Presentation on theme: "Evolution is defined as gradual change over time"— Presentation transcript:
1Evolution is defined as gradual change over time Time being one critical element of the definition.
2Jean Baptiste Lamarck Author of first systematic theory of evolution Theory on the evolution of acquired characteristicsBelieved that modifications of form due to environmental circumstances
3Lamarck’s Theory Use it or lose it Internal drive toward complexity caused inheritance of acquired characteristicsThe giraffe’s neck is the classic example
4Lamarck’s theoryAt some point in the past, giraffe’s found themselves in an environment where they had difficulty reaching food on the tops of tree. They had to stretch their necks and in doing so, physically lengthened them.This longer neck was passed on to the next generation, who stretched even further, resulting over time in giraffes having long necks.
6Lamarck’s Theory of Evolution Inheritance Of Acquired TraitsTraits Acquired During Ones Lifetime Would Be Passed To OffspringClipped ears of dogs could be passed to offspring!
7Lamarck’s Theory of Evolution Tendency Toward PerfectionOrganisms Are Continually Changing and Acquiring Features That Help Them Live More Successfully In Their EnvironmentExample: Bird Ancestors Desired To Fly So They Tried Until Wings Developed
8Lamarck’s MistakesLamarck Did NOT Know how traits were inherited (Traits are passed through genes)Genes Are NOT Changed By Activities In LifeChange Through Mutation Occurs Before An Organism Is Born
10Charles Darwin The Author of the On the Origin of Species The most notable evolution theorist of our timeKnown for his famous voyage on “The Beagle”
11Charles Darwin Born in England Wealthy, sophisticated English family 1827 dropped out of medical school & entered Cambridge to prep for the clergyBecame a meticulous observer of natural phenomena & collector of specimensat 22 was taken aboard HMS Beagle as a naturalist on a scientific expedition around the worldArrived at the Galapagos Islands on September 15th, 18355 week stay – was on land 19 days collecting & observing
12In 1831, the young naturalist Charles Darwin set off on a five-year sail around the world that would profoundly change not just his life, but the course of science as well. Commissioned to collect samples of flora and fauna from the HMS Beagle’s ports of call, Darwin left England firmly believing, like everyone else, that God had created every living thing on Earth exactly as it appeared. His specimens told him otherwise, however, and when the Beagle docked in England, core tenets of the theory of evolution had been shaped. Yet it would be 20 years before he would make his ideas public; Darwin feared that disclosing his radical views would be the equivalent of committing career suicide and was moved to publish only when another scientist independently arrived at the same conclusions as he. That event sparked a debate that continues to this day.
13Charles DarwinIn 1831 he sailed to the Galapagos Islands in the HMS BeagleHe left England on this voyage at 22 yrs. OldHe published his theory of evolution 30 years later
14The HMS BeagleTHE BEAGLE WAS 90 FEET LONG, WITH 74 PEOPLE ABOARD
15Darwin returned 5 years later in 1836 Darwin Left England in 1831Darwin returned 5 years later in 1836
1613 major islands, 6 minor islands, & 40 smaller rock formations & reefs – 3000 square miles of land covering 17,000 miles of ocean located 600 miles west of Ecuador
17Galapagos IslandsVolcanic in origin – oldest are 325 million years oldHot spot formation theoryStill active volcanoesNever connected to the mainlands
18Galapagos IslandsUntil their discovery in 1535, life here evolved in isolation producing strange & marvelous species8 Habitats to accommodate a large variety of species:Open sea Rocky isletsRocky shores Sandy beachesMangrove coasts Arid zoneTransitional zone Highlands
29Galapagos Tortoise Tortoise nesting video There are currently only 11 subspeciesLeft in the world today.
