Movement of substances into & out of unicellular organisms
Passive diffusion in and out
Bulk Transport requiring energy

Cell Specialisation in Simple Multicellular
Organisms
Sponge feeding

Corals
Most reef-building corals have a symbiotic relationship with photosynthetic algae, called
zooxanthellae. which live in their gastrodermis tissue.
The zooxanthellae convert sunlight, carbon dioxide, and water into oxygen and carbohydrates that feed the coral polyps and help them produce reef-building calcium carbonate.
In return, the corals provide the zooxanthellae with protection and the compounds they need for photosynthesis. Pigments in zooxanthellae also give corals their beautiful orange, red, purple, and yellow colors.

Cnidarians feeding

Animal’s bodies are composed of different systems, each system has it’s own functions.
All together these systems work together to enable the animal to survive.
http://video.nationalgeographic.com/vid eo/player/science/health-humanbody-sci/human-body/human-bodysci.html

• Animals are heterotrophs must consume food in order to obtain nutrients and energy.
• Animals are adapted to obtain food in a variety of ways python vs croc

• Carbohydrates - source of immediate energy for all living organisms. The monosaccharide glucose is broken down to make ATP in cellular respiration.
• Lipids Fats and oils required for cell membranes, hormones and vitamins.
• Amino Acids The building blocks of proteins. The body can make some amino acids but others it can’t make these are the 9 essential amino acids.
Need to be regularly eaten.
• Vitamins - Organic compounds needed for cellular processes, e.g. making enzymes.
• Minerals needed for structural components and for enzyme molecules.

The Digestive System
• Ingestion - intake of food into the body
• Digestion - physical and chemical breaking down of food
• Absorption - nutrient molecules move into the circulatory system and ultimately into the cells.
• Egestion/ Elimination - removal of waste from the body

Physical digestion.
– Food physically broken it down into smaller pieces in order to increase
surface area and enable maximum efficiency of chemical digestion.

Chemical Digestion
Breakdown of macromolecules by
enzymes- made in the gut, salivary glands and pancreas into molecules small enough to be absorbed through the alimentary lining.
Amylases- Break down starches into simple sugars
Proteases- Break down protein-into amino acids
Lipases- Break down lipids into glycerol & Fatty acids

Introduction to the Human Alimentary System animation
Human digestion overview

• Stomach majority of digestion occurs
– Mechanical digestion occurs as the muscles crush and move the food.
– Chemical digestion also occurs in the stomach, with the secretion of gastric juices with have enzymes that break down the food.
• Small intestine further digestion occurs but only on proteins and carbohydrates to break them down into their amino acid building blocks.
Digestion-video.htm

Most occurs in the small intestine.
Food at it’s smallest is then absorbed by the cells of the intestine and passed along to the blood stream.

• Different diets require different digestive systems.
• Breaking down cellulose requires the enzyme cellulase.
• Mammals can’t make this enzyme.
• Cows have a 4 chambered stomach.
• They chew and then regurgitate their food and chew it again before sending it to the rumen where heaps of cellulose digesting bacteria live and allow the breakdown of the cellulose to occurs.

Caecum: a pouch extension at the junction of the small
& large colon which in herbivores contains cellulose digesting bacteria.
Herbivorus mammals with higher fibre diets may have larger caecums to maximise the opportunity for cellulose digestion by bacteria.

Most (not all) birds have :
• a crop for temporary storage
• a glandular part the proventriculus which secretes mucus , HCl & enzymes
• a muscular gizzard which may contain grit or small stones which grinds and mixes the food and enzymes etc.