LECTURE 18 STUDY GUIDE (CHORDATES/FISHES)

what is the phylogenetic relationship of the deuterostome phyla: echinodermata, hemichordata, cephalochordata, urochordata, and chordata?

infrakingdom deuterostomia

in which phylum are acorn worms classified?

hemichordata

where is the nerve cord(s) found in acorn worms?

• has ventral nerve cord (in all invertebrates)

• has a dorsal nerve cord (hollow in the area of the collar) (in all chordates)

what do acorn worms eat?

ingest sediments through their mouth (between proboscis and collar) and excrete mud tubes in their wake

in which phylum are chordates classified?

chordata

which four characteristics characterize chordates?

1. notochord

2. dorsal hollow nerve cord

3. post-anal tail

4. pharyngeal arches/slits or gill arches/slits

what is a notochord? what function(s) does it provide?

flexible rod that provides longitudinal support and elastic recoil during swimming

what happens to the notochord in chordates called gnathostomes?

articulating vertebrae/spine

what is the nerve chord in chordates?

• the dorsal hollow nerve chord is filled with CSF fluid

• forms during neurulation from dorsal ectoderm

• forms central nervous system: brain & spinal cord

how does the location of nerve cord in vertebrates compare to invertebrates?

• nerve cord is in the dorsal part in vertebrates

• nerve cord is in the ventral part in invertebrates

what function does a post-anal tail serve in basal chordates?

provide thrust during swimming

what function does a post-anal tail serve in more derived chordates?

• balance

• store food

• communicate

• deter aggressors

• attract mates

• thermoregulates

what role(s) does the collection of gill arches/slits in the pharynx serve in ancestral chordates and extant aquation chordates?

filter-feeding and gas exchange

which structures likely formed from some gill arches according to contemporary theory?

jaws and other structures

why are lancelets considered chordates?

• has a notochord

• has dorsal hollow nerve cord

• has a pharyngeal slits

• has post-anal tail

what subphylum are lancelets in?

cephalochordata

why are lancelets not considered vertebrates?

lack a backbone

how do adult lancelets feed?

sessile filter feeders

what is the path of water in a lancelet?

cilia move water into mouth —> pharynx —> gill slits —> atrium —> atriopore —> outside bodyw

what is the path of food in a lancelet?

food is trapped on mucus-covered pharyngeal arches —> digestive tract

what are oral cirri used for in a lancelet?

deters large items from entering the mouth

are lancelets monoecious or dioecious?

dioecious

do lancelets use internal or external fertilization?

external fertilization

why are tunicates considered chordates?

• has notochord

• has dorsal nerve hollow nerve cord

• has pharyngeal gill slits in larva and adult tunicates

why are tunicates not considered vertebrates?

does not have a backbone

how do adult tunicates feed?

marine filter feeders

what is the morphology of larval tunicates?

• has a notochord

• has post anal tail

• has a dorsal hollow nerve cord

• has pharynx slits

what is the morphology of adult tunicates?

• only has a pharynx with numerous slits

• has no notochord or post anal tail

• has no dorsal hollow nerve cord

which name is given to larval tunicates?

tadpole

are tunicates monoecious or dioecious?

monoecious and uses cross-fertilization

what subphylum are tunicates and salps in?

urochordata

what are the characteristics of taxa in the subphylum vertebrata?

• has cartilaginous/boney skull

• has vertebrae that usually forms a spine or backbone

how many HOX gene clusters do they possess?

has at least two

how does the number of HOX gene clusters compare in invertebrates?

invertebrates have one HOX gene clusrer

what is significant about increasing the number of HOX gene clusters?

more control over genes expressed meaning new features can be expressed due to mutation

which other characteristics do vertebrates possess?

• greater musculature/higher metabolic rate

• peristalsis hearts with 2+ chambers

• closed circulatory systems

• RBC with hemoglobin

• kidneys

what are HOX gene clusters?

controls the spatial pattern of their development and neural crest tissue that forms a skull and peripheral nervous system (PNS)

how do taxa within the infraphyla agnatha and gnathostomata differ?

infraphyla agnatha are jawless while gnathostomata have jaws

what are examples of tax within each infraphylum?

infraphyla agnatha —> hagfish and lamprey

infraphyla gnathostomata —>shark, fish, frog, human

why are hagfish considered vertebrates?

• has a cartilaginous skull

• has a notochord

how do adult hagfish feed?

marine scavengers

uses bifurcates rasping tongue to feed off of fish/whale carcasses

locate food via four pairs of oral tentacles

what do hagfish use their slime glands for?

to foul predators gills

are hagfish monecious or dioecious?

monecious but become dioecious often serialy hermaphroditic

what development do hagfish undergo?

direct development

why are lampreys considered chordates?