30Lonesome George George is a Pinta Island Tortoise He is the very LAST one known in existenceThere is a reward of $10,000 offered by the zoo association if a female is found
31Charles Darwin Research Center International, nonprofit organization for scientific research, environmental education & conservationFounded in 1959Captive breeding program for endangered giant tortoises & land iguanas
35Animals of the Galapagos Sea LionsSally Lightfoot CrabsMarine iguana
36Darwin’s IdeasDarwin at 31Evolution is due to genetic variation and natural selection on heritable charactersRecognized natural selection as the mechanism in 1838Sketch of genetic line
37Darwin’s 5 Major Theories 1. The organisms steadily evolve over time (evolution theory)2. Different kinds of organisms descended from a common ancestor (common descent theory)3. Species multiply over time (speciation theory)4. Evolution takes place through the gradual change of populations (gradualism theory)5. The mechanism of evolution is the competition among vast numbers of unique individuals for limited resources under selective pressures, which leads to differences in survival and reproduction (natural selection theory)
38Weaknesses in Darwin’s natural selection theory 1. Blending inheritance was favoured rather than discrete Mendelian genes (which was unknown at the time)2. No knowledge of Mendelian genetics was available3. Phyletic gradualism was favoured as the type of speciation4. Fecundity (fertility) was not emphasized in the description of fitness5. Sexual selection: Sexually selected characters were seen as ornaments but they may be advertising genuine male qualities (Hamilton & Zuk, 1982)
39Evidence used in Darwin’s Natural Selection Theory 1. Biogeography: Distinct features of cosmopolitan species and the presence of endemic species (Darwin's finches: of the 14 finch species of the Galapagos islands, 13 are endemic)2. Morphology and embryology: Homologous structures among related species; similarities in the embryos of related speciesHomologous Structure-features that are similar in structure but appear in different organisms and have different functions; offers support for common ancestorAnalogous Structure-perform a similar function but are not similar in orgin3. Palaeontology: Gradual change in the fossil record, evident extinctions4. Taxonomy and systematics: Morphological similarities among related taxa
43Compare Lamarck & Darwin Concept of SpeciesPopulation all same (identical characteristics) capable of transformation during lifetimePopulation w/similar characteristics, variation common depending on environment. No transformation in lifetime, only through genetic meansMechanism of new speciesModified during life & then inherited by offspring. Change directed to meet survivalNatural Selection. Variation exists regardless of organisms' needs. Those most fit survive & reproduceExampleGiraffe’s neck, fiddler crabGalapagos finch, eyesight of the hawkPotential ProofAdaptationsAdaptations, fossil records, homologous structures, biogeographical diversity patterns
45Natural SelectionDarwin is credited with the theory of evolution by natural selection.Natural selection is that the strongest survive and propagate and therefore increase the strength of the species“Survival of the Fittest”Fitness-an organism’s ability to survive & reproduce
47Darwin FinchesOnce on the islands, various species established themselves and determined territoriesEvolution then set in and many unique species, such as Darwin’s finches resulted
48Darwin Finches and Natural Selection The finches probably descended from one type of ancestor and due to isolation and through chance, different climates, natural forces, and food type, evolved into the 13 different types of finches
49Darwin Finches on the Galapagos 1. Small billed ground finch Geospiza fuliginosa 2. Medium billed ground finch Geospiza fortis 3. Large billed ground finch Geospiza magnirostris 4. Sharpbill ground finch Geospiza difficillis 5. Cactus finch Geospiza scandens 6. Large cactus finch Geospiza conirostris 7. Vegetarian finch Platyspiza crassirostris 8. Small tree finch Camarhynchus parvulus 9. Medium tree finch Camarhynchus pauper 10. Large tree finch Camarhynchus psittacula 11. Carpenter finch Cactospiza pallida 12. Mangrove finch Cactospiza heliobates 13. Warbler finch Certhidea olivacea
51The Darwin Finches are the most common birds on the Galapagos Islands and can be seen in the arid and wet zones. Of the 14 species of Darwin Finch in the world, thirteen are found on these islands and the fourteenth species on the Coco Islands. Some populations are commonly found but others such as the mangrove finch which has a population of approximately 100, is only found in one particular area on Isabella Island.
52Feeding of the Finches some eat fruit and seeds other insects some can even suck the blood from marine birds on the islands when they can't find their usual food.Certain varieties of finch clean the ticks from the shells of the giant tortoises.
57Natural Variation Some cows give more milk Some plants bear larger fruitSome humans are taller than othersMuch of this variation is inherited & passed on to the next generationHumans may take advantage of this variation by breeding certain organisms together with the desired trait (artificial selection)
58Natural selection -Something like artificial selection occurs in nature – called natural selectionHowever, the traits being selected contribute to an organism’s fitness without human controlThere is always a struggle for existence & the “fitness” of an organism depends on its survival & its reproductive success (survival of the fittest)Example:faster = better predatorcamouflagebehaviorbetter protection from extremes
59Evidence for evolution by natural selection in contemporary populations: 1. The resistance of the house fly (Musca domestica) to DDT first reported in 1947,2. The change in the frequencies of differently colored peppered moths with industrial revolution in England3. The resistance of bacteria to antibiotic drugs
60AdaptationThese changes increase the chance of survival & thus the traits that allow for survival are passed on the next generation
61Speciation Formation of a new species As new species evolve, populations become reproductively isolated from each other (they cannot interbreed) called reproductive isolationBehavioral isolation occurs when 2 populations are capable of interbreeding but have differences in courtship rituals & are then not attracted to each otherGeographic isolation – 2 populations are separated by geographic barriers such as rivers, or mountainsTemporal Isolation occurs when 2 organisms reproduce at different times