Lecture Sixteen - Animal diversity II Flashcards
Define invertebrate.
Include all bilateria.
All bilateria are triploblastic and bilaterally symmetrical.
The way the coelom is formed determines what kind o invertebrate is formed (coelomate, acoelomat or blastocoelomate).
What is the function of the coelom?
Circulate and store metabolites.
Cushioning and space for organs.
Incrfease in size.
Hydrostatic skeleton.
How are the bodyt cavities (coelom) formed in deutrostomes and protostomes?
Cleavage:
Protostome - Spiral and seterminate cleavage (asymmetrical cells).
Deutrostome - Radial and intermediate cleavage (symmetrical cells).
Coelmon formation:
Protostomes - Schizocoelous: Solid masses of mesoderm split to form coelom.
Deutrostomes - Enterocoulous: Folds of archenteron form coelom.
What is the fate of the blastopour:
Protostomes - blastopour becomes mouth.
Deutrostomes - blastopour becomes anus.
Describe the phylum platyhelminthes (flatworms).
From the lohotrochozoa lineage.
Bilaterally symmertrical.
Triploblastic.
Acoelomates.
Germ layers:
Ectoderm = epidermus.
Endoderm = blind gut.
Mesoderm = fills the space between.
NO:
Skeletal, respiratory or circulatory systems.
Flattness allows for diffusion.
Anatomy:
Locomotion - cilia and muscles.
Limited cephalisation - eyes, frontal ganglia and nerve chrods.
Feeding - Blind gut (no anus) and absorption in tape worms.
Describe the Phylum Annelida (segmented worms).
Part of the lophotrochozoan lineage.
Bilaterally symmetrical.
Triploblastic.
Coelomates.
Segmented body - series of rings.
Eucoelomates - true coelom (mesoderm lines all sides of the coelom).
Anatomy:
Cephalisation - nerve ring and cerebral ganglia.
Closed circulatory system.
Complex digestive system - pharynx, oesophogus, crop and intestine).
Muscles:
Longitudinal and circular muscles.
Locomotion:
Each segment is a compartement filled with coelomic fluid.
Two muscle groups act on a hydrostatic skeleton.
Describe the Phylum Nematoda (roundworms).
From the ecdysozoan lineage.
Bilaterally symmetrical.
Triploblastic.
Blastocoelomates.
Germ layers:
Ectoderm = secretes tough cuticle.
Endoderm = gut.
Mesogerm = various organs.
Blastocoelom:
Mesoderm lines the outer wall of the body cavity only.
Not a true coelom.
Digestive system:
One way - mouth to anus.
Muscular pharynx.
Tough exoskeleton:
Cutile - requires moulting to grow and blastocoelomic fluid under pressure.
NO:
Circulatory, extretory or respiratory systems.
Locomotion:
Only longitudinal muscles.
Move by undulations or wiggling.
Describe the Phylum Arthropoda.
From the ecdysozoan lineage.
Bilateral symmetry.
Triploblastic.
Coelomates (limited coelom).
Higherst number of species in this phyum (2/3 of all species).
Most divers.
Most wide spread.
Verstile exoskeleton:
Tough, non-cellular layer excreted by the epidermus.
Made from chitin, protein and calcium carbonate in crustations.
Advantages:
Protection.
Reduced water loss via evapouration.
Support for muscles.
Dissadvantages.
Energy expensive to make.
Vulnerable when shedding.
Limits size of organism.
Open circulatory system.
Terrestrial challenges and their adaptations:
Gas exchange needs water = trachea/ book lungs.
Avoid desication = impermiable (waxy) cuticle.
No medium to support body = exoskeleton/legs.
Different sources of food = adaptable mouth parts (e.g. jaws).
