Laboratory - WolfWare WordPress Projects

113

lab

ora

tory

7

7 LaboratoryS

alto

v/S

hutt

erst

ock

.com

LEARNING OBJECTIVES

Students will….

• work as a class to figure out how scientists construct and use dichotomous keys by

following along with an example and by creating their own practice dichotomous

key that they will present to the class.

• record detailed information on various groups of fungi and invertebrates as they

observe live, preserved, and microscopic specimens in the lab; and they will use

that information to construct and interpret dichotomous keys.

• apply their knowledge of various fungi and invertebrate group characteristics by

answering specific questions in lab, identifying unknown organisms, and complet-

ing a “webquest.”

INTRODUCTIONSuppose you come upon an unknown organism. Before you can classify that organism

you will need to identify it. The most widely used type of key is the dichotomous key

that is based on a set of paired choices. For example, does the individual fly or not fly?

Does it make its own food or feed on others? Eventually you move through the key or

series of statements until you arrive at an answer. It would be very difficult to do this

for all organisms living on this planet. Generally, keys are limited to identifying a col-

lection or range of organisms such as the dragonflies of Canada, the organisms found

in ponds or, as in your example, the United States currency in the collection on the

next page.

A Survey of the Invertebrates and Fungi

and Construction of a Dichotomous Key

NOT FOR DISTRIBUTION - FOR INSTRUCTORS USE ONLY

114

Laboratory 7 A Survey of the Invertebrates and Fungi and Construction of a Dichotomous Key

Example

A dichotomous key could be constructed of the following collection of U.S. currency:

a ten-dollar bill, a five-dollar bill, a one-dollar bill, a quarter, a dime, a nickel, and a

penny.

1. a. Composed of paper ............................................................................................. go to 2

b. Composed of metal ............................................................................................. go to 4

2. a. George Washington is pictured ...........................................................one-dollar bill

b. George Washington is not pictured ................................................................ go to 3

3. a. Abraham Lincoln is pictured ...............................................................five-dollar bill

b. Alexander Hamilton is pictured ...........................................................ten-dollar bill

4. a. The edges have ridges ......................................................................................... go to 5

b. The edges do not have ridges ............................................................................ go to 6

5. a. Smaller than 15 mm in diameter ..........................................................................dime

b. Larger than 15 mm in diameter. ..................................................................... quarter

6. a. Silver in color ..........................................................................................................nickel

b. Copper in color ..................................................................................................... penny

How would you change the key to include a twenty-dollar bill? At some point, we

have all received Canadian coins (Figure 7-1) such as a quarter or a dime. How would

you include them in the above key?

Figure 7-1. Canadian Coins


115


Activity One: Practice Key Construction 1. Gather all of the people sitting at your table and compare your shoes. You do not

need to take them off.

2. Construct a key that can be used to identify each of your shoes. Use the format of

the currency example. You can ultimately identify each shoe by group member’s

name and style of shoe, for example, “John’s boots.”

Key to Shoes

Scientists use taxonomic keys to determine the identity of an unknown organism.

Today in class, you will design two different keys: one for various fungal groups and

one for invertebrates. You will be provided with a table of features for each group,

which we will refer to as characters, short for characteristics. You are also encouraged

to make your own observations and record data that are specific to the “collection”

found in the lab. The keys you will construct will be based on characters that were

once used by taxonomists to divide fungi and invertebrates into major groups based

on “lifestyle.” However, the phylogeny of these two groups is undergoing dramatic

revision based largely upon molecular “characters.” We will, therefore, be using this

exercise as a way to examine lifestyle and to gain an appreciation for the important

roles these groups play in many environments.

Fungi form important beneficial symbiotic relationships with plants. Recall the in-

formation on fossil plants that gave testament to the age of this relationship. Fungi

are also important in recycling dead material into the soil in a form that can be used

by other organisms. An appreciation for these and other pivotal roles played by fungi

will prove crucial to understanding community structure and ecological relationships

among species in general.

Invertebrate animals make up over 90% of the animal kingdom. We would be very

negligent in examining the animal biodiversity if we failed to look at major represen-

tatives of this kingdom. Constructing and/or examining keys are a very user-friendly

way to begin to examine these large groups that you will be working with throughout

the course and your career as a biologist. NOT FOR DISTRIBUTION - FOR INSTRUCTORS USE ONLY

116


Activity Two: Familiarity with the Fungi

BACKGROUNDWe need to briefly review the life cycle of fungi before proceeding. Variations in life

cycles are used as one of the main characters to divide fungi into different groups.

