Lesson 2 Animal nutrition and digestive organ systems

• Chemoheterotrophs→ Animals require organic molecules as a source of chemical energy and carbon 
• These organic molecules also allow animals to assemble new molecules, cells and tissues.
• Macromolecules are used as a source of energy and building blocks.
• Herbivores→ Planta or algae
• Carnivores → Other animals
• Omnivores→ consume animals as well as plants and algae
• Nutrition→ Balance between nutrient intake and the needs of the body 
• ATP (chemical energy) is required to support activities of cells, tissues, organs and animals in general. 
• Biosynthesis→ Breaking down nucleic acids, carbohydrates, proteins and lipids to produce molecules the animal needs to grow
• Essential nutrients→ substances that an animal requires but cannot synthesize in adequate amounts and must be obtained from diet.
• Essential nutrients→Help enzyme function → act as substrates, coenzymes and cofactors.
• Vitamin C → Vitamins are required to allow the citric acid cycle.
•  Animals require 20 aminoacids to make proteins

  Essential amino acids → The ones that must be obtained from food (cannot be self-synthesised) → Can get them through meat, eggs and cheese. As well as vegetables.
• Essential fatty acids→ Those that animals cannot make because of the inability to produce certain double bonds.
• Minerals

  Inorganic nutrients→ Required in a small amount (less than 1 mg to 2500 mg per day ) 

  Ex: Iron, Sodium, Potassium, etc.
• Ingestion → act of eating or feeding
• Filter feeders: organisms that eat small organisms or food particles suspended in water. (Ex: whales)
• Substrate feeders:  animals that live on or in the food source (ex; caterpillars)
• Fluid feeders: suck nutrient-rich fluid from the host (ex: mosquitos)
• Bulk feeders : Eat large pieces of food, have teeth, claws, tentacles, to kill or skin their prey (ex: python)
• Digestion→ Food is broken down into small molecules for the body to absorb. 
• Mechanical digestion (chewing helps to make the parts even smaller)
• Chemical digestion→ Necessary to absorb the nutrients→ Here is when we get the macromolecules. A cell makes a macromolecule by linking together smaller components.
• Absorption → Animal’s cells take up small molecules such as aminoacids and sugars
• Elimination→ Completes the process as undigested material passes out of the digestive system. 
• Porifera (sponges) → Lack digestive organ system → Digest food intracellularly → Food particles are engulfed by phagocytosis  
• Single opening for ingestion and elimination--> no separation of digestive and excretory functions --> Gastrovascular cavity 
• Gastrovascular cavity → functions in Ingestion, digestion, absorption and elimination.
• Two openings dedicated exclusively to ingestion or elimination --> Complete digestive system
• Gizzard (thick muscular tissue used to pulverize the food) this is used by

  Small birds do not use gizzard.
• Digestive compartments

  This allows animals to digest food without digesting their own cells and tissues (made up of the macromolecules). Can be intracellular (food vacuoles). Extracellular (digestive organs and systems) 
• Intracellular digestion → Hydrolysis of food inside vacuoles → the food vacuoles fuse with lysosomes (organelles that contain hydrolytic enzymes) → Enzymes digest the food allowing digestion to occur.  PHAGOCYTOSIS 
• Extracellular digestion → Breakdown of food in compartments that are continuous with the outside of the animal’s body .
• Stomach: mechanical and chemical digestion.

  Made up of three sheets of muscle tissue
• Peristalsis: Rhythmic involuntary contractions t
• Small intestine → Dudenu→ Ileum → Jejunum → Ileocecal sphincter.