Lecture 11: The invertebrates I Flashcards
The Parazoa
- no gastrulation
- no true tissues
- some specialised cells
Phylum Porifera (sponges)
- 5000 - 10,000 species
- simple body plan
- lack muscles, nervous system, organs
- may be asymmetrical
- resemble a rigid, sessile,perforated sack
parazoa feeding:
water flows in to spongocoel where amoebocyte with choanocyte are attached. Amoebocyte are mobile. Choanocyte have flagellum waft food into collar of choanocyte, amoebocyte able to move to whereas is needed. water flow pushed out top of osculum
The radiata
- radial symmetry
- diploblastic
Phylum Cnidaria (jellyfish, corals)
- 10,000 species
- simple form - a blind sac with a gastrovascular cavity
- mouth = anus
- polyp (mouth up) or medusa (mouth down) form
- no brain, but simple nerve network
- contractile bundles of microtubules act like muscles
poly form:
mouth up
medusa form:
mouth down
cnidocytes:
A cnidocyte is an explosive cell containing one giant secretory organelle that defines the phylum Cnidaria
nematocysts
specialized cell in the tentacles of a jellyfish or other coelenterate, containing a barbed or venomous coiled thread that can be projected in self-defence or to capture prey.
within the phylum Cnidaria what are the main 4/5 classes
- hydrozoan
- scyphozoan
- cubozoan
- anthozoan
- tetraplatia???
protostomia are a
clade of animals
protostome features:
- characteristic cell division and coelom formation, early cell determination, mouth forms first
- ventral nerve cord
- includes most known animal species
two groups of protostomes?
- Lophotrochozoa
- Ecdysozoa
Phylum Platyhelminthes (Lophotrochozoa) known as –> Flatworms:
(planarians, tapeworms)
- 20,000 spp
- once considered the earliest bilateral animals due to simple body plan (gastrovascular cavity, no coelom)
- now believed to have had a coelom then lost it
- triploblastic with true mesoderm
- mesoderm -> true organs, organ systems and muscles
- cephalisation and sensory/motor system development
- lack gas exchange and circulatory organs
Phylum Platyhelminthes (Lophotrochozoa), Class Turbellaria
- free-living marine animals (predators or scavengers)
- blind gastrovascular cavity with complex folding
- eyespots detect light
- regenerate or reproduce sexually
- hermaphrodites
hermaphrodites:
a person or animal having both male and female sex organs or other sexual characteristics
New Zealand Flatworm
- exotic species imported by accident in 1960s (SCOTLAND)
- 6-12cm long, feeds on earthworms
- few natural enemies, but ground beetle larvae eat them
Phylum Platyhelminthes (Lophotrochozoa), Class Trematoda
-parasitic flukes, usually of vertebrates
parasitic fluke lifecycle
HUMAN HOST
1, mature flukes in blood vessels of intestine
2, blood flukes reproduce sexually in human host. Fertilised eggs exit host in faeces
3, Eggs develop in water into ciliated larvae. Larvae infect snails
SNAIL HOST
4, Asexual reproduction within snail results in another type of motile larvae
5, larvae penetrate skin and blood vessels of humans
Phylum Platyhelminthes (Lophotrochozoa), class Cestoidea
- parasitic tapeworms, consists of scolex and proglottids
Phylum Annelida (Lophotrochozoan), known as segmented worms 12,000 spp
- Body linear and metameric (segmented)
- Coelom divided by septa
- each segment has ganglia, circular blood vessel, & paired metanephridia
- circular and longitudinal muscle in body wall
- dorsal & ventral blood vessels in a closed circulatory system
- digestive tract has specialised regions
Phylum Annelida (Lophotrochozoan), known as
segmented worms
12,000 spp
Annelids: class Oligochaete
3,500 spp
(earthworms)
-terrestrial and freshwater segmented worms
Annelids: Class Polychaeta
- 8,000 spp
- marine segmented worms, well developed head and feet
