Simple triploblasts
- Created by: Abbie Storah
- Created on: 18-03-16 17:13
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- Simple triploblasts
- Bryozoa
- 'Moss animals'
- 4,500-8,000 species
- Live in colonies of up to 2 million individual zooids
- Quite common
- Most marine
- Some in fresh water
- Oscillate and rotate their lophophore to increase contact with prey
- Sexual reproduction
- Sperm released into water
- Internal fertilisation
- Developing embryo brooded released as larvae
- Some zooids have jaws to protect from grazing
- Brachiopoda 'armed foot'
- Lamp shells
- Solitary, sessile and marine
- Feed with motile lophophore
- Cilia on lophophore beat to withdraw water with food particles
- 335 extant species but 26,000 fossils
- Two-part hinged shell
- Similar to bivalve mollusc but dorsal & ventral rather than lateral
- 4-6 cm long
- Attached by short, flexible stalk to rock or into sediment
- Trochophore larvae settle after a few days and develop into adults
- Rotifera
- 'Wheel-bearers'
- Small, mostly fresh water
- Some free moving, some sessile
- 1,800 species
- Complete gut
- Move by beating cilia
- Coronal cilia sweep particles into mouth
- Food ground up in gut by mastax
- Frequently have fixed number of cells (~1000)
- Males and females in most species
- Some only have females
- Reproduce partheno-genetically
- Some only have females
- Genetic diversity sustained by picking up fragments of genes from environment
- Platy-helminthes (flatworms)
- Significant parasites of vertebrates
- Important to medicine, veterinary science & agriculture
- Free-living flatworms can predate other invertebrates
- Most are endo or exoparasites of vertebrates
- Some free living marine, fresh water or terrestrial
- 25,000 species
- Lack organs for transporting oxygen
- Flat form enabled gas exchange by diffusion
- Digestive tract has one opening, gut often branched
- Excretory organs called proto-nephridia
- Flame cell and duct - pore
- Some have ganglia, nerve trunks and sense organs
- 4 CLASSES
- Turbellaria
- 4,500 species
- 4-600 mm long
- Some are parasitic
- Many have more than one host
- Mostly predators or scavengers
- Skin is single cell layer
- Ciliated on lower body and sometimes all over body
- Enables movement
- Some species swim by muscular undulations
- Sense organs
- Simple eyes
- Balance organs
- Chemo-sensors
- Herma-phrodites, internal fertilisation
- Small portions can regenerate into a completely new worm
- Trematoda
- Flukes, often internal parasites
- Ventral suckers for attachment
- Complex life cycles specialised for parasitism
- Enormous number of offspring
- Definitive host plus a number of staged intermediate hosts
- Mongenea
- External parasites, mainly of fish
- Cestoda (tapeworms)
- 3,400 species
- Two or more hosts
- Specialised parasites of vertebrates
- Most organ systems reduced
- No gut
- Nutrients absorbed through skin
- Head relatively tiny scolex that attaches to host's gut lining
- Neck continually produces chain of reproductive segments called proglottids
- Turbellaria
- Significant parasites of vertebrates
- Bryozoa
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