Hemichordata Flashcards
1
Q
Intro
3 points
A
- Two main body types
Enteropneusts
Pterobranchs - Share features with Chordata
- Benthic [deep sea, difficult to study] marine environments
2
Q
Classification
A
Kingdom: Metazoa
Phylum: Hemichordata
Class:
Enteropneusta
Planctosphaeroidea [not in
exam]
Pterobranchia
3
Q
Key characteristics
6 points
A
- Bilaterally symmetrical
- Trimeric
Tissues, organs, nervous system (with mesodermal nerve chord), open circulatory system and excretory structure - Ciliated pharyngeal [in pharanxy] gill slits [tell you about species you’ve got.]
- Through (enteropneusta), or U-shaped gut (pterobrancia)
- Dioecious
- Tornaria larvae, unique to Enteropneusts
4
Q
Body structure
3 points
A
- Ciliated epidermis (no cuticle)
- Trimeric
Prosome, mesosome and metasome - Enterocoelic body cavities
Protocoel [not paired], mesocoel and metacoel
5
Q
Feeding
Enteropneusts
2 points
A
- Deposit feeders
2. Suspension feeders
6
Q
Feeding
Pterobranchs
3 points
A
- Ciliary mucus suspension feeders
- Arms and tentacles derived from mesosome
- Interdigitate their tentacles
7
Q
Reproduction
sexual
4 points
A
- Dioecious, no sexual dimorphism
- Enteropneusts
External fertilisation - Indirect development
- Tornaria larvae
8
Q
asexual reproduction
4 points
A
- Fragmentation
- Dioecious,
- sexual dimorphism
- budding
9
Q
Pterobranchs reproduction
3 points
A
- External fertilisation
- Mixed development
- Ciliated larvae
10
Q
Class Enteropneusta
4 points
A
- Elongated body (≤ 2.5m)
- Solitary, mobile
- Long proboscis; short collar with no arms/tentacles; long trunk with gill slits
- Well developed neurocord and excretary glomerulus
11
Q
Class Pterobranchia
4 points
A
- Small (~10mm) and colonial
- Sedentary, tube-dwelling
- Disc-shaped proboscis; collar with paired arms and tentacles; short trunk, one pair of gill slits
- Neurocord absent and poorly-developed glomerulus
