W7 LECTURE 1: Animal digestion feeding strategies

Feeding

• Process of obtaining and ingesting food

• Must target food that meets nutritional needs

• Success depends on feeding mechanism

– Feeding apparatus and behaviour

• Balance between energy expenditure and intake – evolutionary driver

Food sources

• Sources of energy - Trophic levels, about 90% loss of energy via heat at each trophic level

• Food availability can vary - E.g. seasonality

Feeding mechanisms

• Feeding on organisms that are individually attacked and ingested

• Suspension feeding

• Symbioses

Feeding on organisms that are individually attacked and ingested

Requires that food organisms are

• Located - find the organism

• Identified - find the correct organism

• Subdued

• Ingested

- Includes carnivores and herbivores e.g. Carnivorous mammals, Grazing mammals, Carnivorous fish, Birds of prey, sea stars, nectar feeding, gastropods

Some use toxic compounds

• Work by inflicting structural damage and/ or subdue prey

• Examples

• Scorpions

• Spiders

• Jellyfish

• Snakes - secretes a neurotoxins

Suspension feeding

• Common in aquatic organisms

• Feeding on organisms that are very small in comparison with the feeding animal

• Has evolved often

• Feeding on organisms lower on food chain

• Increase of energy available

• E.g. Bivales - filter ingested water that contains food particles (planktons), Basking/Whale sharks, Baleen whales, Humpback whale

Symbioses

– With autotrophic microbes - use inorganic compounds

– With heterotrophic microbes - use organic compounds, e.g. Gut microbiome

Reef corals

photoautotrophic microbes - algae use light to produce food for the coral

Hydrothermal vent species

chemoautotrophic microbes

• No photosynthesis as there is no light

• Chemoautotrophic bacteria ensures oxidation of chemicals similar to photosynthesis to produce organic compounds

• E.g.Giant tube worm

Ruminants

Fermenters

Diversity in digestive structures

• Invertebrates

– Blind guts (incomplete digestive tract)

– Complete digestive tract

Hydra

• Blind guts, one opening that works as a mouth and an anus

Nematode

• complete digestive tract

Insect digestive system

 

Bivalve digestive system

Starfish digestive system

• everted stomach

Mouth - Tongues

• Present in almost all vertebrates

• Used to gather food, speech development

Mouth - Teeth

Makes food more accessible for the digestive system

 Mouth - Salivary glands

Makes food more accessible for the digestive system

 

Mouth - Salivary glands

• Contains enzymes that digest carbohydrates in the mouth

• Not all vertebrates E.g.fish have salivary glands

Esophagus

• Esophagus: moving food to stomach

• Crop: food storage in birds

Stomach

• HCl

• Pepsinogen - protein digestion

Gizzard

• Mechanical grinder

• Used to grind grains and seeds

• Seen in some birds

Rumen

multichambered stomach that holds microorganisms

Ceca

• Binding pouches

  – Important in non-ruminant herbivores

  – House microorganisms, cellulose digestion

Intestines

Used for breakdown and absorption of food with less energy