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Home , Allopatric speciation, Evolution of the wolf, Extinct in the wild, Hybrid inviability, Parapatric speciation, Plate tectonics

2 Evolution • The evolution of is directly connected to the evolution of .

• Evidence: – – – • Similarities in types • Glaciation • distributions

Plate

Alfred (1880-1930) His was based on several 1915 – he suggested that 300 observations: mya all of the 1. The fit of the continents. formed a that 2. Similarity of rock types across he called “Pangea”. Atlantic. 3. Glacial “tracks”. 4. Fossil distributions.

Plate Tectonics Plate Tectonics Continental Margins

1 Plate Tectonics Plate Continental Margins Tectonics

Near perfect fit when continents are joined by continental margins.

South America

Plate Tectonics Plate Tectonics

Glacial striations reveal ancient continental connections. Matching rock assemblages across the Atlantic .

Plate Tectonics Plate Tectonics

Glacial striations reveal ancient continental connections. Glacial Striations

2 Plate Tectonics Plate Tectonics

Glacial Striations Glacial Striations

Plate Tectonics Plate tectonics

New evidence supporting Overlapping Fossil Wegener: assemblages 1. floor spreading 2. Magnetic sea floor patterns 3. Sea floor age patterns

Plate Tectonics Plate Tectonics

Evidence of sea floor spreading

The planet experience periodic reversals in the poles. Rock reflect direction of magnetism when they are created. Sea floor reveals a mirror image of .

3 Plate Tectonics Plate Tectonics

Evidence of sea floor spreading Sea floor spreading

The planet experience Age of seafloor N . A periodic reversals in the increases at m a e n ri poles. equal rates i ca h relative to C Rock reflect direction of oceanic . Africa magnetism when they The oldest sea are created. floor is near the Sea floor reveals a continents. mirror image of rock S. America magnetism.

Evolution Evidence of Evolution Focus on how life changed after it began Evidence Fossils – buried remains and impressions of • Fossils – evidence of ancient life that lived in the past • Biogeography – continental movement – stratified layers of are a • Comparative – homologous historical record of life structures – the fossil record provides a uniformly good • Patterns of Development – similarities documentation of the life of the past • Comparative Biochemistry – cellular, – relative and absolute dating methods molecular • Current Observations – speciation, selection

Evidence of Evolution

Biogeography – involves continental movement – Theory of – Plate Tectonics – Distributions of fossils and descendants Dromaeosaurus Archaeopteryx

4 2 1 3 PTEROSAUR

Homologous Evidence of Evolution 4 Bones 1 CHICKEN 2 Radius 3 Comparative Morphology – evidence of 2 descent with modification 3 1 Stem 2 3 – juvenile hoatzin and Archaeopteryx 4 1 5 PORPOISE

– forelimbs 2 4 3 5 1 – vestigial structures 2 BAT – transitional forms 3 4 5 1 2 HUMAN 3 Figure 17.9 from 4 page 266 of your text 5

Homologous Structures Radius Vestigial Structures

whale hind limbs

Vestigial Structures – Indicate Relatedness Whale Evolution

5 Whale Evolution – Transitional Transition – Fish to Ambulocetus lived both on and in water. It is believed that this is a linking species between modern whales and terrestrial whale ancestors.

Latimeria menadoensis coelacanth

Transition – Fish to Tetrapod Evidence of Evolution

Patterns of Development – during some stages of development, organisms exhibit ancestral features in whole or incomplete form. – whale hind limb buds in the embryo – vertebrate embryo similarities

Vertebrate Whale Embryo Hind Limb Bud Embryo Similarities

Fish Salamander Chick Human

6 Cytochrome c Evidence of Evolution Comparisons

Top row=yeast Comparative Biochemistry – at the Figure 17.14 from =identical sequences Middle row=wheat page 270 of your cellular and molecular level living things text =identical for 2 Bottom row= are remarkably similar to each other – and cells have mostly same organelles – cytochrome c similarities – nucleic acid hybridization

Evidence of Evolution Artificial Selection

Current Observations – speciation, selection – artificial selection (breeding) – – experiments – speciation

Natural Selection Experimental Evidence

Female guppies prefer to mate with brightly colored males. John Endler transplanted predators in a stream without predators and strong selection quickly

Increasing Number of Predators of Number Increasing produced males with a duller coloration.

