Laboratory - NCSU

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LEARNING OBJECTIVES

Students will….

• identify associations between plants and pollinators by analyzing flower structures

and determining potential pollination strategies for each plant.

• practice communication and presentation skills by presenting their findings on

flower structure and pollination strategies to the class.

• practice microscopy skills and extend their knowledge of symbiotic relationships

by making slides of live specimens of microscopic organisms that aid in digestive

processes.

• analyze endo- and ectoparasite groups by observing live, preserved, and micro-

scopic specimens and using online materials; and they will present their findings

to the class.

• apply their knowledge of parasitic relationships by locating and identifying para-

sites on the surface and internal organs of a fish specimen.

• demonstrate their knowledge of fish anatomy by pointing out morphological and

anatomical structures.

• extend their knowledge of symbiotic relationships by answering and discussing

specific questions at the end of lab.

INTRODUCTIONAssociations between organisms of different species are known as interspecific inter-

actions. The organisms involved may benefit from, be harmed by, or not be affected

by the interaction. By this definition, we can use the term symbiosis to represent any

Species Relationships: Symbiosis

NOT FOR DISTRIBUTION - FOR INSTRUCTORS USE ONLY

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Laboratory 8 Species Relationships: Symbiosis

association between organisms, excluding interactions between members of the

same species, or intraspecific interactions. Symbiotic relationships exist between all

types of organisms including bacteria, protozoans, fungi, plants, and animals.

Various types of symbioses, whether beneficial or harmful, are described by the terms

mutualism, commensalism, and parasitism. In these relationships, we refer to the

symbiont as the organism that lives inside (endoparasites) or on (ectoparasites)

another organism, the host. In symbioses where the organisms interact with each

other, either living inside or on the other, both organisms are termed symbionts.

In mutualistic relationships, both partners benefit equally. Most commonly, organ-

isms enable the acquisition of nutrients for one another. An example of a mutualistic

relationship is the one between Aiptasia pallida, a small sea anemone found in the

Caribbean and along the east coast of the United States, and a dinoflagellate algae.

The dinoflagellate is called an endosymbiont, because it lives inside the sea anemone,

its host. The sea anemone receives oxygen and photosynthetic products from the

dinoflagellate, whereas the dinoflagellate receives protection and molecules for pho-

tosynthesis from the sea anemone.

The protozoans found in the stomach of herbivores, which help the animals digest

food, receiving nutrients in the process, represent another mutualistic relationship.

Protozoans also inhabit the gut of termites, helping them digest wood material. You

will have the opportunity to observe these protozoans when you complete the nutri-

tion lab. Mutualistic relationships also occur between plants and fungi. Fungi called

Mycorrhizae form an association with the roots of a plant, in which they help plants

to extract nutrients from nutrient-poor soils and in exchange receive organic com-

pounds from the plant’s photosynthetic processes. Another important symbiotic

relationship involves a fungi and a photosynthetic organism like an algae, which un-

dergoes a remarkable change during their association, resulting in a new entity called

a lichen.

An association in which the symbiont benefits while the host organism is neither

harmed nor benefited is called commensalism. The relationship between the tube

worm Chaetopterus and pea crabs is an example of a commensalistic relationship.

In this relationship, the worm shares its tube-like dwelling with a crab. The crab gets

protection from the tube and receives food and oxygen from the water that passes

into the tube. The shark and sucker fish Echeneis is another example of commensal-

ism. The sucker fish rides along with the shark by sticking to its underside with a

modified dorsal fin shaped like a suction disc. Close proximity to the shark allows the

sucker fish to scavenge bits of food left over from the shark’s meal.

Parasitism is a symbiosis in which the symbiont benefits at the expense of the host.

As in most symbiotic relationships, the driving force behind parasitic associations

is usually food/nutrients, since the parasite obtains its food from the host. Parasitic

relationships affect the host to varying degrees. Some parasites are so patheno-

genic (disease-causing) that they cause symptoms in the host almost immediately

after infection. In these cases, the host may die, but most parasites do not kill their

host until they have reproduced and completed their life cycles (see life cycle Figures

8-2 through 8-8). Some parasites need more than one host. Hosts are then either


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intermediate or final. You will have a chance to observe some of these parasites in the

laboratory. Hosts can also serve as reservoirs for a parasite (a breeding ground and

source of infection for another host) without showing signs of infection themselves,

or they can be vectors—carriers of the parasite to a final host. Plants can also be

parasitic. There are thousands of parasitic plant species, ranging from trees to small,

herbaceous plants. The best-known group of parasitic plants is mistletoe. There are

about 800 species, most occurring in the tropics and subtropics (Paracer and Ah-

madjian 2000). Mistletoe parasitize tree branches, but the giant mistletoe, Nuylsia,

forms a tree that grows as high as 10 meters and parasitizes roots of nearby grasses

and plants.

