Transcript Section 26.4 Summary– pages 711-713

Sponges are pore-bearers
Water out
Central
cavity
 Sponges are mainly sessile
organisms.
 Because most adult sponges
can’t travel in search of food,
they get their food by a process
called filter feeding.
Water
in
Digestion in cnidarians
• Cnidarians are predators that capture or
poison their prey using nematocysts.
• A nematocyst (nih MA tuh sihst) is a capsule
that contains a coiled, threadlike tube.
• The tube may be sticky or barbed, and it
may contain toxic substances.
• Nematocysts are located in stinging cells
that are on tentacles.
Digestion in cnidarians
• Once captured by nematocysts, prey is brought
to the mouth by contraction of the tentacles.
Mouth
Polyp
Gastrovascular
cavity
Mouth
Medusa
Hydra eating daphnia
Digestion in cnidarians
• The inner cell layer of
cnidarians surrounds a space
called a gastrovascular (gas
troh VAS kyuh lur) cavity.
• Cells adapted for digestion line the
gastrovascular cavity and release enzymes
over captured prey. Any undigested materials
are ejected back out through the mouth.
Roundworm parasites of
humans
 Infection by Ascaris (ASS kuh ris) is the
most common roundworm infection in
humans.
 Children become infected more often
than adults do.
 Eggs of Ascaris are found in soil and enter a
human’s body through the mouth.
Roundworm parasites of
humans
 The eggs hatch in the intestines, move
into the bloodstream, and eventually to
the lungs, where they are coughed up,
swallowed, and begin the cycle again.
Roundworm parasites of
humans
 Pinworms are the most common human
roundworm parasites in the United States.
 Pinworms are highly contagious because eggs
can survive for up to two weeks on surfaces.
Roundworm parasites of
humans
 Its life cycle begins when live eggs are ingested.
They mature in the host’s intestinal tract.
 Female pinworms exit the host’s anus—
usually as the host cell sleeps—and lay eggs
on nearby skin.
 These eggs fall onto bedding or
other surfaces.
Roundworm parasites of
humans
 Trichinella causes a disease called trichinosis
(tri keh NOH sis).
 This roundworm can be
ingested in raw or
undercooked pork,
pork products, or wild
game.
Trichinella
Roundworm parasites of
humans
 Hookworm infections are common in
humans in warm climates where they
walk on contaminated soil in bare feet.
 Hookworms cause
people to feel weak and
tired due to blood loss.
Roundworm parasites of other
organisms
 Nematodes can infect and kill pine
trees, cereal crops, and food plants
such as potatoes.
 They are particularly attracted to plant
roots and cause a slow decline of the
plant.
Roundworm parasites of other
organisms
 They also can infect fungi and can form
symbiotic associations with bacteria.
 Nematodes also can be used to control pests.
Echinoderms have varied nutrition
 All echinoderms have a mouth, stomach, and
intestines, but their methods of obtaining food
vary.
 Sea stars are carnivorous and prey on
worms or on mollusks such as clams.
Echinoderms have varied nutrition
 Most sea urchins are herbivores and graze on
algae.
 Brittle stars, sea lilies, and sea cucumbers
feed on dead and decaying matter that drifts
down to the ocean floor.
How reptiles obtain food
 Most turtles and tortoises are too slow to be
effective predators, but that doesn’t mean they
go hungry.
 Most are
herbivores, and
those that are
predators prey
on worms and
mollusks.
How reptiles obtain food
 Snapping turtles, however, are extremely
aggressive, attacking fishes and amphibians,
and even pulling ducklings under water.
How reptiles obtain food
 Lizards primarily eat insects.
 The Komodo dragon,
the largest lizard,
is
found on several
islands in Indonesia,
north of Australia. It
is an efficient predator,
sometimes even of
humans.
How reptiles obtain food
 Snakes are also
effective predators.
 Some, like the
rattlesnake, have
poison fangs that
they use to
subdue or kill
their prey.
How reptiles obtain food
 A constrictor wraps
its body around its
prey, tightening its
grip each time the
prey animal exhales.
What is a
mammal?
 Mammals,
like birds,
are
endotherms.
Most mammals have specialized teeth
 Mammals with teeth
have different kinds
that are adapted to
the type of food the
animal eats.
Most mammals have specialized teeth
 The pointed incisors of moles grasp and hold
small prey.
 The chisel-like incisors of beavers are
modified for gnawing.
Most mammals have specialized teeth
 A lion’s canines
puncture and
tear the flesh of
its prey.
Most mammals have specialized teeth
 Premolars and molars are used for slicing or
shearing, crushing, and grinding.
Most mammals have specialized teeth
 Many hoofed mammals have an adaptation
called cud chewing that enables the
cellulose in plant cell walls to be broken
down into nutrients they can absorb and use.
 When plant material is swallowed, it moves
into the first two of four pouches in the
stomach where cellulose in the cell walls is
broken down by bacteria.
Most mammals have specialized teeth
 The partially digested food, called cud, is
repeatedly brought back up into the mouth.
Most mammals have specialized teeth
 After more chewing, the cud is swallowed again
and when the food particles are small enough
they are passed to the other stomach areas,
where digestion continues.