Vertebrate Anatomy Exam I
Terms
undefined, object
copy deck
- 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
- Analogy
- features of two or more organisms that perform similar function not derived from a common ancestor
- Phylogeny
- evolutionary history of a group/groups of organisms; based on ancestor descendant relationships
- Phylocode
- summarize lineages by giving names that don’t necessarily have taxonomic rank – assign names to lineages based on phylogeny that constructs monophyletic groups
- taxon
- group of organisms
- Homoplasy
- similarity that is related to function
- node
- represent the common ancestor
- lineage
- 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
- Apomorphy
- derived character state
- Plesiomorphy
- ancestral character state
- Synapomorphy
- shared, derived characteristics
- Synplesiomorphy
- 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
- monophyletic
- group with one evolutionary history/lineage; groups contain ALL and ONLY members of a lineage from a common ancestor
- polyphyletic
- group has members from a different lineage (non-linear lineage)
- paraphyletic
- group is missing some of its members
- eukaryote
- membrane-bound nucleus and organelles
- heterotrophic
- 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
- eucoelomate
- true tissue
- deuterostome
- blastopore becomes anus; radial, indeterminate cleavage
- notochord
- axial rod situated on long axis of the body
- what are some characteristics of a notochord?
-
- flexible – can bend but incompressible – “skeletonâ€
- 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
- stomochord
- notochord-like structure; more hydrostatic than notochord
- endostyle
- homologous in form and function to the thyroid; iodine based organ
- fertilization
- all cells in multicellular body derived from fertilized egg; haploid sperm and haploid egg
- zygote
- fertilized egg; diploid
- cleavage
- mitotic divisions of the zygote
- Describe the first 2 divisions of cleavage in deuterostomes.
- longitudinal
- Describe the 3rd division of cleavage in deuterostomes.
- equatorial
- Describe cell division during the cleavage stage
- cells divide without growing
- blastula
- ball of cells at the end of cleavage
- blastocoel
- hollow, fluid-filled space of blastula
- blastodisc
- forms when cells are so dense that only cytoplasm cleaves
- gastrulation
- 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 - archenteron
- 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
- endoderm
- 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
- neuralation
- 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 - somite
- more distinct clusters posterior to the head
- What are the three regions of the somite
- dermatome, myotome, and sclerotome
- dermatome
- musculature of dermis of the skin of somite
- myotome
- paraxial muscles of somite
- sclerotome
- vertebrae of somite
- epimere
- 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 - mesomere
- gives rise to kidney structures
- hypomere
- gives rise to the gonads
- induction
- interactions among tissues to determine cell fate
- What are some synapomorphies of vertebrates?
- neural crest, placodes, “headâ€, 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?
- Hagfishes
- 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?
- braincase
- 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