feeding and digestion Flashcards
(70 cards)
1
Q
Heterotrophy
A
The ingestion of food in order to satisfy energy requirements
2
Q
Strategies for the ingestion of small particles
A
- pseudopodial/ciliated oral groove (protozoa)
- ciliate (bivalve molluscs)
- tentacular (cnidarians, annelids, bryozoa)
- mucoid (tunicates)
- setous (crustaceans, baleen whales, flamingos etc)
- deposit (annelids)
3
Q
Setae
A
- extensions of exoskeleton, endoskeleton or dermally derived extensions involved in feeding
- crustaceans, baleen whales, flamingos etc
4
Q
Strategies for the ingestion of large particles
A
- scraping/boring (gastropods)
- seizure of prey (carnivores)
- traps (spider webs, pits etc)
- fluid feeding
- direct absorption
5
Q
Fluid feeding
A
- sucking without penetration (honeybees, hummingbirds, butterflies etc)
- sucking with penetration (leeches, ticks, aphids etc)
6
Q
Direct absorption
A
- across body surface (endoparasites, aquatic invertebrates)
- from symbiotic partners (corals, ruminants)
7
Q
Phagocytosis
A
- simplest form of heterotrophy, size restricted organisms
- protozoa, sponges
- create pseudopodia that surround food particle and engulf it
- create phagosome, food vacuole
- lysosome (digestive vacuole containing enzymes) fuse with phagosome
- digestion occurs inside phagolysosome, waste excreted via anal pore
- some protozoa have oral groove lined with cilia that beat, creating a current into their cytopharynx where phagosomes are formed
8
Q
Ciliate feeding
A
- common in marine vertebrates and marine invertebrate larvae (suspension feeders)
- cilia in larvae for feeding and swimming, channels water down to mouth
- bivalves have a pair of gills covered in cilia
9
Q
Ciliate feeding in bivalves
A
- mussels, oysters, clams etc
- pair of gills in mantle cavity covered in cilia
- 3 types of cilia, lateral, frontal and laterofrontal
- all beat, creating inhalant and exhalant current (unidirectional flow of water)
- particles trapped on cilia on inhalant current
- particles passed down gill to food grove at bottom
- trapped by a string of mucous that passes directly down into the stomach through a winding motion
10
Q
Feeding through mucous nets
A
- tunicates (Cordate, non-vertebrate with a notochord), majority benthic
- large central atria (pharynx) lined with endostyle layer with stigmata (holes)
- inhalant current, water through incurrent siphon, though stigmata into pharynx
- particles trapped by iodine rich (homologous to vertebrate thyroid gland) mucous net
- very fine net, capable of trapping bacteria
- net periodically passed down into stomach, particles digested in stomach and intestine
- water flows out on exhalant through excurrent siphon
- anus next to excurrent siphon, faeces also carried out by exhalant current
11
Q
Setae in crustaceans
A
- bristles, extension of exoskeleton, can’t use cilia for feeding because of exoskeleton
- larger than cilia but very efficient
- trap particles suspended in the water column and pass to the mouth
- krill, very fine setae project from walking legs at front, in winter they use them to brush algae off underside of ice (also shrink as there is little food)
- copepods have maxillipeds, feeding appendages with setae that beat
- copepods and krill are important zooplankton (2nd trophic level in marine food chain)
12
Q
Setae, gill rakers
A
- setae derived from endoskeleton in filter feeding fish
- on first gill arches anterior to gill filaments
- swim with mouth open
- water passes along the side of gill rakers, catches suspended particles
- particles removed and periodically swallowed and digested
13
Q
Baleen whales (Mysticeti), setae
A
- dermally derived baleen plates primarily composed of keratin
- many rows of frayed fibres along sides of top jaw
- whale opens mouth, water comes in through front
- whale closes mouth and reduces volume, forcing water laterally through baleen plates
- small fish and krill trapped by plates, tongue used to wipe plates clean, swallowed and digested
14
Q
Deposit feeding
A
- ingestion of organic matter from the soil or sea floor
