Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 24 The Origin of Species

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: The “Mystery of Mysteries” In the Galápagos Islands Darwin discovered plants and animals found nowhere else on Earth Video: Galápagos Tortoise Video: Galápagos Tortoise

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Speciation, the origin of new species, is at the focal point of evolutionary theory Microevolution consists of adaptations that evolve within a population, confined to one gene pool Macroevolution refers to evolutionary change above the species level

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Two basic patterns of evolutionary change: – Anagenesis (phyletic evolution) transforms one species into another – Cladogenesis (branching evolution) is the splitting of a gene pool, giving rise to one or more new species Animation: Macroevolution Animation: Macroevolution

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Biological Species Concept Members of a biological species are reproductively compatible, at least potentially; they cannot interbreed with other populations. Similarity between different species. Diversity within a species.

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reproductive Isolation Reproductive isolation is the existence of biological factors (barriers) that impede two species from producing viable, fertile hybrids Two types of barriers: – Prezygotic – Postzygotic

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Prezygotic barriers impede mating or hinder fertilization if mating does occur: – Habitat isolation – Temporal isolation – Behavioral isolation – Mechanical isolation – Gametic isolation

LE 24-4a Prezygotic barriers impede mating or hinder fertilization if mating does occur Postzygotic barriers prevent a hybrid zygote from developing into a viable, fertile adult REDUCED HYBRID VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN HABITAT ISOLATION TEMPORAL ISOLATION BEHAVIORAL ISOLATION MECHANICAL ISOLATION GAMETIC ISOLATION Reduced hybrid viability Fertilization Viable, fertile offspring Reduced hybrid fertility Hybrid breakdown Mating attempt Gametic isolation Fertilization Mechanical isolation Behavioral isolation Temporal isolation Habitat isolation Individuals of different species

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Temporal isolation: Species that breed at different times of the day, different seasons, or different years cannot mix their gametes

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Behavioral isolation:

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mechanical isolation:

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Gametic isolation: Video: Blue-footed Boobies Courtship Ritual Video: Blue-footed Boobies Courtship Ritual Video: Giraffe Courtship Ritual Video: Giraffe Courtship Ritual Video: Albatross Courtship Ritual Video: Albatross Courtship Ritual

LE 24-4aa Prezygotic barriers impede mating or hinder fertilization if mating does occur HABITAT ISOLATION TEMPORAL ISOLATION BEHAVIORAL ISOLATION MECHANICAL ISOLATION GAMETIC ISOLATION Mating attempt Gametic isolation Fertilization Mechanical isolation Behavioral isolation Temporal isolation Habitat isolation Individuals of different species

LE 24-4ab Postzygotic barriers prevent a hybrid zygote from developing into a viable, fertile adult REDUCED HYBRID VIABILITY REDUCED HYBRID FERTILITY HYBRID BREAKDOWN Reduced hybrid viability Fertilization Viable, fertile offspring Reduced hybrid fertility Hybrid breakdown

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Postzygotic barriers prevent the hybrid zygote from developing into a viable, fertile adult: – Reduced hybrid viability – Reduced hybrid fertility – Hybrid breakdown

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reduced hybrid viability: Genes of the different parent species may interact and impair the hybrid’s development

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Reduced hybrid fertility: Even if hybrids are vigorous, they may be sterile

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hybrid breakdown: when hybrids mate with either parent species, offspring of the next generation are feeble or sterile

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 24.2: Speciation can take place with or without geographic separation Speciation can occur in two ways: – Allopatric speciation – Sympatric speciation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Allopatric (“Other Country”) Speciation In allopatric speciation, gene flow is interrupted or reduced when a population is divided into geographically isolated subpopulations A. harrisi A. leucurus

LE 24-7a Initial population of fruit flies (Drosophila pseudoobscura) Mating experiments after several generations Some flies raised on maltose medium Some flies raised on starch medium

LE 24-7b Female Starch Maltose Starch Maltose Male Same population Different populations Male 20 8 Mating frequencies in experimental group Mating frequencies in control group Same population Different populations 9 22

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Sympatric (“Same Country”) Speciation In sympatric speciation, speciation takes place in geographically overlapping populations

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Polyploidy Polyploidy is presence of extra sets of chromosomes due to accidents during cell division It has caused the evolution of some plant species Failure of cell division in a cell of a growing diploid plant after chromosome duplication gives rise to a tetraploid branch or other tissue. Gametes produced by flowers on this tetraploid branch are diploid. Offspring with tetraploid karyo- types may be viable and fertile—a new biological species. 2n = 6 4n = 12 4n4n 2n2n

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Habitat Differentiation and Sexual Selection Sympatric speciation can also result from the appearance of new ecological niches In cichlid fish, sympatric speciation has resulted from nonrandom mating due to sexual selection Normal light Monochromatic orange light P. pundamilia P. nyererei

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Adaptive Radiation Adaptive radiation is the evolution of diversely adapted species from a common ancestor upon introduction to new environmental opportunities

KAUAI 5.1 million years OAHU 3.7 million years HAWAII 0.4 million years 1.3 million years MAUI MOLOKAI LANAI Argyroxiphium sandwicense Dubautia linearis Dubautia scabra Dubautia waialealae Dubautia laxa N The Hawaiian archipelago is one of the world’s great showcases of adaptive radiation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Tempo of Speciation Niles Eldredge and Stephen Jay Gould coined the term punctuated equilibrium to describe periods of apparent stasis punctuated by sudden change The punctuated equilibrium model contrasts with a model of gradual change in a species’ existence

LE Time Gradualism model Punctuated equilibrium model

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 24.3: Macroevolutionary changes can accumulate through many speciation events Macroevolutionary change is cumulative change during thousands of small speciation episodes

Complex camera-type eye Pinhole camera-type eye Eye with primitive lens Patch of pigmented cells Eyecup Pigmented cells (photoreceptors) Epithelium Nerve fibers Fluid-filled cavity Epithelium Pigmented layer (retina) Optic nerve Pigmented cells Nerve fibers Cornea Cellular fluid (lens) Optic nerve Cornea Lens Optic nerve Retina Some complex structures, such as the eye, have had similar functions during all stages of their evolution

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Evolution of the Genes That Control Development Genes that program development control the rate, timing, and spatial pattern of changes in an organism’s form as it develops into an adult

Copyright © 2005 Pearson Education, Inc. publishing as 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 Allometric growth is the proportioning that helps give a body its specific form Animation: Allometric Growth Animation: Allometric Growth

LE 24-15a Differential growth rates in a human Newborn Age (years) Adult

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Different allometric patterns contribute to the contrasting shapes of human and chimpanzee skulls Chimpanzee fetus Chimpanzee adult Human fetusHuman adult Comparison of chimpanzee and human skull growth

LE Ground-dwelling salamander Tree-dwelling salamander Heterochrony has also played a part in the evolution of salamander feet

Copyright © 2005 Pearson Education, Inc. publishing as 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

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Changes in Spatial Pattern Homeotic genes determine such basic features as where wings and legs will develop on a bird or how a flower’s parts are arranged – Hox genes provide positional information in the development of fins in fish and limbs in tetrapods

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hox Genes

LE Chicken leg bud Region of Hox gene expression Zebrafish fin bud