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
Origin of Species Ch. 14 Ms. Haut The origin of species is the source of biological diversity Speciation, the origin of new species Is at the focal point of evolution Figure 14.1 CONCEPTS OF SPECIES What Carolus Linnaeus, a Swedish physician and botanist is a species? Used physical characteristics to distinguish species Developed the binomial system of naming organisms Linnaeus’ system established the basis for taxonomy The branch of biology concerned with naming and classifying the diverse forms of life Species Similarities between some species and variation within a species Can make defining species difficult Figure 14.2A Figure 14.2B What is a species? The Biological Species Concept The biological species concept defines a species as A population or group of populations whose members can interbreed and produce fertile offspring Reproductively isolated by various factors preventing mixing with other species Reproductive barriers keep species separate Reproductive barriers Serve to isolate a species’ gene pool and prevent interbreeding Are categorized as prezygotic or postzygotic Table 14.3 Prezygotic Barriers Prevent mating or fertilization between species Habitat isolation —species live in same general area but not the same places Behavioral isolation —special signals recognized Temporal isolation —breeding occurs at different times Mechanical isolation —anatomically incompatible Gametic isolation —gamete recognition Temporal isolation Two species breed at different times Figure 14.3A Behavioral isolation There is little or no sexual attraction between species, due to specific behaviors Figure 14.3B Mechanical isolation Female and male sex organs or gametes are not compatible Figure 14.3C Postzygotic Barriers Operate after hybrid zygotes are formed Prevent the hybrid zygote from developing into a viable, fertile adult Reduced hybrid viability —embryo aborted Reduced hybrid fertility —offspring sterile Hybrid breakdown —offspring of hybrids sterile Hybrid sterility Offspring between two species are sterile and therefore cannot mate Figure 14.3D MECHANISMS OF SPECIATION Geographic isolation can lead to speciation In allopatric speciation A population is geographically divided, and new species often evolve A. harrisi A. leucurus Figure 14.4 Allopatric Speciation Geographic isolation in Death Valley Has led to the evolution of new species of pupfish Figure 14.5B A pupfish http://faculty.uca.edu/~benw/biol4402/lecture3/sld005.htm http://faculty.uca.edu/~benw/biol4402/lecture3/sld005.htm http://faculty.uca.edu/~benw/biol4402/lecture3/sld005.htm MECHANISMS OF SPECIATION New species can also arise within the same geographic area as the parent species In sympatric speciation New species may arise without geographic isolation Sympatric Speciation Many plant species have evolved by polyploidy Multiplication of the chromosome number due to errors in cell division Results in extra sets of chromosomes Zygote Parent species Meiotic error Offspring may be viable and self-fertile Selffertilization 4n = 12 Tetraploid 2n = 6 Diploid O. lamarckiana Unreduced diploid gametes Figure 14.6A O. gigas Adaptive radiation may occur in new or newly vacated habitats In adaptive radiation, the evolution of new species Occurs when mass extinctions or colonization provide organisms with new environments Island chains Provide examples of adaptive radiation Cactus-seed-eater (cactus finch) A 1 B 2 B B C B 3 C 4 C C 5 D Tool-using insect-eater (woodpecker finch) Seed-eater (medium ground finch) Figure 14.8A Figure 14.8B CD D Plant speciation 1. Seeds blown over from mainland and form small colony 2. Gene pool isolated—evolves into new species B 3. Storms/other agents blow seeds to nearby island and evolve into species C 4. Some of species C recolonize the first island and cohabit with species B and some populate a new island 5. Speciation continues between new areas and previously colonized areas The tempo of speciation can appear steady or jumpy According to the gradualism model New species evolve by the gradual accumulation of changes brought about by natural selection Figure 14.12a The tempo of speciation can appear steady or jumpy The punctuated equilibrium model draws on the fossil record Species diverge in spurts of relatively rapid change, instead of slowly and gradually Figure 14.12b Nannippus Pliohippus Hipparion Neohipparion