Invertebrates Flashcards
What are invertebrates?
Animals without vertebra
Why are invertebrates important?
- Pollination
- Decomposition
- Medicine
- Food chain
How are cells indirectly connected?
Through an extracellular matrix (ECM)
What is the phylum Porifera?
Sponges
Describe the body plan of Porifera
- Mainly suspension feeders, trap food from circulating water
- Flagellated choanocytes line the spongocoel & generate a water current & ingest food particles by phagocytosis
- Body consists of 2 layers of cells separated by mesophyl
What are the 3 types of asexual reproduction for Porifera?
1- Fagmentation
2- Budding
3- Gemmule-formation
What is fragmentation?
Where small bits regrow
What is budding?
Uncommon, but seen as projections from outer wall in some species and as stalked buds in others
What is gemmule-formation?
freshwater species form “survival capsule” in autumn (cluster of archaeocytes surrounded by spongin ‘shell’). Hatches through micropyle in spring. Gemmules from more than one sponge can combine
How does Porifera sexually reproduce?
- By broadcasting sperm (sometimes eggs) through the osculum
- Sperm develop from choanocytes, which are dispersed in excurrent channels in the sponge and ‘inhaled’ into other sponges
- Sperm cells are not phagocytosed (digested), but transform to become amoeboid carrier cells, which fertilise oocytes
What are spicules?
Structural elements providing support & deterring predators
What are the 3 major classes of spicules?
- Calcarea
- Demospongiae
- Hexactinellida
What is Calcarea?
Calcium carbonate spicules, simple in structure or may
have up to 4 rays
What is Demospangiae?
Largest and most diverse class, both freshwater and marine species, siliceous or spongin spicules
What is Hexactinellida?
‘Glass sponges’, distinct siliceous spicules with six rays
What is the body plan of Cnidaria?
- Diploblastic
- Basic body plan is a sack with central digestive cavity with single opening (mouth + anus)
What are the 2 body forms of Cnidera?
- Polyp - cylindrical form adhering to substrate via aboral end.
- Medusa - flattened, mouth-down, moves freely in water by passive drifting and contractions of bell-shaped body.
Describe Cnidarians
- Carnivores - use tentacles to capture prey and push food into gastrovascular cavity
- Tentacles armed with cnidocytes (specialist stinging cells), bulb-shaped capsules containing coiled thread structure within – hair-trigger cnidocil fires hook end of thread at prey
- Discharges venomous proteins from inside nematocyst to paralyze prey
Describe the movement of Cnidarians
- Muscles and nerves in simplest forms
- Cells of epidermis and gastrodermis have bundles of microfilaments arranged in contractile fibres – gastrointestinal cavity acts as hydrostatic skeleton against which contractile cells work
- Movements coordinated by nerve net and associated with simple sensory receptors distributed radially around body
What 2 ways do Cnidaria asexuallyreproduce?
- Longitudinal and transverse fission
- Budding
What are the 3 classes of Cnidaria
- Hydrozoa
- Scyphozoa
- Anthozoa
What are the 2 types of symmetry?
- Radial symmetry/no symmetry
- Bilateral symmetry
Give an advantage of radial symmetry
Sessile organisms conserve energy, take full advantage of a favourable location and can usually prevent competitors from establishing themselves nearby
Give an advantage of bilateral symmetry
- Motile organisms can move to other locations according to conditions
- They can flee from predators and search for mates
