CH. 6HOW

ANIMALS STAY ALIVE

L E SS O N 1

H O W A N I M A L S G E T A N D D I G E S T T H E I R F O O D

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.