biology€¦ · roundworms and human disease ascarid worms ascaris lumbricoides is a serious...

End Show

Slide

1 of 33

Copyright Pearson Prentice Hall

Biology

End Show

Slide

2 of 33


27–2 Roundworms

End Show

27–2 Roundworms

Slide

3 of 33


What Is a Roundworm?


Most species of roundworms are free-living,

inhabiting soil, salt flats, aquatic sediments, and

water, from polar regions to the tropics.

Others are parasitic and live in hosts.

End Show

27–2 Roundworms

Slide

4 of 33


Roundworms are unsegmented worms

that have pseudocoeloms and digestive

systems with two openings—a mouth

and an anus.


End Show

27–2 Roundworms

Slide

5 of 33


This cavity is partially lined with tissue derived from

the mesoderm and is called a pseudocoelom,

meaning, “false coelom.”


End Show

27–2 Roundworms

Slide

6 of 33


Roundworms have a digestive tract with two

openings.

Food moves in one direction through the digestive

tract of roundworms.

Any food that is not digested leaves the body through

the anus.


End Show

27–2 Roundworms

Slide

7 of 33


Form and Function in Roundworms

Feeding

Many free-living roundworms use grasping

mouthparts and spines to catch and eat other

small animals.

End Show

27–2 Roundworms

Slide

8 of 33



Respiration, Circulation, and Excretion

Roundworms exchange gases and excrete

metabolic waste through their body walls.

They depend on diffusion to carry nutrients and

waste through their bodies.

End Show

27–2 Roundworms

Slide

9 of 33



Movement

Fluid in the pseudocoelom and muscles extending the length of their bodies function as a hydrostatic skeleton.

Aquatic roundworms contract muscles to move like snakes through the water.

Soil-dwelling roundworms push their way through the soil by thrashing around.

End Show

27–2 Roundworms

Slide

10 of 33



Reproduction

Roundworms reproduce sexually.

Most species have separate sexes.

Parasitic roundworms often have life cycles that

involve two or three different hosts or several

organs within a single host.

End Show

27–2 Roundworms

Slide

11 of 33

Human Ascarid Reproduction


End Show

27–2 Roundworms

Slide

12 of 33


Roundworms and Human Disease

Parasitic roundworms include

trichinosis-causing worms, filarial

worms, ascarid worms, and hookworms.


End Show

27–2 Roundworms

Slide

13 of 33



Trichinosis-Causing Worms

Adult Trichinella worms live and mate in the

intestines of their hosts.

Larvae travel through the bloodstream and burrow

into organs and tissues.

50 µmEncysted juveniles Muscle tissue

End Show

27–2 Roundworms

Slide

14 of 33


Trichinella completes its life cycle only when another

animal eats muscle tissue containing these cysts.

Humans can get trichinosis by eating raw or

incompletely cooked pork.


End Show

27–2 Roundworms

Slide

15 of 33



Filarial Worms

Filarial worms are threadlike worms that live in

the blood and lymph vessels of birds and

mammals.

They are transmitted by mosquitoes.

Causes Elephantiasis

End Show

27–2 Roundworms

Slide

16 of 33



Ascarid Worms

Ascaris lumbricoides is a serious parasite of

humans and many other vertebrate animals.

It absorbs digested food from the host’s small

intestine.

End Show

27–2 Roundworms

Slide

17 of 33


Ascaris Life Cycle

Human ingests food or

water containing Ascaris

eggs.


1

End Show

27–2 Roundworms

Slide

18 of 33


Ascaris Life Cycle

The eggs travel to

the small intestine

and develop into

larvae.


2

End Show

27–2 Roundworms

Slide

19 of 33



Ascaris Life Cycle

Larvae enter blood

vessels and are

carried to the lungs

3

End Show

27–2 Roundworms

Slide

20 of 33


Ascaris Life Cycle

Larvae are coughed

up and swallowed.

They then travel to

the small intestine

where they develop

to maturity


4

End Show

27–2 Roundworms

Slide

21 of 33


Ascaris Life Cycle

Eggs are released

and leave the host

in faces.


5

End Show

27–2 Roundworms

Slide

22 of 33

Ascarids


Ascarids taken from children of one village.

End Show

27–2 Roundworms

Slide

23 of 33

Heartworm


End Show

27–2 Roundworms

Slide

24 of 33



Hookworms

Hookworm eggs hatch and develop in the soil.

They use sharp toothlike plates and hooks to

burrow into the skin and enter the bloodstream.

End Show

27–2 Roundworms

Slide

25 of 33


Hookworms travel through the blood of their host to

the lungs and down to the intestines.

There, they suck the host’s blood, causing weakness

and poor growth.


End Show

27–2 Roundworms

Slide

26 of 33

Rare Nematode Attacks!


Gigantus wormius

End Show

- or -

Continue to: Click to Launch:

Slide

27 of 33


27–2

Resources/ch27_sectn02_quiz.qtb



End Show

Slide

28 of 33


27–2

In roundworms, the body cavity that forms

between the endoderm and mesoderm is the

a. ganglion.

b. hydrostatic skeleton.

c. pseudocoelom.

d. coelom.

End Show

Slide

29 of 33


27–2

All of the following are parasitic roundworms

EXCEPT

a. tapeworms

b. filarial worms

c. hookworms

d. ascarid worms

End Show

Slide

30 of 33


27–2

Characteristics of roundworms include a

digestive system with

a. one opening and a pseudocoelom.

b. one opening but no pseudocoelom.

c. two openings and a pseudocoelom.

d. two openings but no pseudocoelom.

End Show

Slide

31 of 33


27–2

Gas exchange and excretion of metabolic

wastes in roundworms occurs

a. via a complex system of alveoli.

b. through their body walls by diffusion.

c. through excretory tubules.

d. by flame cells.

End Show

Slide

32 of 33


27–2

The roundworms called ascarids cause harm by

a. causing serious body swelling.

b. burrowing into body tissues and causing

pain.

c. causing malnutrition.

d. causing internal bleeding.

END OF SECTION

biology€¦ · roundworms and human disease ascarid worms ascaris lumbricoides is a serious...

Documents