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Download Ch. 15.2 Evidence ofEvolution
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Ch. 15.2 Evidence of Evolution Ch. 15.3 Objectives: •Describe how fossils provide evidence of evolution •Discuss morphological evidence of evolution •Explain how biochemistry provides evidence of evolution Evidence supporting evolution • Fossil record – shows change over time • Anatomical record – comparing body structures • homology & vestigial structures • embryology & development • Molecular record – comparing protein & DNA sequences • Artificial selection – human caused evolution 1. Fossil record • Layers of rock contain fossils – new layers cover older ones • creates a record over time – fossils show a series of organisms have lived on Earth • over a long period of time Fossils shape ideas about evolution Fossils: direct or indirect remains of organisms preserved in media such as sedimentary rock, amber, ice, or tar Ammonite casts –Fossilized organic matter in a leaf –Fossilized organic matter in a leaf Ice Man” Fossils tell a story… the Earth is old Life is old Life on Earth has changed Fossils tell a story… the Earth is old Life is old Life on Earth has changed What has the fossil record shown us? • The creatures alive today haven’t OBSERVATION always been around Different species lived in the past We found the fossil — no joke! Land Mammal ? ? ? Complete series of transitional fossils Someone’s idea of a joke! But the joke’s on them!! Ocean Mammal ? Evolution from sea to land • 2006 fossil discovery of early tetrapod – 4 limbs • Missing link from sea to land animals 2. Anatomical record Animals with different structures on the surface But when you look under the skin… It tells an evolutionary story of common ancestors Compare the bones • The same bones under the skin – limbs that perform different functions are built from the same bones Homologous structures • Structures that come from the same origin • homo- = same • -logous = information • Forelimbs of human, cats, whales, & bats – same structure • on the inside – same development in embryo – different functions • on the outside – evidence of common ancestor But don’t be fooled by these… Analogous structures look similar on the outside same function different structure & development on the inside How is a bird like a bug? different origin no evolutionary relationship Solving a similar problem with a similar solution Analogous structures Dolphins: aquatic mammal Fish: aquatic vertebrate both adapted to life in the sea not closely related Watch the tail! Vestigial organs structure—a body structure in a present-day organism that no longer serves its original purpose, but was probably useful to an ancestor. • Hind leg bones on whale fossils Why would whales have pelvis & leg bones if they were always sea creatures? Because they used to walk on land! Comparative embryology • Development of embryo tells an evolutionary story – similar structures during development all vertebrate embryos have a “gill pouch” at one stage of development 3. Molecular record • Comparing DNA & protein structure – everyone uses the same genetic code! • DNA Human Macaque Dog Bird Frog 32 45 67 Lamprey compare common genes compare common proteins number of amino acids different from human hemoglobin 8 125 0 10 20 30 40 50 60 70 80 90 100 110 120 Building “family” trees Closely related species are branches on the tree — coming from a common ancestor 4. Artificial selection • How do we know natural selection can change a population? – we can recreate a similar process – “evolution by human selection” “descendants” of wild mustard Selective Breeding Humans create the change over time “descendants” of the wolf Artificial Selection gone bad! • Unexpected consequences of artificial selection Pesticide resistance Antibiotic resistance Insecticide resistance • Spray the field, but… – insecticide didn’t kill all individuals • variation – resistant survivors reproduce – resistance is inherited – insecticide becomes less & less effective Adaptations: Evidence for Evolution • an adaptation is any variation that aids an organism’s chances of survival in its environment. • According to Darwin’s theory, adaptations in species develop over many generations • Learning about adaptations in mole-rats can help you understand how natural selection has affected them. Structural adaptations arise over time • camouflage, an adaptation that enables species to blend with their surroundings. • Because wellcamouflaged organisms are not easily found by predators, they survive to reproduce. Structural adaptations arise over time • Mimicry is a structural adaptation that enables one species to resemble another species. • Predators may learn quickly to avoid any organism with their general appearance Physiological adaptations can develop rapidly • In general, most structural adaptations develop over millions of years. • However, there are some adaptations that evolve much more rapidly. • The evolution of insecticide resistance is an example of natural selection in action Convergent evolution • 3 groups with wings – Does this mean they have a recent common ancestor? They just came up with the NO! same answer! Flight evolved 3 separate times — evolving similar solutions to similar “problems” Convergent evolution led to mimicry • Why do these pairs look so similar? Monarch male Viceroy male poisonous edible Which is the moth bee? fly vs.vs. thethe bee? fly bee moth bee The Evolution of Species • Significant changes in the gene pool could lead to the evolution of a new species over time. • The evolution of new species, a process called speciation occurs when members of similar populations no longer interbreed to produce fertile offspring within their natural environment. The Evolution of Species • Geographic isolation occurs whenever a physical barrier divides a population. • A new species can evolve when a population has been geographically isolated. Reproductive isolation can result in speciation • Reproductive isolation occurs when formerly interbreeding organisms can no longer mate and produce fertile offspring • A change in chromosome numbers- polyploidy can lead to speciation Speciation rates • Gradualism is the idea that species originate through a gradual change of adaptations • Some evidence from the fossil record supports gradualism. • In 1972, Niles Eldredge and Stephen J. Gould proposed a different hypothesis known as punctuated equilibrium. • This hypothesis argues that speciation occurs relatively quickly, in rapid bursts, with long periods of genetic equilibrium in between.