- gain nutrition from microorganisms stuck to particles or lumps of organic matter
- cheap feeding strategy, not much movement required
- subsurface or surface feeders
- non-selective or selective feeders
15
Q
Deposit feeders, lugworm
A
-Arenicola marina
- marine annelid found on sandy beaches
- eats microbes that grow on sand particles
- selective subsurface feeder, uses proboscis to select particles of a specific size, smaller particles increase surface area microbes can grow on, only live on beaches with fine sand
- adult can grow up to 1ft, can burrow 20cm
- Sand cast on surface = faeces at top of tail shaft, dimple next to faeces = top of feeding funnel
- peristaltic contractions along body draws in water down tail shaft, along gills and out feeding funnel
- liquefies sand at feeding shaft, making it continuously fall down towards mouth
- well at top of feeding funnel creates turbulence in water flowing over it, organic matter suspended in water collects in funnel, provides carbon for the microbes it feeds on
- constantly feeding, limited by bacterial productivity
- bioturbation, turns over sediment
- lives in anoxic sediment (black sand), aerates surrounding sediment through irrigation
- critical to the ecology of sandy beaches
16
Q
bioturbation
A
- turning over/reworking of the top 5-10cm sediment
- from feeding, burrow construction and maintenance, respiration, burrowing etc
- increases organic matter (nitrogen), facilitates species interaction (increases diversity), increases water content (easier to burrow), alterations in sediment biogeochemistry (O2 delivered alters chemical reactions) etc
17
Q
rasping radula
A
- molluscs
- toothed tongue that scrapes/rasps surface of food
- radula along with cellulases critical to mollusc success
- teeth sit on cartilagenous rod
- tongue highly muscularised, protractor and retractor muscles
- new teeth continually synthesised at back and slowly passed to front at front teeth worn down
- limpet teeth though to be hardest know biological material (rasp rock)
18
Q
examples of modified radula
A
- modified into harpoon or drill, specialised for carnivory
- oyster drills, drills into oyster, secretes digestive enzymes and eats oyster
- cone snail, harpoon with neurotoxin venom, predate on fish
19
Q
carnivory in arthropods, crustacea
A
- modified chelate legs (pincers)
- chelae consist of last segment of leg (dorsal dactylus) with second last segment extending under (ventral propus)
- handedness, one crushing pincer (larger), one cutting pincer (smaller)
- location of crushing pincer depends on prey mollusc shell spiral direction, specialised to make it easier to break
- consume molluscs etc
20
Q
carnivory in arthropods, chelicerata
A
- chelate pedipalps
- often used for mating in male spiders
21
Q
traps
A
- capture passing prey
- Turbellaria, slime containing neurotoxins (flatworm)
- chelicerata, silk
- pits, Myrmeleiontidae
22
Q
traps, pits
A
- Myrmeleiontidae (antlions)
- create pit in sand
- sit and wait for prey in burrow at bottom of pit
- steeply sloped pit (critical angle of repose), any disturbance of sand by prey will cause sediment to destabilise and sides to collapse, causing prey to fall into pit
23
Q
evolutionary adaptations of vertebrate digestive systems
A
- correlate with diet
- craniodental modifications (skull and jaw)
- stomach and intestinal adaptations
- mutualistic adaptations
24
Q
hagfish
A
- deepsea marine scavengers, feeding opportunities rare so conserve energy and eat almost anything
- acute chemosensory organs
- agnathe (jawless), 2 plates in mouth with sharp tooth-like structures
- plates come forward when mouth opens, interdigitates when mouth closes (cutting motion)
- tentacles surround mouth for detection of prey
- can uptake dissolved organic matter directly across integument
- when it finds intact prey it embeds teeth in animal, knots tail and passes know forward to head to use as a lever to rip flesh (expensive strategy, only uses to make first incision in carcass)
25
Chondrichthyes/elasmobranchs, filter feeding
