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Evolution And the Origin of Species Question: How did the giraffe get its long neck? Why are there 9 subspecies of giraffes? History of Evolutionary Thought In 1831, Charles Darwin, a 22-year-old naturalist, accepted a position aboard the ship HMS Beagle that began a voyage around the world. Darwin made observations of animals that inhabited the island - a study of BIOGEOGRAPHY - tortoises - iguanas - finches The Voyage of the Beagle Darwin’s Theory of Evolution by Natural Selection Finches on the Galápagos Islands resembled a mainland finch but there were more types. Galápagos finch species varied by nesting site, beak size, and eating habits. Darwin proposed that each bird was descended from the mainland species. - this idea is known as COMMON DESCENT Charles Darwin and Alfred Wallace had similar ideas about how species changed over time….Natural Selection 1. Characteristics (variations) are inherited 2. More offspring are produced than can survive 3. Those with the most favorable characteristics survive ADAPTATION Descent with Modification Each generation will have more individuals with those traits than the previous generation. Taxonomy is the science of classifying organisms. Carolus Linnaeus developed a binomial system of nomenclature two-part names for each species GENUS SPECIES Homo sapiens Canis lupus Giraffa camelopardalis Giraffe camelopardalis angolensis (Angolan giraffe) Giraffe camelopardalis camelopardalis (Nubian giraffe) Giraffe camelopardalis reticulata (Reticulated giraffe) Masai Giraffe (Giraffa camelopardalis tippelskirchi) Thornicroft Giraffe Giraffa camelopardalis thornicrofti Biogeography study of the distribution of species and ecosystems in geographic space and through geological time A cladogram shows how these giraffes are related. Why are there so many different subspecies and why in distinct locations? Are all of these giraffes descended from one common ancestor? How does natural selection explain the finches on the Galapagos? The Definition of Evolution Evolution is the change in allele frequencies, or a change in the gene pool, of a population. You don’t need to see an animal change physically, you only need to measure changes at the DNA level. IMPORTANT!!! 1. Individuals do not evolve. (they either live or die) *POPULATIONS EVOLVE* 2. Evolution does not have a direction. Organisms aren’t “trying” to be anything. 3. Fitness refers to an organism's ability to survive in their environment - it doesn’t necessarily mean “stronger” These stickleback fish have different levels of armored scales. 3. Individuals differ in FITNESS (relative fitness) - fitness measures an organism’s reproductive success - it does not necessarily mean “stronger”. A black panther is the melanistic color variant of any Panthera species. Black panthers in Asia and Africa are leopards (Panthera pardus) and black panthers in the Americas are black jaguars (Panthera onca). Selection Strength How strong does the environment push for the survival or elimination of a polymorphism? Examples: White- Striped Clover & Rock Pocket Mouse Divergent vs Convergent Evolution Phenotypes are similar, though these organisms are not closely related. Review Evolution in 3 steps: The aye-aye survived!?? 1. Variation (polymorphisms) 1. Relative fitness (who survives selection?) 2. Reproduction and inheritance And the blobfish and naked mole rat?? See “Strange Animals” Boredpanda.com Evidence of Evolution 1. 2. 3. 4. 5. The Fossil Record Anatomy Embryology Biogeography Molecular Biology FOSSIL EVIDENCE Fossil Record traces the history of life Shows transitional fossils ….Archaeopteryx Hominid Species EVIDENCE: FOSSIL RECORD Transitional species show links between ancestors and modern organisms. ANATOMICAL EVIDENCE Homologous structures – similar structures inherited from a common ancestor (ex. Arm bones) Vestigial Structures Structures that appear to serve no purpose and are derived from ancestral populations. Fossil record indicates that whales evolved from land animals. They retain many of the features of land tetrapods, including vestigial pelvic bones. In humans ….. The palmaris longus muscle is vestigial Gill Slit Embryological development – all vertebrates have the same basic pattern of development BIOGEOGRAPHICAL EVIDENCE How Plants and Animals are distributed worldwide Why are these animals only found in Australia? Molecular Genetics Gene sequences are similar across animal groups. The more similar the genes, the more closely related the organisms. Myths of Evolution 1. 2. 3. 4. Evolution is just a theory Individuals evolve Evolution explains the origin of life Organisms evolve on purpose (or is directional) What other myths or questions have you heard regarding evolution? 18.2 Formation of New Species Species = individual organisms that can interbreed and produce fertile offspring Liger Zonkey Hybrid = cross between two species = often produce infertile offspring (mules) Speciation = formation of two species from one original species Allopatric “Other homeland” California Salamander Speciation vs Sympatric Speciation “Same homeland” What type of speciation is this? Adaptive Radiation One ancestral species branches into many, each occupying a different NICHE Hawaiian Honeycreepers Reproductive Isolation - what prevents interbreeding between species? Prezygotic Barriers Temporal Isolation (breeding at different times) - Blocks reproduction from taking place at all Habitat Isolation (living in different places) Mechanical & Gamete Barriers (anatomy & egg/sperm problems) Behavioral Isolation Damselfly penis (mating, courtship behaviors) Post-zygotic barriers - egg and sperm produce offspring that don’t survive or are sterile Rates of Speciation Slow change, small steps Rapid change, due to a major environmental disruption Is a hybrid grizzly-polar bear a “PIZZLY” or a “GROLAR BEAR”