Feeding Strategies & Digestion

Ingestion

the process of bringing food into the digestive tract

What does ingestive provide?

chemical energy for synthesizing ATP, carbon-containing compounds and minerals for building complex macromolecules

Digestion

mechanical and enzymatic breakdown of food

Why is digestion required?

difficult for macromolcules to enter the cell

Alimentary Canal

complete digestive tract that consists fo a tube with a mouth at one end and an anus at the other end

Digestive System

alimentary canal + organs; functionally connected to all body systems & anatomically connected to nervous, cardiovascular, endocrine, and lymphatic systems

Digestive System order

mouth → esophagus → stomach → small intestine → cecum → large intestine → anus

Mouth

buccal cavity; mechanical digestion (teeth, tongue, saliva moistens) & chemical digestion (saliva)

Salivary amylase

digests carbohydrates

lingual lipase

digests lipids (fats)

Esophagus

long, muscular tube that transports food to the stomach; lined with epithelial cells to resist abrasion; no digestion/nutrient absorption; uses peristalsis

peristalsis

smooth muscles contract and relax in coordinated fashion

Stomach

mechanical digestion (muscle contraction), chemical digestion (gastric juice- HCl lowers pH to 1.5-2.0 & mucous to protect stomach lining), enzymatic digestion; no nutrients are absorbed

pepsin

digests proteins

nervous system stimulates gastric cells to produce

gastric juice

chyme

an acidic mixture of food and gastric secretions that passes from the stomach to the small intestine; made by muscles contractions mixing materials

Small Intestine

major site of nutrient absorption; digestion of protein, fats, carbohydrates; undigested food sent to colon; uses peristalsis

How does the small intestine increase surface area?

folding with villi and microvillia

Villi

highly folded surface containing finger-like projections

Epithelial cells

absorb nutrients from digested food; in small intestine

Dense Capillary network

in villi/small intestine; allows nutrients to be released to blood stream; rapidly transports absorbed products

Suspension feeder

any strategy to take food particles out of water column; active and passive; usually can’t move

passive filter feeder

straining suspended matter and food particles from water with a mesh; depends on water flow

passive filter feeder examples

barnacles

Active filter feeder

create own water currents to strain food with mesh; makes own water flow with pump

Active filter feeder examples

mussels, tunicates

Songes

intake through small pores (ostia); expel water out osculum

Deposit feeder

obtaining nutrients from particles that settle on substrate; gain nutrients from microalgae and bacteria

Deposit feeder examples

spaghetti worms; sea cucumbers

Sea Cucumbers

use branched, sticky tentacles to collect organic particles from mud or sand; sediment passes through their alimentary canal where organic matter is digested; inorganic particles are excreted

Herbivores

eat plants or seaweeds

Herbivore examples

muskox, periwinkle snails

Periwinkle snails

use radula to scrape plant material or biofilm off rocks; radula rolls food particles back toward the mouth

Radula

ribbon-like structure covered with hundreds of microscopic chitinous teeth

Consumers

receive energy by consuming other organisms

Carnivore

an animal that feeds on fleshc

carnivore examples

nemertean worm, orcas, sea anemones

Omnivore

food of both plant and animal origin

Nemertean worm

feeds on polychaete worms that burrow in the sand; everts it’s proboscis (elongated appendage from the head of an animal), latches onto its prey and injects with a neurotoxin

Defenses for Prey

chemical, morphological, behavioral

Chemical defense examples

sponges, algae

Morphological defenses

color, spines, shells

Aposemantism

(color) highly noticeable and distinct from harmless organisms; show harmful so don’t eat

Crypsis

(color) avoid detection by other organisms; blends in

Nematocysts

explosive organelles found in all Cnidaria; capsule contains a coiled, hollow, usually barbed thread; projected in self-defense or to capture prey

Behavioral defense example

scallops, urchins, snails

Sea anemone

escape response when touched by sea star; “floats” away; feels touch by chemical cues

Cymothoa exigua

eats tongue of fish; sits in tongue space to eat food that the fish gets