- diverse strategies, filter feeding to carnivory
- filter feeding using gill rakers
26
Chondrichthyes/elasmobranchs, carnivory
- cranial kinesis, motility within the head skeleton enables the consumption of large prey items
- hyostylic jaw suspension allows the jaw to be placed into multiple positions and
protrusion of the upper jaw
- palatoquadrate = upper jaw
- mandible = lower jaw
- teeth on palatoquadrate large, serrated and recurved
- teeth sunk into prey by protruding upper jaw
- lateral undulations of body moves head and rips flesh
* very sensitive chemoreceptors and electroreceptors (ampullae
of Lorenzini), detect very weak electrical signals from prey
27
actinopterygii, teleosts
- evolution of specialisation of the jaw directly related to diet
- protrusible pharyngeal jaws important in this group, second set of jaws further back that can move forward
- diversity of feeding mechanisms from simple prey grabbing to specialised suction devices e.g. John Dory (evolved 3 or 4 times in different teleost clades)
28
feeding via symbiosis
- autotrophic: chemosynthetic e.g. Riftia (hydrothermal vents, thioautotrophic bacteria, feeds on sulphides), phototrophs e.g. coral and zooxanthellae
- heterotrophic e.g. ruminants
29
photoautotrophic symbionts
- very common to marine invertebrates
- coral (Cnidaria) and zooxanthellae (dinoflgellate, Symbiodinium microadriaticum, various different strains)
- live in a nutrient poor environment so coral relies on nutrition from symbiont
- can lose symbiont temporarily (coral bleaching, alga provides pigment), coral ingests or expels them in stressful conditions
- coral recycles CO2 back to zooanthellae
- different combinations of strains in different coral and different strains in different parts of coral
- anemones and zoochorellae (green alga, Zoochorella parasitica), more separate than corals
30
heterotrophic symbionts, vertebrate gut microbes
- vertebrates cannot digest cellulose, so many rely on fermentation by microbes (protists, fungi and bacteria)
- 3 main groups
- foregut (fermentation chamber part of stomach), ruminants including cattle, sheep, giraffes, non-ruminants including kangaroos, sloths etc
- mid gut (fermentation chamber part of small intestine), very rare, found in herbiverous and omniverous fish like tilapia, carp etc
- hind gut (fermentation chamber part of large intestine), rabbits, horses, elephants, ostriches etc
31
herbivore foregut fermenters
- multi-chambered stomach
- rumen (anoxic), reticulum and omasum for storage and microbial processing (non-acidic)
- abomasum for digestion (acidic)
- very slow fermentation but effective, allows for digestion of moderately fibrous food
- less craniodental specialisations as chewing is less important
32
foregut fermenters, rumen
- anoxic and non-acidic fluid environment
- protists, bacteria and fungi break down cellulose into short chain fatty acids (SCFAs), acetic, propionic, butyeric
- vitamin B and essential amino acids also synthesised
- urea from blood transferred into rumen, symbionts convert urea into ammonium to use as a nitrogen source for protein synthesis
- SCFAs and amino acids absorbed, some ruminants digested to be able to absorb vitamin B
33
hindgut fermenters
- simple stomach and intestine, enlarged caecum or colon
- microbial breakdown of cellulose to form SCFAs
- relatively fast fermentation process, allows for ingestion of very fibrous food
- thought to be ancestral condition other forms of fermentation evolved from
- problem with fermentation occurring after small intestine, vitamin B and essential amino acids not absorbed/digested, nitrogen recycling cannot occur
- 2 strategies, coprophagy e.g. rabbits, chewing e.g. horses
34
coprophagy and chewing
- allows more absorption of vitamins/ amino acids
- coprophagy, rabbits have 2 types of faeces
- know when material is emptied from the caecum, eaten directly from anus, can access B vitamins as it passes through the small intestine
- horses reliant on eating and chewing a lot to obtain nutrients
35
