Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
The Selfish Gene wikipedia , lookup
On the Origin of Species wikipedia , lookup
Population genetics wikipedia , lookup
Hologenome theory of evolution wikipedia , lookup
Inclusive fitness wikipedia , lookup
The Descent of Man, and Selection in Relation to Sex wikipedia , lookup
Sexual selection wikipedia , lookup
Genetics and the Origin of Species wikipedia , lookup
Natural Selection Professor Andrea Garrison Biology 11 Illustrations ©2010 Pearson Education, Inc. , unless otherwise noted Natural Selection • Mechanism for change in species over time • Proposed by Charles Darwin in 1859 Natural Selection 2 Historical Perspective • Concept of change in plant and animal species not new with Charles Darwin • Presence of fossils recognized as evidence of former living organisms by ancient Greeks • 1600s – 1800s views of church predominant – Archbishop Ussher: earth ~6,000 years old Natural Selection 3 Historical Perspective • Theory of Uniformitarianism (Hutton, late 1700s) – Same geological processes mold the earth today as in the past, at same rate – Gradual change is the norm – Implies very old age for earth • Charles Lyell (1830) -- Principles of Geology • Earth millions of years old Natural Selection 4 Historical Perspective • William Smith (1769-1839) – Surveyor during Industrial Revolution – Went into mine shafts and surveyed for canals to move coal – Older rock strata covered by younger rock strata – Fossils can be used to identify same rock layers in different parts of England • Presence of different fossil species in different rocks strata evidence of change in species over time Natural Selection; picture from http://en.wikipedia.org/wiki/William_Smith_(geologist) 5 Historical Perspective • Geologists established a view of a very old earth built layer by layer and molded by slow geological processes Natural Selection 6 Historical Perspective • Geologists set stage for biologists • Buffon (1707-1788) – Divine creation for many species – “Lesser families” developed over time by degenerative processes Natural Selection; http://en.wikipedia.org/wiki/Georges-Louis_Leclerc,_Comte_de_Buffon 7 Historical Perspective • Erasmus Darwin (mid- to late1700s) – Species historically related – Species changed with environment – Offspring could inherit those changes – No model to explain how this happened Natural Selection; picture Erasmus Darwin by Joseph Wright of Derby (1792), http://en.wikipedia.org/wiki/Erasmus_Darwin 8 Historical Perspective • Inheritance of Acquired Characteristics (Jean Baptiste Lamarck, 1801) – Changes in species induced by environment • Environmental changes cause changes in organisms’ needs – Demands on certain body parts → better developed parts – Body parts no longer needed → degenerate from lack of use – Example: giraffe stretches neck to get at leaves in tree tops » Offspring inherit the longer neck Natural Selection 9 Historical Perspective • Inheritance of Acquired Characteristics (Jean Baptiste Lamarck,1801) What’s wrong with this concept? Natural Selection 10 Historical Perspective • Inheritance of Acquired Characteristics (Jean Baptiste Lamarck,1801) What’s wrong with this concept? If I work out every day, my baby will have strong muscles (really ???) Natural Selection 11 Historical Perspective • Inheritance of Acquired Characteristics (Jean Baptiste Lamarck,1801) What’s wrong with this concept? If I work out every day, my baby will have strong muscles (really ???) TRAITS MUST BE GENETIC TO BE PASSED ON TO OFFSPRING! Natural Selection 12 Historical Perspective • Cuvier 1769-1832 – Foremost expert in fossils – Established extinction as a fact • Many fossils have no living members of the species • Many scientists had believed that fossils were remnants of species which still existed somewhere – Strong opponent of change in species Natural Selection; picture from http://en.wikipedia.org/wiki/Georges_Cuvier 13 Historical Perspective • Theory of Catastrophism (Cuvier, 1796) – Predominate view of early 1800s – Extinctions caused by series of natural disasters – After each extinction, new species used resources and filled ecological vacancies • Never explained where the new species came from • They had already been created, but fossils hadn’t yet been found in other strata, so appeared new • Cuvier’s followers taught the a series of divine creations replaced species lost with each catastrophe Natural Selection 14 Natural Selection • Charles Darwin (1809-1882) – Studied for medicine and clergy – Enjoyed observing and collecting wildlife – Age 22 became naturalist for HMS Beagle (1831-1836) – Was given copy of Lyell’s book Principles of Geology before he left Natural Selection 15 Natural Selection Natural Selection 16 Natural Selection • Darwin impressed by – sheer number of different species Natural Selection 17 Natural Selection • Darwin impressed by – sheer number of different species – striking adaptations for organisms’ lifestyles Natural Selection 18 Natural Selection Natural Selection 19 Natural Selection • Darwin impressed by – sheer number of different species – striking adaptations for organisms’ lifestyles – Fossils in S. America more closely related to local living species than fossils on other continents • Seemed to show relationship over time Natural Selection 20 Natural Selection • Darwin impressed by – sheer number of different species – striking adaptations for organisms’ lifestyles – Fossils in S. America more closely related to local living species than fossils on other continents • Seemed to show relationship over time – Animals in different climates of So. America seemed more similar to each other than to animals of similar climates on other continents • Seemed to show relationship based on location Natural Selection 21 Natural Selection • Galapagos islands were especially interesting Natural Selection 22 Natural Selection • Galapagos Islands were similar in climate and topography to the Cape Verde islands off No. Africa – Plants and animals very different from those of Cape Verde Islands Natural Selection 23 Natural Selection • Species on Galapagos Is. similar to those on mainland – But there were differences • Species similar on different islands, but with their own differences Natural Selection 24 Natural Selection Natural Selection 25 Natural Selection • Darwin noticed that plants and animals appeared to have come to the Galapagos Islands from the mainland, then gone through a series of slightly different changes on each island Natural Selection 26 Natural Selection • Darwin read Lyell’s book on the journey – Earth much older than 6,000 years – Gradually changing physical environment • Back in England, Darwin looked at his collections and notes – Began to see a pattern that could be explained by species changing over time as their environment changed – Could not