Symbioses between plants and their pollinators (Figure 8-1) are considered a prime

example of coevolution of these two groups of organisms over the past 200 million

years. So remarkable is the “fit” between pollinator and flower that a fairly novice

observer can predict the type of pollinator for which a flower is adapted by examining

the flower’s color, shape, scent, and other characteristics. Similarly, specialized struc-

tures on a pollinator, like the shape and length of the proboscis (the tubular feeding

organ) closely match the flower’s anatomy. Pollinators, usually insects or some other

animal, carry pollen from the anther of one plant where it is produced to the stigma of

another plant, while plants provide the animal with a food source in the form of nectar

or pollen (see Figure 8-1). Nearly 70% of flowering plants rely on insects for pollination

and 30% of our food comes from bee-pollinated crops (Kearns and Inouye 1997).

Symbiotic relationships between animals and microorganisms are also important in

the process of nutrient acquisition (you will learn more about specific nutritional

adaptations in the nutrition lab). Ruminants and other animals rely on certain spe-

cies of bacteria and protists within their digestive tracts for digesting tough, cellulose

material. The most advanced fiber processing digestive tract, which is found in graz-

ing types of mammals, is the ruminant system. Cows, sheep, and deer, among many

others, are ruminants. These animals are often described as having four stomachs,

because the stomach is partitioned into four chambers that each have a specific func-

tion for digesting plant material before reaching the small intestine. In order, the

chambers are: rumen, reticulum, omasum, and abomasum. Symbiotic bacteria and

protists in the first two processing chambers use enzymes to degrade the plant ma-

terial and yield large quantities of a waste product called volatile fatty acids through

fermentation reactions. These fatty acids are absorbed into the blood and are trans-

ported to the liver where they are converted to sugars that are used in metabolism.

The fluid from these chambers is often referred to as “rumen fluid,” since the rumen

is the largest chamber that contains microorganisms. The third chamber of the ru-

minant stomach acts as a particle sieve keeping the larger, less degraded particles in

the first two chambers. It also reabsorbs water. The final chamber acts as the “true

stomach,” with acids and enzymes that break down materials just as they do in the

stomach of an animal with a monogastric system.

The alimentary canals of animals also possess symbiotic bacteria housed in spe-

cialized intestinal structures, such as the cecum. In herbivores, the cecum can be a

large fermentation chamber. For example, the koala has a long, tubular cecum with

abundant symbiotic bacteria. Bacteria in the cecum use enzymes to break down the


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fibrous eucalyptus leaves, which are the sole food source of the koala. On the other

hand, carnivores have a small cecum, since plant material is not common in their

diets. Regardless of the anatomical structures present, most animals possess gut mi-

croorganisms collectively known as the “gut flora.” In addition to helping with the

digestion of dietary fiber, these microorganisms perform other important roles. For

instance, in mammals, beneficial intestinal Escherichia coli synthesize vitamin K. A

healthy “gut flora” is also essential for maintaining a healthy gastrointestinal system

and plays an important role in the immune system.

In the invertebrates, termites are a classic example of a type of organism that has a

coevolutionary relationship with gut microorganisms. Termites rely on bacteria and

protists to digest cellulose from the wood they consume. Termites and their diverse

community of microorganisms form obligate symbiotic relationships in which one

cannot live without the other. In this lab, you will have the opportunity to analyze the

content of a termite gut and find some of these microorganisms. The most common

organism you will find is a protist called, Trychonympha spp. You will also observe

rumen fluid from a cow to view the gut flora.

Activity One: Plants and Pollinators

PROCEDURE

1. Read Table 8-1. It describes various pollinator and flower characteristics (you

may also refer to pictures of flowers seen in Appendix F). You will also watch a

series of video clips on pollination.

2. Work in groups at your laboratory bench during this activity to try to predict the

type of pollinator for the flowers you observe in the laboratory. Fill out Table 8-2

as you make your observations. Each group should present their findings to the

class.


