Theory of Evolution

Theory of Evolution Chapter 16

What is evolution? • Evolution

Idea of Evolution • Charles Darwin (1809-1882) • English naturalist • Took a trip around the world on a ship calledH.M.S. Beagle • Mostly fascinated with the Galapagos Islands • Best known for his theory of evolution by natural selection

Darwin’s Journey • Began in 1831 • Sailed on a ship called the H.M.S. Beagle • Five year voyage sailing around the coast of SouthAmerica and Australia

Observations Aboard the Beagle • Darwin collected 68 species of beetles • Wrote about the different characteristics of habitats and species that live there • Species vary globally • There are similar organisms around that world with similar ecological habitats • Ex: Rhea birds in S. America and ostriches in Africa

Observation Aboard the Beagle • Species vary locally • Related animals species often occupy different habitats within a local area • Ex: Tortoise shellshape among Galapagos Islands

Observation Aboard the Beagle • Species vary overtime • Some fossils of extinct animals were similar to living species • Ex: Armadillo fossils compared to modern day armadillos

Darwin’s Findings • Galapagos Islands • Groups of animals vary from island to island • Ex: tortoises on each island resemble each other but differ in the shape and function of their shells • Ex: finches on each island resembled each other but differ in the shape and function of their beaks • Darwin believed these unique animals all came from a commonancestor and they changed/adapted to their environment

Idea of Evolution • Evolution • Development of new types of organisms overtime • Heritable change in the characteristics within a population from one generation to the next

Ideas of Darwin’s Time • Scientists thought all species were permanent and unchanging • The Earth was believed to only be a few thousand (not billions) of years old • During Darwin’s time, new research was being done to figure out the geology of the Earth

Ideas that Influenced Darwin • James Hutton was a geologist in 1700’s • Made connections between mountains, valleys, and layers of rock • Believed the Earth was older than thousands of years -- a time so old for the human mind to image • The Earth changes very slowly and some layers can accumulate as the environment is changing

Ideas that Influenced Darwin • Charles Lyell was a English geologist that believed the Earth’s surface continues to change • He explained that past processes that occurred are still occurring now • Ex: Volcanoes erupted in the past and still today • Published a great work called PrinciplesofGeology in 1830 that built on the work of Hutton • Darwin read this book while on his journey around the world

Ideas that Influenced Darwin • Jean-Baptiste Lamarck • French naturalist that supported the idea that populations of organisms change over time

Ideas that Influenced Darwin • Proposed two hypotheses: Called Theory of AcquiredTraits • Organisms could change during their lifetime by using or not using selected parts of the body • Individuals could pass these acquired traits on to their offspring • Ex: Giraffes could lengthen their neck by stretching over a period of time to get the height they needed to eat and survive and then pass the longer neck trait to their offspring

Ideas that Influenced Darwin • Thomas Malthus was an English economist in the 1790s • Reasoned that if the human population grew continuously, there would not be enough resources for everyone • His reasoning explained why plants and animals produced more a high amount of offspring since a portion will not survive due to environmental factors • Ex: Maple tree produces thousands of seeds each summer • Ex: Oysters produce millions of eggs each year with the understanding that only a fraction will survive

Darwin’s Ideas • Around the same time Darwin and Wallace formed theory to explain evolution • Darwin was able to publish his book first called OntheOriginofSpecies in 1858 • Book explained how evolution occurs by means of naturalselection

Artificial Selection • Darwin studied animal breeders • Farmers would select to breed only trees with the largest fruit, or the cows that produce the most milk • Darwin called this process artificialselection • Nature provides the variations, and humans select hose they find to be useful and allow them to breed and pass on traits to offspring

Evolution by Natural Selection • Mechanism from descent with modification • 1. Struggle for Existence • Organisms produce more offspring than can survive • Ex: grasshoppers lay over 200 eggs at a time, but only a fraction survive • 2. Variation and Adaptation • Traits vary within a species and their environment called adaptations • These adaptations help increase ability to survive • Ex: Mimicry with coral snake and scarlet snake