see a mechanism for such a change in species Natural Selection 27 Natural Selection • 1838—Darwin read Thomas Malthus’ Essay on the Principle of Population (1798) – Malthus wrote that plants and animals reproduced more offspring that could survive, and humankind would do the same if left unchecked – Darwin recognized the forces he’s seen at work in nature • Realized this was the basis of the mechanism to explain changes in species Natural Selection 28 Theory of Natural Selection • Members of a population vary in structure or behavior; traits hereditary (differed from Lamarck in recognizing this) Natural Selection 29 Theory of Natural Selection • Members of a population vary in structure or behavior; traits hereditary (differed from Lamarck in recognizing this) Natural Selection 30 Theory of Natural Selection • Members of a population vary in structure or behavior; traits hereditary (differed from Lamarck in recognizing this) • Organisms have high reproductive capability – Produce more offspring than environment can support Natural Selection 31 Theory of Natural Selection • Members of a population vary in structure or behavior; traits hereditary (differed from Lamarck in recognizing this) • Organisms have high reproductive capability – Produce more offspring than environment can support • Resources are limited in environment – Therefore competition exists between species Natural Selection 32 Theory of Natural Selection • • Members of a population vary in structure or behavior; traits hereditary (differed from Lamarck in recognizing this) Organisms have high reproductive capability – Produce more offspring than environment can support • Resources are limited in environment – Therefore competition exists between species • Individuals whose traits best adapted for environment survive, others die Natural Selection 33 Theory of Natural Selection • Those “best-fit” for environment more likely to survive and reproduce to pass on inherited traits which make them so well suited for that particular environment – Unsuitable traits not passed on Natural Selection 34 Theory of Natural Selection • Those “best-fit” for environment more likely to survive and reproduce to pass on inherited traits which make them so well suited for that particular environment – Unsuitable traits not passed on • THUS, ENVIRONMENT SELECTS FOR THOSE ORGANISMS WHICH ARE BEST SUITED TO IT (NATURAL SELECTION) Natural Selection 35 Theory of Natural Selection • BUT . . . • Organism only best fit for the environment that selected for it Natural Selection 36 Theory of Natural Selection • • Organism only best fit for the environment that selected for it If environment changes, so will traits necessary for survival – Thus, species will slowly change as environment selects for those members of the population which are best suited to the environmental changes -OR– Species will die out Natural Selection 37 Theory of Natural Selection • • Organism only best fit for the environment that selected for it If environment changes, so will traits necessary for survival – Thus, species will slowly change as environment selects for those members of the population which are best suited to the environmental changes -OR– Species will die out • Eventually the new species may be very different from the original species ( = evolution) Natural Selection 38 Theory of Natural Selection • Natural selection supported by strong evidence • Natural selection = microevolution • Most biologists today agree that natural selection is the mechanism for major changes over time (= macroevolution or evolution) Natural Selection 39 Theory of Natural Selection • Important to note: – Natural selection does not make a change in an individual • Entire species changes over time – takes many generations Natural Selection 40 Theory of Natural Selection • Important to note: – Natural selection does not make a change in an individual • Entire species changes over time – takes many generations – Natural selection does not create new traits • New traits originate by chance and environment selects for or against them Natural Selection 41 Theory of Natural Selection • Important to note: – Natural selection does not make a change in an individual • Entire species changes over time – takes many generations – Natural selection does not create new traits • New traits originate by chance and environment selects for or against them – Natural selection does not result in new, intricate organs all at once • Each step is a very small change Natural Selection 42 Theory of Natural Selection – EXAMPLE: vertebrate eye • • Probably originated as patch of light sensitive cells Gradually accumulated modifications that increase survival value Natural Selection 43 Theory of Natural Selection – EXAMPLE: vertebrate eye • • Probably originated as patch of light sensitive cells Gradually accumulated modifications that increase survival value – Idea of irreducible complexity • • Gradual changes would not be selected for if they didn’t provide new value Organs so complex as eye require many different fully formed parts all functioning at once – Any one of them does nothing on its own to be selected for Natural Selection 44 Theory of Natural Selection • Darwin’s theory of natural selection worked out in 1838 • Worked on it for next 20 years for perfection • 1858 Alfred Russell Wallace sent Darwin a manuscript for comment – He had developed same theory as Darwin – Two men presented in same issued of Journal of Linnaean Society in 1858 • Darwin published Origin of Species in 1859 Natural Selection 45 Theory of Natural Selection • 1865 Mendel published his research on genetics • Today we know about DNA, chromosome and genes – Recognize that changes in outward traits due to chance changes in genetic material (mutations) and also new combinations of traits due to sexual reproduction Natural Selection 46 Theory of Natural Selection Natural Selection 47 Theory of Natural Selection Natural Selection 48 Theory of Natural Selection Natural Selection 49 Adaptive Radiation • Major pattern of change in species seen by Darwin in Galapagos finches – Sudden (in geological time) emergence of several species from a common ancestor – Caused by sudden availability of new or unused resources Natural Selection 50 Adaptive Radiation • 13 different species of finches in Galapagos – Now believed to have arisen from single pair or pregnant female from So. American mainland • Rafted to islands by storm • Population size increased and resources decreased • Individuals capable of using other resources did so to survive • Natural selection gradually selected for those groups that could best use the several available resources • Result: several different species Natural Selection 51 Adaptive Radiation Natural Selection 52 Figure 22.6 (b) Insect-eater (a) Cactus-eater (c) Seed-eater Natural Selection 54