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Vertebrate Anatomy Exam I


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What is microevolution?
change in the genetic structure of population(s) over a “short” period of time
What are the necessary conditions for microevolution?
existing genetic variation for the existing trait (via mutations, recombinant, etc.)
Name three mechanisms of microevolution.
1. natural selection – the differential reproductive success of an organism within a population based on some genetic allele
2. bottleneck – very small population size causes loss of rare alleles; nonselective, just random – not related to genetically based trait
3. genetic drift – “founder effect” – only a few individuals move to separate location, limiting genetic variation
What is macroevolution?
evolution above the species level
How does macroevolution differ from microevolution?
1. More pronounced differences among organisms
2. Novel structures – things that don’t have obvious homology
3. Historically – long time
What are four mechanisms of macroevolution?
1. Gradualism – gradual accumulation of small changes
2. “hopeful monsters” – big mutation that occasionally results in an advantage
3. Novel structures
4. Selection at species level (i.e. extinction and rapiad speciation)
What is gradualism?
gradual accumulation of small changes
What are novel structures?
Gene duplication- allows additional sets to mutate w/o loss of original function
Changes in genes that regulate other genes
What is homology?
features in two or more organisms derived from a common ancestors
features of two or more organisms that perform similar function not derived from a common ancestor
evolutionary history of a group/groups of organisms; based on ancestor descendant relationships
summarize lineages by giving names that don’t necessarily have taxonomic rank – assign names to lineages based on phylogeny that constructs monophyletic groups
group of organisms
similarity that is related to function
represent the common ancestor
line of descent from an ancestor from any node
sister group
two lineages from a single node or common ancestor
What are the criterion of relatedness in a phylogeny?
recency of common ancestor; based on best available evidence about common ancestry of different taxa
derived character state
ancestral character state
shared, derived characteristics
shared unmodified character; unmodified ancestral state so all forms should retain ancestral form unless there is modification
Are synapomorphies informative for looking at relationships within that group? Why?
NO, because all members within that group should have that characteristic; need other characteristics to resolve relationships within that group
group with one evolutionary history/lineage; groups contain ALL and ONLY members of a lineage from a common ancestor
group has members from a different lineage (non-linear lineage)
group is missing some of its members
membrane-bound nucleus and organelles
must eat; no photo or chemasynthesis
bilateral symmetry
one plant that divides into mirror images; one head and one tail
radial symmetry
more than one plane of symmetry
true tissue
blastopore becomes anus; radial, indeterminate cleavage
axial rod situated on long axis of the body
what are some characteristics of a notochord?
- flexible – can bend but incompressible – “skeleton”
- not a huge part in all chordates, but in most adults there is remnants of its presence
- expressed at some stage of development
- bend side to side but cannot compress end-to-end; allows lateral motion
pharyngeal gill slits
occur at some stage in development in every chordate but don’t necessarily pierce the wall; originally used for filter feeding
post-anal tail
structure supported by the notochord or vertebrae past the anus
dorsal hollow nerve cord
located dorsal to notochord; brain and spinal chord; hollow space is fluid filled
notochord-like structure; more hydrostatic than notochord
homologous in form and function to the thyroid; iodine based organ
all cells in multicellular body derived from fertilized egg; haploid sperm and haploid egg
fertilized egg; diploid
mitotic divisions of the zygote
Describe the first 2 divisions of cleavage in deuterostomes.
Describe the 3rd division of cleavage in deuterostomes.
Describe cell division during the cleavage stage
cells divide without growing
ball of cells at the end of cleavage
hollow, fluid-filled space of blastula
forms when cells are so dense that only cytoplasm cleaves
rearrangement of cells in the blastula
What forms during the gastrulation stage?
- Formation of the archenteron – “primitive gut” – will become the digestive tract and associated structures
- Establishes germ layers – ectoderm, mesoderm, and endoderm
How are the steps of gastrulation achieved?
- Cell shape changes
- Cell surface contacts with extracellular matrix and with other cells
- Cell movements using pseudopodia
Describe the steps of gastrulation.
