Evolution

EvolutionVariation in Living ThingsSPECIES - Group of organisms that interbreed

VARIATION - small differences between individuals of a species Some neither helpful nor harmful Some enable organism to be better suited to its environment.Variation in Living ThingsEnvironment constantly changing Some gradual - global warming; change in climates Some sudden - eruption of a volcano; landslide

Environmental changes may result in organisms Dying Migration to new area

Some organisms may have helpful variations that enable them to survive the changes and reproduce. Helpful variation inherited by offspring. Eventually environment contains a large number of individuals that have the helpful variationVariation in Living ThingsADAPTATION

Process by which an organism becomes better suited to a change in the environment. Helpful variation - permits survival - individual better suited to its environment.

Examples :Body Structure or Function Flat teeth and powerful jaws of horses - chewing grassSharp pointed teeth of tigers - tearing meat. Coloration - Tiger's stripes - camouflage Behavior - Nest building of birds

Evidence of EvolutionEVOLUTION - Based on present scientific data The theory that describes changes in living things and links them to changes in the environment. Change over a period of time - not rapid.

Evidence of EvolutionChanges in the Earth and its Environs

Earth about 4.5 billion years old

Early planet was ball of hot rock Bombarded by meteorites Volcanic eruptions released gases into the atmosphere Surface cooled - below boiling point of water Water vapor condensed and fell to earth as rain Collects forming oceans - 3.8 - 3.9 billion years ago.

Early atmosphere of the earth. Contained ammonia, methane, hydrogen, and water vapor Bombarded by solar radiation particularly ultraviolet

Evidence of EvolutionAlexander Oparin - Russian scientist, 1924

Proposed that life molecules formed from materials in early atmosphere

Theorized that energy from lightning, volcanic eruptions, ultraviolet radiation from sun, and natural radiation of earth may have split some of the molecules of the early atmosphere. Molecules reformed - larger, more complex organic molecules Molecules washed from atmosphere; collected in shallow pools and oceans - formed an "organic soup" - complex molecules Molecules worked together forming first cells. Evidence of EvolutionOparin's idea tested by Stanley Miller - 1953. Passed mixture of gases through a flask containing electrodes - simulated lightning Another flask contained boiling water - provided water vapor for "rain" "Rain" washed molecules in a collecting pool. Organic molecules found - amino acids

Evidence of EvolutionThe First Cells Quite similar to some present-day bacteria Prokaryotic - no true nucleus Heterotrophic - "ate" molecules in organic soup Probably Anaerobic - atmosphere had little or no oxygen

Primitive cells flourished - food supply abundant

Numbers increased, food supply used up - competition increased - Cells evolved that could make their own food - autotrophic. Photosynthetic organisms most successful autotrophsResembled blue-green bacteria - prokaryotic, no chloroplast. Autotrophs changed atmosphere - oxygen becomes abundant

Evidence of EvolutionEukaryotic Cells Probably appeared about 1.5 billion years ago Began as a small colony of prokaryotic cells; mutual survival Individuals may have become organelles. Mitochondria - aerobic bacteriaChloroplasts - blue-green bacteriaTheory doesn't explain all differences between eukaryotes and prokaryotes - doesn't explain how nuclear membrane came into being.

Evidence of EvolutionMajor Types of Evidence

Fossil EvidenceAnatomical EvidenceEmbryological EvidenceBiochemical EvidenceEvidence of EvolutionFossil Evidence

Fossils Remains or traces of organisms that lived in the past. Found in sedimentary rock - buried in sediment Must be buried in sediments soon after death slows/stops decay Types Imprints - from soft body parts; usually carbon remains. Mold - cavity takes shape of trapped hard body parts Cast - Filled mold. Petrified Fossils - Hard parts are replaced by minerals. Whole Organisms Frozen in ground or ice (glaciers)In amber (hardened plant resin)

Evidence of EvolutionInterpreting Fossils Fossils provide evidence that surface/climates have changed. Fossils of ocean dwelling species in inland areas - Coral fossils in cold areas - grow in warm areas Ferns/palm tree fossils in cold areas - warm, humid areas Fossils used as evidence of changes in life forms Example - Horse Fossils Fossils of horses - size of dog to present size Change from 4 toes on foreleg and 3 toes on hindleg to 1 toe (hoof) on each leg. Indicate many different living things have existed in the past. Extinct - organisms that no longer lives on earth.Evidence of EvolutionDating Fossils

Fossils are useful only if scientists can tell how long ago they lived. Relative Age - Putting events in their proper sequence No reference to age - order event occurLaw of Superposition - sedimentary rocks, bottom layers deposited before upper layers - each layer is younger than layers below it and older than the ones above it. Absolute Age - how many years ago an event occurred; measured in actual years. Uses Radioactive Decay - measure of half-life of element. Half-Life - Time it takes for of quantity of element to breakdown to another element. Carbon 14 decays to Nitrogen 14 - half-life = 5730 years.

