Zoology 403 Notes Week 2 PDF

**[Lecture 2 Monday September 9th, 2024 - Vertebrate Development ]** Lecture 2: Vertebrate Development Synapomorphies/apomorphies see d2L post to take notes - - - Learning Objectives By the end of this lecture, you will be expected to be able to: 1. 2. 3. 4. [Why are we talking...

**[Lecture 2 Monday September 9th, 2024 - Vertebrate Development ]** Lecture 2: Vertebrate Development Synapomorphies/apomorphies see d2L post to take notes - - - Learning Objectives By the end of this lecture, you will be expected to be able to: 1. 2. 3. 4. [Why are we talking about vertebrate development?] -Why talking about dev not dev bio course, in image, all same stage dev most vertebrate groups, hard to tell which vertebrate groups are which in early stages further into dev some more differentiation amphibian like org - [The steps of early vertebrate development:] 1. 2. 3. 4. 5. 6. \*Note: after gastrulation, steps can blend together -Gen 6 steps for all vertebrates - - - - 1.  -Gastrulation 1st stage: Diff fish amphibians compared to rest of vertebrates b/c gastrulation takes place in spherical form, state of gastrula, it maintains spherical shape as goes through estab of 3 diff germ layers -Result of involution invagination of cells come around enter through indentation then eventually form 3 diff germ layers ectoderm outside, mesoderm middle part and endoderm inside \*Note notochord already present this part in time, pay attn to apical portion for neurulation -Vid d2l (take notes), shows how go from single cell to multiple cells then really quick involution of cells to form gastrula -For gastrulation for the rest of vertebrates, we exist as thin plate embryo, at this stage of dev single layer of cells - - - 2. Stage 2: Fish and amphibian apical portion, still looking at plate of cells but a few diff layers ectoderm mesoderm and endoderm, positioning still same in relation to amphibians and fish  -There's a notochord but where's dorsal hollow neural tube? - forms as result of ectoderm folding in on itself -Folding ectoderm, pinches at apical portion and hollow tube forms (dorsal hollow nerve cord/tube) - -Dorsal stiff notochord very inflexible, if put that as controlling factor into plate, adds weight and releases signaling molec to inform ectoderm to do this process -notochord is behind folding of ectoderm to form neural tube (pulls down + releases signaling molec allows to fold in on itself allows for closure), and then neural tube folds off of ectoderm so now its own character - [What do germ layers make?] -Now that we have pre germ layers and dorsal hollow nerve tube, imp to understand what germ layers are making  -Ecto: a few specific characters, skin feather scales and teeth (ectodermal organs for the reasons that derived from ectoderm outside of body) - - -Meso: this germ layer contrib to a lot - subdivision of this germ layer allows for many characters to form - - - - - -Endo: Contrib to resp and circulatory/urinary repro system a bit, and makes germ line going to go into gonads - 3.  -Next step = division of mesoderm, imp germ layer in terms of what making and supplying result of division and subdivision -First Layer subdivision mesoderm: neural tube notochord now mesoderm middle layer split into 3 diff components: - - - - - - 4. -Form in anterior to posterior fashions - head of dev vertebrate and tail, forms as little blocks beside neural tube and form in weight model on timer of formation -When somites form, start subdividing even further, division of somites = division into dermatome, myotome, and sclerotome - - - - 5.  -Formation of body cavities very imp: while somites continue on in somatogenesis, formation of cavities that hold viscera or guts -What happens during somitogenesis to lateral plate mesoderm is that it's folding down and surrounding endoderm becomes gut tube, lateral plate has folded down and started to encompass gut -Later in dev sep of lateral plate from dermatome and myotome that come up and form muscles around body cavity, but lateral plate is already forming around gut - -How this happens is 2 diff layers of lat plate mesoderm, 2 sides to this, fold together and fuse - - - - - 6. -Last stage neural crest migration, concerted things happening throughout period of dev of vertebrates, not that each one is happening in sequential steps, lots intermixed relative to how interacting w/ each other -What happened to cells resulting from of neural tube - neural crest cells after fusion of ectoderm to form epidermis, cells no longer interacting w/ each other - - -Neural crest forms a bunch of diff tissues throughout body b/c now mesenchymal ability can migrate to wherever in body to supp certain characters - - - - - [Neural Crest Derivatives ]  -Pharyngeal arches are neural crest derived, formed from neural crest but also help it -All arches are derived from neural crest w/ out formation neural crest to form arches no imp migrations