7 Species and Biological • The biological species concept defines a species as groups of actually, or potentially, interbreeding natural populations of organisms that are “Species are groups of interbreeding reproductively isolated from other such natural populations that are groups. reproductively isolated from other such groups.” •A is defined as a unit of a species comprising those organisms that are actually interbreeding.

Morphology & Species Variable Morphology

• Morphological traits may not be useful in Grown in water Grown distinguishing species on land – Members of same species may appear different because of environmental conditions – Morphology can vary with age and sex – Different species can appear identical

Arrangements of Populations Within a Species • Allopatric populations: when the geographic • Cornerstone of the biological species ranges of 2 populations do not overlap we say concept. the populations are allopatric (geographic isolation). • Speciation is the attainment of • Parapatric populations: populations abut reproductive isolation. • Sympatric populations: populations overlap in • Reproductive isolation arises as a by-product of genetic change.

8 Mechanisms of Reproductive Reproductive Isolating Isolation Mechanisms A. Pre–zygotic 1. Spatial isolation • Prezygotic isolation 2. Ecological isolation – Mating or zygote formation is prevented 3. Temporal isolation 4. Behavioral isolation 5. Mechanical isolation • Postzygotic isolation 6. Gametic isolation – Takes effect after zygotes form B. Post–zygotic – Zygotes may die early, be weak, or be sterile 1. Hybrid inviability 2. Hybrid sterility 3. Hybrid breakdown

Hybrid Ecological Sterility: Isolation A Postzygotic Barrier

Tiglon – a hybrid Liger – a hybrid

Male Tiger X Female Lion

9 Speciation in Progress Ensatina eschscholtzii in Gulls Can hybridize except for 2 species at endpoint of ring

4 Fates of a A Lineage 1. Populations can appear the same phenotypically over . We call this stasis. Examples: crocodilians, beetles, horseshoe crabs. Lineage – a group of organisms related by 2. The populations may change over time, either due to natural selection or because of chance effects (e.g., descent from a common ancestor - A or founder effects), but these changes are all temporal view. anagenetic effects. They don’t lead to any separation of one lineage from another. Examples: peppered moths over the last 100 years, horses. 3. When changes do lead to separation of a lineage from other lineages, we call these changes cladogenetic because new arise that are genetically separated from other lineages. When flow stops between two populations or two lineages, the lineages are reproductively isolated from one another. Example: . 4. There is a fourth possible outcome for changes within populations – . Example: .

Stasis Stasis Leaf Beetles 30 Million Years Old from amber

Recent crocodilians

10 4 Fates of a Lineage 1. Populations can appear the same phenotypically over Stasis time. We call this stasis. Examples: crocodilians, beetles, horseshoe crabs. Horseshoe 2. The populations may change over time, either due to Crabs natural selection or because of chance effects (e.g., genetic drift or founder effects), but these changes are all anagenetic effects. They don’t lead to any separation of one lineage from another. Examples: peppered moths over the last 100 years, horses. 3. When changes do lead to separation of a lineage from other lineages, we call these changes cladogenetic because new clades arise that are genetically separated from other lineages. When stops between two populations or two lineages, the lineages are reproductively isolated from one another. Example: mammals. 4. There is a fourth possible outcome for changes within populations – extinction. Example: dinosaurs.

Anagenesis 4 Fates of a Lineage 1. Populations can appear the same phenotypically over time. We call this stasis. Examples: crocodilians, Form C beetles, horseshoe crabs. 2. The populations may change over time, either due to natural selection or because of chance effects (e.g., genetic drift or founder effects), but these changes are all anagenetic effects. They don’t lead to any separation of one lineage from another. Examples: peppered moths over the last 100 years, horses. Form B 3. When changes do lead to separation of a lineage from other lineages, we call these changes cladogenetic Time because new clades arise that are genetically separated from other lineages. When gene flow stops between two populations or two lineages, the lineages are reproductively isolated from one another. Example: mammals. 4. There is a fourth possible outcome for changes within Form A populations – extinction. Example: dinosaurs.

