Evolution Genetic change in a lineage over time first convincing case put forth by –Charles Darwin

Artificial Selection in Agriculture

Agriculture Corn looks very different from its ancestor Artificial Selection

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Fig SCIENTIFIC THINKING Question: Can artificial selection lead to substantial evolutionary change?

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. SCIENTIFIC THINKING Question: Can artificial selection lead to substantial evolutionary change? Hypothesis: Strong directional selection will quickly lead to a large shift in the mean value of the population. Experiment: In one population, every generation pick out the 20% of the population with the most bristles and allow them to reproduce to form the next generation. In the other population, do the same with the 20% with the fewest number of bristles.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Bristle number in Drosophila Number of Individuals SCIENTIFIC THINKING Question: Can artificial selection lead to substantial evolutionary change? Result: After 35 generations, mean number of bristles has changed substantially in both populations. Low population Initial population Mean High population Hypothesis: Strong directional selection will quickly lead to a large shift in the mean value of the population. Experiment: In one population, every generation pick out the 20% of the population with the most bristles and allow them to reproduce to form the next generation. In the other population, do the same with the 20% with the fewest number of bristles.

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Bristle number in Drosophila Number of Individuals SCIENTIFIC THINKING Question: Can artificial selection lead to substantial evolutionary change? Result: After 35 generations, mean number of bristles has changed substantially in both populations. Low population Initial population Mean High population Hypothesis: Strong directional selection will quickly lead to a large shift in the mean value of the population. Experiment: In one population, every generation pick out the 20% of the population with the most bristles and allow them to reproduce to form the next generation. In the other population, do the same with the 20% with the fewest number of bristles. Interpretation: Note that at the end of the experiment, the range of variation lies outside the range seen in the initial population. Selection can move a population beyond its original range because mutation and recombination continuously introduce new variation into populations.

Darwin’s finches Evidence of Natural Selection

Peter and Rosemary Grant studied medium ground finch Evidence of Natural Selection

Natural Selection

Figure 21.4 Selection against melanism.The red circles indicate the frequency of melanic Biston betularia moths at Caldy Common in Great Britain. Green diamonds indicate frequencies of melanic B. betularia in Michigan, and the blue squares indicate corresponding frequencies in Pennsylvania.

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings For patients treated with the drug 3TC, which interferes with genome replication in HIV, 3TC-resistant strains become 100% of the population of HIV in just a few weeks. Fig Evolution of Super bugs: MRSA, or methicillin-resistant Staphylococcus aureus. Multi-drug resistant tuberculosis; Clostridium difficile, etc

Whale “missing links” Fossil Evidence of Evolution

Vestigial structures: have no apparent function, but resemble structures their ancestors possessed Anatomical Evidence for Evolution Vestigial structures of a whale

Humans –Muscles for wiggling ears Boa constrictors –Hip bones and rudimentary hind legs Manatees –Fingernails on their fins Blind cave fish –Nonfunctional eyes Anatomical Evidence for Evolution

Homology of the bones of the forelimb of mammals Anatomical Evidence for Evolution

Convergent evolution of fast swimming predators Anatomical Evidence for Evolution

Developmental similarities reflect descent from a common ancestor Anatomical Evidence for Evolution

Evolution A unifying theme in Biology Explains the diversity and unity we observe

Charles Darwin Naturalist on HMS Beagle in 1831 Galapagos Islands the origin of new species

Origin of Species, 1859 Two main points –1. Evolution explains the unity and diversity of life “descent with modification” –2. Natural selection was the main cause of evolution differential reproductive success leads to adaptation

Evolution Individuals do not evolve Populations are the smallest units that can evolve –a group of interbreeding individuals belonging to a particular species sharing a common geographic area Discussed “microevolution” in BIO 150

Origin of New Species Biological species concept –a population or group whose members have the potential to interbreed with one another in nature to produce viable, fertile offspring, but who cannot successfully interbreed with other such groups –does not work for everything asexual, extinct, geographically separated???