1. Displacement of blastoceol toward animal plane
2. Cells move inward over the dorsal lip of the blastopore
3. Cavity formed by invaginating cells = archenteron
4. Blastopore is retained – becomes anus
5. Blastoceol shrinks; ultimately lost
6. By end of gastrolation, embryo has three germ layers
cavity formed by invaginating cells (primitive gut)
What derives from ectoderm?
epidermis of skin, nervous system, neural crest and its derivatives
What derives from mesoderm?
notochord, dermis of skin, muscle, urogenital systems, components of skeleton, lining of coelom, heart and blood vessels
lining of gut, digestive glands, lungs
neural crest
a paired strip of tissue that separates from the dorsal edges of the nueral groove as it forms the neural tube
formation of the nerve cord; ectoderm is beginning to change, cells that become dorsal hollow nerve cord begin to form
What are the steps of nueralation?
1. invagination of neural plates – neural fold
2. neural tube detaches from overlying ectoderm
3. neural crest tissue adjacent to neural tube
4. neural crest cells migrate
more distinct clusters posterior to the head
What are the three regions of the somite
dermatome, myotome, and sclerotome
musculature of dermis of the skin of somite
paraxial muscles of somite
vertebrae of somite
region of the development of mesoderm – “paraxial mesoderm” – extends along the long axis of the embryo notochord
What are the regions of the epimere? Describe them.
- somatomers – clusters of mesoderm cells in the head
- somites – more distinct clusters posterior to head divided into dermatome, myotome, and sclerotome
gives rise to kidney structures
gives rise to the gonads
interactions among tissues to determine cell fate
What are some synapomorphies of vertebrates?
neural crest, placodes, “head”, muscular derivative hypomere, calcium phosphate, pronephros, eucoelomate, bilateral symmetry, eumetazoan
What characteristics define vertabrates?
eukaryotic, heterotrophic, multicellular, deuterostomes, notochord does not extend beyond brain, epidermal layer of skin is stratified (2+ layers of skin), bone (calcium phosphate) and/or cartilage, vertebral elements, cranium, nephron function of kidney, brain well developed, 10-12 pairs of cranial nerves, embryonic tissue – neural crest
What characteristics define Myxini?
jawless, no trace of vertebrae on or around their notochord, body fluid composition is similar to surrounding seawater
What major group constitutes myxini?
What synapomorphy defines gnathostomes?
jawed vertabrates
What characteristics define gnathostomes?
bony jaw, bones – calcium phosphate
Name the groups that constitute Gnathostomes.
placoderms, chondrichtyes, ancanthodii, osteichthyes, amphibia, lepospondyii, reptilia, aves, mammalia
What are the major characteristics that define chondrichthyans?
similar fin structures, cartilaginous skeleton, and pelvic claspers in males, placoid scales
What major groups constitute chondrichthyans?
Elasmobranches and holocephalans
What are the characteristics that define elasmobranches?
tooth replacement in most sharks, electric organs in some rays
What groups comprise elasmobranches?
sharks and rays
What are characteristics of holocephalans?
body does not end in an enlarged propulsive caudal fin; instead it is long and tapered to a point, operculum covers gill slits, scales are absent, males have cephalic clasper in addition to pelvic clasper
What is the major group that comprises holocephalans?
chimaera (ratfish)
What are some synapomorphies of teleostomes?
mouth terminal, narrow-based braincase, three otoliths in ear
What are the characteristics that define teleostomes?
jaw opening, gill cover (ossified), and gill flap (branchistegal rays)
What major grups constitute teleostomes?
bony fishes and tetrapods
What characteristics define acanthodians?
spiny on top and sides of body, each fin except the caudal fin was defined on its leading edge by a prominent spine that probably supported a thin web of skin, notochord served as major mechanical strength for the body, nonoverlapping scales, extinct
What are the synapomorphies of the group actinopterygians?
air bladder, vertebral development, brain development
What characteristics define actinopterygians?
ossified bone, most have swim bladder that provides neutral buoyancy, lepidotrichia (slender rods that provide internal support to fins), ray-finned fishes, fins supported by lepidotrichia, muscles that control fins are located within body wall, fins rays attached directly to limb girdles
What are the synapomorphies of sarcopterygians?
stylopodium: proximal element of limbs (humerus or femur or homologues)
What characteristics define sarcopterygians?
ossified bone, most have swim bladder that provides neutral buoyancy, lepidotrichia (slender rods that provide internal support to fins), paired fins rest at the ends of short, projecting appendages with internal bony elements and soft muscles; “fleshy-finned fishes” or “lobe-finned fishes” (lobe between fin rays and limb girdles; lobe is supported by stylopodium
What major groups comprise sacropterhgians?