nutrition
diet must supply
- chemical energy (ATP) and organic carbon and nitrogen for biosynthesis of complex molecules
- compounds that cannot be synthesised, essential nutrients including amino acids, fatty acids, vitamins and minerals
36
amino acids
- 20-200 amino acids required for the synthesis of all proteins in animals
- animals cannot create 8-10 essential amino acids
- animal products are 'complete', contain all essential amino acids
- plant products are 'incomplete', a variety of plants need to be eaten to obtain all essential amino acids
37
fatty acids
- essential fatty acids must be obtained from diet
- mammals cannot create double bonds at omega-3 and -6 positions, must be obtained from diet by consuming alpha-linoleic acid and linileic acid
- cholesterol important in maintaining fluidity of membranes and synthesising hormones
- fatty acid deficiencies very rare
- carbohydrates can also be converted into fats
38
vitamins
- must be obtained through the diet
- organic molecules required in small amounts
- diverse functions, cofactors for enzymes etc
- 2 groups
- fat soluble: A (retinal), D (absorbing calcium), E (antioxidant *OH), K (blood clotting)
- water soluble: B, C (antioxidant *OH)
39
minerals
- must be obtained through diet
- inorganic molecules required in small amounts (<1mg to ~2500mg)
- diverse functions, cofactors for enzymes, metalloproteins etc
- Ca and P for bone building and maintenance
- Ca for nerve function
- Fe for haemoglobin and cytochromes
- other include selenium, zinc, copper etc
- can become toxic in large amounts but unusual
40
digestion
= the breakdown of food molecules by enzymes into smaller molecules to facilitate distribution
2 types:
- extracellular = digestion occurs outside cells within 'digestive cavity' (evolved after intracellular)
- intracellular = digestion occurs within cells lining 'digestive cavity'
41
absorption
= the transfer of nutrients from outside
of the animal across the gut wall and into the blood or haemolymph
42
Digestion, phylum Cnidaria
- intracellular and extracellular digestion
- evolution of digestive (gastrovascular) cavity, significant evolutionary step
- indigestible material rejected through mouth
- nutrients pass around animal via diffusion
43
Cnidaria, gastrodermis
lines gastrovascular cavity, has flagella to mix food
4 cell types
- enzymatic gland cells, secrete protolytic enzymes for extracellular digestion
- nutritive muscular cells, ingest food via pseudopodia for intracellular digestion
- mucous gland cells, concentrated around mouth, lubricant for prey entering and waste exiting
- nerve cells, make up nerve net, fewer in number
44
digestion in free living Platyhelminthes
- no through gut
- food enters mouth and muscular protrusible pharynx into gastrovascular cavity
- some are simple and unbranched, others divided into lobes to increase surface area
- enzymes released by cells, extracellular digestion
- nutrients pass around animal through diffusion
- majority carnivores, feed on dead or injured organisms
45
digestion in parasitic Platyhelminthes, Tapeworm (Taenia)
- no sensory organs, gut or mouth
- specialised hooks/suckers to attach to wall of small intestine
- already digested materials from small intestine absorbed across body
- protective cuticle highly resistant to digestive enzymes
46
evolution of through-gut and extracellular digestion
- as volume increases a greater SA for absorption and digestion is needed
- majority of animals have a through-gut,
staring with a mouth and terminating at the anus
- allows for specialization of
the gut into various structures, stomach, intestine etc
- efficient digestion and
absorption.
47
food processing
- ingestion, insoluble food in via mouth, chewing/mastication starts the digestion process
- digestion, mechanical and chemical (enzymes) breakdown
- absorption and assimilation, soluble product taken across gut wall and assimilated
- egestion, undigested material ejected as faeces
48
Phylum Annelida, eathworms
- consume decaying organic matter (or microbes on OM?)
