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Where did all the species come from?
Origin of Species Where did all the species come from?
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1) Macroevolution The formation of new taxonomic groups
Over immense time, organisms develop completely different body systems and physiology
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2) Microevolution – variations within a “type” genus or family
Minor changes within similar body systems and physiology
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3) Speciation Formation of new species of similar organisms that can reproduce with fertile offspring
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4) Anagenesis Linear evolution
The accumulation of changes in a population, transforming the population into a new species
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5) Cladogenesis Branching evolution
Two new species arises from a single species population Both species have same Common ancestor
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Barriers that isolate populations
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6) Prezygotic barriers Hinder or impede the formation of a zygote (sperm united with egg that starts to divide)
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7) Habitat isolation – (Ecological)
Two species live in different habitats even in the same area Ex. Water snake and land Snake
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8) Geographic isolation
Habitat isolation by barrier River Mountain
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9) Behavioral isolation
2 species may differ in signals used to attract a mate Ex. albatross
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Ex. Blue footed boobies Have very specific mating rituals
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Mating songs differ
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10) Temporal isolation Two similar species may mate at different times
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Cicadas can have different mating cycles of 13 years or 17 years
The different cycles can’t mate
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11) Mechanical isolation
2 species may be stopped from mating because they are anatomically incompatible
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Mechanical isolation in plants
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12) Gametic Isolation The egg and sperm of different species may not recognize each other
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13) Post Zygotic isolation
Prevent the hybrid zygote from developing into a viable, fertile adult
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14) Reduced hybrid viability
The hybrid fails to develop or to reach sexual maturity Mules Zorse
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15) Reduced Hybrid fertility
Hybrids are infertile
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16) Hybrid breakdown The offspring of hybrids are infertile or dead
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Some times “some” of the hybrid offspring are viable
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Alternate species concepts
Other than biological species concept (fertile offspring)
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17) Ecological species concept
Based on an ecological niche Includes asexual organisms
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18) Pluralistic species concept
Looks at all factors for different species
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19) Morphological species concept
Based on structural features
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20) Genealogical species concept
Based on genetic history
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Modes of speciation How species occur
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21) Allopatric speciation
Populations are geographically isolated Different environmental pressures cause variation and selection Ex. squirrels in grand canyon
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22) Sympatric speciation
No geographic isolation Populations together but diverge
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23) Adaptive radiation Diversity among a species with single ancestor
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24) Polyploidy More than 2 sets of chromosomes for a character
Causes more diversity
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25) Gradualism Many small changes
Each small change builds up to a major change over millions of years
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26) Punctuated equilibrium
Large sudden changes drastically change the population over relatively short time This is followed by long period of very little change
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27) Phylogeny, Systematics and Cladistics
Traces the evolutionary history of an organism
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28) Absolute Time The actual date or age of an object Example
Tree rings Carbon 14 dating dating – measuring radioactive particles
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29) Relative Time Determines relative age of fossil by the rock it is in comparing younger and older rocks in layers It is Not the actual age Ex law of superposition
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30) Geologic time – entire history of life on earth
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31) fossils Evidence of life in rock
can help tell us what geologic time period a rock is from
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32) Systematics The Science of tracing the Phylogeny
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33) Cladististics - Uses a cladograms for phylogeny – A branching diagram to show evolutionary relationships
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34) Vertebrate cladogram
Each juncture has a division point Out group – The First group to separate. Most like the common ancestor
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Invertebrate cladogram
Similar types will branch from same point
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Evolution of bird shown in cladogram
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Formation of Clads Clads are formed based on fossil evidence and suppositions by scientists In some cases the common ancestor exists. In many it has not been found so is inferred.
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How did a four chamber heart evolve
How did a four chamber heart evolve? Use to analyze two models of evolution A) bird/mammal homologous Clad immediate common ancestor, Reptiles _______ B) Bird/mammal analogous Clad, Reptiles ________ distant common ancestor Mammals and birds have 4 chambered heart. Reptiles have 3 ½ chambers
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