Natural Selection (cont’d) • 3. Survival of the Fittest • Organisms best adapted for an environment will survive best and reproduce • The ability for an organism to reproduce and pass on adaptations • 4. Natural Selection • Process by which organisms with variations most suited to their local environment survive and leave more offspring • Organisms choose their mate based on desired traits

Common Descent • Idea that every species must have descended by reproduction from pre-existing species that arrange over time • Ex: finch beaks at Galapagos • All species – living and extinct – are descended from ancient common ancestors

Transitional Species • Organisms with features that are between hypothesized ancestors

Age of the Earth & Fossils • Noted that fossils of extinct animals resembled living species • Relative Age • Age compared to other fossils in order of old to young • Absolute Age • Using radioactive dating to get actualnumber age

Age of the Earth and Fossils • Age of the Earth • Geologists are certain based on evidence via radioactive dating to indicate the Earth is about 4.5billion years old • Fossils • Remains of an organism that died long ago • Many fossils form a series that can trace back to an ancient extinct ancestor • Superposition • Idea that strata form in layers where the layers closest to the top are the younger than below

Biogeography • Study of where organisms live now and where they and their ancestors lived in the past • Darwin used this method when exploring islands and observed animals vary based on their environment • Closely related but Different • Darwin believed that the finches of the Galapagos all came from a common ancestor in the mainland • Over time, natural selection produced a variation of species of finches • Distantly Related but Similar • Darwin noted that organisms that are distantlyrelated and inhabit similar environments have similar qualities

Anatomy and Embryology • Anatomy: study of the body • Embryology: study of development • Homologous structures • Anatomical structures that originated from the same common ancestor • Ex: bones in arms of humans, penguins, alligator and bat • Related structure but function may differ

Anatomy and Embryology • Analogous Structures • When structures have similar function, but did not develop the same way • Ex: wings of bat vs. bird • Vestigial Structures • Organs that no longer serve a function in an organism • Ex: human tail bone, appendix

Anatomy and Embryology • Embryology • Similar patterns of embryological development provide further evidence that organisms have descended from a common ancestor • Many animals look similar during development and produce homologous tissue

Genetics and Molecular Biology • At the molecular level, the geneticcode and homologous molecules provide evidence of common descent

Phylogeny • Relationships among groups of organisms • Can make a “tree” of animals evolved • Trunk of the tree would represent species that are closely related • Branches represent a separate population or lineage

Caribbean Anole Lizard • Found in the Caribbean islands of Cuba, Hispaniola, Jamaica, and Puerto Rico • Each lizard species body type differs by their habitat • Ex: stocky body and long legged lizards are best adapted for tree truck environments, slender bodies and long tails are best adapted for grassy environments • Hypothesis #1: An ancestral anole species specialized for living on twigs originally lived on one island and later migrated to other islands OR • Hypothesis #2: Each twig-dwelling species evolved independently on each island from distant ancestor anole species

Evolution in Action • Biologists tested the hypothesis by comparing DNA from the various species • DNA evidence supported hypothesis 2that each lizard evolved independently on each island • Convergent Evolution • Process by which different species evolve similar traits • Ex: twig-dwelling species came from different ancestors but evolved similar adaptations to their environment

Divergence & Radiation • Divergence evolution • Process by which the descendants of a single ancestor diversify into species that each fit different parts of the environment • Ex: All breeds of dog share a common ancestor with wolves

Divergence & Radiation • Adaptive Radiation • Pattern of diversity when a new population in a new environment undergoes divergent evolution

Coevolution • Evolution is on-going and many species may evolve together • Coevolution • When two or more species have evolved adaptations to each other’s influence • Ex: • Predator/Prey Interactions • Introduction of new species • Creating antibiotics

Theory of Evolution