CH. 6
HOW ANIMALS
STAY ALIVE
LESSON 1
H OW A N I M A L S G E T A N D D I G E S T T H E I R
REMEMBER…
• Unlike plants, algae, and some bacteria, animals cannot make their own food.
• Animals must get their food from other organisms by consuming, or eating, them.
• Animals have different ways of getting their food.
FILTER FEEDING
• Many animals living in water get food though filter feeding.
– Filter Feeding- A way of getting food by straining it out of water.
• For example, sponges strain bacteria and protists out of water that passes through their body.
• Sponges cannot move from place to place, so filter feeding allows them to consume food
without chasing it.
• https://www.youtube.com/watch?v=T7E1rq7zHLc
OTHER ANIMALS THAT FILTER FEED
INCLUDE…
• Barnacles
– They use their legs to filter out food from water
• Mollusks like clams and oysters
– They use their gills to filter out food from water
FEEDING ON FLUIDS
• Some animals get their food from the fluids of
plants or other animals.
• Aphids and Cicadas are insects that use their hard
piercing mouths to drink sap from plants’ stems,
roots, and leaves.
• Bees, butterflies, and humming birds get their
food from drinking the nectar out of flowers.
• Leaches, Mosquitos, and Horseflies consume the
blood of vertebrates, including humans.
CONSUMING LARGE PIECES OF FOOD
• Most animals consume, eat, large pieces of solid food.
• Some animals eat entire organisms.
• These animals have different body structures to capture and consume food.
– For example…
• Hydras and Jellyfish have stinging tentacles. They use their tentacles to catch small animals in the water and
then bring it to their mouth.
INSECTS
• Money insects have hard mouth parts that allow
them to cut up pieces of food that are small
enough for them to eat.
• Grasshoppers, termites, and beetles use their
chewing mouth parts to feed on plants.
• Dragonflies and praying mantises also have
chewing mouth parts, but they use theirs to eat
other insects.
TEETH
• Vertebrates are the only animals that have teeth.
• Mammals have teeth of different sizes and shapes.
• Each type of tooth has a special job.
• Front chisel like teeth are for cutting and tearing food.
• Long pointed teeth are for gripping and piercing food.
• Flat back teeth are for grinding and crushing food.
PICKY EATERS
• Herbivores- Are animals that only eat plants. They
get all the nutrients they need from eating parts of
plants.
– Herbivores have large flat teeth for grinding up plants
• Carnivores- Are animals that only eat meat from
other organisms. They get all their nutrients from
eating parts of other animals.
– Carnivores have long sharp teeth for tearing flesh.
• Omnivores- Are animals that eat both plants and
animals to get the nutrients they need.
– Omnivores have both kinds of teeth.
• What are you?
– What kind of teeth do you have?
DIGESTING FOOD
• Remember: foods contain fats, proteins, and carbohydrates.
• These chemicals give animals the energy they need to live.
• These chemicals are often too large for animal cells to use right away.
• So the chemicals have to be broken down before they can be used.
• The process of breaking down food into chemicals is called Digestion.
BREAKING IT DOWN
• Animals digest food by secreting digestive enzymes.
– Secreting- To form and release, or give off.
– Enzyme- A substance that speeds up chemical change.
• Animals like sponges digest food inside their cells.
• But, most animals, including humans, digest their food outside their cells.
GASTROVASCULAR CAVITIES
• Cnidarians, like hydras and jellyfish, and flatworms
digest their food in a hollow space called a
gastrovascular cavity.
• This tube only has one opening. Food enters and
waste leaves the same opening.
• Food goes in, special cells digest food and absorb
nutrients, then the what’s left over is excreted through
the same opening.
DIGESTIVE TRACTS
• Animals that are more developed have a digestive tract.
– Digestive Tracts- A tube-like digestive space with an opening at each end.
• Food moves through the digestive tract one way through the body.
• https://www.youtube.com/watch?v=JnzwbipJuAA
THE MAIN FUNCTIONS OF THE
DIGESTIVE TRACT ARE…
• Storing food
• Digesting food
• Absorbing nutrients
FOOD’S PATH
• Food enters the digestive tract through the mouth.
• It passes down the throat into the esophagus to the
stomach.
• In the stomach, food mixes with stomach acid and
digestive enzymes.
• The mixture then moves through the small then large
intestines.
• Nutrients is absorbed through the intestine walls
• Finally, waste is excreted through the anus.
DIFFERENT DIGESTIVE TRACTS
• Birds have organs called gizzards that
help them break down food. They also
have a crop that allows them to store
food.
• Humans do not have these organs in
their body. The stomach does the job of
a gizzard and a crop.