Macroevolution Series of microevolution Speciation – the formation of new species when one ancestral species evolves more than 1 typical descendant. Since speciation occurs when one species evolves into more than 1 new species, it increases the number of species that exist.

Patterns of Macroevolution These are theories/models of evolution A. Mass Extinctions B. Adaptive Radiation C. Convergent Evolution D. Coevolution E. Gradualism F. Punctuated Equilibrium

Patterns of Macroevolution Species that are Unrelated Related form in under under in in Intense environmental pressure Inter-relationships Similar environments Small populations Different environments can undergo can undergo can undergo can undergo can undergo Convergent evolution Punctuated equilibrium Adaptive radiation Coevolution Extinction

Mass Extinctions Event in which many types of living things became extinct at the same time.  Period in which huge numbers of species disappeared. Whole ecosystems were wiped out Left habitats/niches open Resulted in burst of evolution of new species in new habitat Disrupted energy flow throughout the biosphere and caused food webs to collapse

Mass Extinctions Possible causes Asteroids hitting earth Volcanic eruptions Continental drift Sea levels changing http://images.google.com/imgres?imgurl=http://www.rosssciencesociety.org.uk/Past%2520Events/Past%2520E3.jpg&imgrefurl=http://www.rosssciencesociety.org.uk/Past%2520Events/Past%2520Events.htm&h=1024&w=1280&sz=91&hl=en&start=8&um=1&tbnid=o1POjijL8bK1pM:&tbnh=120&tbnw=150&prev=/images%3Fq%3Dmass%2Bextinctions%26svnum%3D10%26um%3D1%26hl%3Den%26rls%3DGGLB,GGLB:1969-53,GGLB:en%26sa%3DN

Adaptive Radiation The evolution of an ancestral species, which was adapted to a particular way of life, into many diverse species, each adapted to a different habitat Many new species diversify from a common ancestor . The branching out of a population through variation. The new species live in different ways than the original species did.

Adaptive Radiation http://cache.eb.com/eb/image?id=54911&rendTypeId=4

Convergent Evolution Opposite of divergent evolution (adaptive radiation) Unrelated organisms independently evolve similarities when adapting to similar environments, or ecological niches Analogous structures are a result of this process Example: penguin limb/whale flipper/fish fin The wings of insects, birds, pterosaurs, and bats all serve the same function and are similar in structure, but each evolved independently

Convergent Evolution

Convergent Evolution http://www.wasted-disk-space.com/2007/0825/P8257787-2.jpg http://en.wikivisual.com/images/2/24/Oceanic_Whitetip_Shark.png

Convergent Evolution Similar body shapes and structures have evolved in the North American cacti...and in the euphorbias in Southern Africa http://images.google.com/imgres?imgurl=http://www.micro.utexas.edu/courses/levin/bio304/evolution/convergent.ex1.gif&imgrefurl=http://www.micro.utexas.edu/courses/levin/bio304/evolution/macroevol.html&h=405&w=350&sz=115&hl=en&start=12&um=1&tbnid=FeV6DLuetThgTM:&tbnh=124&tbnw=107&prev=/images%3Fq%3Dconvergent%2Bevolution%2Bof%2Bcacti%26svnum%3D10%26um%3D1%26hl%3Den%26rls%3DGGLB,GGLB:1969-53,GGLB:en%26sa%3DN

Coevolution The mutual evolutionary influence between two species When two species evolve in response to changes in each other They are closely connected to one another by ecological interactions (have a symbiotic relationship) including: Predator/prey Parasite/host Plant/pollinator Each party exerts selective pressures on the other, thereby affecting each others' evolution

Coevolution http://www.zo.utexas.edu/faculty/sjasper/images/30.18.jpg

Coevolution Praying Mantis simulates plant to protect itself from predators and eats pests that are attracted to and feed on the plant, so it protects the plant. http://www.zo.utexas.edu/faculty/sjasper/images/30.18.jpg

Gradualism The evolution of new species by gradual accumulation of small genetic changes over long periods of time Emphasizing slow and steady change in an organism Occurs at a slow but constant rate Over a short period of time it is hard to notice

Gradualism http://www.critters-2-go.com/prehistoric/horse-evolution-species.jpg

Gradualism http://www.edwardtbabinski.us/whales/whales-graph.jpg

Punctuated Equilibrium Stable periods of no change (genetic equilibrium) interrupted by rapid changes involving many different lines of descent Opposite of gradualism It is rare, rapid events of branching speciation Characterized by long periods of virtual standstill ("equilibrium"), "punctuated" by episodes of very fast development of new forms

Punctuated Equilibrium

Gradualism or Punctuated Equilibrium

Why won’t our lungs evolve to deal with air pollution? Limits to adaptation: A change in the environment can only lead to adaptation for traits already present in the gene pool Reproductive capacity may limit a population’s ability to adapt If you reproduce quickly (insects, bacteria) then you can adapt to changes in a short time If you reproduce slowly (elephants, tigers, corals) then it takes thousands or millions of years to adapt through natural selection Most individuals without trait would have to die in order for the trait to predominate and be passed on

When faced with a change in environmental condition, a population of a species can: Adapt via natural selection Migrate (if possible) to an area with more favorable conditions (Mars & Atlantis?) Become extinct Natural selection can only act on inherited alleles already present in the population—do not think that the environment creates favorable heritable characteristics!