into front of face to form vertebrate face has to be in place for this to happen in dev, if change one small thing, cascade of events leads to new adaptation or new organ character evolved [How is it all organized? ] -Vertebrate dev stages, how does this happen? - comes down to specific type of genetic dev element related to homeobox domains -Definition: - - - -What happens if one of genes go wrong? - where we get homeotic mutants - -Hox genes = subset of homeobox genes that organize body plan using homeobox controlled transcription factors [Application to Vertebrates]  -Hox genes = reason we have limbs: - - - -Also hox code teeth - in dev of teeth pre set out code if have certain transcription factors operating get molar/premolar if only these ones operating, or while these ones are working others aren't - - -Jaws: Hox gene expression only exists in the last 5 gill arches, 7 in total - the first 2 form upper and lower jaw - - - - **[Lecture 3 Wednesday September 11th, 2024 - Cyclostomes (Jawless fish)]** Lecture 3: Jawless fish [Learning Objectives] By the end of this lecture, you will be expected to be able to: 1. 2. 3. 4. -1st Groupings within vertebrates specifically - cyclostomes hagfish and lampreys, higher order classification Cyclostomata, if use cyclostomes lowercase c - [Review of vertebrate phylogeny ]  [Why are cyclostomes known to be basal?] -Why placed at bottom of phylo tree of vertebrates, what makes them so basal? - lacked jaws and mineralized tissues - consid characteristic to define them for very long time, (in notes remove or, should be jaws and mineralized tissues), once get into other vertrbates start experimenting with jaws and mineralized tissues, long time characterized by lack of jaw (anapids), but revisited b/c makes no sense to name group based on what don't have, wishy washy in evo bio - - -  [What characters unite cyclostomes?] What defines the group if not united by lack of jaws and mineralized tissues ? - Synap: - - - - -  -In the image, Midline sxns, anatomy diff view median nostril hagfish in lamprey also consid nasal hypoxial duct - connected to organ of adenohypophysis homologue in later vertebrate of not quite adrenal gland but anterior pituitary gland already estab base of vertebrates ant pituitary, regulates many hormones like growth hormones, and kidney hormones, thyroid (like endostyle), set up hormone signaling operating in cyclostomes -Branchial pouches midline little ducts leading into midline gill struc - gill struc entirely cartilaginous no mineralized struc in cyclostomes once get to chondrichthyans will tweak definition a bit -Velum looks like epiglottis divides where water and food goes where digesting vs breathing goes, then larger aspects like tongue muscles lingual cartilage and keratinized teeth on tongue, both groups fxning in orienting rasping tongue relative to mouth to feed on prey items - [Myxiniformes: Hagfish anatomy ] -Some characters imp is degenerate eyes, don't really have eyes benthic ind live on sea floor and scavenge -Barbells: use as primary sensory struc on head, where brain is, direct connection to env like antenna -Singular semicircular canal to tell them where they are in space like your ears, relies on hair cells, imp in orientation and releasing signal which does neuron firing to tell where rest of body where it is oriented/positioned - - - - - - -Vary amt of gill openings Last character = single medial fin fused w/ caudal fin [Hagfish ecology ]  [Video] - benthic predators/scavengers, known for 2 characteristic predations of knotting and slime, don't have oral hood that lampreys do, can't suction on to predators can't latch on so characteristic behavioural motion called knotting knot themselves up releases tension to rip flesh off scavenged items - why did it do it in vid even though no prey? - could have been stress related b/c of observers, that's how they dev tension allowing them to rip flesh off -Other characters is slime - - - [Petromyzontiformes: lamprey anatomy ] -First unique characteristic of lampreys is the amt of fins have relative to other cyclostomes 2 dorsal fins and 1 caudal fin, also pair of fxnal eyes, what does this tell us about ecology, where situated in water column? - where light is, on that note w/ idea of light also have pineal eye - - - -Also 2 semicircular canals instead of 1 orientation now have horizontal one and vertical, efficient syst of moving head fwds signaling both canals, lateral side by side one vertical one horizontal to detect that -Also buccal funnel oral hood can suction onto prey items with [Lamprey ecology] -Ecology diff them from other cyclostomes (myxiniformes) - - - -  Also change position in H20 go from fresh to salt water imp b/c great lake syst from inland to outside, exact pattern/movement lampreys go through, when out here and adults getting ready to nest, go back up coast inland and lay eggs then eggs hatch, then juveniles, then move out, like