" The Big Picture!" by Mr C

Biology 11

Name: ___________ _______________ Date: _________________ Block: _____________

 

 

Phylum Nematoda (Greek: nema = “thread”)

The “Roundworms”

Pages 314-317

 

1. Background:

 

• 2 Major Classes:
  1. _______________________________
  2. _______________________________
• ~ 80000 species known

 

DID YOU KNOW!!!: Nematodes are the most abundant multicellular lifeforms on earth!!!

 

• The Nematodes have evolved to live in every habitat on the planet from marine to fresh water, the polar regions to the tropics and from the highest elevations to the lowest.
• Nematodes can be ____________________________ or _______________________

 

1. Body Plan/Structure:

 

• Nematodes demonstrate a __________________________ symmetrical body plan
• They have a _________________and ____________________________ body
• They lack a ______________________
• They have three germ layers:
  1. ______________________
  2. ______________________
  3. ______________________
• Nematodes are the fist phylum we will look at that has a _____________________________________________ with a _________________ and an _____________ connected by __________________________
• The mouth is connected to the intestines by a muscular _______________________
• Nematodes are ___________________________________ which means that they have an internal body cavity but this cavity is not lined with __________________________
• They do have muscles but only ___________________________ ones
• They have ____________________ in their __________________ end which is connected to two __________________________ that run down the length of the body on the ________________ and ____________________ sides
• Nematodes secrete a thick _______________________ that surrounds the body and protects them from their surroundings

 

DID YOU KNOW!!!: Nematodes are born with the same number of cells that they will have for

their entire life. This means that as Nematodes grow they do not get new cells; instead their cells just get larger!!!

 

III. Feeding:

 

• The free-living Nematodes usually eat bacteria, fungi, protozoans along with other decomposing material
• Parasitic Nematodes live off of their host organism
• Food is ingested through the mouth by muscular contractions of the _________________
• The food is digested in the ________________________
• Undigested food is passed out of the _______________

 

1. Respiration:

 

• Respiration occurs by simple _____________________ where oxygen is taken up by the body cells from the surroundings and carbon dioxide is released from the body cells into the surroundings

 

1. Internal Transport:

 

• The Nematodes lack a true _______________________________; However, nutrients diffuse from the intestines into the __________________________ where they circulate throughout the body

 

1. Excretion:

 

• Wastes and undigested nutrients are released out of the _____________ of Nematodes
• They also have _____________________________________ on either side of their body which release wastes into the surroundings from the pseudocoelome

 

 

 

 

VII. Response:

 

• Nematodes can have the ability to sense and respond to three stimuli:
  1. Sense and respond to ________________
  2. Sense and respond to ______________________
  3. Sense and respond to _________________

 

VIII. Movement:

 

• Since Nematodes lack __________________________ muscles and only have _________________________ muscles they can only slash around from side to side

 

1. Reproduction:

 

• Sexual reproduction (free-living):

• Most Nematodes are either ________________ or _______________ (though some are hermaphroditic)
• When a female and a much smaller male Nematode meet the male will wrap his ________________ around the female
• One or more ______________________ will move out of his anus and will be inserted into the females _____________________ and sperm will be transferred
• The fertilized eggs are released from the female into the surroundings to mature

 

1. Ecological Roles:

Parasitic Nematodes:

 

Like the Platyhelminthes there are many forms of Nematodes that are parasitic. They

Are mostly parasitic on vertebrates and can cause serious illness. They also have very complicated lifecycles:

 

Ex. Trichenella spiralis (causes Trichinosis)

 

• These Nematodes only need one host to mature but can be passed from host to host
• The adult Nematodes live in the intestine of their host (pig/rat/human)
• When they undergo sexual reproduction the larva burrow into the muscles of their host and create a capsule around themselves called an encyst
• After maturing the larvae travel back to the intestines to begin the lifecycle again

 

DID YOU KNOW!!!: Most Humans get Trichinosis from eating undercooked pork which

contains the larvae filled encysts!!!

Genetics:

 

The Nematode known as Caenorhabditis elegans (C. elegans) was the first multicellular organism ever to have its entire genome mapped. Researchers found that C. elegans have

~ 100 million base pairs that code for ~20000 genes. Research in this area began way back in 1974 and it was completed in 2002. Since then the scientists involved in the research have won multiple Nobel Prizes in medicine and physiology. Also, since C. elegans has been extensively researched it has been used as a model organism to demonstrate cell differentiation and development, cell death, neuronal development, genetic processes, meiosis and many other processes.