Evolution Evolutionary Process Human Evolution

Evolution Evolution = progressive change in characteristics of organisms as a result of changes in genetic compositionEvolution = progressive change in characteristics of organisms as a result of changes in genetic composition Two important aspectsTwo important aspects –Descent from a common ancestor –Adaptation to the environment Adaptation = characteristic that makes it more likely that an organism will survive and reproduce in its environmentAdaptation = characteristic that makes it more likely that an organism will survive and reproduce in its environment

Evidence for Common Descent From the Fossil Record Living Organisms resemble extinct fossil forms.

Evidence for Common Descent From the Fossil Record Progressive changes from simpler to more complex organisms can be seen in the fossil record.

Biogeographical Evidence for Common Descent Plants and animals of each continent are distinctive.

Biogeographical Evidence for Common Descent Different island species resemble each other. Different island species resemble each other.

Biogeographical Evidence for Common Descent Island Populations resemble those on nearby land. The Galapagos finches resembled the grassquit found on the coast of Ecuador.

Anatomical Evidence for Common Descent: Homologous Structures Flying Swimming Running Grasping

Anatomical Evidence: Vestigial Structures Functional hindlimb in salamander Remnants of hindlimb seen in boa and whale

Evidence for Common Descent from Biochemistry

Evidence for Evolution from Biochemistry Similarities in sequence measured by ease of separating DNA strands by heat Similarities in sequence measured by ease of separating DNA strands by heat

A Flowchart of Evolutionary Reasoning Potential for rapid reproduction Relatively constant resources and population over time Variability in structures and behaviors Some variability is inherited; adaptations increase in future generations (observations) (conclusions) Competition for survival and reproduction (1) NATURAL SELECTION On average, the fittest organisms leave the most offspring (2) EVOLUTION: The genetic makeup of the population changes over time, driven by natural selection (3) Formation of new genotypes leads to phenotypic variation Adaptation

Originally, giraffe neck length varied. Competition for resources causes long-necked giraffes to have the most offspring. Due to natural selection, most giraffes now have long necks. Darwin’s proposal Natural Selection as the Mechanism for Evolution

Applying Your Knowledge A.The mechanism for evolution is B.A progressive change in the characteristics of organisms is C.A trait that makes a species survival more likely is called a(n) 1.Adaptation 2.Evolution 3.Natural selection

Primate Evolutionary Tree Prosimians Anthropoids Hominoids Lemur Gibbon Orangutan Gorilla Chimpanzee Hominid Angiosperms evolve MYA and forests spread. Primate ancestor enters trees Millions of Years Ago (MYA) PRESENT Old World Monkey New World Monkey Tarsier Common ancestor may have resembled a tree shrew ~45 MYA: There was a common ancestor for monkeys, apes and hominids ~15 MYA: There was a common ancestor for all apes and hominids ~7 MYA: There was a common ancestor for African apes and hominids bipedal posture

Adaptations of Primates Opposable thumbOpposable thumb Well-developed brainWell-developed brain Nails instead of clawsNails instead of claws Single birthSingle birth Extended period of parental careExtended period of parental care Emphasis on learned behaviorEmphasis on learned behavior Australopithecus afarensis An early hominid

Hominid Evolution Homo erectus Homo habilis Australopithecines Genus Homo Homo sapiens Homo neandertalenis Australopithecus robustus Homo ergaster Australopithecus boisei low forehead projecting face 400 cm 3 brain Australopithecus africanus Australopithecus afarensis distinct forehead flat face 700–1,300 cm 3 brain Ardipithecus ramidus Ardipithecus ramidus kadabba Millions of Years Ago (MYA) Possible ancestor of both A. africanus and Genus Homo Possible ancestor of modern humans In Asia In Africa

Human Evolution Genus AustralopithecusGenus Australopithecus –walked upright –product of mosaic evolution = different body parts change at different rates Smaller brain resembles apesSmaller brain resembles apes Bipedal locomotion resembles humansBipedal locomotion resembles humans –ancestors of genus Homo (not certain which species led to Homo habilis)

Human Evolution Genus HomoGenus Homo –Homo habilis = “handy man” produced toolsproduced tools teeth supported omnivorous dietteeth supported omnivorous diet enlarged speech area in brainenlarged speech area in brain –Homo ergaster (in Africa) advanced tools, use of fireadvanced tools, use of fire larger brain, taller bodylarger brain, taller body striding gaitstriding gait –early Homo sapiens (based on Cro-Magnon fossils) compound toolscompound tools larger brainlarger brain language and culture, including artlanguage and culture, including art neck of femur femur femur neck is longer than in modern humans Homo ergaster

Two Hypotheses for the Origin of Modern Humans interbreeding EUROPE Homo ergaster Homo sapiens EUROPE Homo ergaster Homo sapiens Out of Africa Multiregional continuity migration of Homo ergaster migration of Homo ergaster migration of Homo ergaster migration of Homo ergaster ASIAAFRICAASIAAFRICA Millions of Years Ago (MYA) Homo ergaster evolves into modern humans in Asia, Africa, and Europe. Modern humans evolve in Africa and migrate to Asia and Europe.

DNA Analyses Related to Human Origins Visit and choose Mitochondrial Control Region Media and Animations Solving the Mystery of the Neanderthals Other Applications of DNA Analysis can be found at Choose Applications, then Human Origins

A Newly-Discovered (but extinct) Species of Genus Homo Homo erectus Homo floresiensis Homo sapiens

Applying Your Knowledge A.Which species is the closest ancestor to Homo sapiens? B.Which species was the first to use tools? C.Which species is the earliest hominid? 1.Homo habilis 2.Australopithecus afarensis 3.Homo ergaster