Evolution of the Gut Flashcards
What are the six main functions of the gut?
- Receive ingested food
- Store food temporarily
- Reduce food physically
- Reduce food chemically
- Absorb products of digestion
- Eliminate undigested waste
What was the first invertebrate to develop an alimentary canal (one way movement from mouth - anus)?
Nematodes
What do most invertebrates possess?
Gastrovascular cavity
What is a protostome?
Mouth developed from blastopore(Most inverts)
What is a deuterostome?
Anus developed from blastopore (Echinoderms and chordates)
What was the first multicellular gut like?
Like a bag - food flowed in through mouth and waste flowed back out the same way - bacteria helped digest food within these two cell thick structures
What is Cnidarian gut structure like?
Mouth and a blind Gastrovascular cavity - lined with phagocytic, secretory and ciliated cells
What is Nematoda gut structure like?
Evolved a more efficient system - tubular so that food flowed in the same direction and exited the anus
What is a Mussel’s gut structure like?
Filter feeders - take in water and their gills strain particles.
Gill sheets with cilia, mouth and stomach
What is Annelia gut structure like?
Consists of a head gut (mouth, buccal cavity, muscular pharynx) - secretion and digestion and foregut (oesophagus, crop and gizzard) and the intestine.
What is Arthropoda gut structure like?
Most crustaceans are filter feeders and their foreguts are lined with chitinous ridges. Their midgut contains glandular ceca.
What are most insect’s guts like?
Headgut, foregut, midgut and hind gut.
The headgut is specialised for sucking, chewing or piercing.
What is the role of the crop and proventriculus in insects?
Food storage and controlling the passage of food into the midgut - can contain teeth in some species.
What were ancestral vertebrates guts like?
Probably filter feeders such as: lampreys. They had simple digestive systems and mucus moved to gut by cilia.
Why are lancelets good indicators of evolutionary origins of vertebrates?
Genomes hold clues of how vertebrates have employed old genes for new function
What is a lancelets gut like?
Gut is a simple tube from mouth to anus with a diverticulum which secretes digestive enzymes into lumen. Absorption occurs by diffusion into epithelial cells.
What advantage did fish have over earlier organisms?
Evolved teeth, livers and kidneys which could remove poisons. These specialised parts prepared the food for the body, their cells were able to get more energy out of the food with less work
What is an Agnathan gut like?
No jaws but have cyclostomes (rasping organs like tongues) No stomach or oesophagus but have a straight intestine
What is an amphibian’s digestion like?
Frogs evolved to have a tongue to help catch and digest their food. They also evolved to have a pancreas, gallbladder and separated intestines. They also separated their faeces from urine. The tongue and saliva helped to predigest food so cells could get more energy from molecules of food. Frogs have more energy to jump around on land
What are the main characteristics of a tetrapod digestive system?
Increased lubrication and then limited chemical and physical digestion. Salivary glands lubricate and predigest food. Fleshy and movable tongue usually present.
What are the characteristics of a reptilian gut?
Similarly to amphibians. Birds possess gizzards rather than teeth. Evolved to have beaks instead.
Longer ciliated oesophagus, stomach is simple and curved.
What are some characteristics of a birds gut?
Storage organ called a crop.
Stomach is separated into two parts - anterior proventriculus: produces enzymes
Posterior ventriculus or gizzard - muscular for grinding food which is sometimes aided by pebbles eaten by bird
What are the characteristics of a mammals gut?
Long oesophagus, stomach is sac like or compartmentalised, 2-6 body lengths intestine in carnivores and insectivores and 20-25 body lengths in marine mammals.
Which diet comprises the longest intestines?
Herbivores
