reason for a structure or feature is because of adaptations Ultimately, natural selection results in either an organism changing traits, OR it dies

Theory of Natural Selection Alfred Wallace Developed a similar theory Sent his manuscript to Darwin Wanted to publish the same findings Darwin had 1858 – Darwin receives Wallace’s manuscript; Wallace asked him to review it and forward to Lyell Darwin forwards to Lyell – Lyell presents Wallace’s paper and some excerpts of Darwin’s work In the end Wallace agrees that is was Darwin’s theory and he should receive the credit

Theory of Natural Selection Publication On the Origin of Species Darwin was nervous about publishing It challenged every fundamental scientific belief Lyell had tried to get Darwin to publish his manuscript even though Lyell didn’t believe in it.

Theory of Natural Selection Four main principles of Natural Selection Variation Overproduction Adaptation Descent with modification

Theory of Natural Selection Variation Exist in all populations Result from differences in genetic make up Parents Mutations

Theory of Natural Selection Overproduction Produce more offspring More chance for survival Increase competition

Theory of Natural Selection Adaptation An inherited trait that improves the organism’s chance of survival Successful adaptations make animals better suited to their environment Adaptations can be anatomical, structural, characteristics, physiological, or functions Individuals with low levels of fitness , that is adaptations that are not well suited for survival, will either die or leave few offspring Individuals with high fitness, are well adapted to their environment, will reproduce most successfully

Theory of Natural Selection Descent with modification These adaptations will lead to different species over time Different: Structures Niches Habitats Niches are physical and biological conditions in which an organisms lives and the way in which the organism uses those conditions

Theory of Natural Selection Common descent All living things have a common ancestor

Theory of Natural Selection

Theory of Natural Selection Fitness - the ability of an individual to survive and reproduce Fitness happens because of adaptations

Theory of Natural Selection The Grant’s Studied finches on Daphne Major 1977 Drought Reduced the number of seeds Drop in species numbers After the droought the medium ground finch feeders reduced in numbers because of the drop in the number of seeds Large beak birds increased in numbers because of the availability of the large tough seeds

Theory of Natural Selection Grant’s predicted a trait already in the population would survive This was passed on to future generations Increase in numbers As environments change, different traits become beneficial In 1984 the number of large seeds decreased and an unusual wet period followed-small seeds returned and medium ground finches increased again.

Theory of Natural Selection Adaptations and Compromise Some adaptations become new functions Panda thumb Panda paws reveal a 6th finger which is actually part of the wrist

Evidence of Evolution Fossil Evidence Bone structure, age, location of discovery Fossils found in deeper layers are older than more superficial layers

Evidence of Evolution Geographic Distribution Species move from place to place Ancestral species to islands Certain traits may be beneficial when moving Ex. Finches Biogeography Study of the distribution of organisms around world One ancestral species of finches made it to Galapagos and then had the ability to survive different habitats on different islands

Evidence of Evolution Similarities in Embryology Crab and barnacle larvae Vertebrate embryos look very similar early in development Evidence for common descent

Evidence of Evolution

Evidence of Evolution Homologous Body Structures Structures that come from the same embryonic tissues Homologous structures – bat wing and human hand Analogous structures – bird wing and insect wing Researchers began to notice a lot of similarity between reptiles, birds, and mammals extremities However, these extremities had been adapted in a way that benefitted each organism Homologous structures indicate similar ancestor Analogous structures indicate convergent evolution and no common ancestor

Evidence of Evolution Vestigial organs – organs with little to no function Natural selection has caused the organ to shrink or “disappear”

Evolutionary Biology Today Paleontology Study of fossils No fossil evidence to contradict evolution has been found

Evolutionary Biology Today Molecular and Genetic evidence DNA sequencing Pseudogenes Homeobox genes Protein comparisons DNA sequencing – the more related two organisms the more similar their DNA Pseudogenes – sequences of DNA that serve no purpose but are still part of the DNA Homeobox genes – these control development of certain structures and are similar in living organisms Protein comparisons – can find similar proteins in related species (myosin in humans and yeast)

Evolutionary Biology Today Evolutionary biology is a fast growing field New technology New discoveries Benefits? How does the idea of a common ancestor help understand new diseases? Genes are similar if from a common ancestor-closely related species can be suseptible to similar treatments