coelocanth, lungfishes, rhipidistians (extinct)
What characteristics define temnospondyls?
extinct sister group to amphibians
What characteristics define lissamphibians?
sister group to temnospondyls, eggs lack shells and extraembryonic membranes are laid in water or moist locations, paired lungs, mucous glands of the skin keep them moist, and granular glands produce toxic or unpleasant chemicals, respire through their skin, have pedicellate teeth with a suture dividing the tooth base fro the tip and have auricular operculum (extra bone in ear)
What groups constitute lissamphibians?
frogs and toads (anurans), salamanders (urodeles), Caecilians
What are the characteristics of amniotes?
presence of membrane surrounding embryo (embryo enclosed inside an amniotic egg
What are the characteristics of sauropsids?
What groups constitute sauropsids?
– birds, dinosaurs, modern reptiles
What are the characteristics of parareptilia?
distinctive ear region where the eardrum is supported by the sqamosal and retroarticular process, the digits of the foot articulate with the ankle bones
What groups constitue parareptilia?
only extant are turtles (testudinata)
What characteristics define the group testudinates?
shell made up of a dorsal carapace of expanded ribs and surface skin plates and a connected ventral plastron of fused boney pieces
What characteristics define the group Eureptilia
two openings in temporal region of skull
What groups constitue Eureptilia
diapsida (archosaurs (includes birds) and lepidosaurs)
What characteristics define Archosaurs?
anteorbital foramen, trend towards bipedalism (two foot locomotion)
What groups constitue Archosaurs?
dinosaurs, birds, crocodiles and related groups
What groups constitute lepidosaurs?
snakes, lizards, and tuatara
What are the characteristics of birds?
members of archosaurs, lay eggs encased in shells, amniotes, capacity for flight, feathers, talons
What are the synapomorphies of synapsids?
features of skull and pectoral girdle
What are the characteristics of synapsids?
amnioties with a single temporal bar, transition from ectothermic to endothermic amniotes
What groups comprise synapsids?
Pelycosaurs, therapsids
What characters define the group pelycosaurs?
sail-backed reptiles supported by neural spines, extinct
What characteristics define the group therapsids?
most terrestrial group, greater diversity in ody design, quadrupedal and had five digits on feet, legs positioned directly under body, specialized teeth, became endothermic
What are the characteristics of mammals?
– hair, mammary glands, endothermic, nourished from birth from milk secreted by mothers, sebaceous and sweat glands, anucleate red blood cells, large brain in comparison to body size, maintenance of high body temperature
What are the characteristics of montremes?
hair, suckle their young, are endotherms, embryos are developed in shelled eggs
What are the characteristics of marsupials?
tiny young are born at an early developmental stage, pull themselves into their mother’s pouch, and suckle there until considerable larger
What are the characteristics that define placental mammals?
nutritional and respiratory needs of young are provided through placenta
What are the characteristics of deuterostomes?
indeterminate/radial cleavage, blastopore becomes anus (1st opening is anus, 2nd opening is mouth)
What groups constitute deuterostomes?
echinoderms, hemichordates, chordates
What are the characteristics of echinoderms?
body symmetry is radial, adults have no head and are relatively sessile, larva have head and are free swimming
What groups constitute echinoderms?
sea stars, sea cucumbers
What are the characteristics that define protosomes?
determinate cleavage, blastopore is mouth
What are the characteristics that define cephalochordates?
notochord extends entire length, gill slits, dorsal nerve cord, post anal tail, endostyle, circulation (but no heart), midgut cecum (precursor to liver and pancreas)
What are the characteristics that define urochordates?
sessile as adults, more like other chordates as larva, , filter feeders as adults; AS LARVA: notochord, dorsal hollow nerve cord, post anal tail, endostyle, pharyngeal gill slits; AS ADULTS: pharyngeal slits and endostyle
What groups constitute urochordates?
sea squirts, larvacea, thaliacea
What are the characteristics of hemichordates?
gill slits, nerve cord region – dorsal hollow only in part, but no notochord, no post anal tail, and no endostyle; larval form very similar to echinoderm larval form (molecular evidence suggest a strong relationship)
What group constitutes hemichordates?
acorn worm

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