- specialised compartments along alimentary canal
- mouth
- pharynx (muscular, generates sucking motion for ingestion)
- oseophagus (peristaltic contractions)
- crop, main storage organ
- gizzard, secondary structure involved in mechanical breakdown of food, often contains swallowed stones
- intestine, symplified tube (no large and small) with typhlosole, indentation along dorsal side to increase surface area
- pygmidium, anus
49
Phylum Arthropoda, exoskeleton
- exoskeleton lining/cuticle also runs into and lines the the foregut and hingut
- doesn't line midgut as this is where absorption takes place
50
Phylum Arthropoda, insects
- crop and gizzard/proventriculus for storage
- ceca (midgut), principle site of digestion and symbionts if present
- malpighian tubules in hindgut for osmoregulation
- rectum and anus
51
Phylum Arthropoda, crustaceans
Foregut:
- anterior/cardiac stomach, cuticle of exoskeleton serrated (gastric mill) for mechanical digestion
- posterior/pyloric stomach, some enzymatic action (enzymes move up from midgut), fine cuticular bristles (setae) strain particles on way to midgut
Midgut:
- hepatopancreas, large surface area for digestion, storage of certain lipids and toxin sequestration
- ceca (symbionts if present)
Hindgut/anus
52
components of vertebrate digestive system
- 4 parts (foregut divided into headgut and foregut)
- headgut, mouth, tongue and pharynx, capture/engulfment and preparation of food for digestion (mastication)
- foregut, oesophagus and stomach (or crop and gizzard), move food from headgut to stomach and start of mechanical digestion
- midgut, small intestine, main site of chemical digestion and absorption
- hindgut, large intestine, absorption of water and minerals, storage of waste prior to defecation
53
Myxini, Hagfish
- unique adaptations, lacks specialisation
- propels food along alimentary canal using ciliary action (unusual, usually peristaltic contractions)
- food enclosed within a mucoid bag which is secreted by the gut wall, permeable to enzymes (in) and digestive products (out)
- indigestible material secreted in the membrane
- unique to hagfish, functional significance unknown
- similar structure in blood sucking insects so could be an adaption to eating food with a high bacterial load (hagfish often eat carcasses)
54
Actinopterygii
- diversity of alimentary canal related to diet
- mouth with teeth and specialised jaws for prey capture etc
- many fish also have pharyngeal teeth/jaws for mastication
- oseophagus
- stomach, specialised
- pyloric sphincter to regulate food movement
- pyloric cacae at start of midgut, finger like extensions to increase surface area
- intestine (no large and small)
- diffuse pancreas, not obvious structure, found along length of intestine and around cacae
- anus
55
Actinoperygii, stomach specialisation (frequency of feeding)
- some fish have no stomach, deposit feeders that are constantly eating so do not need a food storage organ (also no acid phase of digestion)
- some fish have a straight stomach
- some fish have a U or Y shaped stomach, more storage space for intermittent feeders
e.g. mackerel, starve for 4-5 months so food needs to be stored and needs to be able to eat large amounts of food at once when food is available
56
Actinopterygii, stomach specialisations (type of diet)
- carnivores e.g. rainbow trout have less specialisations and a relatively short intestine (meat easy to digest)
- omnivores specialising in animal sources e.g. Catfish, larger stomach, slightly longer intestine
- omnivores specialising in plant sources e.g. carp have a longer intestine (slows down digestion, plants harder to digest)
- Milkfish, microphagous planktivore (plants and animals) has a well defined gizzard and very long intestine
57
Class Aves
- specialisation of the oesophagus, crop for storage, feeding young (regurgitation, 'crop milk', nutritious fluid secretions e.g. in pigeons, important when food is scarce)
- stomach subdivided into proventriculus (chemical digestion) and gizzard (mechanical digestion)
- small intestine for chemical digestion and absorption
- ceca if present
- large intestine
