Echinodermata & Vertebrate (Beginning) Flashcards
1
Q
What distinguishes the Protostomia?
A
- Spiral mosaic cleavage
- Mouth from blastopore
- Coelom from schizocoely
2
Q
What distinguishes the Deuterostomia?
A
- Radial regulative cleavage
- Anus from blastopore
- Coelom by enterocoely
3
Q
What is the Phylum Chaetognatha?
A
- Arrow worms
- Pelagic marine predators
- Has been variously placed in Protostomia and Deuterostomia
- Developmental characters suggest that they are deuterostomes
anus arises from blastopore
coelom formation is enterocoelous - Molecular data suggests that they are protostomes
additionally, cleavage is similar to crustaceans and nematodes
4
Q
What is the Phylum Hemichordata?
A
- Formerly considered a subphylum of chordates
reclassified because they do not have a true notochord - Worm like bottom dwellers
5
Q
What is the Phylum Echinodermata?
A
- Sea stars, brittle stars, sea urchins, sea cucumbers and sea lillies
- A puzzle to biologists (strange symmetry)
- Echinoderms (and hemichordates) are the closest living relatives to chordates
6
Q
What are the key characteristics of the Phylum Echinodermata?
A
1) Endoskeleton
2) Pentaradial symmetry
3) Water vascular system
7
Q
Explain the spiny endoskeleton
A
- Skeleton or supporting framework within the living tissues of an organism
- Contrasts with exoskeleton
- Made of small calcareous plates bound together with connective tissue
- This endoskeleton is beneath the epidermis, but calcareous spine poke through
- Echinoderms are unappealing prey (exception: a few fish with strong teeth, other echinoderms, sea otters eat sea urchins)
8
Q
Explain the pentaradial symmetry
A
- Radial symmetry in five parts
- Some sea stars have more than five arms (start development with five)
- Bilateral symmetry is adaptive for motile animals
- Radial symmetry is adaptive for sessile animals
- Echinoderms are free moving but radial (unusual combination)
- Larvae of echinoderms are bilaterally symmetrical
- Earliest echinoderms were likely bilaterally symmetrical
at some point during evolution they become sessile and radial - Evolution has favoured the motile descendants of these sessile organisms
even though they are still radial - Some groups have secondarily evolved a superficial bilateral organization
they still have pentaradial organization of skeletal and most organ systems
9
Q
Explain the water vascular system
A
- Unique to echinoderms
- Comprised of canals and specialized tube feet
- Functions: locomotion, food gathering, respiration and excretion
10
Q
What are the classes to the phylum Echinodermata?
A
Asteroidea (sea stars)
Ophiuroidea (brittle stars and basket stars)
Echinoidea (sea urchins, sand dollars, heart urchins)
Holothuroidea (sea cucumbers)
Crinoidea (sea lilies and feather stars)
11
Q
What is the class Asteroidea
A
- Sea stars
- Central disc that merges with tapering arms
- Pentaradial symmetry (typically five arms, may have more)
- Oral surface (near mouth)
on underside of body - Aboral surface (opposite mouth)
- Ambulacral groove runs along the oral surface of each arm
- Tube feet are found along the ambulacral grooves
- Madreporite is the structure where water enters the water vascular system
12
Q
What is the water vascular system of the Asteroidea?
A
- Systen opens to the outside through the madreporite (on aboral surface)
- Madreporite leads to a series of canals
- Canals are connected to the podia (tube feet)
- Podia stick through the ossicles in the ambulacral groove
- Muscles and valves control the amount of fluid flowing into the podia (creates movement)
13
Q
What is the feeding and digestive system of the Asteroidea?
A
- Many sea stars are carnivorous
feed on molluscs, crustaceans, polychaete, echinoderms, and sometimes small fish - The lower part of the stomach can be everted through the mouth during feeding
- Steps to eating a clam (if you are a sea star)
Wrap yourself around prey
Attach podia to valves and pull apart
Insert soft everted stomach into the gap between valves
Begin digestion
Pull stomach back in
14
Q
What is the regeneration of the Asteroidea?
A
- Sea stars can regenerate lost parts
- Regeneration can take several months
- Some species can regenerate a whole new sea star from a severed arm (fragmentation)
For most asteroids, the arm must contain a portion of the central disc
In other species a whole individual can regenerate form an arm - fisherman used to kill sea stars collected from their oyster beds by chopping them in half (not a good idea)
15
Q
What is the reproduction and development of the Asteroidea?
A
- Sexual reproduction
Dioecious
External fertilization - Most sea stars produce free swimming planktonic larvae
The larvae are bilaterally symmetrical
Metamorphosis involves a dramatic reorganization
Bilateral larva becomes a radial juvenile - Asexual reproduction in some species
By fragmentation and regeneration
16
Q
What is the class Echinoidea?
