Presentations today: Derek/Travis Nick/Dustin Rachel/Arianne Erica/Jordan David/Dalton Colton/Taylor Katie/Dylan Dewayne/Ciera

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Presentations todayDerek/TravisNick/DustinRac
hel/ArianneErica/JordanDavid/DaltonColton/Taylo
rKatie/DylanDewayne/Ciera
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PHYLUM NEMATODA

• The Roundworms

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Section 26.4 Summary pages 711-713
Nematoda (Roundworms)

• widely distributed
• living in soil, animals,
• fresh and marine water

• Most are free-living
• many are parasitic.

Roundworm
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Nematoda (Roundworms)

• tapered at both ends
• no segments

• thick outer covering Cuticle
• protects them in harsh environments
• Stomach acid
• Covering is shed 4 times as they grow.

Tapered ends
Round body shape
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Nematoda (Roundworms)

• no circular muscles
• lengthwise (longitudinal) muscles

• one muscle contracts
• another muscle extends
• causes them to move in a thrashing motion from
  side to side

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Section 26.4 Summary pages 711-713
Nematoda (Roundworms)

• Have a pseudocoelom
• simplest animals with a one way digestive tract
  mouth to anus

Intestine
Anus
Mouth
Round body shape
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Section 26.4 Summary pages 711-713
Nematoda (Roundworms)

• Eyespots very reduced in parasitic roundworms.

• Approximately half of species are parasites
• about 50 species infect humans.

Examples Ascaris, Pinworms, Trichenella, and
Hookworms
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Section 26.4 Summary pages 711-713
Ascaris

• the most common roundworm infection in humans

• children infected more often than adults
• Why?

• Eggs in soil
• enter through the mouth of humans

• Life Cycle--
• hatch in intestines
• move into bloodstream
• eventually to lungs
• coughed up
• swallowed
• begin the cycle again.

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Pinworms

• most common human roundworm parasites in U.S.

• highly contagious
• eggs can survive for up to two weeks on surfaces

• live eggs ingested
• mature in hosts intestinal tract

• female pinworms exit hosts anus itching!
• lay eggs on nearby skin

• eggs fall onto bedding or other surfaces
• Reintroduced to intestine by mouth

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Section 26.4 Summary pages 711-713
Trichinella

• Trichinella causes a disease called trichinosis

• Found in raw or undercooked meat
• Can be sexually transmitted

Trichinella
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Section 26.4 Summary pages 711-713
Hookworms

• common in humans in warm climates
• Obtained when walking barefoot on contaminated
  soil

• Hookworms cause people to feel weak and tired due
  to blood loss.

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Roundworm Parasites

• 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.

• They also can infect fungi and can form symbiotic
  associations with bacteria that help plants
  obtain nitrogen from air

• Nematodes also can be used to control pests

• Life on Earth is very dependent on nematodes

• Billions of nematodes in every one - symbiosis