Evolution

EvolutionEvolution

Evolution: A summaryEvolution: A summary• Evolution - The process of change

– Evolution applies to the universe also. Matter and the nature of matter has changed over time

– Evolution applies to life, implies that life is not static, but responds to the environment.

• Previous western thought held the universe, earth animals, and man were created by a greater being/entity.– Held the earth and life were created in the thousands of years in the

past..– Life and the earth were thought to be static and unchanging.

• Modern evolution holds that the universe is billions of years old (between 9-12b years)

• Earth was created approx 4.5b years ago.• Human existence is only a small fraction of time since the

beginnings of the universe.

The Cosmic CalendarThe Cosmic Calendar

• If the 12 billion year history of the universe was fit into a calendar year, it would look like this…..

Cosmic Calendar (From The Dragons of Eden - Carl Sagan)

Pre-December Dates

Big Bang January 1

Origin of Milky Way Galaxy May 1Origin of the solar system September 9Formation of the Earth September 14Origin of life on Earth ~ September 25Formation of the oldest rocks known on Earth October 2Date of oldest fossils (bacteria and blue-green algae) October 9Invention of sex (by microorganisms) ~ November 1Oldest fossil photosynthetic plants November 12Eukaryotes (first cells with nuclei) flourish November 15

Sunday Monday Tuesday Wednesday Thursday Friday Saturday

1 Significant oxygen atmosphere begins to develop on Earth.

2 3 4 5 Extensive vulcanism and channel formation on Mars.

6

7 8 9 10 11 12 1314 15 16

First Worms. 17 Precambrian ends. Paleozoic Era and Cambrian Period begin. Invertebrates flourish.

18 First oceanic plankton. Trilobites flourish.

19 Ordovician Period. First fish, first vertebrates.

20 Silurian Period. First vascular plants. Plants begin colonization of land.

21 Devonian Period begins. First insects. Animals begin colonization of land.

22 First amphibians. First winged insects.

23 Carboniferous Period. First trees. First reptiles.

24 Permian Period begins. First dinosaurs.

25 Paleozoic Era ends. Mesozoic Era Begins.

26 Triassic Period. First mammals.

27 Jurassic Period. First birds.

28 Cretaceous Period. First flowers. Dinosaurs become extinct.

29 Mesozoic Era ends. Cenozoic Era and Tertiary Period begin. First cetaceans. First primates.

30 First evolution of frontal lobes in the brains of primates. First hominids. Giant mammals flourish.

31 End of Pliocene Period. Quaternary (Pleistocene and Holocene) Period. First humans.

DECEMBERDECEMBER

December 31

Origin of Proconsul and Ramapithecus, probable ancestors of apes and men ~ 1:30 p.m.

First hominids A. afarensis ~ 10:30 p.m.

Widespread use of stone tools by Homo habilis 11:00 p.m.Domestication of fire by Homo erectus 11:46 p.m.Beginning of most recent glacial period. Homo Neanderthalis & Homo sapiens evolve 11:56 p.m.Seafarers settle Australia 11:58 p.m.Extensive cave painting in Europe 11:59 p.m.

Invention of agriculture 11:59:20 p.m.

Neolithic civilization; first cities. Colonization of North and South America across Bering straits 11:59:35 p.m.

First dynasties in Sumer, Ebla and Egypt; development of astronomy 11:59:50 p.m.

Invention of the alphabet; Akkadian Empire 11:59:51 p.m.

Hammurabic legal codes in Babylon; Middle Kingdom in Egypt 11:59:52 p.m.

Bronze metallurgy; Mycenaean culture; Trojan War; Olmec culture; invention of the compass 11:59:53 p.m.

Iron metallurgy; First Assyrian Empire; Kingdom of Israel; founding of Carthage by Phoenicia 11:59:54 p.m.

Asokan India; Ch'in Dynasty China; Periclean Athens; birth of Buddha 11:59:55 p.m.

Euclidean geometry; Archimedean physics; Ptolemaic astronomy; Roman Empire; birth of Christ 11:59:56 p.m.

Zero and decimals invented in Indian arithmetic; Rome falls; Moslem conquests 11:59:57 p.m.

Mayan civilization; Sung Dynasty China; Byzantine empire; Mongol invasion; Crusades 11:59:58 p.m.

