Learning Goal 3 – Digestion and Excretion Plants Digestion – Excretion – Invertebrates Digestion Intracellular – Extracellular – Excretion Aquatic – Terrestrial – Vertebrates Carnivores vs Herbivores –

Unit II Organs and Organ Systems Learning Goal 3 Examine the processes of digestion and excretion in various types of organisms.

Plants Digestion Plants don’t have to digest their food the way animals do because they take in very small nutrients and make their own sugar molecules.

Excretion The stomata act as openings through which by-products of photosynthesis and cellular respiration exit (CO2 O2, and H2O)

Invertebrates Digestion Intracellular digestion Small particles of food enter cells, and are broken down, then nutrients are passed to other cells. Examples: sponges, jellyfish

Extracellular digestion Food is broken down outside of cells in a digestive cavity or tract then absorbed by cells. Examples: mollusks, annelids, arthropods

Excretion: Aquatic Invertebrates Ammonia (a toxic by-product of protein break down) moves out of cells directly into surrounding water.

Terrestrial Invertebrates Tube-like structures called nephridia turn ammonia into less toxic substances like urea and uric acid, then release it into the environment.

Vertebrates Digestion All vertebrates have extracellular digestion with digestive organs suited for different feeding habits.

Carnivores have short digestive tracts, while herbivores have longer digestive tracts.

Excretion Most vertebrates rely on kidneys to get rid of nitrogenous waste.

As proteins are broken down, ammonia forms but is converted to less toxic urea or uric acid, then eliminated by the kidneys. Kidneys are also important in regulating water and other substances in body fluids.