BIO2242 Lecture Notes - Lecture 5: Bivalvia, Choanocyte, Midgut
30 May 2018
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FEEDING
• What gives the most energy:
1. Nectar; sugar and water
2. Muscle; iron, nutrients, carbohydrates, and fibre
3. Grass; water, carbohydrates, and fibre
4. Soil (can also be sticks)
5. Sticks (can also be soil
• Which is easiest to get:
1. Soil
2. Sticks
3. Grass
4. Muscle
5. Nectar; seasonal
• There is limited number of food sources and animals feeding is constrained by environment and
body form
• Food materials: plant, animal, symbiosis
• Digestive system: no gut cavity, gut cavity present
• Basic feeding modes: deposit feeding, suspension feeding
INVERTEBRATE FEEDING PATTERNS:
Plant material as food:
o Abundant
o low quality (lower density of nutrients)
o low assimilation efficiency (lower % incorporated into body)
o has cell wall
o Requires special enzymes (humans an’t eak don ell all
Animal material as food:
o High quality
o high assimilation efficiency
o Defended -> needs sophisticated feeding strategies (needs to hunt)
Symbionts and their
products
o Host must be able to accommodate
o Bacteria, algae or protozoans; produce food used by the host
Eg. Algae (photosynthetic endosymbionts) in sponges
Gut flora in herbivorous mammals
Deposited food
o Sediments (soil)
o Abundant yet dilute (organic material mixed in inorganic)
o Must sample large amounts of sediment
Nonselective:
o Swallow sediment whole ->
digest as much as possible
-> spit out the rest
o Need to eat a lot
Selective:
o Eat specific parts of
sediment
Food in suspension
o Dilute: small quantities of food -> large volume of media
Requires a net (trap food) and current (move food towards you)
find more resources at oneclass.com
find more resources at oneclass.com
• Very small food: endocytosis followed by intracellular digestion (single cell engulf single food
particles)
• Larger food: extracellular digestion (partially break down food before swallowing)
Gut -> add enzymes -> absorb nutrients
• Digestive systems:
No gut cavity
o Gut isn’t euied if ey thin
o Food engulfed by endocytosis
Eg. Protozoans and sponges
Gut cavity
o Some digestion by enzymes in gut (extracellular)
o Allows ingestion of larger food masses
o Greatly increases surface area for absorption (great infolding,
microvilli -> more nutrients absorbed)
Simple sac-like gut
o Single opening – 2 way
flow
Eg. Flat worms
Tube-like gut
o 2 openings (mouth and anus) – 1
way flow
o Allows specialisation of gut regions
o To eat big food
• Feeding mechanisms in invertebrate groups:
Porifera; Sponges
o Filter feeders (food suspended in water; need net and current)
o No gut cavity
o Have perforated tube (small holes)
o Current created by choanocytes (flagella)
o Intracellular digestion (engulf food particles)
o Sort particles by size
o Use algae as photosynthetic Symbionts (provides 40-80% of energy)
o Carnivores -> capture prey such as fish using spicules
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Gut flora in herbivorous mammals: sediments (soil, abundant yet dilute (organic material mixed in inorganic, must sample large amounts of sediment. Nonselective: swallow sediment whole -> digest as much as possible. Selective: eat specific parts of sediment, need to eat a lot. Food in suspension: dilute: small quantities of food -> large volume of media. Requires a net (trap food) and current (move food towards you: very small food: endocytosis followed by intracellular digestion (single cell engulf single food particles) Larger food: extracellular digestion (partially break down food before swallowing) Gut -> add enzymes -> absorb nutrients: digestive systems: Gut cavity: gut isn"t (cid:396)e(cid:395)ui(cid:396)ed if (cid:448)e(cid:396)y thin, food engulfed by endocytosis. Protozoans and sponges: some digestion by enzymes in gut (extracellular, allows ingestion of larger food masses, greatly increases surface area for absorption (great infolding, microvilli -> more nutrients absorbed) Simple sac-like gut: single opening 2 way. Tube-like gut: 2 openings (mouth and anus) 1 flow.
