BIO2242 Lecture Notes - Lecture 4: Echinoderm, Mollusca, Body Plan
Lecture 4 – Animal Structure and Function
Importance of food and feeding
• You are what you eat
• What you eat determines who you are
• Which food gives the most energy
o Muscle > nectar > sticks > grass > soil
Limited number of food sources
• Only a few fundamental ways to obtain food
o Herbivory, carnivory, detrivory, symbiosis
• Different ways of obtaining food
Diversity of specific ways in which animals feed
• Constrained by environment
o Food in sediment, or catch fast moving food
• Constrained by body form
o E.g. mollusc, arthropod, echinoderm
Obtaining Energy and Nutrients
• Autotrophs
o Synthesis complex molecules from simple inorganic substances
o Need energy
▪ Light, chemicals
o E.g. plants, some protists, some bacteria
• Heterotrophs
o Obtain energy by consuming other organisms
o Ingest and digest
▪ Animals, bacteria, fungi
• Food materials
o Plants
o Animal
o Symbiosis
▪ Bacteria, algae or protozoans
▪ Produce food used by the host (parasite)
▪ Host must accommodate the symbiont
▪ E.g. sponges, photosynthetic endosymbionts, termites well
cellulose digesting micro organisms, herbivorous mammals
• Basic feeding modes
o Deposit feeding
o Suspension feeding
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Plant material as food
Animal material as food
Properties
• Abundant
• Low quality
• Low assimilation efficiency
• Cell wall
Properties
• High quality
• High assimilation
• Efficiency
• Defended
Requires
• Ability to bite and chew
• Space and time
• Special enzymes
Requires
• Sophisticated feeding strategies
Food size
• Very small food
o Endocellular digestion – inside cell
o Endocytosis followed by intracellular digestion
• Larger food
o Digestive system
o Extracellular digestion
o Often partially break down food before swallowing
Digestive systems
• No gut cavity
o Gut not required if very thing
o Food engulfed by endocytosis
▪ E.g. protozoans, sponges
• Gut cavity present
o Some digestion by enzymes in gut (extracellular digestion)
o Ingest larger food masses
o Greatly increase surface area for absorption
Types of guts
• Simple sac-like gut
o Single opening – 2 way flow
o E.g. flatworms
• Tube-like gut
o Two openings, mouth and anus – 1 way flow
o Allows specialisation of gut regions
Deposited Food
• Sediments
o Abundant yet dilute
o Mixed with large volumes of inorganic matter
• Must sample large amounts of sediment
o Non selective – continuously eating
o Selective
Food in Suspension
• Dilute
o Small quantities of food
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