Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings PowerPoint ® Lecture Presentations for Biology Eighth Edition Neil Campbell and Jane Reece Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp Chapter 25 The History of Life on Earth

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Adaptive Radiations Adaptive radiation is the evolution of diversely adapted species from a common ancestor upon introduction to new environmental opportunities

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Worldwide Adaptive Radiations Mammals underwent an adaptive radiation after the extinction of terrestrial dinosaurs The disappearance of dinosaurs (except birds) allowed for the expansion of mammals in diversity and size Other notable radiations include photosynthetic prokaryotes, large predators in the Cambrian, land plants, insects, and tetrapods

Fig Millions of years ago Monotremes (5 species) ANCESTRAL CYNODONT 0 Marsupials (324 species) Eutherians (placental mammals; 5,010 species) Ancestral mammal Adaptive Radiation of Mammals

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Regional Adaptive Radiations Adaptive radiations can occur when organisms colonize new environments with little competition The Hawaiian Islands are one of the world’s great showcases of adaptive radiation

Fig Close North American relative, the tarweed Carlquistia muirii Argyroxiphium sandwicense Dubautia linearis Dubautia scabra Dubautia waialealae Dubautia laxa HAWAII 0.4 million years OAHU 3.7 million years KAUAI 5.1 million years 1.3 million years MOLOKAI MAUI LANAI These plants had a common ancestor 5 million years ago

Fig a HAWAII 0.4 million years OAHU 3.7 million years KAUAI 5.1 million years 1.3 million years MOLOKAI MAUI LANAI Pacific Tectonic plate has been moving to the west, with it the formation of the Hawaiian islands occured causing variation between the islands' topography and weather, causing the formation of different environments and with it different species

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Studying genetic mechanisms of change can provide insight into large-scale evolutionary change Evolutionary Effects of Development Genes Genes that program development control the rate, timing, and spatial pattern of changes in an organism’s form as it develops into an adult Concept 25.5: Major changes in body form can result from changes in the sequences and regulation of developmental genes

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Changes in Rate and Timing Heterochrony is an evolutionary change in the rate or timing of developmental events It can have a significant impact on body shape The contrasting shapes of human and chimpanzee skulls are the result of small changes in relative growth rates

Fig (a) Differential growth rates in a human (b) Comparison of chimpanzee and human skull growth Newborn Age (years) Adult Chimpanzee fetus Chimpanzee adult Human fetus Human adult Heterochrony Arms and legs grow faster than head and trunk parts of body skuls of human and chimp are similar at the fetus stage, but become much diffe- rent once adults

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings In paedomorphosis, the rate of reproductive development accelerates compared with somatic development The sexually mature species may retain body features that were juvenile structures in an ancestral species gills fish-like tail

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Changes in Spatial Pattern Substantial evolutionary change can also result from alterations in genes that control the location/placement and organization of body parts Homeotic genes determine such basic features as where wings and legs will develop on a bird or how a flower’s parts are arranged

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Hox genes are a class of homeotic genes that provide positional information during development If Hox genes are expressed in the wrong location, body parts can be produced in the wrong location For example, in crustaceans, a swimming appendage can be produced instead of a feeding appendage

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Evolution of vertebrates from invertebrate animals was associated with alterations in Hox genes Two duplications of Hox genes have occurred in the vertebrate lineage These duplications may have been important in the evolution of new vertebrate characteristics

Fig Vertebrates (with jaws) with four Hox clusters Hypothetical early vertebrates (jawless) with two Hox clusters Hypothetical vertebrate ancestor (invertebrate) with a single Hox cluster Second Hox duplication First Hox duplication

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings The Evolution of Development The tremendous increase in diversity during the Cambrian explosion is a puzzle Developmental genes may play an especially important role Changes in developmental genes can result in new morphological forms

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Changes in Genes New morphological forms likely come from gene duplication events that produce new developmental genes A possible mechanism for the evolution of six- legged insects from a many-legged crustacean ancestor has been demonstrated in lab experiments Specific changes in the Ubx gene have been identified that can “turn off” leg development

Fig Hox gene 6 Hox gene 7 Hox gene 8 About 400 mya Drosophila Artemia Ubx

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Changes in Gene Regulation Changes in the form of organisms may be caused more often by changes in the regulation of developmental genes instead of changes in their sequence

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Concept 25.6: Evolution is not goal oriented Evolution is like tinkering—it is a process in which new forms arise by the slight modification of existing forms

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Evolutionary Novelties Most novel biological structures evolve in many stages from previously existing structures Complex eyes have evolved from simple photosensitive cells independently many times Exaptations are structures that evolve in one context but become co-opted for a different function Natural selection can only improve a structure in the context of its current utility

Fig (a) Patch of pigmented cells Optic nerve Pigmented layer (retina) Pigmented cells (photoreceptors) Fluid-filled cavity Epithelium (c) Pinhole camera-type eye Optic nerve Cornea Retina Lens (e) Complex camera-type eye (d) Eye with primitive lens Optic nerve Cornea Cellular mass (lens) (b) Eyecup Pigmented cells Nerve fibers Limpet slit shell Nautilus Murex Loligo gahi upload.wikimedia.org

Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings Evolutionary Trends Extracting a single evolutionary progression from the fossil record can be misleading Apparent trends should be examined in a broader context

Fig Recent (11,500 ya) Neohipparion Pliocene (5.3 mya) Pleistocene (1.8 mya) Hipparion Nannippus Equus Pliohippus Hippidion and other genera Callippus Merychippus Archaeohippus Megahippus Hypohippus Parahippus Anchitherium Sinohippus Miocene (23 mya) Oligocene (33.9 mya) Eocene (55.8 mya) Miohippus Paleotherium Propalaeotherium Pachynolophus Hyracotherium Orohippus Mesohippus Epihippus Browsers Grazers Key The End