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what is an example of homologies?
vertebrate limbs
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homoplasies
- bird and bat wings, thylacine and timber wolf, nubian vulture and turkey vulture
- panda's thumb
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how to determine if it is homologous?
- same fundamental structure
- same relations to surrounding bones
- same embryonic development
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what is the difference between ancestral and derived homologies?
- one is present in common ancestor and one evolved after
- the distinction is called character polarity
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what is the common ancestor of whales?
pakicetus
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cladogram
diagram used in cladistics to show relations among organisms
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phylogram
the evolutionary history of a group of organism, length of branch indicates amount of evolution
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what are three main statistical technique
- unrooted tree
- principal of parsimony
- principle of max likelihood
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principle of max likelihood
the most likely phylogeny is the one that has the highest probability of having produced the observed sequences
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what is population genetics
study of patterns of genetic variation
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if population is fixed for an allele, what does it mean
when population exhibits only one allele at a particular gene
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allele frequency
- relative frequency at a particular locus
- fraction
- it is the fraction of all chromosomes in the population that carry that allele
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what is evolution
change in allele or genotype frequency over time.
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what is balancing selection
acts to maintain two or more alleles in a population
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does genetic drift lead to adaptation why?
the alleles whose frequencies are changing are not affecting an individuals ability to survive or reproduce
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what does adaptive radiation result from?
- diversity of resources
- natural selection accelerates the rate of speciation and adaptation
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how can speciation occur without natural selection?
by genetic drift
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paraphyletic
includes some but not all descendants of common ancestor
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what its the closest relatives of four legged land vertebrates
fish
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characteristics of tiktaalik
fins, gills, scales (fish), but skull was flat,functional neck and ribs
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synamorphy
shared by two or more taxa and present in most recent ancestor
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eusthenopteron
first bits of our upper arm and leg
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first true finger and toes, lacked wrist
amphibian acanthostega
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ichthyostega
flat skull (amphibian, beginning to walk on land), transitional between fish and tetrapods
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when are genetic switches that make fingers, arm bones and toes do their thing?
during 3-8th week after conception
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what is zone of polarizing activity
- patch of tissue that causes pinky side to be diff from thumb side
- when removed or injected with vitamin A creates mirror image of duplication
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what genes in flies make one body segment look different from another?
- hedgehog gene
- sonic hedgehog gene (chicken)
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what is the difference in teeth in carnivores vs. plant eaters
- carnivores have blade like molars (cut meat)
- plant eaters: flatter teeth (macerate leaves)
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what is the mineral that makes enamel hard?
hydroxyapatite
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what is different about us and reptile teeth?
reptiles change teeth all the time
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where is tritheledont found and what is it?
- nova scotia
- between mammal and reptile
- starts to show teeth in front is different from back
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what are actually conodonts
- most common fossil between 500-250 MYA
- teeth of ancient jawless fish (no hard bones)
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lampreys
very primitive fish with no jaws, made living by attaching to other fish and feeding on their bodily fluids
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first animal with bony heads
- ostracoderms
- head, covered by teeth
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simplest cranial nerve
attach to one muscle or organ
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cranial nerve
nerves that supply the muscles
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trigeminal nerve
control muscles and carry sensory info from our face to our brain
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otx gene
active in front where first gill arch forms
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amphioxus
- dichotomy between vertebrates (notochord and nerve cord) and invertebrates (worm)
- closest relatives to animals with heads (worms with gill slits)
- 530 million years ago
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when does blastocyst attach to uterus so embryo can join bloodstreams
6th day
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what are the features of tube within a tube arrangement shared by
all animals with backbone four weeks after conception
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major difference between human and shark
humans' first arch forms some ear bones, we do not see in sharks
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important patch of tissue containing all info for cell to develop was
- the organizer
- noggin was another example
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until what month is the earth dominated by single cell microbes
june
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where was the most primitive versions of our body plans from?
sea anemone
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teeth, cartilage, bone which is hardest
teeth, bone then cartilage
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martin boraas
single cell alga, introduced predator, then alga evoked to form 8 cells
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what is the closest microbe relatives of animals with bodies like sponge and placozoans?
choanoflagellate
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what constitutes tree bodies
have molecular rivets (hold them together) and cell communication tools
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what is the most common protein in animals
collagen
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after how much time are we tube within a tube and have three germ layers
fourth week after conception
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how many sets of hox genes does humans have
four
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which part of ear is most ancient and sends nerve impulses to our brain?
inner
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what are we humans trading smell for?
sight
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what have whales and dolphins traded olfactory genes for?
breathing ones
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most primitive fish alive on planet today (jawless, single nostril), have both air and water smelling genes
lampreys and hagfish
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how much does light sensing cells make up in the sensory genes
70%
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what is opsin used for?
convey info from outside to inside of cell
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camera like eye is common to what
every creature with a skull
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how can we see rich colors?
we have more color receptor
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how did our eye color increase congruent with evolution
diversification of forests 55 million years ago
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Aniridiae
miss large pieces of their eyes
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pax6
eyeless gene in mouse
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