Coeloms, Molluscs, Platyhelminthes, Annelids, Nematodes Flashcards
What is the fate of the blastopore in protostomes?
Mouth
Protostomes develop the mouth from the blastopore during embryonic development.
What is the fate of the blastopore in deuterostomes?
Anus
Deuterostomes develop the anus from the blastopore during embryonic development.
What type of cell division pattern do protostomes exhibit?
Spiral cell divisions
This refers to the arrangement of cells during early embryonic development.
What type of cell division pattern do deuterostomes exhibit?
Radial cell divisions
This refers to the arrangement of cells during early embryonic development.
Define acoelomates.
No body cavities
Examples include Platyhelminthes and nemertines.
Define coelomates.
All other triploblast animals
Coelomates have a body cavity fully lined by mesoderm.
What is a haemocoel?
Blastocoel remains filled with blood
It can have forming vessels in annelids or an open circulation in arthropods and molluscs.
What is a pseudocoelomate?
Coelom is bound on one side by mesoderm
Examples include nematodes and rotifers.
What defines true coelomates?
Coelom is bound on all sides by mesoderm
Examples include annelids, molluscs, and chordates.
What are the two types of coelom formation in animals?
- Schizocoelic (protostomes)
- Enterocoelic (deuterostomes)
Not all deuterostomes exhibit enterocoelic formation.
What is a key feature of triploblast metazoans?
Most have a body cavity
Cavities form by various embryonic routes.
What is the significance of the fate of the blastopore?
It is a key feature in classifying animals
The blastopore’s fate is crucial for understanding animal phylogeny.
Describe the general morphology of molluscs.
- Mostly marine
- Ventral muscular foot
- Dorsal shell
- Radula
- Gill (ctenidium)
- Small coelom
- Limited cephalisation
Molluscs exhibit a wide range of forms and adaptations.
What are the two main groups of molluscs?
- Aculifera
- Conchifera
Aculifera have spicules while Conchifera have shells.
What defines bivalves?
- Body compressed
- 2 symmetrical shells
- Muscular foot for burrowing
- Almost all marine
- No head end
- Ctenidia evolved for filter feeding
- Siphons for water inhalation and exhalation
- Adductor muscles hold shells shut
Bivalves are a significant class within the molluscs.
What are the main characteristics of Platyhelminths?
- No body cavities
- No circulatory system
- No respiratory system
- Mouth, no anus
- Locomotion by cilia
- Majority are parasitic
- Flat bodies facilitate diffusion
Platyhelminths are also known as flatworms.
What are the main characteristics of cephalopods?
- Well-developed brain
- Some with or without shell
- Fast moving
- Pelagic predators
- Muscular foot for jet propulsion
- Tentacles for prey manipulation
- Jaws to chew prey
Cephalopods are highly advanced molluscs.
What are the three classes of annelids?
- Polychaeta
- Oligochaeta
- Hirudinea
Each class has distinct characteristics and habitats.
What feeding types are found in annelids?
- Filter feeders
- Carnivores
- Detritivores
This diversity allows annelids to occupy various ecological niches.
What is the significance of longitudinal muscles in nematodes?
Allows movement left and right
They have a fluid-filled body cavity that aids in movement.
What type of skeleton do annelids have?
Hydrostatic skeleton
This type of skeleton is crucial for their locomotion and support.
