Exam 1 Flashcards
What are the three subphyla of the phylum chordata?
- vertebrata
- urochordata
- cephalochordata
What 5 characteristics do all Chordata have?
- notochord
- dorsal hollow nerve tube (DHNT)
- pharyngeal gill slits
- postanal tail
- endostyle/thyroid gland
What is the notochord?
- flexible, rod shaped structure running from the head to the tail through the body
- major muscle attachment point
What does the notochord aid in?
- movement -> it controls forward movement and drives body into substrate
What is the dorsal hollow nerve tube (DHNT)?
The basis for the central nervous system (brain and spinal chord
What does the DHNT allow for?
Allows response to environment stimuli through increased sensory capabilities
What do the pharyngeal gill slits do?
- allow for “one way” flow of water
- used for filter feeding
- particles are captured through gill slits by mucus and cilia that line the structures. mucus then moves into the digestive tract
What does the muscular post-anal tail do?
- increases mobility
- allows for exploration of new habitats, new foraging opportunities, foraging success, and less predation risk
What does the endostyle/thyroid gland do?
Manages iodine metabolism
Why is it hard to tell how/when chordates rose in time?
We have a very limited fossil record. Early chordates were only composed of soft tissue which rarely fossilizes
What were the two fossils of early chordates?
Yunnanozoan lividum
Pikaia gracitens
Urochordata characteristics
- marine
- mobile larval stage (free swimming)
- filter feeders
Cephalochordata characteristics
- marine
- free-swimming filter feeders as they swim and when immobile in sands
What are the SEVEN living classes of vertebrata?
- Agnatha
- Chondrichthyes
- Osteichthyes
- Amphibia
- Reptilia
- Aves
- Mammalia
Class Agnatha consists of…
Jawless fish (hagfish)
Class Chondrichthyes consists of…
Cartilaginous fishes (sharks, rays)
Class Osteichthyes consists of…
boney fish
Class Amphibia consists of…
Amphibians (salamanders, frogs/toads)
Class Reptilia consists of…
Reptiles (crocodiles, snakes, lizards)
Class Aves consists of…
Birds
Class Mammalia consists of…
mammals
What are the TWO extinct classes of Vertebrata?
- Placodermi
- Acanthodii
Class Placodermi consists of….
Placoderms
Class Acanthodii consists of…
Spiny Sharks
What FOUR traits are shared by all vertebrates
- vertebral column
- cranium
- neural crest cells
- duplication of Hox gene complex
What is the vertebral column?
- rigid column of individual integrated vertebrae
- provides structural/stability for body and serves as support
- protects spinal chord and associated nervous system
What is the cranium?
- surrounds and protects the brain
- protective aspect, allows expansion for brain complexity
What are neural crest cells?
- They form when the DHNT sinks into the body, a layer of cells is pinched off, and then they migrate around the vertebrate embryo
- they drive formation of different cell types
What are Hox genes?
- “master genes”/blueprints of body plans
- serve as transcription factors
- drives changes/differences in body plan
How many hox-gene clusters do non-chordate phyla have?
1
How many hox-gene clusters do non-vertebrate chordates have?
1
What are the implications of Hox cluster duplication
As the hox numbers rise, it allows vertebrates to overcome genetic constraints of the body plan which allows for a rise in complexity of vertebrates
What what Garstang’s hypothesis on larval tunicates?
Larval tunicates face two opposing selective pressures that affect their likelihood of reproduction: competition and predation
What was the conclusion in saving larvae from predation and competition?
Garstang said one way to handle these competing pressures was to develop mature gonads while retaining the ability to keep swimming
What did Gans and Northcutt believe?
That neural cells drove transition to modern vertebrates
What did the NCC do for modern vertebrates?
- provided flexibility in the body
- increased sensory complexity
- larger brains
- developed jaws/teeth
- powerful pumping throats
What do powerful pumping throats do?
Benefit feeding and helps increase gas exchange
Early pro-vertebrates were…
NOT complex at all. Had little/dorsal fin, no teeth or jaws, and a very little post-anal tail
Is there evidence for provertebrates?
Yes but VERY little due to the soft-tissue. Soft tissue rarely fossilizes
What are the four fossils for provertebrates?
Haikouella lanceolata
Mylokunmingia fegjiao
Haikouichthys ercaicunensis
Metaspriggina walcotti
What structures did the pro-vertebrates have?
- conodont elements
- teeth
- large eyes
- DHNT
- myomers
- mouth opening
- notochord
What were the Ostracoderms
early jawless fish
- name means “shell skin” which suggests armoring plates on the skin
Ostracoderm characteristics
- some dermal armoring
- vertebrae and cranium
- mineralized gill supports
- well developed sensory detection
What did ostracoderm armor eventually evolve into and why?
They evolved into scales because armoring was very heavy and not flexible which made the organism slow down and use a lot of energy. Scales where less energy expendable
Why selection for scales in Ostracoderms?
- lighter and more flexible
- uses less energy, increases speed and mobility while still retaining protection qualities
Pteraspidomorphi (Ostracoderms) characteristics
- mostly marine (mainly benthic)
- had multiple deep filtering head plates
- subterminal mouths, dorsal eye placement, dorso-ventrally flattened body
- negatively boyant
- heterocercal tail
Heterocercal tail
bottom lobe is larger than top lobe; pushes and propels fish upwards
Benthic
living on the bottom; bottom dwelling
Pelagic
open water; above the ocean floor
Anaspida (Ostracoderm) charactersitics
- mostly marine
- mostly pelagic
- limited/no armoring on head
- had cartilaginous ring-held mouth open
- well developed sensory systems
- openings in body wall that detect changes in H2O movement/vibrations
- heterocercal tail
Cephalaspidomorphi (Ostracoderm) charactersitics
- marine (mostly benthic)
- has large, single pieced head shield
- paired fin- like projections/lobes to act as stabilizers while swimming
- well developed sensory structures
Thelodonti (Ostracoderm) characteristics
- mostly marine (mainly palagic)
- tooth-like scales on body
- paired fin-like extensions for stability
Hagfish (Myxini) facts
- 76 species (many near endangered or are endangered)
- strictly in deepwater ocean
- body size 18-127 cm
- skin is scaleless, smooth skin
- isotonic to water
what sensory systems do hagfish have?
- a single nostril/olfactory sac (associated with chemosensory abilities)
- tentacles (touch)
- vision (two eye spots; suggests that there might have been a well developed visual system)
- vibration detection (lateral lines only on the head)
feeding abilities of hagfish?
- feed off dead/rotting corpses
- eat live prey
- absorb amino acids through water across skin and gills
type of teeth hagfish have?
lingual teeth on their tongue
- can tear off chunks of flesh from corpses or grab live prey and drag out of its burrow to eat
what about the mucus produced from a hagfish?
- acts as an anti-predator/lubricant for burrowing
- can rapidly produce huge amounts
- releases a small peptide to gel/solidify seawater
food digestion of a hagfish
- digestive tract secretes a semi-permeable mucosal bag
- digests the food -> desirable nutrients diffuse out of the bag
- harmful waste stays in the bag
circulatory system of a hagfish?
OPEN circulatory system
- deoxygenated blood empties into cavities
