Digestion in Animals – Part 1

All Living things get food somehow

• Most unicellular organisms, like bacteria, secrete enzymes and absorb nutrients.

• However, In the Protist Kingdom, unicellular organisms are very specialized to obtain food. – Ingestive heterotrophs or autotrophs

Amoeba

Paramecium structure

Oral groove

euglena

Fungi Kingdom• Secrete enzymes then absorb nutrients –

decomposers. Absorptive Heterotrophs

Animal Kingdom

• There is an increasingly complex system that allows animals to obtain nutrients from food.

• Ingestive heterotrophs

All animals eat; all animals poop (eliminate undigestible

material)!

Simple animals have simple methods of getting and using

food• Porifera: filter feeder – no digestive system

Water & food

Water & waste

Collar cellEpidermal cell

Collar cell

Spicule

Incurrent pore

amebocyte

flagellum

food

nucleus

Phylum Cnidaria (formerly called Coelenterata)

• All have stinging cells (cnidocytes)• Two body forms:

– Medusa – like a jelly fish– Polyp – like a hydra

• Radial symmetry• Have tentacles

Cnidarian Cnidocyte

Have you ever been stung by jellyfish?

Cnidarian Life Cycle – medusa and polyp alternate

medusa

egg

larva

polyp

Polyp body form

Hydra on water plants

Hydra Anatomymouth

tentacles

bud Gastrovascular

cavity

Basal disc

ovary

testis

•Digestion in cnidarians Extracellular – occurs In gastrovascular cavity

- enzymes are released from cells lining cavity and food is digested within the cavity.

- Nutrients are absorbed by cells in cavity and waste is expelled out the mouth (yuch!).

Coral is actually a colony of polyps, most of which are the size of a single hydra – they just make a case around them for their

home.

Here are a variety of anemones – polyp body form

Phylum - Platyhelminthes• Have flat bodies• Some are parasitic• Most are free-living

These are free-living flatworms

Planaria

Tapeworms – the ultimate parasite – the only highly developed system is its reproductive system – hermaphroditic

Digestion– absorbs host’s already digested food.

Scolex – head with hooks and suckers

Phylum Nematoda - roundworms

• Body rounded • Tube-within-a-tube body format• Mouth – digestive tube – anus –more efficient –

can have specialized organs along the way• Most free-living • Some parasitic

Look like threads

in the microscope

Some are parasitic to humans• Hookworm

– Enters through soles of feet

– Larvae in human feces

– Causes fatigue – may cause physical and mental retardation if children have it

• Trichina– From

undercooked pork

– Causes severe muscle aches when larvae migrate from intestine to muscles

• Filaria•Causes elephantiasis•No treatment •Carried by mosquitoes

This lesion is caused by a nematode infestation

-Caused by filaria – the worm blocks the lympatic vessels and the area swells with lymph.

No treatment is available

(except amputation)

Phylum Annelida

• Segmented worms• Includes earthworms and leeches• Most are free-living• Complex body with organ systems• hermaphroditic

Leech Earthworm

Eats dirtEats blood

Earthworm Anatomy

Earthworm eats dirt • Pathway of food :Mouth pharynx esophagus crop gizzard intestine anus 1 2 3 4 5 6 7

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6

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Earthworm help the environment by:

• Adding nutrients to soil

• Aerating soil

• Helping get rid of dead organic matter

Phylum Mollusca

• Soft-bodied animals• All have the same kind of larva• Three types

– Gastropods – stomach-footed• Snails and slugs

– Cephalopods – head-footed• Octopus and squid

– Pelecypods – hatchet-footed• Clams, mussels, oysters, scallops

slug

slug

clam

snail

squid

octopus

Digestion in Mollusks

Clams:Mucus-feedersTrap food in Mucus on gillsThen swallowsBoth food and mucus

Octopus and squid catch live prey using their tentacles and eat them

Snails scrape food off surfaces using their radula

Phylum Echinodermata

• Spiny skinned animal– Starfish– Sand dollar– Sea cucumber

• Turn stomach inside out to eat – stomach gives off digestive juices and the digested mess is swallowed along with the stomach when it is brought back into the body.

• Radial symmetry – no head, tail, front or back• Move using tube feet – part of water vascular system

Sea urchins, sand dollars, and starfish

Phylum Arthropoda•Jointed legs

•Chitinous exoskeleton

•Ventral nerve cord

•Must molt to grow

•Some undergo metamorphosis

•Includes insects, crustaceans, spiders, millipedes and centipedes, and horseshoe crabs

Class Insecta•Six legs

•May have wings

•Undergo metamorphosis

•Varied mouthparts

•Breathe using spiracles

Some common insects

Some of these are insects, some are not….

Can you tell which is which?

Class Arachnida – 8 legs, no antennae,

simple eyes, chelicerae,

spiders

scorpion

Dust mites tick

Class Crustacea – two body regions = cephalothorax

most live in water

Millipedes and Centipedes

The endThe end