Ch. 22 Descent with ModificationThere are no direct measurements in evolution—like cosmologyEvolution has several misconceptions- Species evolve into “higher” beings-ex human thought, Star Trek- Any kind of dramatic mutations are possible, causing the evolution of a new “race” of beings—ex X Men- An organism can evolve during its lifetime—ex Pokémon- An organism can influence the evolution of its own structures—ex DilbertEvolution is the process of change in organisms throughout the earth’s history. It is- Not by choice- Not in the lifetime of the individual- Limited by genetic material and the history of the organismDarwin did not spontaneously discover evolution on his ownHistorical context- Antiquity through the 1600so Plato thought that there were “ideal forms” of each species; deviations from the ideal form were lesser. He taught his student Aristotle this.o Aristotle categorized the “fixed ideal species” by features. He created the “Scala Naturae” or Scale of Nature. Plants were the lowest and humans were the highesto Biblical Creation fit with Aristotle’s form. Early Christians added the angels and God to his system and created the Great Chain of Being. They also thought that the earth was not that old, only a few thousand years.- 1700so Newton published Principia and began the Age of Enlightenment and the Age of Reasono Carolus Linnaeus was a Swedish naturalist that developed a nested classification system of organismso Le Comte de Buffon was a French naturalist who wrote about fossils and rocks. He proposed that the earth was very old and that at least six epic changes had happened in its historyo Erasmus Darwin (Grandfather) was a natural philosopher. He wrote Zoonomia where he speculates as to the origin of life. The Temple of Nature (1802) is a poem exploring the possibilities of the origin of life.- Early 1800so George Curvier was a French naturalist and paleontologist. He interpreted the living context of fossils. It was originally thought that fossils were an ancient form of art; he saw living creatures and inferred where they lived. He also inferred that strata in the rocks were caused by floods and favored catastrophism.o Charles Lyell was a Scottish geologist and the “father of modern geology” He wrote “Principles of geology” which gave evidence for gradualism. He inferred that changes were uniform in time and rate (i.e. 1 inch of sand = 32 years of accumulation). These rates held true today and in the past, he then inferred that the Earth is very old. He later became a mentor to Darwin.o Jean-Baptiste de Lamarck was a French naturalist. He proposed that present life descended from earlier (extinct) life (i.e. evolution). He proposed evolution was due to adaptations of species to the environment. His proposed Mechanism: the inheritance of acquired characteristics” was wrong and focused on “use and disuse”. (Epigenetic variation in a phenotype outside of the genotype that MAY be passed down)o Thomas Robert Malthus was an English economist. He published an essay on human population growth which shows the potential for exponential population growth. He saw in very poor areas that even though humans produced more offspring than the environment could support, growth was restrained. When thereare limited resources, there is competition and the weakest and poorest suffer the mostDarwin born Feb 12 1809 (same day as Lincoln). He was the son of a physician and an amateur naturalist as a young man. His father wanted him to go to medical school but Darwin hated it and dropped out. He got a degree in theology to become a clergyman. He married his wealthy cousin, Emma. They had ten kids, two of which died in early childhood and three of which became famous scientists. He died at the age of 73Voyage—He set sail on the HMS Beagle in 1831-1836 at the age of 22. He was the companion of the ship’s captain and paid his own way. He collected plants, animals, fossils and shipped them to England and studied them when he got back.Theory—He fully developed the theory in 1844, but hesitated to publish it. In 1858 he received a letter form Alfred Wallace which proposed the same idea. He published Origin of Species in 18959. Thomas Huxley was one of his biggest supporters.Darwin’ Darwin’s Theory (2 parts)Part 1. All present life is related through descent with modification from a common ancestor in the past. Linnaeus’ classification system reflected the relatedness. (EVOLUTION)Part 2. Natural selection is the mechanism for evolution. These parts were based on observations and inferences.- Observation 1o All species tend to produce more offspring than the environment can support. Limiting resources keep the population in check.- Observation 2o There is heritable individual variation within a species.- Inference 1o Individuals with certain heritable traits will tend to leave more offspring than others. (Unequal reproductive success is the result of the ability to survive AND reproduce)- Inference 2o These heritable favorable traits accumulate over time, leading to adaptation to the environment.Adaptation: the traits that enhance the survival and reproductive success of and individual. Itultimately leads to new species. Different adaptations are favored in different environments.Not explained in Darwin’s Theory- Origin of life- How variation arises (didn’t know about Mendel)- How inheritance works- Why variation still exists- “Sudden” changes in the fossil record- The source of totally “new” characteristicsEvidence in support of Darwin’s Theory- Direct observation of Natural Selection (soapberry bug, drug resistant bacteria)- The fossil recordo Older rocks lack present day groupso 3.5 BYA-only prokaryotes-428MYA only fish, no amphibianso Older rocks have many extinct specieso Evidence of transition of form to a new major group (horses to whales)- Homology- Convergence- BiogeographyHomology-similarity in form as a result of common ancestry- Homologous structure (mammalian forelimb) is a common ancestral form with similar structure- Evolution trees are based on shared homologous forms - Vestigial structures are remnants of structures that are no longer adaptive (bling cave salamanders have eyes)- Developmental HS are homologous structures that appear during the development of offspring- Molecular/Cell H are genetic code