Renaissance in Europe; voyages of discovery from Europe and from Ming Dynasty China; emergence of the experimental method in science

11:59:59 p.m.

Widespread development of science and technology; emergence of global culture; acquisition of the means of self-destruction of the human species; first steps in spacecraft planetary exploration and the search of extraterrestrial intelligence

Now: The first second of New Year's Day

Darwin & Natural SelectionDarwin & Natural Selection•Modern evolutionary thought arose through the Modern evolutionary thought arose through the inquiries of inquiries of Charles DarwinCharles Darwin..•Darwin was a Naturalist aboard an exploration Darwin was a Naturalist aboard an exploration ship called the ship called the HMS BeagleHMS Beagle..•Collected and catalogued biological specimens Collected and catalogued biological specimens for return to England.for return to England.

The Voyage of the BeagleThe Voyage of the Beagle

The Galapagos FinchesThe Galapagos FinchesWas fascinated by the species of Was fascinated by the species of Finches he observed in the Finches he observed in the Galopagos Galopagos IslandsIslands..Found that these birds were quite Found that these birds were quite similar to a species found on mainland similar to a species found on mainland South America. However they differed South America. However they differed significantly in the shapes of their significantly in the shapes of their beaks.beaks.Darwin reasoned that these species of Darwin reasoned that these species of finches arose from a common ancestor, finches arose from a common ancestor, and gradually changed over to and gradually changed over to accommodate their particular diets.accommodate their particular diets.Led him to develop his theory of Led him to develop his theory of evolution through evolution through Natural SelectionNatural Selection

Darwin & EvolutionDarwin & Evolution• The notion of evolution was dominated by 2 theories.The notion of evolution was dominated by 2 theories.• Lamarckian Theory of Lamarckian Theory of Inheretance of acquired characteristicsInheretance of acquired characteristics

– Held that traits acquired throughout life of an organism would be passed on to Held that traits acquired throughout life of an organism would be passed on to offspring.offspring.

– "Use it, or lose it principle""Use it, or lose it principle"– Eg. If you lifted weights during your life, your children would be stronger or, if you Eg. If you lifted weights during your life, your children would be stronger or, if you

did'nt exercise your children would be weakerdid'nt exercise your children would be weaker– Theory has been replaced by Darwin's theory of natural selection.Theory has been replaced by Darwin's theory of natural selection.

• Natural selectionNatural selection::– Based on following premises:Based on following premises:

• There are not enough resources for all organisms to survive.There are not enough resources for all organisms to survive.• Some organisms are more "fit" to survive.Some organisms are more "fit" to survive.• Fitness refers to:Fitness refers to:• The ability of an organism to survive in its environment.The ability of an organism to survive in its environment.• The ability of an organism The ability of an organism to survive long enough to reproduceto survive long enough to reproduce..• Natural pressures "weed-out" those individuals "less fit" to survive. Thus changing a Natural pressures "weed-out" those individuals "less fit" to survive. Thus changing a

species over time.species over time.– New genes/traits arise from random mutations.New genes/traits arise from random mutations.– Most are either Neutral (no effect), or disadvantageous (decrease an organism's Most are either Neutral (no effect), or disadvantageous (decrease an organism's

chance for survival).chance for survival).

Natural Selection : The Peppered Moth:Natural Selection : The Peppered Moth:

• The peppered moth is a species of The peppered moth is a species of moth which uses camouflage against moth which uses camouflage against tree bark to avoid being eaten by birds. tree bark to avoid being eaten by birds. It is normally a light grey color.It is normally a light grey color.

• During England's industrial revolution, During England's industrial revolution, pollution caused a darkening of the pollution caused a darkening of the bark of the trees.bark of the trees.

• There was a natural variation in moth There was a natural variation in moth coloration with some being darker than coloration with some being darker than others.others.

• Those moths of a lighter color, were Those moths of a lighter color, were easier to spot and eat by birds. And easier to spot and eat by birds. And were eaten at a faster rate.were eaten at a faster rate.

• The survivors tended to be darker, and The survivors tended to be darker, and when they mated, their offspring when they mated, their offspring tended thus to be darker also.tended thus to be darker also.

• Over time, this resulted in the species Over time, this resulted in the species becoming darker in color.becoming darker in color.

Lamarck vs. DarwinLamarck vs. Darwin

Effects of Natural SelectionEffects of Natural Selection

• Natural selection can have many different effects on species phenotypes.