Anagenesis

Cladogenesis

11 Patterns of Change Many branchings of Evolutionary Tree Diagrams the same lineage. in a Lineage Adaptive has taken place. Species formed Rapid change in traits. • Cladogenesis through gradual Traits of new species did change. not change much after. – Branching pattern – Lineage splits, isolated populations diverge

• Anagenesis (phyletic evolution) – No branching – Changes occur within single lineage – Gene flow throughout process

Adaptive Radiation of Mammals

• Burst of divergence Burst of divergences • Single lineage gives rise to many giving rise to many new species new species. • New species fill vacant adaptive zone • Adaptive zone is “way of life”

Figure 17.26 from page 279 of your text

4 Fates of a Lineage 1. Populations can appear the same phenotypically over time. We call this stasis. Examples: crocodilians, Extinction beetles, horseshoe crabs. 2. The populations may change over time, either due to natural selection or because of chance effects (e.g., • Irrevocable loss of a species genetic drift or founder effects), but these changes are all anagenetic effects. They don’t lead to any separation of • Mass have played a one lineage from another. Examples: peppered moths over the last 100 years, horses. major role in evolutionary history 3. When changes do lead to separation of a lineage from other lineages, we call these changes cladogenetic • Fossil record shows 20 or more because new clades arise that are genetically separated from other lineages. When gene flow stops between two large-scale extinctions populations or two lineages, the lineages are reproductively isolated from one another. Example: • Reduced diversity is followed by mammals. adaptive radiation 4. There is a fourth possible outcome for changes within populations – extinction. Example: dinosaurs.

12 Moa A mere 1,000 years ago, giant flightless Dodo called moas inhabited the of The dodo bird inhabited the . There were more than a of Mauritius in the dozen species of moa and the largest of , where it lived these may have weighed more than 200 undisturbed for so long that it kilograms and stood 2 to 3 meters high. lost its need and ability to fly. Human beings did not colonize New It lived and nested on the Zealand until about 1,000 years ago ground and ate fruits that had when the first Polynesians arrived. These new arrivals hunted the moas and it fallen from trees. seems unlikely that any of the species The combination of human survived into the time of the first contact exploitation and introduced with Europeans in 1770. species to the eventually led to their demise with extinction in 1681.

Tasmanian (Thylacine) Caribbean Monk Seal

This remarkable animal looked like a wolf with tiger stripes on its back and tail, but it The Caribbean Monk seal is probably extinct. Caribbean Monk was more closely related to kangaroos than to either tigers or . The Tasmanian seals were sometimes spotted with a green-flecked back, probably tiger-wolf was a ; it had a pouch for its young just like a kangaroo. are found almost exclusively in Australia and certain surrounding islands caused by an algal growth. The pups were born in December and such as . The population was decimated by an unknown disease in the early had a woolly coat. The last time a Caribbean Monk seal was sighted 1900s. Determined extinct in 1936. was in the early 1950s.

Stellar’s Sea When the sea cow was Passenger Pigeon Cow discovered in , it was already rare; there were perhaps 1,000 to 2,000 The passenger pigeon became individuals. Bering’s crew extinct in 1914, after the last killed many of the remaining individual, Martha, died in sea cows for their meat and captivity in the Cincinnati Zoo. hides, as their ship was The passenger pigeon was one stranded in Alaska and they of the most abundant bird were forced to remain there. species on Earth. It was driven Subsequent expeditions to the to extinction by uncontrolled area killed the rest. The commercial hunting for their Steller’s sea cow probably was meat which was desired by extinct by 1768. Euroamerican settlers.