Species are based on interfertility, not physical similarity. For example, the eastern and western meadowlarks may have similar shapes and coloration, but differences in song help prevent interbreeding between the two species. In contrast, humans have considerable diversity, but we all belong to the same species because of our capacity to interbreed. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 24.2

Speciation Evolution of reproductive barriers –the key biological event in the origin of new species –any factor that impedes two species from producing fertile hybrids, thus contributing to reproductive isolation –prezygotic and postzygotic

Tab. 22.1

Tab contd.

Later found Prezygotic isolation- different songs

Types or Modes of Speciation Fig 24.6

Types of Speciation Allopatric speciation –speciation event in which the initial block to gene flow is a geographic barrier that physically isolates the populations

Reasons for Geographic Isolation

Example of Allopatric speciation Fig 24.7

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. a. b. Glaciation snowfieldsnowline fringestony debrisshelteredboggy Mountain populations become isolated, permitting divergence and speciation. Alpine zones are reconnected. Separately evolved species come back into contact. Glaciers link alpine zones into one continuous range. Glaciers recede a(1): © Photo New Zealand/Hedgehog House; a(2): © Jim Harding/First Light; a(3): © Colin Harris/Light Touch Images/Alamy; a(4)-(5): © Focus New Zealand Photo Library. Periodic Isolation in Alpine Buttercup

The key to allopatric speciation is whether the separated populations have become different enough that they can no longer interbreed and produce fertile offspring when they come back in contact. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 24.8

Types of Speciation Sympatric speciation –formation of new species within the range of the parental population –Much less common –Polyploidy –Or disruptive selection

Polyploidy and Sympatric Speciation

What Causes Reproductive Isolation to Evolve? Selection –May cause the initial isolation if populations are adapting to different environments –May lead to reinforcement of isolating mechanisms Random changes

Reinforcement in European Flycatchers Pied flycatcher Pied flycatcher Collared flycatcher Collared flycatcher

Macroevolution Origin of taxonomic groups higher than the species level evolutionary change substantial enough to view its products as new genera, families or phyla Has a random component

Macroevolution The study of –major evolutionary innovations bird feathers, insect wings

Macroevolution The study of –evolutionary trends

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Hyracotherium Orohippus Epihippus Mesohippus Anchitherium Miohippus Megahippus Hypohippus Eocene Oligocene Miocene browsers grazers mixed feeders Kalobatippus Archaeohippus Desmatippus Parahippus Merychippus Pseudhipparion Neohipparion Hipparion Nannippus Cormohipparion Protohippus Calippus Pliohippus Astrohippus Onohippidion Dinohippus Equus Merychippus (mixed feeders) Neohipparion (grazers) Nannippus (grazers) Equus (grazers) Anchitherium (browsers) Hyracotherium (browsers) Mesohippus (browsers) Pleistocene 5MYA 10MYA 15MYA 20MYA 25MYA 30MYA 35MYA 40MYA 45MYA 50MYA 55MYA 60MYA Pliocene

Macroevolution The study of –trends in biodiversity extinctions and radiations

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ordovician Devonian Permian Triassic Cretaceous Millions of years ago Number of families

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display Oldest eukaryotes First signs of life Plants Insects and amphibians Reptiles Mammals and dinosaurs First hominids Oldest fossils 2700 Millions of years ago Extinction of the dinosaurs Flowering plants and first birds Colonization of land by animals Vertebrates Diversification of multicellular life and algae Oxygen increases in the atmosphere

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ground and Cactus Finches Vegetarian Tree Finch Warbler Finches Certhidea fusca Platyspiza crassirostris Certhidea olivacea Tree Finches Cactospiza pallida Camarhynchus pauper Camarhynchus parvulus Geospiza conirostris Geospiza magnirostris Geospiza fuliginosa Geospiza fortis Geospiza scandens Geospiza difficilis Camarhynchus psittacula Cactospiza heliobates

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Second set of jaws Leaf eater Snail eater Insect eater Zooplankton eater Algae scraper Fish eater Scale scraper

Macroevolution The study of –pace of evolution

Fig Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Time a. Gradualismb. Punctuated equilibrium Pace of Evolution

Macroevolution Fossil record provides the outline of macroevolution must also study extant species to provide the details