Lecture #3 Origin of Species Cartoon gentleman and

Lecture #3  Origin of Species Cartoon  gentleman and

Lecture #3 Origin of Species Cartoon gentleman and ape 1 Key Concepts:

Species concepts Development of reproductive isolation Patterns of speciation Macroevolution Human evolution Evolution continues.. 2 My pet

peeve is. specie Species is both singular and plural 3 Major Species Concepts Biological Morphological Phylogenetic

Diagram variation in beaks between species 4 Biological species the basic standard for separating species (Ernst Mayr, 1942) Species are defined by natural reproductive isolation

Individuals that can produce successful offspring are considered the same species Image Sarracenia rubra Image Sarracenia flava 5 Critical Thinking Biological species are defined by natural reproductive isolation

Individuals that can produce successful offspring are considered the same species Definition doesn't always work why not??? 6 Critical Thinking Biological species are defined by natural reproductive isolation Individuals that can produce successful offspring are considered the same species

Definition doesn't always work Speciation often occurs as the gradual divergence of multiple populations Fuzzy boundaries during divergence Also, cant be used to classify extinct species 7 Morphological species the first way to

separate species (Linnaeus, ~1750 & others) Species are defined by differences in form Individuals with the same morphology and/or anatomy are considered the same species Image Hymenocallis coronaria Image Hymenocallis floridana 8

Critical Thinking Morphological species are defined by differences in form Individuals with the same morphology and/or anatomy are considered the same species Definition doesn't always work why not??? 9 Critical Thinking Morphological species are defined by

differences in form Individuals with the same morphology and/or anatomy are considered the same species Definition doesn't always work Some species have a lot of natural phenotypic variation But, the only way to classify extinct species and species that lack sexual reproduction Also important in describing new species

10 Phylogenetic species the new standard for separating species??? Species are defined based on evolutionary history Species defined by the smallest monophyletic group in an evolutionary tree Monophyletic = lineage is derived from a common ancestor Definition doesn't always work

Dont have good phylogenies for all species or groups Also, imperfect agreement on interpretations 11 Development And Maintenance Of Reproductive Isolation: the essence of speciation It is generally accepted that natural reproductive isolation defines and preserves separate species in sexually reproducing organisms

What constitutes a barrier to reproduction? How do reproductive barriers develop? 12 Pre-zygotic Barriers Remember, the zygote is the fertilized egg cell The first cell of the new offspring Pre-zygotic barriers prevent the formation of the zygote Natural, evolved incompatibilities prevent successful fertilization

Habitat isolation Behavioral isolation Temporal isolation Structural isolation Chemical isolation Image blue-footed boobies mating behavior 13 Critical Thinking

Natural, evolved incompatibilities prevent successful fertilization Think of some examples of: Habitat isolation Behavioral isolation Temporal isolation Structural isolation Chemical isolation Euphorbia in very xeric habitat

14 Critical Thinking Habitat isolation different ecological niches Behavioral isolation changes in mating behaviors. Temporal isolation the timing of reproductive events Structural isolation mutations that change morphology of reproductive structures Chemical isolation gametes must be

compatible, pollen must match 15 Post-zygotic Barriers Post-zygotic barriers prevent successful development of offspring Hybrids dont develop properly Hybrids dont reach sexual maturity Hybrids dont produce viable gametes Hybrid lineages fail over time Natural genetic incompatibilities prevent

successful long-term reproduction Horse x Donkey = robust but sterile Mule 16 Critical Thinking The Darwinian fitness of an individual is measured by a. its ability to reproduce. b. how long it lives. c. the number of mates it attracts. d. the number of its offspring that survive

to reproduce. e. its physical strength. 17 Critical Thinking The Darwinian fitness of an individual is measured by a. its ability to reproduce. b. how long it lives. c. the number of mates it attracts. d.the number of its offspring that survive

to reproduce. e. its physical strength. 18 Patterns of Speciation Barriers result from separations that persist long enough that eventually new species have developed Diagram different species of fish in separated ponds 19

Patterns of Speciation Pattern depends on the mechanism of gene flow interruption Allopatric speciation occurs when populations are separated by a geographical barrier Sympatric speciation occurs in the absence of a geographic barrier 20 Critical Thinking

Allopatric speciation occurs when populations are separated by a geographical barrier Such as???? How could such barriers form??? 21 Critical Thinking Allopatric speciation occurs when populations are separated by a geographical barrier Such as rivers, canyons, mountains, oceans, glaciers..