13 Genetic Change and The last Quagga, a mare at an Amsterdam zoo, Speciation died in 1883. It went extinct in the wild in the • Any structural, functional, behavioral difference that 1870s. lived in brings about reproductive isolation environments in • Africa. These social – Geographic barrier were closely related to the modern-day populations of one species (gold) and horses. Figure 17.2 Quaggas were herbivores from page who ate grasses. They 262 of your text were nomadic and spent most of their time grazing. populations of a daughter species (green)

Speciation & Natural Selection Genetic Divergence

• Gradual accumulation of differences in • Natural selection can lead to speciation the gene pools of populations. • Speciation can also occur as a result of other microevolutionary processes • Natural selection, genetic drift, and – Genetic drift can contribute to divergence. – Mutation • Gene flow counters divergence

Mechanisms of Speciation

• Speciation in geographically isolated populations. • Allopatric speciation • Probably most common mechanism. • • Some sort of barrier arises and prevents gene flow. • • Effectiveness of barrier varies with species.

14 Extensive Divergence Vicariance & Dispersal Prevents Inbreeding Vicariance: • Species separated by geographic • Populations can be separated by some barriers will diverge genetically. geographic change, like a river or a range. • If divergence is great enough it will prevent inbreeding even if the barrier Dispersal: later disappears. • Subpopulations can leave a population for a new habitat – migration to an island.

Allopatric Speciation Rainbow wrasses in Wrasses • arose and separated wrasses in Atlantic and Pacific.

• Since separation, for certain enzymes have diverged in structure.

• Divergence may be evidence of speciation in progress.

Allopatric Speciation Archipelagos

• Island chains distant from continents. – Galapagos Islands Ammospermophilus Ammospermophilus harrisii leucurus – Hawaiian Islands • Colonization of islands followed by genetic divergence sets the stage for speciation.

Grand Canyon, Arizona

15 Allopatric Speciation Hawaiian Islands on an Isolated Archipelago • Volcanic origins, variety of .

Physical barrier prevents • Adaptive : gene flow between – Honeycreepers - In absence of other bird populations of species species, they radiated to fill numerous niches. – Fruit flies () - 40% of fruit fly species are found in

Figure 17.20 from page 275 of your text

Allopatric Speciation in Allopatric Speciation Hawaiian Honeycreepers in Hawaiian Drosophila

• New arrival in species – Poor habitats on an isolated Archipelago – Start of allopatric speciation

Figure 17.7 from page 265 of your

Galapagos Islands Galapagos Islands

16 Darwin’s finches Speciation without a Barrier

•Example of dispersal • Sympatric speciation allopatric speciation. – Species forms within the home range of the •Example of adaptive radiation. parent species.

• Parapatric speciation – Neighboring populations become distinct species while maintaining contact along a common border.

Sympatric Speciation in Sympatric Speciation

African Map of Lake Barombi Mbo in Cameroon, West Africa

• Studied fish species in two lakes – Species in each lake are most likely descended from single ancestor. Nine kinds of cichlids evolved in • No barriers within either lake. this isolated crater lake • Some ecological separation but species in each lake breed in .

Parapatric Speciation Possible Evolution of Wheat

Adjacent populations evolve into BULLOCK’S BALTIMORE distinct species ORIOLE ORIOLE Triticum Unknown T. turgidum T. tauschii T. aestivum monococcum species of (wild emmer) (a wild (one of the (einkorn) wild wheat CROSS-FERTILIZATION, relative) common while maintaining FOLLOWED BY A bread SPONTANEOUS wheats) contact along a common border DOUBLING 14AAX 14BB 14AB 28AABBX 14DD 42AABBDD

HYBRID ZONE

17 Barriers to Gene Flow Gradual Model

• Whether or not a physical barrier • Speciation model in which species emerge through many small morphological changes deters gene flow depends upon: that accumulate over a long time period – ’s mode of dispersal or locomotion • Fits well with evidence from certain lineages – Duration of time organism can move in fossil record

Punctuation Model Punctuation Model

• Speciation model in which most changes in morphology are compressed into brief period near onset of divergence

• Supported by fossil evidence in some lineages

Evolutionary Rates We’re All Related

• These two models illustrate that evolution does not proceed at a • All species are related by descent constant rate. • Evolutionary rates may be lineage • Share genetic connections that extend dependant, environmentally dependant back in time to the prototypical or a combination of both.

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