A
- Sea urchins, sand dollars, heart urchins
- Dermal ossicles have become closely fitting plates which form a shell
- Spines protrude in living specimens (long in sea urchin, shorter and softer in sand dollars and heart urchins)
- Lack arms, but have the typical pentamerous plan of echinoderms
17
Q
What is the body symmetry of the Echinoidea?
A
- Most living species are regular (radial symmetry)
- Sand dollars and heart urchins are irregular
radial symmetry
secondary bilateral symmetry
18
Q
What is the class Holothuroidea?
A
- Sea cucumbers
- Odd animals in an odd phylum
- Elongated oral aboral axis
- Ossicles are reduced (soft bodied)
- Pentaradial symmetry
- Secondarily evolved a degree of bilateral symmetry (as adults)
all echinoderm larvae are bilaterally symmetrical - Some species cast out a part of their viscera (guts) as a defence mechanism
- Strong muscular contraction either ruptures the body wall or everts its contents through the anus
- Lost parts are regenerated
19
Q
What are characters of Chordates?
A
- Bilateral symmetry
- Anterior posterior axis
- Complete gut
- Coelom “tube within a tube” arrangement
- Metamerism
- Cephalization
- Chordates are deuterostomes, so also
Radial cleavage
Anus derived from blastopore
Coelom formed by enterocoely (but most vertebrates from coelom by schizocoely)
20
Q
What are the Protochordata?
A
- Not a monophyletic group
- Includes two subphylum
Urochordata (tunicates)
Cephalochordata (lancelets, ‘amphioxous’) - These subphyla are the only invertebrate chordates
21
Q
What is the subphylum Urochordata?
A
- Commonly called tunicates
- Most sessile as adults, some free living
- The name Tunicate describes the tough, nonliving tunic (or test) that surrounds the animal
- Only the larval form bears all the chordate hallmarks
- solitary or colonial
22
Q
What is the subphylum Cephalochordata?
A
- Lancelets
- Originally bore the generic name Amphioxus
- Modern survivors of an ancient chordate lineage
- Slender, laterally compressed, translucent animals
- Inhabit sandy sediments of coastal waters
- 5 distinct characteristics of chordates but in simple form
- Lack features found in true vertebrates
no brain
no true vertebrae
23
Q
What are the 5 hallmarks of the Phylum Chordata?
A
1) Notochord
2) Dorsal hollow nerve cord
3) Pharyngeal pouches or slits
4) Endostyle for filter feeding
5) Postanal tail for propulsion
24
Q
Explain the notochord
A
- Flexible, rod like body of fluid filled cells enclosed by a fibrous sheath
- All members of phylum Chordata possess a notochord
- Can be restricted to early development
- Organizational role in nervous system development
- Persists throughout life in jawless vertebrates and protochordates
- Becomes the vertebral column in all jawed vertebrates
25
Explain the dorsal hollow nerve cord
- Nerve cord is dorsal to the digestive tract and notochord
- Nerve cord is hollow
- In craniates
Anterior end of nerve cord becomes enlarged to form the brain (the rest is the spinal cord)
Nerve cord passes through vertebrae and the brain is surrounded by a bony or cartilaginous cranium
- Invertebrates can also have a nerve cord, but it is ventral to the digestive tract and solid
26
Explain the pharyngeal pouches/slits
- Openings that lead from the pharyngeal cavity to the outside (pharyngeal cavity = opening of the pharynx)
- Pharynx = the part of the digestive tract between the mouth and the esophagus that, in vertebrates, is common to both the digestive and the respiratory tracts
- They take on different forms in different groups
27
How does the pharyngeal slits look in the protochordates?
Perforated pharynx functions as a filter feeding apparatus (original evolutionary role)
28
How does the pharyngeal slits look in the aquatic chordates?
Pharyngeal slits bear gills used in gas exchange in some aquatic chordates
29
How does the pharyngeal slits look in the tetrapods?
- Pharyngeal pouches are inly present in the embryonic stage
- Give rise to several different structures including Eustachian tube, middle ear cavity, tonsils, and parathyroid gland
30
Explain the endostyle/thyroid gland
- Occurs in all chordates and no other animals
- Endostyle is present in protochordates and lamprey larvae
The endostyle secretes mucus that traps food particles brought into the pharyngeal cavity
Cells in the endostyle secrete iodinated proteins (homologous with the iodinated-hormone-secreting thyroid gland)
- Adult lampreys and remainder of vertebrates have thyroid glands
Thyroid gland regulates metabolism and helps to produce and regulate other hormones
31
Explain the postnatal tail
- In protochordates (larval tunicates and amphioxus), the postanal tail provides motility
- Increases in fishes
- Present in humans only as a vestige (the coccyx, a series of small vertebrae at the end of the spinal column)
- Most other mammals have a waggable tail as adults