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Table 8-1. Flower attractants commonly associated with pollinators

BIRDS BUTTERFLIES MOTHS BATS FLIES BEES WIND

Color Bright;

scarlet red,

orange,

yellow

Bright; red,

orange, yel-

low, or pink

Pale yellow

or bright

white

Dull greenish,

yellowish, or

purple; often

creamy white

Light colors Bright; most

commonly

yellow or blue,

cannot see red

Very pale;

drab

Scent None Weak to

moderate

Strong, sweet

like perfume

Strong,

musky

Mild; often

fungal

Sweet None

Flower

shape

Tubular and

usually long,

to house the

bird’s bill

Showy flow-

ers; often

tubular

Very con-

cealed

nectar; often

tubular

Big and wide;

sometimes a

brush-type

or bowl-

shaped

Flat or

concave;

reward

exposed;

shallow

Complex;

reward often

concealed

No petals;

mainly

anthers

and

carpels

Pollina-

tion time

Day Day Dusk and

night

Night Day Day None

Flower

position

Lack

landing

platforms,

stigma/

anthers pro-

trude well

beyond the

petals; flow-

ers often

hanging

Have land-

ing platform

of clustered

flowers,

stigma/

anthers

protrude

beyond

petals

Often hang-

ing; erect or

horizontal

Exposed on

sturdy stems

or tips of

branches

Mostly

erect

Have landing

platforms for

pollen attach-

ment; many

positions; of-

ten hanging

Erect

Reward Nectar in

the tube

(large quan-

tity)

Nectar in

the tube

Nectar (more

than in bee-

pollinated

flowers)

Highest nec-

tar quantity,

pollen

Pollen,

nectar

Nectar, pollen None

Other Birds hover

while pol-

linating

Butterfly-

pollinated

flowers

resemble

bird-

pollinated

flowers but

are smaller

and contain

less nectar.

Moths are

nocturnal

and usually

find females

by following

a pheromone

or other

chemical

trail; good

sense of

smell

Carrion

flies are at-

tracted to

mottled

purple or

dark blue

flowers that

smell like

rotting meat

and are of-

ten near the

ground

Flowers are

not red be-

cause bees

cannot see

red light well;

often show

patterns (nec-

tar guides)

visible only

in ultraviolet

light that bees

can perceive


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Table 8-2. Record of observed pollinators and flowers

FLOWER NAME OR TYPE

PREDICTED POLLINATOR

JUSTIFICATION

©Hayden-McNeil, LLC

Anther sheddingpollen onto bee

Flower nectaries

Petal

Bee proboscis

Stigma receivingplatform for pollen

Figure 8-1. Flower–Pollinator Interaction


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Activity Two: Symbiosis in Termites

Termites are invertebrates that possess a complete digestive tract. They consume

wood, which is primarily composed of cellulose; however, they cannot manufacture

a key enzyme necessary for its breakdown. Instead they rely on a symbiotic relation-

ship with bacteria and protozoa to digest the cellulose and absorb the waste products

(volatile fatty acids) produced for use as food.

1. Using forceps, gently remove a termite from the stock culture.

2. Place the termite on a glass microscope slide.

3. Using a dissecting needle, remove the head of the termite and discard it.

4. Place one drop of Insect Ringer’s solution on the termite abdomen and then place

a coverslip over the abdomen and gently press down with your dissecting needle

so that the material in the abdomen is dispersed on the slide.

5. View the symbionts with a compound microscope. (Primarily what you will see

is protozoan, but you can see bacteria on a much higher power with stain.)

6. Draw your observations below.


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Activity Three: Bacteria and Protists in the Rumen

Like the termites, ruminants and other herbivores rely on microorganisms to process

the fibrous cellulose present in plant leaves. Within the rumen chamber, bacteria and

protozoa are suspended in the fiber particle-filled rumen fluid. The microorganisms

attach themselves to the fiber particles and hydrolyze the cellulose. As with the ter-

mites, the waste products of their metabolism are absorbed by the host animal and

used for food. One major benefit to having the rumen before the true stomach of the

animal is that, as bacteria die and flow through the digestive tract, they can be used

as a source of dietary protein.

1. Take a microscope slide and place 2–3 drops of rumen fluid on it, using the plas-

tic pipette.

2. View this slide, with a coverslip, under 40# power. You should be able to see large

protists moving around on the slide.

