Worms

Chapters 26.3, 26.4, and 27.2

Animal Classification

Animals

Invertebrates

Vertebrates

SpongesCnidariansWormsMollusksArthropodsEchinoderms

Ectotherms(cold-blooded)

Endotherms(warm-blooded)

FishesAmphibiansReptiles

BirdsMammals

Worms

- Phylum Platyhelimenthes- Phylum Nematoda- Phylum Annelida

Flatworms

Phylum Platyhelimenthes (Greek) platy = flat helmins = worm

The least complex worm Acoelomates About 14,500 species exist found in marine,

freshwater, and land The most commonly studied flatworm is the

planarian

Nervous Control

Most of the nervous system is located in its head

The nervous system consists of two nerve cords that run the length of the body

Nerve cords

Nervous Control

Eyespots can detect the presence or absence of light

Sensory cells can detect chemicals and movement in water

Eyespots

Sensory cells

Sensory cells

Nervous Control

Ganglion A small swelling of the nerve cord Receives messages from the eyespots and

sensory pits, then communicates with the rest of the body

Ganglia

Reproduction

Most flatworms are hermaphroditic Can reproduce sexually and asexually Sexual reproduction

Two planarians will exchange sperm Internal fertilization occurs Zygotes are then released in water where they will

hatch

Reproduction

Asexual reproduction Planarians can regenerate when damaged

Regeneration – The replacement or regrowth of missing body parts

Feeding and Digestion in Planarians A planarian feeds on dead or slow-moving

organisms Planarians are not parasitic

To eat, a planarian extends its pharynx from its mouth Pharynx – a tube-like, muscular organ (also

known as the throat)

Extended pharynx

Feeding and Digestion in Planarians Enzymes breakdown the food outside the

body, and then food particles are sucked into the digestive tract

Food is digested in individual cells Waste leaves through its one opening

(mouth)

Feeding and Digestion in Planarians Excretory system – eliminates waste from the

body Flame cells – excess water is removed from

the body

Feeding and Digestion in Parasitic Flatworms Parasitic flatworms

have mouthparts with hooks that keep them attached to their hosts

Hook

Sucker

Feeding and Digestion in Parasitic Flatworms Parasitic flatworms

don’t need a digestive system because they obtain nutrients from food that has been digested by their host

Hook

Sucker

Tapeworm

Scolex – a knob-shaped head

Proglottid – detachable, individual sections that contain muscles, nerves, flame cells, and reproductive organs

Hook

Sucker

Tapeworm

Each proglottid can contain up to 100,000 eggs

Can reach up to 33 ft in length and contain over 2,000 proglottids

Hook

Sucker

The larva will enter the snail host for further development

Adult flukes

First larval stage are found in water

Second larval stage

Eggs are passed out the intestinesFluke larva can bore

through the skin, enter the bloodstream, and move to the intestines

Embryo develops in human waste

Roundworms

Phylum Nematoda Greek word nema = thread

Found in soil, animal, freshwater, and marine environments

More than 12,000 species exist Nearly all plant and animals are affected by

parasitic roundworms

Pseudocoelomates Have a complete digestive system with two

openings (mouth and anus) Free-living species have well-developed

eyespots whereas parasitic species have underdeveloped eyespots

Roundworm Parasites of Humans Ascaris is the most common roundworm

infection in humans worldwide More common in subtropical areas Children become infected more often than

adults Timmy plays in a sandbox…

Roundworm Parasites of Humans Pinworms are the most common roundworm

parasites in the U.S. Children are the commonly infected Eggs can survive two weeks on the surfaces

Roundworm Parasites of Humans During night, female pinworms lay eggs

around the anus of host Taping the anus before bedtime is one

method used to eliminate pinworms

Roundworm Parasites of Humans Trichinella can be ingested in raw or

undercooked pork or wild game (turkey) Trichinella can be controlled by properly

cooking meat

Roundworm Parasites of Humans Hookworms are common 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 Humans Hookworm infection from dogs and cats