Natural Selection. Professor Andrea Garrison Biology 3A Illustrations 2011 Pearson Education, Inc., unless otherwise noted

Natural Selection Professor Andrea Garrison Biology 3A Illustrations 2011 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/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 Gradualism (Hutton, late 1700s) Earth s major geological features created over very long periods of slow change Theory of Uniformitarianism (Charles Lyell 1830) Series of books: Principles of Geology Earth millions of years old Same geological processes mold the earth today as in the past, at same rate Gradual change is the norm Geologists established a view of a very old earth built layer by layer and molded by slow geological processes Natural Selection 4

Historical Perspective Erasmus Darwin (mid- to late- 1700s) 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 5

Historical Perspective Cuvier 1769-1832 Foremost expert in fossils Established extinction as a fact Many scientists had believed that fossils were remnants of species which still existed somewhere Opposed concept of change in species Natural Selection; picture from http://en.wikipedia.org/wiki/georges_cuvier 6

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 Natural Selection 7

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: wading birds stretched their legs to keep body dry» Offspring inherit the longer legs Missed the point trait must be hereditary Natural Selection; bottom picture 2014 Cengage Learning 8

Natural Selection Charles Darwin (1809-1882) Age 22 became naturalist for HMS Beagle (1831-1836) Was given copy of Lyell s 1 st book in the series Principles of Geology before he left Natural Selection 9

Natural Selection Natural Selection 10

Natural Selection Darwin impressed by sheer number of different species Natural Selection 11

Natural Selection Darwin impressed by sheer number of different species striking adaptations for organisms lifestyles Natural Selection 12

Natural Selection Natural Selection 13

Natural Selection Darwin impressed by sheer number of different species striking adaptations for organisms lifestyles Fossils more closely related to local living species than fossils on other continents Seemed to show relationship over time Natural Selection 14

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 in same region seemed more similar to each other than to animals of similar climates on other continents Seemed to show relationship based on location Natural Selection 15

Natural Selection Galapagos islands were especially interesting Natural Selection 16

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 17

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 Natural Selection 18

Natural Selection Natural Selection 19

Natural Selection Darwin noticed that it appeared: Plants/animals came to islands from the mainland Went through series of different changes on each island Natural Selection; illustration 2014 Cengage Learning 20

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 Saw 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 21

Natural Selection 1838 Darwin read Thomas Malthus Essay on the Principle of Population (1798) Malthus wrote that plants and animals reproduce more offspring than can survive, and humankind would do the same if left unchecked Darwin realized this was the basis of the mechanism to explain changes in species Natural Selection 22

Theory of Natural Selection Members of a population vary in structure or behavior; traits hereditary (differed from Lamarck in recognizing this) Natural Selection 23

Theory of Natural Selection Members of a population vary in structure or behavior; traits hereditary (differed from Lamarck in recognizing this) Natural Selection 24

Theory of Natural Selection Members of a population vary in structure or behavior; traits hereditary Organisms have high reproductive capability More offspring than environment can support Resources are limited in environment Competition exists between species Natural Selection 26

Theory of Natural Selection Those with adaptive traits ( best-fit for environment) more likely to survive and reproduce to pass on the adaptive traits Unsuitable traits not passed on THUS, ENVIRONMENT SELECTS FOR THOSE ORGANISMS WHICH ARE BEST SUITED TO IT (NATURAL SELECTION) Natural Selection 28

Theory of Natural Selection BUT... 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 29

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 30

Theory of Natural Selection Natural Selection 31

Theory of Natural Selection Natural Selection 32

Theory of Natural Selection Natural Selection 33

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 34

Theory of Natural Selection EXAMPLE: vertebrate eye Probably originated as patch of light sensitive cells Gradually accumulated modifications that increase survival value Natural Selection 35

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 36

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 37

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 38

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 39

Adaptive Radiation Natural Selection 40