what salmon do when migrate up river - [Aquatic Living: Salt \[ \] + diffusion ] -Salt water fresh water physiology, cyclostomes all live in water, one of challenges to life in water is salt \[ \] - - - [Osmoconformation ]  -In vertebrates in gen, gills typically evolve countercurrent exchanger which involves active transp - takes excess salt coming in and pushes salt out using ATP to do so, active transp against diffusion gradient to pump, opp in freshwater, active transp imp in consid ecology and metab in ecologies of vertebrates living in water - - - - - - - - - - - [Osmoregulation ]  -App to humans how do they apply to everyday life: - - - - - **[Lecture 4 Friday September 13th, 2024 - Gnathostomes ]** Lecture 4: Gnathostomes Learning Objectives By the end of this lecture, you will be expected to be able to: 1. 2. 3. -Note last lecture: \- Free living vs parasitic lamprey, correct in hypothesis that non parasitic lampreys that don't eat and more so repro, have a lower metab than those parasitic - - - -Also discussed keratin vs actual teeth mineralized feature and has to do w/ struc - - - - - -  -List of what changes in this transition: - - - - - - - -Dev of pared nasals: tricky in terms of dev of it, imp to understand why these innovations in gnathostomes occur - lots of it revolves around only a few things changing in dev/domino cascade effect of changing positioning of a few things, leads to certain things being able to migrate (neural crest cells), opens up new paths, so cells start interact diff ways, opens up characters - - - - - - - -  -Hox gene expression det where things are (first thing/step that changed to split nasal hypoxia placode into 2 nasal placodes and adeno hypoxia placode), same thing happens with jaws - change in hox gene expression changes position of things and allowing other dev characters to dev large morpho features like jaws and paired nasals - - - - - - - -Now that we paired nasals and jaw have a skull/bones but how do we build it? - we know it exists b/c lack of dev constraint hox genes thrown out window, but need to understand how skull forms -A few diff levels need to understand in terms of vertebrate skull - dev contributors to vertebrate skull - - - - - - - -1st type of bone = Dermal bone: - -Next type of bone = endochondral bone (within cartilage) - cartilage precursor forming, then the type of cell that comes and destroys cartilage (chondroblasts) comes in destroys cartilage so osteoblasts can come in and start populating the area w/ osteocytes, forming mineralized tissues/bones, imp to understand dermal vs endochondral ossification, dermal = just purely making cartilage/bones from osteoblasts making osteocytes, endochondral need both chondro and osteo portion of cells to work together in unison, endochondral = vast majority of skull, communication between chondral and osteo portions of cells = imp for formation of skull - -Every other part of skull = formed from endochondral bone -Endochondral mesoderm helps make up brain case whereas neural crest cells contrib to endochondral and some dermal bone  -Structural modules of vertebrate skull 3 diff portions 1. 2. 3. -  **Chondrocranium (Brain case):** [Dev contributors ] -Neural crest cells and mesoderm (orange blocks in skull image) [Bone types:] -What makes up the chondrocranium: endochondral bones [Fxn:] Chondrocranium forms brain case, cradle brain = situated in **Dermatocranium:** [Dev contributors ] -Neural crest cells for the most part [Bone types:] -Endochondral bones [Fxn:] -Forms covering of brain case, imp to know chondrocranium = more of cradle, dermato cranium forms roof over cradle and forms some portion of palate (upper portion of mouth) shows how relates to upper portion of skull **Splanchnocranium:** [Dev contributors ] -Diff from dermatocranium? - no mostly neural crest cells [Bone types:] -Both dermochondral and endochondral contribution [Fxn:] -Supports gill arches and throat [Qs:] -Brain case by itself not much roofing aside from nasals at front, lots of it is exposed, dermatocranium covers a large portion of it -Same thing as dura matter of human brain vs skull? - good connection in terms of naming, but dura mater = soft tissues 3 layers on top of dermatocranium -Yellow slide shows dev of paired nasals, shows how invasion of mesoderm helps form not only upper lip and some portion of jaw doesn't, if mesoderm helps form jaw, not nec contributing to actual bone but formation of it, not actual bone of it, invasion of mesoderm allows brain case to form w/ neural crest -Bone type means diff types of cell forming tissue: Ex osteoblasts and clasts contrib to dermal vs endochondral ossification - - - - -Can print off/highlight and colour to memorize bones of skull/sections and what forms what/functions 3 components need to know for part bone - - - -  -Now that we have a skull, Q is do all vertebrates have dermal bone mineralized as know it in our skeletons - answer is no - - -