• These types of natural selection have been named as:

1. Directional selection2. Stabilizing selection3. Disruptive selection

Directional Selection:Directional Selection:• Eliminates one extreme variation from an array of

possible phenotypes. Results in a shift towards the other extreme.

Stabilizing SelectionStabilizing Selection::

• Selection acts to eliminate both extremes of an array of phenotypes. Results in an increase in individuals exhibiting an intermediate phenotype.

Disruptive SelectionDisruptive Selection• Selection acts to remove the intermediate

phenotypes favoring the extreme phenotypes:

ConvergenceConvergence • Convergence occurs when

species evolve into a common phentoypic form due to a common need. For example the diagram below portrays a shark, ichthyosaurus, a penguin and a dolphin. These are fish, reptile. bird and mammal respectively (very different families of animals). Yet they all have a torpedo body shape, pectoral, caudal and dorsal fins. This is based on their common need to swim rapidly in an aquatic environment.

Divergence / Adaptive RadiationDivergence / Adaptive Radiation•Divergence occurs when species evolve in several directions away from a common ancestor. This happens usually to fill a vacant ecological niche. Also known as adaptive radiation.

Convergence and Divergence TogetherConvergence and Divergence TogetherBy contrasting North American By contrasting North American placental mammals with placental mammals with Australian marsupials. One can Australian marsupials. One can see how convergence and see how convergence and divergence works together. divergence works together. •In each case an ancestor In each case an ancestor mammal evolved into several mammal evolved into several ecological niches.ecological niches.•Since each niche required a Since each niche required a specific phenotype, what results specific phenotype, what results are 2 groups of mammals which are 2 groups of mammals which have NEVER made contact, have NEVER made contact, evolving into similar shapes.evolving into similar shapes.

Rates of SpeciationRates of Speciation::Two models exist to describe the rates of

speciation.• Gradualism:

– Refers to the model which holds that evolutionary change occurs in a gradual linear fashion. A species will change its morphology over time.

• Punctuated equilibrium – Describes the process in which a species remains

relatively unchanged for relatively long periods of time. Following which, a period of stress causes rapid change, followed by another period of relative stability.

Rates of SpeciationRates of Speciation::

Evidences of EvolutionEvidences of Evolution

Fossilized Trilobite

Fossils:•Formed when animal remains are trapped in sedimentary layers.

•Organic material replaced by minerals over millions of years.•Result is a "mineral cast" of the dead organism.•Where a fossil is located in the sedimentary strata can indicate it's age.

•Successive changes in fossil forms of an organism can help in developing a fossil record of an organism's evolution.•Some rare fossils can show "soft tissues" which give invaluable information on an organism's physiology

•Example: paleontologists recently discovered a dinosaur with a fossilized heart. This indicates that this species was most likely warm blooded.

Fossilized Dinosaur Heart

Radiometric Dating:Radiometric Dating:• Based on the fact that radioactive materials decay at a fixed rate.

– Rate is known as a half-life: The amount of time in which only 1/2 of a radioactive sample remains– By measuring the amount of radioactive material in a fossil, one can determine how old it is.– Example is 14C dating.

• 14C is an isotope of 12C which radioactively decays to 14N.– It occurs naturally in the environment, and is ingested by organisms while alive.– Once an organism dies, 14C intake stops, and the 14C begins to decay– One can then measure the amount of 14C remaining in a sample, and determine its age.

Similarities in Embryological DevelopmentSimilarities in Embryological Development

• In early embryological development, it appears that embryos "play out" their evolutionary history.

• Known as Ontonogy recapitulating Phylogeny.

• Implies that genetically, we have not "forgotten" our evolutionary history, only built upon it.

Homologous StructuresHomologous Structures• Refers to the fact that

organisms' structures are formed from similar anatomy.

• Example the wing of a bird, arm of a man, wing of a bat, and flipper of a whale, all appear to be formed from a common set of bones.

• Implies that these organisms evolved from some common ancestor.

Vestigal Structures:Vestigal Structures:• Refers to the fact that

organisms have structures which are disused

• These structures, however, a remnants of structures the organisms used earlier in their evolutionary history.

• Examples:• Hip bones in whales• Tail in humans• Appendix in humans• Legs/hips in snakes