• has a notochord

• has a small cartilaginous vertebrate

why are lampreys not considered gnathostomes?

they do not have jaws

how do adult lampreys feed?

attaches their buccal funnel and feed via hornified teeth and a rasping tongue

which term is given to lamprey larvae?

ammocoetes

many lampreys are anadromous. what does this mean?

move to ocean to grow/mature then adults swim upstream to mate

what is a buccal funnel?

circular, sucker like mouth

lampreys have hornified teeth. how do lamprey teeth compare to the teeth of mammals?

hornified teeth harden using cross-linked proteins

mammalian teeth harden through mineralization

our teeth arent as sharp

lampreys have a blind nostril. what functional role does a blind nostril have?

food and chemical detection

are lampreys monoecious or dioecious?

dioecious and uses external fertilization

what is a gnathostome?

vertebrates with a jaw and a mouth

which characters do gnathostomes have in addition the characters found in jawless vertebrates?

have jaws that likely modified gill arch supports

how do gnathostomes compare in the number of HOX genes?

gnathostomes have four HOX gene clusters that control the spatial pattern of their development

what do gnathostomes have in terms of brain, visual, and olfactory receptors?

has a more complex brains and better visual and olfactory receptors to help in predation/protection

what is a lateral line system in gnathostomes?

detects pressure waves

what is an ampullae of lorenzini in gnathostomes?

detects electrical fields

what does chondrichthyes mean?

cartilaginous fish

which body parts are mineralized in cartilaginous fishes?

teeth, vertebral articulation surfaces, and denticles on placoid scales

what are examples of animals in superclass chondrichthyes?

sharks, skates, rays, and rat fish

what kind of scales do chondrichthyes possess?

placoid

what is a denticle in chondrichthyes?

small tooth or tooth-like projection on scales

discern among the general pattern of fins in sharks, skates/rays, and rat fish

• have paired pectoral fins (anterior) and pelvic fins (posterior) which are used for lift or propulsion

• most have dorsal fins that stabilize swimming

  • the dorsal fin in ratfish is venomous and used in defense

• caudal fin is in stingrays and sharks

  • in sharks they move their caudal fin side to side for thrust

how does the diet of whale sharks compare to most other sharks?

they live off eating the smallest prey like plankton and gametes

what do sharks use their blind nostrils, ampullae of Lorenzini, and lateral line organs for?

to detect food

what role does the spiral valve (or ridge) serve?

increases retention time and surface area for digestion/assimilation

are sharks monecious or dioecious?

dioecious and sexually dimorphic

do sharks use internal or external fertilization?

internal fertilization

sharks are sexually dimorphic. how do you discern between a male and a female shark?

male sharks possess modified pelvic fins called claspers that are inserted into a female’s cloaca and sperm move through a clasper groove to the female

female sharks are oviparous and lay egg capsules with shark embryos inside called mermaid purses

why do sharks keep swimming?

to pass water over and aerate their gills

what muscles do sharks possess?

pharyngeal muscles which allow them to pulse water over their gills so they can rest like in whitetip sharks

what is an ovoviviparous shark?

mother shark retains her eggs in her body

the embryos feed off eggs and siblings

hatch then pass out her cloaca

what is a viviparous shark?

fed blood derivatives via a yolk-sac placenta (live birth)

what are examples of taxa within the superclass actinopertygii?

boney fish like ray-finned fishes and lobe-finned biota (coelacanths, lungfishes, and tetrapods)

how do their skeletons differ from cartilaginous fishes?

have a mineralized endoskeleton usually of calcium apatite

what do fish use their swim bladders for?

to aid in buoyancy

why are ray-finned fishes named ray-finned fishes?

rays of cartilage are found in their fins and with their fin modification it has allowed them to improve in swimming agility and may aid in defense

what organs do humans share in common with a trout?

• kidney

• heart

• liver

• stomach

• intestine

• anus

• nostril

• brain

• spinal cord

how many heart chambers do fish have?

two chambers

what is the general patter of blood circulation in a fish?

O2 poor blood from systemic circulation —> veins —> atrium —> ventricle —> artery —> gills to be oxygenated —> systemic circulation

which organs do fish use to exchange gases with their water?

gills

how does the counter current system for gas exchange work?

O2 diffuses from the water into blood
O2-poor arterial blood flows in opposition to water flow across gill filaments causing optimal diffusion

what other function do fish use their gills for?

excrete ions, NH4+, and to filter feed

discern between the osmoregulatory challenge of freshwater and marine fishes considering the movement of water by osmosis

• fish uptake or excrete ions and water across gill surfaces and via their kidney to regulate their ion/water balance

• freshwater fish gain water from their hypotonic environs which they then excrete excess water via kidneys

which organ is used to meet such osmoregulatory challenges?

gills

discern between the waste product from nitrogen metabolism in freshwater and marine fish

• most metabolize protein/nucleotides into NH3, a toxic waste product. excess H2O ionizes much to NH4+ and dilutes its concentration lessening its effect until excreted

  • freshwater fish use their kidneys to excrete excess water due to hypotonic environs

• marine fish live in hypertonic habitats so they must combat water loss and do not have the luxury of diluting their nitrogen waste products

  • many further metabolize NH4+ into less-toxic, more water-efficient urea but doing so requires more energy

how has the hydrology of nevada changed during the pass two million years?

nevada was covered in more water compared to now

how has this change impacted speciation in Nevada’s pupfishes?

large lakes have been reduced to small seeps which the pupfishes now reside in

some of nevada’s pupfishes are listed as endangered. what does that mean?

at risk of extinction