3. Bacteria are usually seen in the forms of rods, cocci, and spirilla, but you may not

be able to see them without stain.

4. Draw two of the different endosymbionts that you can see on your slide.


135


Activity Four: Introduction to Parasites

PROCEDURE

1. Work in groups to familiarize yourself with various endo- and ectoparasites of

humans and other animals. Each student group will be assigned one group of

endoparasites and at least one ectoparasite to examine. Your group will then be-

come the experts at identifying these types of parasites, and you will use your

expertise when you move to Activity Five: Examining Fish Parasites. Refer to

Table 8-3 to view your assignment.

Table 8-3. Parasite groups

STUDENT GROUP I

STUDENT GROUP II

STUDENT GROUP III

STUDENT GROUP IV

STUDENT GROUP V

STUDENT GROUP VI

Endoparasites Amoebas Ciliates Flagellates Apicom-plexans

Platyhel-minthes

(flat worms: flukes and

tapeworms)

Nematoda or Nema-

thelminthes (round-worms)

Ectoparasites Tooth amoebas

(Entamoeba gingivalis)

AND Ticks

Bedbugs Fleas Lice Mites Leeches


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2. Use the available prepared slides, biomounts, preserved specimens, Web site in-

formation, laboratory charts, and lab manual to gather as much information as

you need for your selected parasites (see life cycle Figures 8-2 through 8-8).

3. You will have to find the following information to enter into Table 8-4:

a. Example species: Examine at least three species in your endoparasitic group

as well as your given ectoparasite(s). List the scientific names of each parasite

species in the first column of Table 8-4.

b. Description and size: Provide some general background information for

your parasite group, including key characteristics and interesting facts. Give

the average size of your parasites. If looking at slides, note total magnification

and field of view to estimate size. Also, note the life cycle stage of the parasite

you are viewing. For example, size may differ between a cyst (or egg) and

the adult form of your parasite. Your description should have enough detail

(think back to Organism X from lab 1 and how you described it) for someone

else to get a good overview of your parasite. For example, “big and brown” is

not an acceptable description.

c. Exposure: Briefly describe how humans and other animals are exposed to

your particular parasite, for example, contaminated food or drink. If relevant,

include the geographic location of the most frequent exposure.

d. Host(s): List the hosts your parasite uses. If it has multiple hosts, then specify

which one is intermediate and which one is final.

e. Effects/Diseases: List and briefly describe the effects and/or diseases caused

by your parasites. Include symptoms and treatments when possible. Since we

are looking for parasites during the fish dissection (Activity Five), you may

want to note if your parasite affects fish.

4. As a class, you will fill out the entire Table 8-4. Be prepared to describe your

parasites to the class. You will need to familiarize yourself with each group of

parasites in order to find parasites during the fish dissection in Activity Five.

5. Make a drawing or find a picture of a representative endoparasite and ectopara-

site for your given parasitic organisms to share with the class.


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Table 8-4. General characteristics of select endo- and ectoparasites

ENDOPARASITE AND EXAMPLE SPECIES

DESCRIPTION AND SIZE

EXPOSURE HOST(S)EFFECTS AND

DISEASES

Amoebas

Ciliates

Flagellates

Apicomplexans

Platyhelminthes

Nematoda


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ECTOPARASITEDESCRIPTION

AND SIZEEXPOSURE HOST(S)

EFFECTS AND DISEASES

Bedbugs

Fleas

Mites

Ticks

Lice

Leeches

Tooth amoebas


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Life Cycles of Common Endoparasitic Protozoans

2

1

Cyst

Trophozoites

Multiplication

Exitshost

Trophozoites arealso passed in

stool but they donot survive in the

environment

Contaminationof water, food, or

hands withinfective cysts


Trophant

Trophozoites in the host’s skin

Mature trophantwith hundreds ofmaturing tomites

Releaseof tomites

Tomite


Figure 8-2. Giardiasis Figure 8-3. Ichthyophthirius multifiliis

3

1

2

4

Excystation

Cysts

Trophozoites

45

Trophozoites

Multiplication

Exitshost

Mature cystsingested

Cysts andtophozoites

passedin feces ©Hayden-McNeil, LLC

Sporozoites

Liver stageparasites

Merozoites

Gametocytes

Ring

Trophozoite

Schizont(cyst)

Rupturingschizont


Figure 8-4. Entamoeba histolytica Figure 8-5. Plasmodium sp.


