From Molluscs to Chordates Flashcards
1
Q
Phylum: Mollusca
A
- more than 100,000 species
- mostly marine; some freshwater and damp terrestrial
- bilateral
- triploblastic
- coelomate
- protostomes
- NOT segmented (except Neopilina)
- Up to 8 classes
2
Q
Generic Mollusc Characteristic
A
Molluscs have variations on same basic characteristic
- Mantle: dorsal body wall which often forms shell
- Mantle Cavity: space between mantle and main body where gills (or lungs in terrestrial snails) are found
- Muscular foot: used for moving, feeding and manipulation
- Head with specialised mouthparts (radula)
3
Q
Phylum: Molluscs
Class: Polyplacophora
A
- Chiton (coat-of-mail shells)
- exclusively marine
- bilateral
- shell consists of 8 large plates surrounded by a girdle of smaller spicules (Spicules are any of various small needle-like anatomical structures occurring in organisms)
- mostly feed on algae or encrusting organisms but some are predators
- reproduce sexually: some brood their young in their mantle
4
Q
Phylum: Molluscs
Class: Bivalvia
A
- Clams, mussels, oysters
- marine and freshwater
- characterised by two shells; no distinct head
- lost radula; filter feed (sometimes through foot)
- often live buried in sand
- gills function for gas exchange and food collection
- reproduction is usually sexually and external
- trocophore larvae typical
5
Q
Phylum: Molluscs
Class: Gastropoda
A
- slugs and snails
- marine (e.g. whelks, sea slugs), freshwater and terrestrial
- spiral shell (lost in slugs)
- produce slime; aids movement
- well-developed head with eyes and tentacles
- larvae = bilaterally symmetrical
- adult snails = body twisted (torsion)
6
Q
Torsion in snails
A
- as snails develop, their body twists (torsion)
- result: 180 degree turn in body inside shell
- Advantage: mantle cavity anteior (allows withdrawal into shell)
- Disadvantage: anus empties by mouth
7
Q
Detorsion in slugs
A
- slugs have lost shell
- mantle is massively reduced
- mantle cavity disappeared
- detorsion (body twisting it lost)
- may allow slugs to forage in soil or sandy substrates (sea slugs)
8
Q
Phylum: Mollusc
Class: Cephalopoda
A
- Cephalopoda = head-foot
- squid, octupus, cuttlefish, Nautilus
- Marine, free-swimming
- shell reduced to internal support (except in Nautilus)
- Mantle used for propulsion
- Foot covered in tentacles
9
Q
Nautilus Growth
A
- Shell - bouyancy aid
- As Nautilus grows greater buoyancy is needed
- Shell grows and Nautilus seals off gas-filled chambers
10
Q
Other features of Cephalopod
A
- Excellent vision
- Pigment cells - chromatophores
- Visual signals - mate attraction, camouflage
- Most intelligent non-vertebrate?
11
Q
Phylum: Echinodermata
A
- Entirely marine
- 5 main classes
- Sea stars (Asteroidea)
- Sea Urchins (Echinoidea)
- Brittle stars (Ophiuroidea)
- Sea lilies (Crinoidea)
- Sea cucumbers (Holothuroidea)
12
Q
Echinoderm Symmetry
A
- Pentaradial as adults
- Bilateral as larvae - indicates bilateral symmetry ancestry
13
Q
Echinoderm Characteristics
A
- radial
- triploblastic
- coelomate
- deuterostome
- no segmentation
- spiny epidermis - calcareous ossicles
- have a water vascilar system in the coelom - madreporite is the opening of the water vascular system
- locomotion = tube feet
14
Q
Echinoderm Defence
A
Pedicellariae (some Asteroidea species):
- Modified spines with claws and capable of movement
- Used to remove encrusting organism
Ejection of intestines (some Holothurians)
- when startled, some species with expel sticky tubules to entagle predators
- May also discharge a deadly toxin
15
Q
Phylum: Chordata
A
- Marine, freshwater, terrestrial, aerial, subterranean
- Bilateral
- Triploblast
- Coelomate
- deuterostome
- partial segmentation
- reprodction - largely sexual and internal
- Subphylum: Vertebrata
- amphibians, reptiles, fish, birds and mammals