How could such barriers form??? Diagram showing development of a canyon 22 Critical Thinking Allopatric speciation occurs when populations are separated by a geographical barrier Such as rivers, canyons, mountains, oceans,

glaciers.. How could such barriers form??? Geological processes Mountain building River erosion Glaciation Tectonic events Cave formation 23 Critical Thinking

Also. Climate changes that cause large lakes to dry up or form smaller, isolated lakes Colonization events that separate a group from the rest of the population (founder effect) 24 Allopatric Speciation Once populations are physically isolated, speciation may occur due to all the

evolutionary processes we talked about earlier Selection Drift Selective mating Mutation 25 Critical Thinking What if the isolated population is small??? What if the isolated population is from

edge of the range of the original population??? 26 Critical Thinking What if the isolated population is small??? Speciation is likely to occur more rapidly More genetic drift, less gene flow What if the isolated population is from edge of the range of the original

population??? 27 Critical Thinking What if the isolated population is small??? Speciation is likely to occur more rapidly More genetic drift, less gene flow What if the isolated population is from edge of the range of the original population???

It may be even more likely to diverge Probably already adapting to frontier or edge conditions Also, probably more likely to migrate 28 Birds???? Plants???? Allopatric Speciation due to geographic separation

Images different species of chipmunk on either side of the Grand Canyon 29 Speciation may, or may not, occur Diagram sympatric allopatric either sympatric again or not, as a population separates around a mountain range and then re-unites

30 Sympatric Speciation Occurs when a population becomes reproductively isolated without geographic barriers Mutations or selection pressures that lead to changes in behavior, habitat, food source, phenology. Errors in meiosis that lead to polyploidy (some plants can be selffertile, vegetative reproduction) Hybrids that develop into fertile

populations through vegetative reproduction or multiple events (mostly plants) Diagram sympatric speciation in a forest environment 31

Sympatric Speciation Occurs when a population becomes reproductively isolated without geographic barriers Mutations or selection pressures that lead to changes in behavior, habitat, food source, phenology. Diagram meiosis errors Errors in meiosis that lead to polyploidy (some plants can be selffertile, vegetative reproduction) Hybrids that develop into fertile populations through vegetative

reproduction or multiple events 32 (mostly plants) Polyploidy one mechanism for sympatric speciation Diagram errors in meiosis can lead to polyploids Some plants can self-pollinate, or vegetative 33 reproduction can produce multiple fertile individuals

Sympatric Speciation Occurs when a population becomes reproductively isolated without geographic barriers Mutations or selection pressures that lead to changes in behavior, habitat, food source, phenology. Errors in meiosis that lead to polyploidy (some plants can be

self-fertile, vegetative reproduction) Hybrids that develop into fertile populations through vegetative reproduction or multiple events (mostly plants) Image showing hybrid asters 34

Speciation is NOT a Given Must have an interruption to gene flow PLUS Must have enough change in the separated populations to produce a barrier to reproduction 35 Endemic Species and Adaptive Radiation Endemic species = restricted in distribution to a particular place, generally because they evolved

in place Volcanic island chains often contain many endemic species No biota until they were colonized by a few individuals (founder effect) These small populations then evolved into new species Allopatric speciation due to the geographic barrier from the founder effect But also

36 Endemic Species and Adaptive Radiation Many new species develop that are adapted to the diverse new habitats found in such islands Sympatric speciation No geographic barriers Adaptive radiation into new habitats Diagram showing adaptive radiation

37 Adaptive Radiation Galapagos finches and Hawaiian honeycreepers Diagrams adaptive radiation in birds 38 Adaptive Radiation is a common theme both between and within lineages

Diagram mass extinctions over the past 2.5 billion years Diagram diversification of mammals after extinction of the dinosaurs 39 Mass Extinction Events

Mammals Critical Thinking Humans have initiated a mass extinction event Will life cease to exist on the planet??? Can we destroy the planet??? 40 Critical Thinking Humans have initiated a mass extinction

event Will life cease to exist on the planet??? Highly unlikely There will just be a new set of species Can we destroy the planet??? 41 Critical Thinking Humans have initiated a mass extinction event

Will life cease to exist on the planet??? Highly unlikely There will just be a new set of species Can we destroy the planet??? Highly unlikely The earth has survived for at least 4 billion years! Species come and go. 42 Speciation is a Constant

When migration, isolation or other selection pressures force divergence, reproductive isolation can eventually lead to speciation Speciation might be gradual or abrupt (punctuated equilibrium) Transitions (either gradual or abrupt) may or may not be captured in the fossil record 43 Macroevolution: larger-scale changes in organisms

Also contributes to speciation Small, population-scale changes can accumulate Exaptations traits can be co-opted Feathers for thermoregulation feathers for flight Large phenotypic changes can result from small changes in regulatory genes Control over the timing and length of developmental events, or the spatial organization of body parts 44

Critical Thinking Was the evolution of the modern horse a series of directed events ???? Diagram phylogeny of the modern horse

45 Critical Thinking Was the evolution of the modern horse a series of directed events??? No, there are lots of lineages that are now extinct Evolution may look directed, but its not....