140


Life Cycles of Common Endoparasitic Worms

Metacercariae hatch(excyst) in duodenum

(the first part of the smallintestine), pass into the

abdominal cavity, andenter liver.


7

Metacarceriae on aquatic plants canbe ingested by human, sheep, or cattle

6

Adults live in liver andhepatic biliary ducts and

lay thousands of eggseach day.

8

Eggs are passed in feces.

1

Eggs enter water2

Eggs develop and hatch.The larvae are called miracidia.

3

Miracidia penetrate snail anddevelop into free-swimming larvae.

Sporocysts

4

Cercariae form cysts called metacercariaeon aquatic plants. (This is called “encysting.”)

5

4aRediae

4b

Free-swimming larvaecalled cercariae develop.

4c

Figure 8-6. Fasciola hepatica

Encysted larvae are ingested byhumans and develop into adulttapeworm.


Scolex of adulttapewormattaches tointestinal wallof human host

1

2

4

Eggs are encased in a tapeworm segment called a proglottid, which is passed out in feces. The proglottid is termed “gravid” when filled with eggs. Eggs are relased into the environment.

Cattle and pigs become infected by ingesting vegetation contaminated by eggs or gravid proglottids.

Larval cysts called cysticeri develop in muscle tissue.

3

Small intestinal larvae called oncospores hatch out of eggs, penetrate intestinal wall, and circulate to musculature

5

Egg

Proglottid

Adulttapeworm

Scolex

Figure 8-7. Taenia saginata


141



5

Metacarceriae infish can be ingestedby humans

4

Adults live in hepaticbiliary ducts and gallbladder and laythousands of eggseach day.

6

Eggs are passed in feces.

1

Eggs are ingestedby snail and develop

into free-swimming larvae.

Sporocysts

2

Cercariae penetrate the muscletissue of fish and form cystscalled metacercariae.3

Miracidia

2a

Rediae

2b

Free-swimming larvaecalled cercariae develop.

2c

2dMetacercariae hatch

(excyst) in duodenum(the first part of the small

intestine), pass into theabdominal cavity, and

enter liver.

Figure 8-8. Clonorchis sinensis


142


Activity Five: Examining Fish Parasites

PROCEDURE

Work in groups during this activity. Obtain your fish, measure it, and document its

length and type in Table 8-5. Refer to Figures 8-9 and 8-10, and enter all of your data

in Table 8-5 as you complete the following steps. NOTE: As you go through the pro-

cedure, try to identify any parasites you find. Keep in mind that parasites need close

contact with their host and access to host nutrients, be it digested food or nutrient-

rich blood supply. You can use the small sample jars to store and label your specimens

for further observation. Share any interesting findings with your laboratory instruc-

tor and peers. Before you begin, take a few moments to familiarize yourself with the

external anatomy and anatomical planes of your fish.

ANTERIOR POSTERIOR

Nostril

Anterior dorsal fin

OperculumPosterior dorsal fin

Caudal fin

Anal finPectoral fin

Pelvic fin

Lateral line


VENTRAL

DORSAL

Figure 8-9. External Anatomy of a Fish

PART I: EXTERIOR EXAMINATION1. Look for parasites of the skin. Under the pectoral fin is a good place to look,

but make sure to examine your fish thoroughly. Using a scalpel, scrape along

the scales of the fish and collect the scrapings on a microscope slide. Gather the

scrapings on the center of the slide and prepare a wet mount.

2. Remove the operculum (flap of skin that covers the gills on either side) with scis-

sors to expose the gills for attached parasites. If you find an attached parasite,

view it under both the dissecting and compound microscopes.

3. Carefully remove the gills that you have exposed. Try removing them as one unit

and place in a watch glass to observe under a dissecting scope. If upon closer ex-

amination you find anything that may be a parasite, extract it, make a wet mount

slide, and view it on your compound microscope.


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4. Study the inside of the mouth for visible parasites. Scrape the roof of the mouth

and smear the scrapings on the center of a slide. This is called a “tissue smear.”

Put a tiny drop of methylene blue stain on it and let it dry. View it under the

compound light microscope.

PART II: DISSECTION1. Begin the dissection by inserting the tip of a pair of scissors into the anus (also

called the vent) of the fish and making a starting incision. Follow the incision

ventrally (along the fish’s belly) toward the head and stop short of the operculum.

