Bellwork: How are humans adapted for the diet that we eat?

Animal behavior 27.1 Feeding and digestion

What different ways can animals obtain food? All animals are heterotrophic There are 5 different ways that animals can obtain food Filter Feeders Detritivores Carnivores Herbivores Nutritional symbionts

What do filter feeders eat? Often Algae and small animals, plankton etc…. They often utilize modified gills or structures like nets Invertebrate filter feeders are often small or colonial Spend their adult life in one spot Larger filter feeders, such as a whale shark, will feed whilst swimming

What is Detritus? Detritus is made up of decaying bits of plants and animal material Detritivores feed on detritus Energy is also obtained from the bacteria, algae and other micro-organisms that grow on and around it Example – earthworm Often essential component of an ecosystem

How do carnivorous invertebrates catch their food? Through poison tipped darts or venomous fangs All carnivores eat other animals Often utilize teeth, claws, speed and/or stealth to bring down prey

How can a herbivore live on such a simple diet? Animals need complex digestive systems to live on just leaves/grass Due to low nutritional content Can contain poisons Hard parts can damage teeth Some herbivores live on nuts, seeds and fruits Many mammals and birds High energy compounds

What does symbiosis mean? Dependency of one species on another A symbiont is an organism involved in symbiosis Parasitic Symbionts Within or on host organism Some simply nuisance, some cause serious disease Mutualsitic Symbionts Both participants benefit What examples can you remember?

How do animals process food? By either intracellular or extracellular digestion Intracellular Food digested in specialized cells that pass nutrients to other cells by diffusion Example - sponge Extracellular Food broken down in digestive system not specific cells Food can then be absorbed and nutrients taken where they need to go

Extracellular digestion explained… Gastrovascular cavities Single opening for food ingestion and expelling of wastes Cells lining the cavity will secrete enzymes and absorb digested food Other cells surround food particles to digest them Nutrients transported to cells in the body Digestive tracts Many invertebrates and all vertebrates have a digestive tract – two openings Specialized structures perform different tasks – stomach, intestine etc.. Solid waste disposal Some indigestible material will always be left – must be expelled

How are mouth parts adapted for different diets? The mouthparts and digestive systems of many different organisms have evolved many adaptations to different food types Eating meat Designed to capture food, hold it, and slice/dice Eating plant leaves Adapted to rasping/grinding

How can digestive tracts be specialized? Carnivorous invertebrates typically have short digestive tracts that produce fast acting, meat-digesting enzymes No animal produces enzymes for breaking down cellulose Some herbivores have very long intestines or specialized pouches for harboring microbial symbionts Cattle have a pouchlike extension of their esophagus, called a rumen Where symbiotic bacteria digest cellulose Animals with rumina (like cattle) often regurgitate partially digested food and ‘re- chew’

Key Points questions What is a nutritional symbiont? How would a coral be affected if all of its symbiotic algae die? What are the two types of digestion that animals use to breakdown and absorb food? What are the major differences between gastrovascular cavities and digestive tracts? What is the relationship between a ruminant and its microbial symbionts?