Lecture 4 Flashcards
1
Q
adaptaions to feed on plants
A
- mouth/ jaws
- intestinal structure and enzymes
- cellulose and lignin are hard to feed on
2
Q
herbivore/ algivore
A
- sea urchins and gastropods were early herbivores
- on land, gastropods have been. successful
- other terrestrial herbivores are the arthropods and rely on anaerobic microbes for digestion (cellulases are rare)
3
Q
herbivores
A
- grazer-browsers, grazer-scrapers, or shredders
- mobile, feeding on sessile prey without killing them (usually) or scraping surfaces
- food is often plentiful
- on land –> plants, fungi
- in water –> colonial cnidaria, bryozoans, or tunicates; bacterial colonies, multicellular algae (i.e. kelp); periphyton accumulating on substrates
- food is often plentiful, but
- small proportion of digestible material per unit weight
- prey may have chemical defenses
- Adaptive features include specialized guts (extended to allow longer digestion time), enzymes, endosymbiotic microbes, and hard, rasping or biting mouthparts
3
Q
biting and rasping mouthparts
A
- Aristotle’s Lantern (sea urchins)
- Five self-sharpening teeth
- Sea Urchins [Echinodermata; Echinoidea (c)] had developed an ability to feed on seaweed
- 5 Muscularly-independent ossicles
- Calcite and MgCO3 makes ossicles very hard
- Primarily for scraping / rasping
- Found in most molluscs
- firm ribbon of chitinous teeth
- used for scraping / cutting
- new teeth are formed at the posterior, for replacement
- Note the Odontophore [as o], the cartilaginous base of the radula
- It is connected to the musculature and extended
4
Q
how to deal with low digest-ability per unit weight
A
- alimentary symbionts ferment polysaccharides to fatty acids, simple carbohydrates
- Often protein may come from fungus present (in “woody diets”)
- Majority of plant material goes unused and invertebrates play a major role in terrestrial decomposition
- Grinding mouthparts, gut microflora, or cultivating fungi facilitate processing of difficult to breakdown materials
5
Q
how gastropods digest
A
- Gastropods (c) also developed a method to digest plants→endogenous cellulases
- Some also have plant-digesting anaerobic microbes (and guts to facilitate their growth)
- In many herbivorous species, the stomach is greatly reduced
6
Q
arthropod mouthparts
A
- Mandibles of early insects unspecialized
- Sclerotized jaws – “tanned” cuticle
- Biting tip and grinding (“toothed”) surface
7
Q
piercing
A
- Alternative to rasping/biting plant material, is piercing the tough plant wall
- Some herbivores remove cells / fluids using specialized mouthparts inserted in xylem/phloem
- “suck out the juice”
- Evolved numerous times in insects
- May be piercing or non- (i.e. Lepidoptera)
7
Q
true bugs
A
- beak like rostrum/proboscis for piercing and sucking
- long sucking tube is the rostrum
- include aphids, assassin bug, cicada, etc
8
Q
tardigrades
A
- Within Ecdysozoa
- Feed on plants of macroinvertebrates, bacteria
- Meal is pierced by pair of oral stylets; internal fluid is sucked into pharynx/complete gut
- Stylets and sucking pharynx are unique to the
phylum
9
Q
Inefficiency of digestion
A
- Despite adaptations, digestion is quite inefficient
- Results in large amounts of material needing to be consumed
- Large amounts of waste material produced
- This material is full of nutrients that are still available to consumers, esp. deposit feeders
- Important ecological role, moving nutrients from photosynthetic producers to other animals
10
Q
prey defences
A
- chemical toxins
- hormone/pheromones mimics
- structural (secreting projections)
- symbiotic organisms (i.e. ants) that may remove browsers
- Plants responding to herbivores is a nice example of coevolution
- plants adapt to prevent being fed upon
- herbivores adapt to how the plant has changed
- Coevolution has led to many defences being adapted to: detoxification, sequestrations, bypass structural defence, escape defending symbionts with chemical mimicry
