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31 Cards in this Set
- Front
- Back
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• Speciation
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o Origin of new species
o Appearance of new species is the source of biological diversity |
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• Microevolution
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o Changes confined to a single gene pool
o How adaptations evolve in a population |
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• Macroevolution
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o Refers to evolutionary change above the species level
o Instead of individuals, we’re talking about entire species o Ex: the evolution of fish to mammals o Ex: the evolution of dinosaurs to birds |
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• Anagenesis
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o Accumulation of changes that gradually transform a species into a species with different characteristics
o Ex: black butterflies evolve into white butterflies o Doesn’t give rise to biological diversity |
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• Cladogenesis
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o Branching evolution
o Splitting of a gene pool into two or more separate pools which each give rise to one or more new species o Only cladogenesis promotes biological diversity because it increases the number of new species |
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• Biological species concept
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o Emphasizes reproductive isolation
o A species is a population whose members have the potential to interbreed in nature and make viable fertile offspring but are unable to produce viable fertile offspring with other populations o Members in a species are united by being reproductively compatible o Concept cannot be applied to • Fossils • Asexual organisms • Organisms whose reproductive habits are unknown |
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• Reproductive isolation
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o Existence of biological factors that impede members of two species from producing viable fertile hybrids
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o Pre zygotic barriers
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• Habitat Isolation→ isolated by habitat (desert and rainforest)
• Temporal isolation→ breeding during different times of day, seasons, or years • Behavioral isolation→ having different courtship rituals • Mechanical isolation→ morphological differences make mating impossible (bird and a frog) • Gametic isolation→ when it’s impossible for a sperm to fertilize the egg |
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o Post zygotic barriers
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• Reduced hybrid viability→ when the offspring is weak and not viable
• Reduced hybrid fertility→ when the offspring is sterile • Hybrid breakdown→ when first generation hybrids are viable and fertile, but subsequent generations become weaker and more sterile |
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• Morphological species concept
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o A species is characterized by its body shape, size, and other structural features
o Can be applied to asexual and sexual organisms o Can be applied to situations where little is know about the population’s gene flow (aka. Fossils) |
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• Paleontological species concept
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o Focuses on morphologically discrete species known only from the fossil record
o You must use this concept with fossils b/c little is known about a fossil’s mating compatibility |
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• Ecological species concept
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o Views a species in terms of its ecological niche (its role in the biological community)
o Can be used with asexual and sexual organisms o Ex: there are two finches in the Galapagos with similar appearances, but one eats worms and one eats seeds |
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• Phylogenetic species concept
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o Defines a species as a set of organisms with a unique genetic history, as one branch on the tree of life
o Compares species with other species to distinguish where one species ends and the other starts compares species by their genes |
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• Allopatric speciation
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o Based on geographic isolation
o Gene flow is interrupted when a population is divided into geographically isolated subpopulations o Ex: squirrels isolated by the grand canyon evolved to have different appearances o Reduced gene flow and small populations are more likely to undergo significant changes in their gene pool in a short amount of time due to natural selection and genetic drift |
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• Sympatric speciation
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o Based on reproductive isolation
o Speciation takes place with geographic isolation (in geographically overlapping populations) o Happens b/c of polyploidy and nonrandom mating (both of which reduce gene flow) |
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• Polyploidy
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o Causes sympatric speciation
o Happens often in plants o Accidents during cell division result in extra sets of chromosomes which then make that plant unable to reproduce with other plants in its species (b/c their gametes have a different number of chromosomes) o The mutated plant can self fertilize with itself or fertilize with other mutated plants, thus reducing gene flow and creating a new species o Polyploidy can create reproductive isolation without geographic isolation, thus leading to speciation |
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• Autopolyploid
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o Individual that has more than two chromosome sets
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• Allopolyploidy
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o Hybridization between closely related species coupled with errors during cell division lead to fertile polyploid individuals
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• Habitat differentiation
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o Leads to sympatric speciation
o Reproductive isolation can occur when genetic factors enable a subpopulation to exploit a resource not used by the parental population |
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• Hybrids
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o Lead to sympatric speciation
o This happens mostly in plants o When two different species interbreed and produce a hybrid o The hybrid is sterile, but can fertilize itself asexually o The sterile hybrid becomes an allopolyploid in subsequent generations (a fertile polyploid) o Allopolyploids are fertile with each other but cannot interbreed with either parental species (they represent a new species) |
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• Non random mating
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o Lead to sympatric speciation
o When females select males based on appearance, this reduces gene flow and can lead to a splitting of the population o Mate choice based on coloration is a reproductive barrier that keeps the gene pools of two species of cichlids separate |
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• Adaptive Radiation
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o Evolution of diversely adapted species from a common ancestor upon introduction to various new environmental opportunities and challenges
o Ex: finches on the Galapagos→ all originated from one ancestor but branched out because of the environment |
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• Punctuated equilibrium
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o Periods of apparent stasis in the fossil record punctuated by sudden change
o Can be explained • Ex: if a species is alive for 5 million years but most of its morphological changes appeared in the first 1000 years of its life • It would appear in the fossil record as if the species didn’t change at all • Ex: if a species’ biochemistry evolves instead of its physical characteristics, that wouldn’t show up in a fossil record • Changes in behavior, internal anatomy, and physiology cannot be recorded in fossils |
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• Counter argument to intelligent design
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o Complex structures have evolved in increments from simpler versions that performed the same basic function
o It’s false to say that only complicated traits are useful o Ex: flagella example from dover documentary |
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• Heterochrony
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o Mutations in the genes that control an organism’s development can dramatically affect the organism
o Affects the evolution of morphology by altering the rates at which various body parts develop or by changing the timing of a particular part’s development o Ex: mutated genes that control the timing of the development of a salamander’s foot made the toes shorter for better traction o A small amount of genetic change can be amplified into substantial morphological change o Can also influence the timing of reproductive development relative to the development of somatic organs • Heterochrony can make an organism mature faster or slower • Ex: having a baby be sexually mature |
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• Paedomorphosis
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o Occurs when the rate of reproductive development accelerates compared to somatic development
o The sexually mature species can retain body features that were juvenile structures in an ancestral species o Ex: having a sexually mature baby |
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• Allometric growth
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o Proportioning that helps give a body its specific form
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• Homeotic genes
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o Determine basic features like where a pair of wings or legs will develop on a bird
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• Hox genes
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o Type of homeotic gene
o Provide positional information in an animal embryo o Mutations in Hox genes can have a profound impact on morphology o Ex: fish evolved into birds when four of the fish fins evolved into limbs o Ex: Hox genes provide positional information about how far digits and other bones should extend from the limb |
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• Evolution is not goal oriented
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o Organisms don’t evolve in a straight line, sometimes they evolve, sometimes they devolve, but overall they evolve in a certain direction
o Branching evolution can result in an evolutionary trend even if some new species counter the trend |
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• Species selection
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o The species that endure the longest and generate the most new offspring species determine the direction of major evolutionary trends
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