Download Chapter 6, lesson 1: How Animals Get and Digest Food

Biology: Chapter 6, lesson 1: How Animals Get and Digest Food.
(notes)
 Animals cannot make their own food.
 Must get food from other organisms
 Different animals = different ways of getting food
 Filter feeding:
 Filtering or straining food particles from the water. Food must be tiny.
 Many animals that live in water use this method.
 Animals that can’t move to get food:
 Sponges – filter through pores
 Barnacles – use legs (act like screens)
 Mollusks – use gills
 Animals that can move:
 Whales – swim with mouth open, capturing millions of tiny
organisms and filtering through their baleen (combs of thick hair
in place of teeth).
 Feeding on Fluids (liquids):
 Getting food from the fluids of plants or other animals.
 Fluids are rich in nutrients.
 Aphids and cicadas: have piercing mouthparts to draw sap from plants
leaves, roots, and stem.
 Bees, butterflies, and hummingbirds: draw nectar from flowers
 Spiders and assassin bugs: suck fluids from captured insects.
 Leeches, mosquitoes, and horse flies: suck blood from vertebrates.
 Consuming Large Pieces of Food:
 Most animals consume (eat) large pieces of solid food.
 Use different kinds of body structures to capture and consume food.
 Cnidarians: use tentacles with stinging cells to capture food and
eat it whole.
 Insects: many have mouthparts suited for cutting or chewing.
 Grasshoppers, termites, and beetles feed on plants – herbivores
 Herbivores: animals that eat only plants or plant parts
 Dragonflies and praying mantises eat other insects – carnivores
 Carnivores: animals that eat only other animals (meat).
 Omnivores: animals that eat both plants and animals.
(example: human and bears)
 Vertebrates: the only animals with teeth (not all have them).
 Different shapes and sizes do different jobs.
 Chisel-like at front of mouth: cut food into pieces (incisors =
the ones you bite with)
 Long, pointed teeth: grip and pierce food (canines =
“fangs”)
 Flat surface: grind and crush food (premolars and molars =
the ones you chew with).
(chapter 6, lesson 1 continued)
 Teeth type tell what kind of food an animal eats:
 Carnivores: long canine teeth and sharp, pointed molars =
tear flesh.
 Herbivores: use incisors to clip plants, large molars with flat
surfaces = grinding plants.
 Omnivores: have a combination of the types of teeth = tear
flesh and grind plants.
 Digesting Food:
 Food contains fats, proteins, and carbohydrates.
 Provide energy an animal needs.
 Too large for most animal cells to absorb
 Must be broken down into smaller chemicals
 This process is called digestion.
 Digestion occurs by secreting digestive enzymes:
 Secreting = form and release.
 Enzymes = substance that speeds up a chemical change in living
things.
 Digestion inside cells:
 Sponges: cells trap food particles and package them into
vacuoles (storage organelles inside the cell) where digestive
enzymes break down the food and then the cell absorbs the
“food” chemicals from the vacuoles.
 Drawback: food must be small enough to fit inside vacuoles 
tiny food particles.
 Digestion outside cells:
 Most other animals: eat food, digestion occurs outside cells,
then “food” chemicals are absorbed by the cells.
 Advantage: can eat much larger foods.
 Gastrovascular Cavities: (cavity = open space, like a cave)
 (lower animals) Cnidarians and flatworms digest food in a hollow space
 gastrovascular cavity.
 Only have one opening = the mouth.
 Food enters mouth  special cells in cavity secrete digestive
enzymes that break down the food  cells absorb particles.
 Material not digested leaves through the mouth.
 Digestive Tracts: (tract = path)
 More developed (higher) animals have a digestive tract.
 Tube-like digestive space with an opening at each end.
 Food moves in one direction only  entrance to exit direction.
 Different parts of tract carry out different functions.
 Main functions:
 Storing food
 Digesting food
 Absorbing nutrients
 Most digestive tracts are organized in the same way with some
differences.
 Example: Birds
 Food enters through the mouth.
 Travels through the esophagus to the crop: food storage.
 Passes to stomach: food mixes with acid and digestive enzymes.
 Mixture moves to gizzard: grinds food into watery paste.
 Moves into intestines: more enzymes added, nutrients absorbed
through intestine wall, and water is absorbed (to make feces solid).
 Digestion is completed here.
 Anything that can’t be digested: leaves body through the anus.
 Humans and other mammals: don’t have a crop or gizzard
 Stomach carries out the functions: food storage, mixing with acids
and enzymes, and grinds food to watery paste (chyme).