You want to make sure that the incision is above the pelvic (ventral) fins. Now cut

out a rectangle of skin from behind the operculum, ventral to the backbone and

anterior to the anus. Carefully pull apart the skin to expose the internal organs.

2. Look for parasites around the digestive system and liver (esophagus to the anus).

Make sure to look at the stomach and the pyloric ceca (finger-like pouches be-

tween the stomach and small intestine). Examine the wall of the coelom (the

peritoneum), as well.


Swim bladder

Gill filaments

Heart Liver

Intestine

Gonad

Kidney

Vent

Stomach

Pyloric caeca

Figure 8-10. Internal Anatomy of a Fish

3. Cut out the liver and place it in a watch glass to view under the dissecting scope.

Look for parasites and make a slide of any tissue that you want to further examine

under the compound light microscope.

4. Cut out the small and large intestines and use a disposable pipette to flush out

the inside to remove any parasites. Do this over a watch glass. View under the

dissecting scope to locate parasites and make wet mounts as needed to locate

parasites.

5. Once you are done with the digestive system, remove it to expose other organs

such as the swim bladder (also known as the air bladder, it controls the fish’s

buoyancy), gonads, and kidneys. Also look for parasites around these organs.

Use the techniques discussed above to examine your specimen.


144


6. Examine any other organ in your fish and make slides as needed to locate para-

sites.

7. Dispose of the fish remains where directed and wash all equipment and your

laboratory bench with cleaning solution.

8. Discuss your findings with your class.

Table 8-5. Fish parasite data

Fish type:

Fish length:

Parasites

NAME LOCATION (ORGAN) QUANTITYDESCRIPTION/ OBSERVATIONS

REFERENCESDabhill, E. 1995. Access excellence national health museum: Studying living organ-

isms. http://www.accessexcellence.org/AE/AEPC/WWC/1995/parasite.html

Kearns, C.A., Inouye, D.W. 1997. Pollinators, flowering plants and conservation biol-

ogy. Bioscience, 47: 297–307.

Noble, E. R., Noble, G.A. 1982. Parasitology: The Biology of Animal Parasites. 5th Ed.

London: Lea and Febiger Publishing.

Paracer, S., Ahmadjian, V. 2000. Symbiosis: An Introduction to Biological Associa-

tions. Oxford University Press.

Rollinson, D., Anderson, R. M. 1985. The Ecology and Genetics of Host-Parasite

Interactions. Orlando, FL: Academic Press.

Smith, J. D. 1994. Introduction to Animal Parasitology. Cambridge University Press.


[Questions]145


Name Lab/Section

Partner’s Name (if applicable) Date (of Lab Meeting)

1. What was the most interesting flower that you looked at in lab? What did you

predict for its most probable pollinator? Why did you think this?

2. Botanically, a fruit is a structure that is derived from a fertilized flower. Many of

the vegetables that we eat are in fact fruits. Given that most fruits contain seeds,

name three “vegetables” that are actually fruits.

Which pollinators do you think are most important to agriculture? What might

you expect most “vegetable flowers” to look like?

3. Both termites and cows (ruminants) possess a complete digestive system, but on

their own cannot digest their own food. Explain how these animals actually get

their nutrients.


146


4. What is the advantage of a parasitic life cycle? The disadvantages?

5. Name one of the endoparasites you examined at your table. What hosts does this

parasite infect? How are the hosts exposed? What effect can this endoparasite

have on their host?

6. Name one of the ectoparasites you examined at your table. What hosts does this

parasite infect? How are the hosts exposed? What effect can this ectoparasite

have on their hosts?

7. How is the endoparasite from question 5 and the ectoparasite from question 6

similar? How are they different?

8. Compare and contrast the protozoan and worm endoparasitic life cycles.


[Questions]147


Name Lab/Section

Partner’s Name (if applicable) Date (of Lab Meeting)

9. Give an example of an endoparasite that has only one host and another endo-

parasite that uses multiple hosts to carry out its life cycle.

One-host parasite:

Two- or more-host parasites:

What advantage might there be in having just one host OR requiring multiple

hosts to complete a parasitic life cycle?

10. Name three ways a fish may become parasitized.


148


11. Based on your findings from the fish dissection, where did you find the most

parasites? Which organs were most affected by parasites? Why would these loca-

tions/organs be good places for a parasite?

12. List all of the organs of the fish digestive system. How would the health of the fish

be affected if these organs were parasitized?


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