- cloaca, waste storage and water absorption, formation of uric acid
58
Aves, seasonal variation in the alimentary canal
- related to changes in diet, alimentary canal can lengthen up to 20% or shorten
- longer intestines for plant material, requires longer time to digest, more time for enzyme and symbiont action
- smaller intestines for animal material, required less time to digest
59
Hoatzin bird
- foregut fermenter (unusual) in large crop
- had to displace flight muscles to make way for crop so very poor fliers
- primary predator defence is smell from foregut fermentation
60
mammalian alimentary canal
- mouth, teeth (mastication), salivary glands (lubrication, chemical digestion from amylase, antimicrobial)
- oesophagus (peristaltic contractions)
- sphincter prevents acid burning oesophagus (risk of oesophageal cancer)
- stomach, pepsin enzymes (chemical breakdown, requires pH 2), storage, mucous lining protects stomach lining from acid, churning (muscle contraction) for mechanical breakdown, water and ethanol absorbed
- emptying of stomach into duodenum (start of small intestine) highly regulated by sphincter
- secretions from gallbladder neutralises stomach acid
- chemical breakdown and absorption (some mechanical) in small intestine, enzymes secreted from pancreas and walls of small intestine
- large intestine (ascending, transverse and descending colon) reabsorbs water secreted from blood to assist with enzyme action
61
Mammalian pancreas
- secretes digestive enzymes important in protein breakdown (and lipid and carbohydrate breakdown)
- pancreatic amylase
62
Mammalian biliary system
- secretes bile, neutralises acid and emulsifies fats (lipases are hydrophilic, lipids are hydrophobic, so breaks down lipids into very small droplets, increasing surface area)
- bile contains sodium hydrogen carbonate to neutralise acid and bile salts to emulsify fats
- released by gallbladder and recycled by blood
63
Mammalian digestion, muscular activity
- peristalsis and segmentation
- moving and regulating food through the alimentary canal
- mechanical digestion
64
Chemical digestion
= the breakdown of food molecules into constituent parts that can then be absorbed by the action of enzymes
- requires hydrolytic enzymes, needs water
65
Types of digestives enzymes
- intraluminal, secreted into lumen, disperses freely with food
- membrane associated, attached to the epithelial cell membrane, food in contact with the cell, in the wall of small intestine with active sites pointing outwards
- intracellular, inside the cells, food must be taken into the cytoplasm
66
Breakdown of carbohydrates
- relatively easy to break down as all the same bonds (repeated glucose subunits)
- 2 enzymes required, polysaccharide to disaccharide to monosaccharide
- amylase breaks down starch to form the disaccharides maltose and isomaltose
- maltase breaks down maltose into glucose
- other disaccharidases include sucrase, lactase, trehalase etc
67
Breakdown of proteins
- different bonds so more complicated to break down
- requires exopeptidases to break bonds at ends and endopeptidases to break bonds in middle
- zymogen or proenzymes, inactive precursor enzymes
- pepsin released by stomach as pepsinogens (protects against self digestion)
68
Pancreatic peptidase
- endopeptidases include trypsin, chymotrypsin, elastase, collagenase
- exopeptidases include carboxypeptidases A and B
69
Types of enzymes needed for protein digestion
- all 3 mechanisms of actions required
- intraluminal enzymes break down proteins into free amino acids and oligopeptides
- oligopeptides further broken down via membrane associated proteins
- intracellular peptides complete the digestion and absorption process
70
Digestion of lipids
- fewer types of enzymes needed than proteins, more than carbohydrates
- problem, enzymes work in water, lipids are insoluble
- bile salts emulsify fats
- pancreatic lipases through luminal action
- breaks fats and oils (triacylglycerols) into free fatty acids, glycerol and 2-monoacylglycerols
- cholesterol and phospholipids require phospholipases and esterases in addition to lipases
