ch 23 (chordates) and ch 24 (fishes)

name the 5 key characteristics for chordates

must be present during some point in development

• notochord → provides support in early development

• dorsal tubular nerve cord (our spinal cord) usually forms along notochord

• post-anal tail — humans have during early development

• pharyngeal pouches/slits → captures food

• endostyle (produces mucus to capture food) or thyroid gland (gland for hormone production)

describe urochordates (tunicates) larvae and adults and adult cephalochordates

urochordate larvae

• notochord

• dorsal tubular nerve cord

• post-anal tail

• pharyngeal pouches/slits

• endostyle or thyroid gland

urochordate adult

• lack some chordate characteristics (no notochord, or dorsal nerve cord)

adult cephalochordate

• has all 5 chordate characteristics

  • notochord

  • dorsal nerve cord

  • post-anal tail

  • pharyngeal slits

  • endostyle

what are protochordates?

includes the subphylums Urochordata (tunicates) and Cephalochordata (lancelets)

why are echinoderms said to have a common ancestor with chordates?

they are both deuterostomes

• shares similar embryonic development (radial cleavage)

• shared coelom structure

• genetic similarities

how might you illustrate that phylogenetic trees and cladograms do not necessarily represent a macroevolutionary relationship between organisms?

phylogenetic trees and cladograms only represent the branching order of common ancestry rather than specific physical transformations

• they often neglect the step-by-step process of macroevolution

what characteristics distinguish the hag fishes and lampreys (superclass agnatha) from all other fishes?

hagfish → eats dead organisms, uses a “knot” for leverage

lamprey → stone sucking (petromyzontidae)

they are both from superclass agnatha, meaning “jawless fish”

• has cartilaginous skeletons with no bone

• their feeding techniques

describe the life cycle of Sea Lamprey (Petromyzon Marinus) and the history (route) of its invasion of the Great Lakes

life cycle:

• eggs are laid in bottom of stream, lives 3-7 years in the soil as ammocoete larvae

• undergoes metamorphosis and emerges from soil

• migrates towards lakes, adult parasitic stage in lakes and ocean

• reproduces in streams, eggs laid in sandy bottom

they were originally in the Hudson River, followed Erie Canal (built early 1800s) over to Great Lakes

• first invaded Lake Ontario

between Lake Erie and Ontario is Niagara Falls — a natural barrier

• Welland Canal was built late 1800’s to bypass the falls, which allowed lampreys to travel to Lake Erie

controlled by: larvicides and sterile male release

what does Gnathostomata mean and who belongs to this group?

“Gnathostomata” → jawed fish (and tetrapods)

• includes class Chondricythes — cartilage+fish (sharks and rays)

give examples of chondricythes. why do sharks and rays have spiracles?

ex. sharks and rays (whale shark, hammerhead shark, manta rays, etc.)

they have spiracles for respiration

• water comes in, over gills, then leaves spiracles

• sharks that do not have spiracles have to keep moving to breath

  • ram ventilation → swimming constantly with open mouths to force water over their gills

describe the lateral line system and ampullary organs of lorenzini in sharks and explain their function

gnathostomata uses lateral line to sense vibrations and pressure (many fish have lateral lines)

• inside lateral line, there are neuromast cells

• capsules have mechanoreceptor hair cells that detect pressure changes in the water

• provides positional information — schools of fish use this to stay with the group

bioelectricity is sensed by ampullary organs of Lorenzini

• detects bioelectricity of other organisms

describe the various breathing mechanisms fish use

gills → water in mouth, over gills, out through opening of operculum (class Actinopterygii, subclass Osteichthyes)

• gill filaments contain lamella (increases surface area)

• blood flow and water flow are counter current

lungs (lungfish) → gulp air, store air, extract it from sac

• different from class Actinopterygii (ray-finned fish)

mouth (electric eel) → supplements oxygen from gills, gulps air, and extracts O₂ from air in mouth

skin (eel) → diffusion

swim bladder (in some its connected to esophagus (garfish))

explain the purpose and function of swim bladder in bony fish. how is gas volume adjusted in the swim bladder?

fish use swim bladder for neutral buoyancy (does not rise or sink) — remain stationary in water column

• swim bladder is impermeable to gas except at ovale and gas gland area

• without swim bladder, fish tissues denser than water → fish would sink

• maintains neutral buoyancy by increasing or decreasing the amount of gas to account for the pressure of the water around it

swim bladder allows fish to be same density as water

• to rise → increase gases

• to descend → decrease gases

how gas fills swim bladder:

• done through a capillary loop

• the gas gland produces lactic acid

• this decreases pH which affects O₂ affinity to Hb

• O₂ wants to leave blood and fill gas bladder

how gas is removed from swim bladder:

• open valves to ovale

• allows gases to diffuse to blood

what is meant by “counter current flow” as it applies to fish gills and compare concurrent and countercurrent flow in fish gills?

(be able to use an illustration to show how in countercurrent systems you maintain a concentration gradient that favors movement of oxygen from the water to the blood throughout the gill lamella)

countercurrent flow → water goes right to left, blood goes left to right in gills

• water loses O₂ as it travels

• blood always has less O₂ than water

• blood continues to pick up O₂ and gets to 100% saturation

• considered the most efficient of any other animal group

concurrent flow → blood and water both go left to right in gills

• about halfway, both become 50% saturated

• now, there is no diffusion gradient, and blood would not obtain more O₂

• so max oxygen saturation % is just 50%

what is meant by the term catadromous as opposed to anadromous?

types of migration

catadromous (eels) — (‘cata’ = down, ‘dromous’ = to run)

• live in freshwater and run down to ocean to reproduce

anadromous (salmon) — (‘ana’ = upward)

• live in saltwater and run upstream to reproduce

describe the following terms: oviparous, viviparous, and ovoviviparous and gravid, pregnant (correctly associate these two terms)

oviparous → egg-laying (the mode of reproduction)

• gravid → state of carrying developing eggs or young internally (associated with oviparous)

viviparous → live birth

• pregnant → specific period and process of internal development (associated with viviparous)

ovoviviparous → produces eggs, but retained in body until hatched and then give live birth (gravid)