Evidence of EvolutionGeologic Time Scale

Set up by scientist using information gained from various dating methods. Divided into 4 large time spans called an ERA Precambrian Era - formation of earth to about 600 million years ago - 4 billion years long - little fossil evidence Paleozoic Era - Lasted about 370 million years Mesozoic Era - (Dinosaurs) - lasted about 160 million years Cenozoic Era - Has lasted about 70 million years - Present 3 most recent Eras divided into Periods Some Periods divided into Epochs

Evidence of EvolutionAnatomical Evidence Anatomy - Study of the structure of living things By comparing structures of organisms, similarities are found Use similarities as evidence of evolution Homologous OrgansBody parts of different species that are similar in structure Examples Seven neck vertebrae of all mammals Whale's flipper, human's arm, bird's wing, etc. Can't be explained by common function; can be by heredity; indicates common ancestor; Vestigial Organs Organs that are reduced in size and appear to have no use. Examples Human appendix Remains of hind limbs in whales

Evidence of Evolution

Evidence of EvolutionEmbryological Evidence Early vertebrate embryos look very similar Believed to have common genetic material - early development similar. Gill slits in vertebrates Notochord

Evidence of Evolution

Evidence of EvolutionBiochemical Evidence Similarities between common proteins found in living organismsSimilarities indicate a close relationshipIndicates similarities between DNA of organisms.Theories of EvolutionLamarck's Theory Jean Baptiste de Lamarck, French biologist; early 1800s Believed giraffes' long necks result of stretchingLow food supply was consumedStretched their necks to reach higher branchesDisuse of an organ could result in its loss. Based on Inheritance of Acquired Characteristics Acquired traits passed on to the next generation Not valid, body cells changes not passed to gametesTheories of Evolution

Theories of EvolutionDarwin's Theory

Background British naturalistPublished book;1859 On the Origin of Species by Means of Natural Selection Ideas formed during 5 year voyage aboard the HMS Beagle Observed many different plants and animals in South America and The Galapagos Islands.Theories of Evolution

Theories of Evolution

Theories of Evolution

Theories of Evolution

Theories of Evolution

Theories of EvolutionMain Hypotheses

The world is not static but is changingLiving things change through time.Organisms with many common characteristics descended from a common ancestor.Evolutionary change is result of natural selection.

Theories of Evolution

Theories of EvolutionNatural Selection

Process by which those organisms that are best suited to their environment survive and reproduce.

Theories of EvolutionFactors Working in Natural Selection

Overproduction Struggle for Existence VariationTheories of EvolutionOverproduction Organisms tend to produce more offspring than could survive. Assumed number of organisms would increase geometrically (1,2,4,8,16,32,64,128,...)

Theories of EvolutionStruggle for Existence Even with overproduction, population tended to remain constant. Concluded lack of population increase was due to "struggle for existence" - competition for food, space, etc., Some individuals not successful; will die. Concluded that individuals and species were "selected" by their environment. Theories of EvolutionVariation

Individuals of a species vary genetically. Not able to explain cause of variations.

Theories of EvolutionNatural Selection and Origin of New Species Better suited organisms survived and reproduced; passed traits to their offspring. Over time many small changes would occur, the whole population would change. Eventually populations become significantly different from past populations New species formed.

Processes of EvolutionGene Pool

All the genes of a given population

Variations in gene pool cause changes in the species.

Processes of EvolutionHardy-Weinberg Law

The frequency of dominant and recessive genes in a population remains the same from generation to generation.

Gene Frequency - indication of relative number of individuals in a population that have a particular gene.

Law applies only under the following conditions Population must be very large No new genes enter the gene pool Mating must be random Natural selection must not be operatingMutations must not occur.Processes of EvolutionMajor Processes at Work

Gene Mutation Adaptation ShiftsMigrationIsolationProcesses of EvolutionGene Mutation

Change in genetic materialResult - change of gene poolProcesses of EvolutionAdaptation Shifts

Changes in frequency of occurrence of certain genes as environment changes. Processes of EvolutionShift in Color of Peppered Moth in Manchester, England Before 1845, peppered moths were light with dark specks In 1845 during a survey only 1 black moth was observed. Light colored moths were difficult to see on light colored tree trunks - not eaten by birds. Manchester - industrial center in mid 1800s Used coal for energy - large amount of soot; Settled on tree bark making it dark By 1895, 99% of moths in area were black Black color permitted hiding Light coloration moths stand out on trees - easy food for birds.