PLIOCENE unequal speciation or unequal survival of species on a branching evolutionary tree Hippidion and other genera Sinohippus Megahippus Callippus Archaeohippus MIOCENE The Equus Merychippus Anchitherium Hypohippus Parahippus Miohippus OLIGOCENE Evolutionary trends reflect species selection Mesohippus Paleotherium Epihippus Propalaeotherium Pachynolophus Orohippus EOCENE PLEISTOCEN E RECENT Evolutionary trends do not mean that evolution is goal directed Hyracotherium Figure 14.13 Grazers Browsers Earth History and Macroevolution Macroevolution Is closely tied to the history of the Earth. The fossil record Is an archive of macroevolution. http://cache.eb.com/eb/image?id=398&rendTypeId=4 Fossilization Most fossils are actually casts of animals or plants. Animal dies and sinks to the sea floor. Tissue begins to decay and is buried under layers of sediment such as mud or sand. These layers become rock. The hard parts of the animal are replaced with minerals such as iron pyrites or silica. These minerals form the fossil. Usually fossils show the hard parts of the animal or plant - such as shell or bones. Trace fossils—evidence of living plants or animals, such as worm burrows or dinosaur footprints. Most fossils are found in sedimentary rocks rocks which were created when shells or small loose bits of rock are laid down in layers (limestone, sandstone, clay and chalk) http://stevekluge.com/geoscience/images/trackwayd.jpg http://science.kennesaw.edu/~jdirnber/Bio2108/Lecture/LecBio diversity/Tracehelminth.jpg Determining Age of Fossils Relative age— determined by position in sedimentary rock http://evolution.berkeley.edu/evosite/lines/images/strat_column.gif Determining Age of Fossils Absolute age—determined by radiometric dating (radioactive isotopes) Based on half-life of an isotope—period it takes for half the radioactive material to decay Carbon-14 C-14 Remaining (atoms) 0 100 1 50 120 100 80 60 40 20 0 1 2 25 3 12.5 4 6.25 5 3.13 2 3 4 5 6 Number of Half-Life Figure 14.17a Number of Half-Life Number of Atoms of C-14 Half-Life of Carbon 14 Plate Tectonics and Macroevolution Figure 14.18 The continents are not locked in place. They drift about Earth’s surface on plates of crust floating on a flexible layer called the mantle. California’s infamous San Andreas fault Is at a border where two plates slide past each other. Plate Tectonics About 250 million years ago Plate movements formed the supercontinent Pangaea. Many extinctions occurred, allowing survivors to diversify. About 180 million years ago Pangaea began to break up, causing geographic isolation. Figure 14.19 http://www.astrobio.net/articles/images/lib/A08.gif Mass Extinctions and Explosive Diversifications of Life The fossil record reveals an episodic history, With long, relatively stable periods punctuated by briefer intervals when the turnover in species composition was much more extensive. Extinction is inevitable in a changing world and occurs all the time. However, extinction rates have not been steady. Extinctions typically eliminate various species of organisms And are followed by explosive diversifications of organisms. Geologic Time Periods and Mass Extinctions Extinction of Dinosaurs http://higheredbcs.wiley.com/legacy/college/levin/0471697435/chap_tut/images/nw0287-nn.jpg The Process of Science: Did a Meteor Kill the Dinosaurs? Scientists discovered an ancient impact crater buried underneath the Yucatán Peninsula in Mexico http://www.sunstarsolutions.com/sunstar/geology/BigB end/Images/Chicxulub.jpg Figure 14.20 Scientists believe that about 65 million years ago, at the end of the Cretaceous period A meteor impact contributed to the extinction of the dinosaurs. Acknowledgements BIOLOGY: CONCEPTS AND CONNECTIONS 5th Edition, by Campbell, Reece, Mitchell, and Taylor, ©2006. These images have been produced from the originals by permission of the publisher. These illustrations may not be reproduced in any format for any purpose without express written permission from the publisher. Unless otherwise noted, illustrations are credited to Pearson Education which have been borrowed from BIOLOGY: CONCEPTS AND CONNECTIONS 3rd Edition, by Campbell, Reece, Mitchell, and Taylor, ©2000. These images have been produced from the originals by permission of the publisher. These illustrations may not be reproduced in any format for any purpose without express written permission from the publisher.