46 Selection is a series of gates!!! 47 A Preview of the Taxonomic Hierarchy: this is how we classify diversity Taxonomic Category Example (taxon)

Domain Eukarya = all eukaryotic organisms Kingdom Plantae, also Metaphyta = all plants Division (phylum) Magnoliophyta = all angiosperms

Class Liliopsida = all monocots Order Asparagales = related families (Orchidaceae, Family Orchidaceae = related genera (Platanthera,

Genus Platanthera = related species (P. ciliaris, P. Specific name/epithet ciliaris = one species Iridaceae, etc) Spiranthes, etc) integra, etc)

48 Images the yellow fringed orchid Platanthera ciliaris 49 Humans can also be classified! Domain eukarya Kingdom animal

Phylum chordates Image of human fossil Sub-phylum vertebrates

Class mammals Order primates Family hominoids Genus Homo Specific epithet sapiens 50 Phyla in the Animal Kingdom: Chordates This and next 6 slides show the phylogenetic placement of

humans in the animal kingdom 51 Sub-phyla in the Chordate Phylum: Vertebrates Sub-phylum 52 Classes in the Vertebrate Subphylum: Mammals

53 Close-up: Classes in the Vertebrate Sub-phylum 54 Orders in the Mammal Class:

Primates 55 Families in the Primate Order: Hominoids a monotypic family 56

Some key steps in the evolution of primates note that our last common ancestor with other modern primates was 6 to 10 MILLION years ago Loss of dinosaurs,

Rise of mammals Diagram showing the different orders of primates 57 Critical Thinking Is your uncle a monkey??? Cartoon showing gentleman and ape

58 Critical Thinking Is your uncle a monkey??? Of course not!!! Humans are NOT evolved from monkeys! Diagram showing phylogenetic relationships between primates 59 Monkeys, apes and humans share a common

ancestor, but have followed different evolutionary pathways for > 6 million years! 60 Two key steps bi-pedalism and large brain Diagram phylogeny of humans 61 Critical Thinking

Why is bi-pedalism so important? 62 Critical Thinking Why is bi-pedalism so important? Bipedalism functionally separates the limbs Legs for energy efficient walking and elevation of the eyes Arms for hunting, gathering, tool use, caring for offspring, artistic endeavors, etc. Current evidence is that this divergence began

6-10mya Complete conversion in hominids by about 2mya 63 Images human fossil and fossil footprints 64 Critical Thinking Why is a large brain so important?

65 Critical Thinking Why is a large brain so important? Large brain allows for complex thought, abstract reasoning, spirituality, creativity, language, complex tools Most of the traits that we consider uniquely human Larger brain began emerging about 2mya, stable for about 200,000 years 66

The fossil record shows changes in our species over time The path of human evolution is not ladderlike We are currently a mono-specific family, but. Human phylogeny reveals many extinct lineages We are animals We are subject to natural selection There is a record! 67

All but one lineage of hominids are extinct Diagram phylogeny of humans 68 Out of Africa Human Migration Diagram multi-regional vs. out of Africa hypotheses for human migration patterns; same diagram on following 2 slides 69

Critical Thinking How would you test these alternate hypotheses??? 70 Critical Thinking DNA evidence supports this

pathway 71 Evolution is a Constant Constant supply of genetic variation + constant application of selection pressures All species are in some degree of flux New species are constantly diverging .and going extinct At any given time, we are just looking at a

cross section of the process A slice through the crown of a multidimensional tree Evolution is NOT finished! 72 .as the tree grows, so grows the tree of life 73

Questions??? .as the tree grows, so grows the tree of life Key Concepts: Species concepts Development of reproductive isolation Patterns of speciation Macroevolution Human evolution

Evolution continues.. 74 Hands On Well be starting with plants next time Bring in samples of plants to examine microscopically and macroscopically Anything that interests you from nature, your kitchen, garden.. Parts or whole plants Save reproductive parts for later in the week

75

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