Biodiversity 3: The protostomes Flashcards
What are the key features of the protostomes?
Spiral cell division
Early cell determination
Body cavity forms from mesoderm
Mouth forms first
Divided into lophotrochozoa (feeding cilia) / Ecdysozoa (shed exoskeleton)
What is the common name for the phylum platyhelminthes?
Flatworm
Describe the platyhelminthes
Simple body plan (no separate anus, no body cavity)
Mesoderm with digestive system and reproductive organs, but no circulatory organs
Simple brain and sensory/motor development and muscles allow active lifestyle
Describe free living marine flatworms
Predators or scavengers
Blind gastrovascular cavity with complex folding
Ganglia and eyespots
Regenerate or reproduce sexually as hermaphrodites
Describe parasitic flukes
Primary host is usually a vertebrate
Secondary host is usually an invertebrate
Can have multiple life stages, some asexual, others sexual
Schistosoma causes schistosomiasis in humans = liver failure and death
Describe parasitic tape worms
Pork tapeworms
Head with hooks for attachments inside the hosts gut
Sacks of eggs (proglottids) break off and are transferred to other hosts through the host’s faeces
Self fertilising hermaphrodite
No sensory organs
What is the phylum Annelida’s common name?
Segmented worms
Describe the Annelida
Body linear and segmented
Body cavity divided by septa
Circular and longitudinal muscles in body wall
- Can move forward
Digestive tract has specialised regions
- Mouth, pharynx (sucks food in), crop (stores food, adds moisture), gizzard (grinding food), intestine (absorption), anus (waste)
Simple brain = can process tactile stimuli and react
Describe Earthworms
Terrestrial and freshwater segmented worms
No head and no legs
Hugely important in soil formation, aeration and releasing nutrients for use by plants (all ecosystem services)
Marine flatworms, Parasitic flukes and parasitic tape worms belong to which phylum?
Platyhelminthes (flatworms)
Earthworms, polychaete worms and leeches belong to which phylum?
Annelida
Describe polychaete worms
Marine segmented worms
Developed head and feet
Describe leeches
Many are specialised blood sucking parasites
Dorsally flattened, segmented
Outwardly resemble flatworms
What are some important evolutionary features of segmented worms?
Well developed body cavity:
Hydrostatic skeleton
Body space for storage and organ development
Cushion for internal organs
Buffers the actions of body wall muscles form the action of muscles in the digestive tract (allows movement while digesting
What does the segmentation of segmented worms allow for?
Specialisation of regions in the body
Name 4 classes that belong to the phylum mollusca
Gastropods, bivalves, cephalopods
Describe molluscs
Not segmented
Diverse, but all share same basic body plan:
Foot = fleshy muscular pad, often used for locomotion
Visceral mass = lump of tissue containing most of the internal organs
Mantle = fold of tissue that covers visceral mass
Often uses calcium carbonate to secrete a shell e.g snails
A lot but not all have a radula = scrapes up food from substrate