Evolution Taxonomy Domains Prokaryotes vs Eukaryotes
Evolution unifying theme in biology Explains Both similarities and differences among living things How groups of organisms are related How organisms of the past are related to organisms of the present
Evolution evidence: The Fossil Record Succession of forms over time Transitional links Vertebrate descent
Fossil Record
How are these similar? How do these differ?
Evolution evidence: Comparative Anatomy Homologous structures (homology) Descent from a common ancestor
Homologous structures Similar structure Similar development Different functions Evidence of close evolutionary relationship recent common ancestor
colored leaves Homologous structures spines leaves succulent leaves needles tendrils
Vestigial organs Modern animals may have structures that serve little or no function remnants of structures that were functional in ancestral species deleterious mutations accumulate in genes for noncritical structures without reducing fitness snakes & whales remains of pelvis & leg bones of walking ancestors eyes on blind cave fish human tail bone
Analogous structures Separate evolution of structures similar functions similar external form different internal structure & development different origin no evolutionary relationship Don t be fooled by their looks! Solving a similar problem with a similar solution
Evolution evidence: Comparative Embryology Pharyngeal pouches, tails as embryos
Evolution evidence: Cytological Evidence
Evolution Evidence: Molecular DNA genetic code DNA RNA (1) transcription (2) translation Proteins ATP energy currency
Evolution evidence: Molecular Similarities in DNA, proteins, genes, and gene products Common genetic code Closely related species have sequences that are more similar than distantly related species DNA & proteins are a molecular record of evolutionary relationships
Mechanisms of Evolution
LAMARCK LAMARCK: (1) Trait acquired (2) Acquired trait passed on to offspring
WEISMAN Weisman: (1) Cut off mice tails for 18 generations (2) All subsequent generations had tails (3) Disproved the 2 nd part of Lamarck s idea; Acquired traits are NOT passed on to offspring
Charles Darwin 1809-1882 British naturalist Proposed the idea of evolution by natural selection Collected clear evidence to support his ideas
Voyage of the HMS Beagle Invited to travel around the world 1831-1836 (22 years old!) makes many observations of nature main mission of the Beagle was to chart South American coastline Stopped in Galapagos Islands 500 miles off coast of Ecuador
But Darwin found a lot of finches Darwin was amazed to find out: All 14 species of birds were finches But there is only one species of finch on the mainland! Finch? Finch? Large Ground Finch QuickTime and a Photo - JPEG decompressor are needed to see this picture. Sparrow? Small Ground Finch How did one species of finches become so many different species now? Woodpecker? Warbler Finch Warbler? Veg. Tree Finch
Darwin s finches Differences in beaks (recall freshman bio lab) associated with eating different foods survival & reproduction of beneficial adaptations to foods available on islands Warbler finch Cactus finch Woodpecker finch Sharp-beaked finch Small insectivorous tree finch Large insectivorous tree finch Vegetarian tree finch Insect eaters Bud eater Cactus eater Seed eaters Small ground finch Medium ground finch Large ground finch
Darwin s finches Differences in beaks allowed some finches to successfully compete successfully feed successfully reproduce pass successful traits onto their offspring
Essence of Darwin s ideas Natural selection variation exists in populations over-production of offspring more offspring than the environment can support competition for food, mates, nesting sites, escape predators differential survival successful traits = adaptations differential reproduction adaptations become more common in population
More observations Correlation of species to food source Whoa, Turtles, too!
sence of Darwin s ideas Natural selection variation exists in populations over-production of offspring more offspring than the environment can support competition for food, mates, nesting sites, escape predators differential survival successful traits = adaptations differential reproduction adaptations become more common in population
Evolution:Evolution the change over time of the genetic composition of populations Natural selection: populations of organisms can change over the generations if individuals having certain heritable traits leave more offspring than others (differential reproductive success) Evolutionary adaptations: a prevalence of inherited characteristics that enhance organisms survival and reproduction November 24, 1859
Natural selection in action Insecticide & drug resistance insecticide didn t kill all individuals resistant survivors reproduce resistance is inherited insecticide becomes less & less effective