3 Jean Baptiste de Lamarck (1809) – He developed a theory of evolution. He related fossils to living animals based on similar appearance.He was the first to statethat organisms changeover time, and new typesare modified descendentsof older types.
4 Lamarck stated that acquired traits could be passed to offspring (The Theory of Acquired Inheritance)
5 This means that according to "All which has been acquired, laid down, or changed in the organization of individuals in the course of their life is conserved by generation and transmitted to the new individuals which proceed from those which have undergone those changes.”This means that according toLamarck, acquired traits couldbe inherited by the nextgeneration.
6 The Giraffe example: The giraffe’s long neck could be the result of generations of giraffes stretching to reach leaves in high branches over their lifetime. Parents slightly stretch their necks and therefore have offspring that inherit this modification acquired during their parents’ life.
7 If a giraffe stretched its neck for leaves, for example, a "nervous fluid" would flow into its neck and make it longer. Its offspring would inherit the longer neck, and continued stretching would make it longer still over several generations.
9 The Long-Legged Bird Example: The long legs of wading birds arose when their ancestors responded to a need to feed on fish. As they waded in deeper water, they stretched their legs to try and keep their bodies dry. This trait would be passed to the next generation.
11 "The development of organs and their force of action are constantly in ratio to the employment of these organs."Lamarck stated that there could bechanges in acquired traits through useor disuse.
12 Lamarck also proposed that organisms were driven from simple to increasingly more complex forms (Darwin argued that increased complexity was the result of adaptation to local environments from one generation to the next.)He did not think species ever went extinct, they just changed into new forms.
14 Charles Darwin (1809 – 1882) After college, a young Charles Darwin (22 yrs old), in 1831, set sail aboard the HMS Beagle as the ship’s naturalist. (The ship was chartered for a five-year mapping mission.)Darwin 1840
15 Darwin was required to collect specimens and carefully record his observations. Darwin was often left at various sea ports for months at a time, which enabled him to collect many fossils and observe thousands of specimens.
17 Darwin read Principles of Geology by CharlesLyell, who stated thatthe geologicalstructure of the Earthresulted from cyclesof observableprocesses thatoperate continuouslythrough time.
18 Extremely long periods of time. He estimated the Earth to Darwin also read aboutJames Hutton’s work:In 1795, Hutton, ageologist,published a theorythat the Earth isshaped bygeologic forces thattake place overExtremely long periodsof time. He estimatedthe Earth tobe millions of years old.
19 During Darwin’s journey, he witnessed a volcanic eruption, & an earthquake that lifted a portion of shoreline and noted that animal life in the water was displaced.
20 Darwin also observed fossil shells of marine organism in rock beds about 4,300 meters (14,100 ft) above sea level.Darwin concluded that if the Earth could change over time, then life could change as well. He also assumed that it would have taken many, many years.
21 The Galapagos Islands are a group of small islands near the equator, about 600 miles off thecoast of South America. The observations andspecimens Darwin collected were especiallyimportant to developing his theory.
29 Since there were so many similarities, he believed this implied that the finches shared a common ancestor.He assumed the differences in the bills of offspring were adaptations to different environments.He also assumed that over many millions of years, many large differences could accumulatebetween species.
30 Darwin’s tortoises: Darwin found that the shapes of tortoise shells corresponded todifferent habitats.
31 The hood Island tortoise has a long neck and a shell that is curved and open around the neck and legs, allowing the tortoise to reach sparse vegetation.The Isabela Island tortoise has a dome-shaped shell & a shorter neck. Vegetation on this Island is more abundant and closer to the ground.Pinta Island tortoises havean intermediate shellbetween these two forms.
32 Another important idea that aided Darwin’s conclusions about the change in organismswas proposed by Thomas Malthus in 1798.He stated that the human population coulddouble & redouble, except forthe presence of war, disease,or limited food supplies.
33 Darwin’s conclusions: 1) Darwin reasoned that all organisms have environmental limits to their growth which decrease their rate of reproduction or increase their rate of death.2) Organisms compete for limited resources.3) Certain traits are beneficial to an organism’s survival, as well as greater reproductive success. If the trait increases the reproductivesuccess, & is inherited, it is passed to many offspring.
34 4) Organisms adapt to their environment . (Adaptations occur as their proportion of genes for favorable traits increases. – Darwin did not know about genes)5) The resulting change in genetic makeup is evolution. The genetic contribution to the next generation termed fitness.6) An individual with a high fitness is well-adapted to its environment and reproducesmore successfully than an individual withlow fitness.These are not Darwin’s – But related to Evolution:
35 Natural Selection -“Survival of the fittest.” Individuals best suitedto their environmentsurvive and reproducethe most successfully,and pass their favorabletraits to offspring. Whilethose with more poorly-suited traits die, orleave fewer offspring.
36 Species change over long periods of time. Natural selection causes the changes inspecies. New species arise, while othersSpecies alive today descended, withmodifications from species that lived in thepast. All organisms on Earth are unitedin a single tree of life by common descent.
38 Artificial Selection and Natural Selection: Breeding organisms with specific traitsin order to produce offspring with identicaltraits is called “Artificial selection.”Darwin used the term“Natural selection” todescribe nature’s forcesSelecting which traitsare favorable and whichorganisms are better fit to survive.
39 Natural Selection, the key evolutionary mechanism Darwin identified, is really four key processes genetic variation (difference in genomes among organisms in a given population)overproduction of offspringstruggle for existence (competition for food, mating resources etc.)differential survival and reproduction (higher fitness, & better adaptation leads to more offspring).
43 Natural Selection and peppered moths: As pollution darkens the trees which mothis favored to survive?
44 Darwin was asked by the naturalist Alfred Wallace, in 1856 (22 years after Darwin returned to England onthe Beagle) to review his paper on “Natural Selection”as a mechanism for Evolution.Darwin decided to publish his own work on evolution.Both papers were presented to the Linnaean Societyof London in 1858.
45 Darwin wrote his now famous book, On the Origin ofSpecies by Means ofNatural Selection, morecommonlyknown asThe Originof Species.
46 What causes changes in a population of organisms? Darwin did not know how heredity worked.Therefore he did not know the source of thevariation that wascentral to his theory,or how these traitswere passed to offspring.
47 Two main sources of genetic variation: 1) Mutations - Mutations do not always affectan organism’s phenotype, but some may enhancean organism’s ability to survive and reproduce.2) Sexual reproduction - The Geneticshuffling that results from sexual reproduction causes variations in a population.Genes mutate from one form to another. New alleles are introduced into the population, and allele frequencies change This can lead to evolution.