The Colourful Lives of Early Aquatic Inverts Flashcards
What are the phylum porifera?
Sponges
What is the porifera feeding mechanism?
Filter feeders
Do porifera move?
No, they are sessile
Porifera have totipotent cells, what does this mean?
Can change form and function
What division of animals are porifera (based off tissues)?
Metazoans, although without well defined tissues and organs. Used to be considered parazoans (no true tissues)
What is the unique cell of cnidarians and what does it do?
Cnidocyte with nematocysts - stings
Do cnidarians move?
Either sessile or slow-moving
What are the 4 main Porifera cell types?
Pinacocytes, archaeocytes, choanocytes, porocytes
What are pinocyte cells?
Form the external epithelium of porifera, can contract to regulate water flow
What are choanocytes?
Flagellated filter feeding cells of porifera.
Explain the filter feeding mechanism of porifera.
Collar of microvilli on choanocytes trap food particles from water. Flagella keep a constant current through the water. Food encapsulated in main cell body then passed to Archaeocytes for digestion
What are archeocytes?
Porifera digestive cells that move in the mesohyl. Are totipotent.
What 3 cell types can archaeocytes differentiate into?
Sclerocytes, spongocytes, collencytes
What are porocytes?
Porifera tubular cells that form pores in simple sponge types (Asconoids).
What are the three body plans of Porifera, from simplest to most complex.
Asconoid, Syconoid, Leuconoid
What is the major difference between porifera and protista?
Porifera - multicellular
Protista - unicellular
What are the advantages of increased body size and complexity in porifera vs protista?
Efficient filter feeding, increased surface area for gas exchange (cellular respiration), better defence (spicules irritate predator mouthparts), structural support (spicules and spongin fibres)
Describe the evolutionary pressures giving rise to polymorphism in Cnidaria. (long answer)
Adaptation to different environment - specialised morphs depending on habitat and benthic/pelagic.
Optimized feeding - gastrozooids are feeding polyps with tentacles and cnidocytes for capturing prey.
Reproduction - gonozooids specialised for reproduction and do not typically engage in feeding activities.
Dactylozooids - specialised defence polyps equipped with nematocysts, protection from predators and environmental threats. Indirectly contributes to reproductive success and colony growth/longevity.
Division of labour allows colony to efficiently allocate resources and energy between feeding, reproduction and defence.
How are cnidarians dimorphic?
Two forms - polyp or medusa
What are the 3 polymorphic forms of polyps?
Gastrozooids, gonozooids and dactylozooids
What kind of symmetry do medusa forms of cnidaria show?
Tetramerous - divided in units of 4
Which form of Cnidaria is free swimming and which is sessile?
Free swimming = medusa
Sessile = polyp
What are the reasons for radial symmetry in Cnidaria? (long answer)
- Primitive body plan without cephalisation
- Allows prey capture in all directions, especially beneficial due to sessile or slow-moving nature
- Radial arrangement of sensory structures allows stimuli detection from multiple directions, allowing rapid responses to wave current, presence of prey and predators
- Defence from predators in all directions
- Release gametes and larvae in multiple directions, increasing likelihood of successful reproduction
- Benefical for benthic and pelagic Cnidarians. Benthic - extend tentacles in all directions while remaining sessile. Pelagic (e.g. jellyfish) - essential for propulsion
Photosynthesis
Energy
Calcification
Stress
Bleaching
Describe the importance of symbiotic algae (zooxanthellae) to coral biology. (long answer)
- Symbiodinium algae provides nutrients through photosynthesis. The products of photosynthesis, such as glucose and oxygen, are released into the coral tissue, providing essential nutrients and oxygen for coral metabolism.
- Zooxanthellae can make up as much as 30% of the total tissue in coral polyps and as much as 90% of their energy frequently comes from the symbionts.
- This allows them to allocate resources towards calcification—the process by which corals build their calcium carbonate skeletons. This enables corals to grow and maintain their structural integrity, contributing to the formation of reef structures.
- Symbiotic algae contribute to the heat tolerance of corals by dissipating excess light energy as heat during periods of high temperature stress, thereby reducing the risk of coral bleaching. Zooxanthellae can be ejected, leading to coral bleaching under high stress which starves corals and polyps die.