Three types of Natural Selection Directional Allele frequencies shift to favor individuals at one extreme of the normal range Only one side of the distribution reproduce Population looks different over time Peppered moths and genetic resistance to pesticides among insects and antibiotics in bacteria Stabilizing Favors individuals with an average genetic makeup Only the middle reproduce Population looks more similar over time (elim. extremes) Diversifying Environmental conditions favor individuals at both ends of the genetic spectrum Population split into two groups

Coevolution Interactions between species can cause microevolution Changes in the gene pool of one species can cause changes in the gene pool of the other Adaptation follows adaptation in something of a long term “arms race” between interacting populations of different populations The Red Queen Effect Can also be symbiotic coevolution Angiosperms and insects (pollinators) Corals and zooxanthellae Rhizobium bacteria and legume root nodules

Niches A species functional role in an ecosystem Involves everything that affects its survival and reproduction Includes range of tolerance of all abiotic factors Trophic characteristics How it interacts with biotic and abiotic factors Role it plays in energy flow and matter cycling Fundamental Niche Full potential range of physical chemical and biological conditions and resources it could theoretically use if there was no direct competition from other species Realized Niche Part of its niche actually occupied Generalist vs. Specialist Lives many different places, eat many foods, tolerate a wide range of conditions vs few, few, intolerant… Which strategy is better in a stable environment vs unstable?

Niche Overlap separation Number of individuals Generalist species Region of niche overlap Generalist species with a broad niche with a narrow niche Niche breadth separation Number of individuals Resource use

Competition Shrinks Niches

Key Concepts: A species consist of one or more populations of individuals that can interbreed and produce offspring Populations of a species have a shared genetic history Speciation is the process by which daughter species evolve from a parent species

Key Concepts: Geographic barriers can start the process of speciation Allopatric speciation With sympatric speciation, a species can form within the range of a parent species Parapatric speciation has adjacent populations becoming distinct species while still coming in contact along a common border

What is a Species? Morphological Species Concept Based on appearance alone Biological Species Concept A species is one or more populations of individuals that are interbreeding under natural conditions and producing fertile offspring, and are reproductively isolated from other such populations

Speciation Two species arise from one Allopatric Sympatric Requires Reproductive isolation Geographic: Physically separated Temporal: Mate at different times Behavioral: Bird calls / mating rituals Anatomical: Picture a mouse and an elephant hooking up Genetic Inviability: Mules Allopatric Speciation that occurs when 2 or more populations of a species are geographically isolated from one another The allele frequencies in these populations change Members become so different that that can no no longer interbreed See animation Sympatric Populations evolve with overlapping ranges Behavioral barrier or hybridization or polyploidy

Reproductive Isolating Mechanisms Any heritable feature of body, form, functioning, or behavior that prevents breeding between one or more genetically divergent populations Prezygotic or Postzygotic

Pre-Zygotic Isolation Mating or zygote formation is blocked Temporal Isolation Behavioral Isolation Mechanical Isolation Ecological Isolation Gamete Mortality

Post-Zygotic Isolation Hybrids don’t work Zygotic mortality - Egg is fertilized but zygote or embryo dies Hybrid inviability - First generation hybrid forms but shows low fitness Hybrid infertility - Hybrid is fully or partially sterile

Speciation Northern Arctic Fox Spreads northward and Adapted to heat through lightweight fur and long ears, legs, and nose, which give off more heat. Adapted to cold through heavier fur, short ears, short legs, short nose. White fur matches snow for camouflage. Gray Fox Arctic Fox Different environmental conditions lead to different selective pressures and evolution into two different species. Spreads northward and southward separates Southern population Northern Early fox

Allopatric Speciation Physical barrier prevents gene flow between populations of a species Archipelago hotbed of speciation

Allopatric Speciation New arrival in species Poor habitats on an isolated archipelago Start of allopatric speciation Hawaiian Honeycreepers

Sympatric Speciation New species forms within home range Polyploidy leads to speciation in plants Self-fertilization and asexual reproduction

Extinction The ultimate fate of all species just as death is for all individual organisms 99.9% of all the species that have ever existed are now extinct To a very close approximation, all species are extinct Background vs. Mass Extinction Low rate vs. 25-90% of total Five great mass extinctions in which numerous new species (including mammals) evolved to fill new or vacated niches in changed environments 10 million years or more for adaptive radiations to rebuild biological diversity following a mass extinction

Extinction in the context of Evolution If the environment changes rapidly and The species living in these environments do not already possess genes which enable survival in the face of such change and Random mutations do not accumulate quickly enough then All members of the unlucky species may die

Species and families experiencing mass extinction years ago Period Era Ordovician: 50% of animal families, Devonian: 30% of animal families, Permian: 90% of animal families, including over 95% of marine species; many trees, amphibians, most bryozoans and brachiopods, all trilobites. Triassic: 35% of animal families, including many reptiles and marine mollusks. Cretaceous: up to 80% of ruling reptiles (dinosaurs); many marine species including many foraminiferans and mollusks. Current extinction crisis caused by human activities. Species and families experiencing mass extinction Bar width represents relative number of living species Extinction Millions of years ago Period Era Paleozoic Mesozoic Cenozoic Quaternary Tertiary Cretaceous Jurassic Triassic Permian Carboniferous Devonian Silurian Ordovician Cambrian Today 65 180 250 345 500