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BIOL3320 WK1
Ancient Fishes
| Term | Definition |
|---|---|
| What is Australia's extinction crisis? | Aus has worst mammal extinction rate anywhere; number of extinctions rise rapidly despite how endemic most of our species are |
| Which vertebrates dominate land mass? | people and their domestic livestock (cattle, sheep etc.) despite mammals only accounting for 8% of vertebrate species |
| What does anterior mean? | cranial so near the head |
| What does posterior mean? | caudal so near the 'tail end' |
| Dorsal vs. ventral | dorsal is on the 'back' usually closest to where spine is; ventral is opposite |
| What is the difference between morphology and anatomy? | Morphology is broader and refers to whole structures; anatomy more refers to specific cells or muscles |
| Words used to describe places on body in morphological sense: | distal, proximal, medial, lateral, superior and inferior (for humans) |
| Distal def | away from the centre of body or point of attachment |
| Proximal def | nearer to centre of body or point of attachment |
| Medial def | pertaining to the middle |
| Lateral def | pertaining to the side |
| Words used to describe places on body in anatomical sense: | central, peripheral, superficial, deep |
| Central def | pertaining to the middle, near, in |
| Peripheral def | pertaining to the side, far, out |
| Superficial def | something near the outer surface of the animal |
| Deep def | further away from the surface |
| What tetrapod features developed during fish evolution? | vertebral column (axial skeleton); cranial elements (skull); girdles and limbs (appendicular skeleton) |
| What organisms where present in the Precambrian stage? | only soft-bodied invertebrates, start of some hard-bodied invertebrates, around 600 mya |
| What happened in the Cambrian explosion? | was a time of rapid evolution and change, also radiation; first early chordates found around this time (fish-like organisms) |
| What are the basic features of the early chordate? | notochord; dorsal, hollow nerve cord; endostyle, pharyngeal slits, postanal tail; muscle segments, brain, mouth, anus |
| 3 basic steps in fish evolution? | 1. pre-vertebrate chordates 2. early vertebrates: Agnathans (jawless fishes) 3. Gnathostomes (jawed fish) |
| How did pre-vertebrate chordates feed? | suspension feeding using gills with cilia and mucus |
| How did Agnathans feed? | used pumping pharynx muscles in suspension feeding; had functioning gills; had diveristy of feeding models including filter and deposit feeding, mud grubbers, scoopers, scrapers etc. |
| How did Gnathostomes feed? | had hard parts around the mouth allowing for macrophagy (eating bigger prey) |
| What makes a true vertebrate? | 1. vertebral column 2. cranium 3. embryonic neural crest cells 4. epidermal placodes |
| What does the vertebral column have/do in vertebrates? | separates bones or cartilage blocks that gradually develop around the flexible, strong notochord and eventually replace notochord; intervertebral discs = compression pads; remnant notochord = gel core of discs between vertebrae (nucleus pulpsus) |
| What does the cranium have/do in vertebrates? | cartilaginous or bony box protects brain and (may have) sense organs |
| What do the embryonic neural crest cells have/do in vertebrates? | bone, pharyngeal arches, nerves, cartilage, connective tissues of some muscles, odontoblasts that form teeth |
| What do epidermal placodes have/do in vertebrates? | are thickenings of head epidermis that give rise to parts of the sensory system; sensory organs, some nerves |
| What happened in the phylogeny of ancient fishes? | all of the major fish groups were present by the Devonian stage but many of them started to die off; only 7 evolutionary lines of fishes are persistent today |
| What are conodonts? | slender soft-bodied vertebrates; no descendants; only appeared for short time then vanished; weird teeth found first; |
| What are agnathans? | jawless fishes; paraphyletic group (don't include all descendants); dominated for 100 million years; first fishes with bone formations on outside (cartilaginous skeleton, bony head shields and scales) |
| What is special about the bones in agnathans? | had outer dermal body armour and head shields; ; gave protection and stability; had surface sculpturing with perforations for sense organs |
| What is special about the heads in agnathans? | intricate sensory system; complex divided brain; earliest lateral line system (detect pressure changes); complex eye muscles; inner ear with 2 semi-circular canals (lined with cilia and filled with fluid, works as motion sensor) |
| What evolved and developed during agnathan evolution? | pectoral limbs (fins, early shoulder girdles); pharyngeal bars (putting structure around slits for breathing); ossified bone around eyes (taking on larger prey??) |
| What were the most primitive agnathans like? | eel-like; small head shield, flexible body armour; hypocercal tail, lift through flicks then sink to sea floor; potentially ancestral to lamprey; some had paired gill openings; flattened bodyq |
| What were the more advanced agnathans like? | developed paired fins (can swim around and maintain positioning in body of water); included osteostraci |
| Features of heterostracans | primitive bony plates; some with wing-like projections; single gill opening; some 'giants' up to 1m |
| Features of osteostracans | solid shield of advanced bone; paired pectoral fins and girdle; up to 10 pairs of gill slits; sclerotic bones around eyes; some with bony oral areas |
| Who are the two potential ancestors to jawed fishes? | osteostracans and thelodonts |
| Features of osteostracans that can link to jawed fishes | pectoral fins with shoulder girdle; cellular bone (external and internal); perichondral bone (around cartilage); 2 dorsal fins; epicercal tail (like sharks); slit-shaped gill openings; complicated ear; sclerotic bone around eyes (maybe precursors to jaws) |
| Features of thelodonts that can link to jawed fishes | stomach (macrophagous prey); broad-based fins; well-developed tail; scales similar to teeth of early jawed fishes ('nipple teeth'); denticles in pharynx |
| Why did most agnathans die out (theories)? | predation by jawed placoderm fishes; outcompeted by jawed fish (lighter, faster, jaws); small, benthic, limited feeding niches |
Created by:
tkeen40
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