Processes of Evolution

Processes of EvolutionMigration

Movement of organisms into and out of a population Brings new genes or removes genes when organism leaves.

Processes of EvolutionIsolation

Separation of members of a population from other members. Separation may lead to Speciation Formation new and distinct species. Geographic Isolation - separation of population members by some geographic barrier River, mountain, canyon, etc. Reproductive Isolation - separation of members of a population by inability to reproduce.

Pathways of Evolution

Processes of evolutionary change that have lead to organisms having similarities or differences.

Pathways of EvolutionDivergent Evolution

Evolutionary pathway where different species have developed from a common ancestorMembers of population spread out, adapt to various environments.Different variations are selectedAdaptive Radiation - process where species adapts to set of environmental conditionsDivergent means "moving apart" Example - Darwin's finches on the Galapagos Islands Ancestor inhabited the islands Offspring gradually filled various environments of the islands Some became seed eaters, others ate insects, one even became a type of woodpecker: uses a thorn as a tool.

Pathways of Evolution

Pathways of Evolution

Pathways of EvolutionConvergent Evolution Process of unrelated species developing similar characteristics. Convergent means "coming together" Examples- Wings of birds and bats Body shape of whales, porpoises, and dolphins and fishFlippers of the mammals and fins of fish Analogous Organs - organs that are similar in appearance and function but not in origin.

Pathways of Evolution

Human HistoryPrimate Characteristics - Order of humans, monkeys, apes

Hands adapted for grasping: Opposable Thumb - touches each finger Well-developed eyes - can see fine detail even in dim light. Stereoscopic Vision - eyes on front of face, see in 3-D 4 types of teeth - incisors, canines, premolars, molars Most are omnivores

Human HistoryHuman Characteristics

Anatomical Characteristics Posture - permit standing erect; Bipedal - walks on 2 limbs Arch of the foot - supports Large toe in line with others; walking rather grasping Pelvis provides better support for internal organs and upper body mass - distributes body's mass onto the legs. Type of Thumb - adapted for refined movements Hand rotates Types of Teeth and Jaw - Teeth are smaller than found in the great apes Jaw more bow shaped Brain Capacity - more highly developed brain

Human HistoryHuman Characteristics

Physiological Characteristics No definite breeding season (heat) as in other primates Develop and age slowerHave longer life span

Human HistoryHuman Characteristics

Behavioral Characteristics Brain capacity gives ability to learn Makes and uses tools Uses symbols to form languages

Human HistoryBiological History of Human Human Fossil Record Hominid - human like Australopithecus africanusDiscovered in 1924 in South AfricaBelieved between 1.5 and 4.5 million years old Australopithecus robustus 1 to 2 million years old Australopithecus afarensis Discovered 1977; 40% complete skeletonFemale; nicknamed "LucyThought to be 3.5 million years oldTheorized as common ancestor of modern humans and the two above mentioned species

Human History

Human History

Human History

Human History

Human HistoryEarly Human Forms

Homo habilis First discovered by the Leakeys in 1950s; Estimated to have lived 1.5 to 2 million years ago Larger, higher, and rounder skull than australopithecines Erect posture and humanlike hand bones

Human History

Human HistoryEarly Human Forms

Homo erectusJava man - 1891, Peking man - 1929 Dated from 1.6 million to 500,000 years ago. Shorter than Homo sapiens thicker and heavier bones Skull structure different - forehead sloped, jaw large, chin smallHuman History

Human HistoryEarly Human Forms

Homo neanderthalensis Lived in Europe and parts of AsiaLived 200,000 to 35,000 years ago Erect posture; heavier and thicker bones Chinless: Sloping forehead Stone tools; Used fireHuman History

Human HistoryEarly Human Forms

Homo sapiens

Cro-Magnon Fossils found in France in 1868. Estimated to have lived 40,000 years ago. High foreheads, small even teeth, large brain cavities Tools, weapons, and implements found; complex culture Made pottery, painted on cave walls, carved bones Lived in different places; adapted to different climates. Only species of Homo now living

Human History

Human History