In most fungi, the haploid, multicellular stage is dominant. Most of the growing

part of a typical mushroom exists underground and consists of haploid cells. These

cells may or may not have cell wall dividers (septa). Small groupings of filaments are

known as hyphae (hypha is singular). A larger concentration of hyphae is called a

mycelium. Within a mycelium, two haploid cells of different strains can fuse, creat-

ing a dikaryotic (2 non-fused nuclei) condition. These dikaryotic cells will grow to

form a dikaryotic fruiting body that we typically call a “mushroom.” These fruiting

bodies generally appear when the environmental conditions are favorable, such as

after a rainstorm. Fungi are distinguished by the complexity and type of fruiting body

observed. Within the “fruiting body,” there will be a nuclear fusion of some cells to

form temporary specialized diploid cells. Meiosis then occurs giving rise to haploid

spores. These spores are dispersed by wind and insects and can withstand many

environmental stresses. The spores will germinate once conditions are favorable, giv-

ing rise to new hyphae, and the cycle continues. When and how haploid hyphae cells

fuse, and for how long individual cells carry two nuclei (the dikaryotic condition),

varies among the different fungal groups.

PROCEDURE

1. Review the life cycle of a common mushroom below.

Gills

Germinationof spores (N)

Hyphae (N)

Dikaryotic (N+N)hyphae

Nuclear fusion (2N)

Meiosis

Basidium

Basidiospores (N)

+

©Hayden-McNeil, LLC

Cytoplasmic fusion (N+N)to form dikaryotic hyphae

Figure 7-2. The Life Cycle of a Mushroom-forming BasidiomyceteNOT FOR DISTRIBUTION - FOR INSTRUCTORS USE ONLY

117


2. We have provided a table of important distinguishing characteristics for you,

since most people are unfamiliar with fungi. You will need to fill in the empty

portions of Table 7-1. This information can all be found at the displays for each

group. Before you start visiting the displays, be sure to understand the basic

life cycle (Figure 7-2) and the terminology listed below. The characters that are

marked with an asterisk “*” on Table 7-1 can be used as the definitive characters

in your dichotomous key.

FUNGAL TERMINOLOGYHyphae: small grouping of filaments that form the fungal tissue. Large concentrated

masses of hyphae are called mycelia.

Septa: crosswalls in hyphae cells. Hyphae can be septate or non-septate (no cross-

walls).

Heterotroph: an organism that obtains organic food molecules by eating other or-

ganisms or their by-products.

Autotroph: an organism that obtains organic food molecules by producing them

from inorganic molecules. Requires energy from the sun or from oxidation of inor-

ganic substances.

Lichen: the symbiotic collective formed by the mutualistic association between a

fungus and a photosynthetic green algae or cyanobacteria.

Mycorrhizae: fungal cells that form a mutualistic association with plant roots.

Sporangium: a capsule in fungi and plants in which spores are produced by mitosis

(asexual spores) or meiosis (spores involved in sexual reproduction).

Spore: a single- or multi-celled unit, either haploid or diploid, produced in the spo-

rangium of a plant or fungus. They are dispersed into the environment to germinate

into a new plant or fungus.

Zygospore: in zygomycete fungi, a sturdy multinucleate structure that can withstand

harsh environmental conditions. Meiosis will occur and produce haploid spores that

will germinate into the next generation of fungus.

Haploid: having one set of chromosomes.

Diploid: having two sets of chromosomes.

Dikaryotic: cells that result from cellular fusion, but the two “parental” nuclei re-

main separate from each other.

Fruiting body: generally a large reproductive structure made up of dikaryotic cells

and specialized spore-producing sporangia.


118


Tab

le 7

-1.

Co

mp

ari

son

s a

mo

ng

fu

ng

i an

d r

ela

ted

gro

up

s

CHAR

ACTE

RSBA

SIDI

OMYC

OTA

(C

LUB

FUN

GI)

ASCO

MYC

OTA

(S

AC F

UNGI

)ZY

GOM

YCET

ESLI

CHEN

SSL

IME

MOL

DS

Co

mm

on

ex

am

ple

s

No

. o

f sp

eci

es

~3

0,0

00

~3

2,0

00

~9

00

~2

0,0

00

~6

00

Siz

e (

ma

cro

- o

r

mic

rosc

op

ic)

Hy

ph

ae

: se

pta

te

or

no

n-s

ep

tate

*

En

vir

on

me

nt*

Mar

ine,

fre

sh

wat

er, t

erre

stri

alM

arin

e, f

resh

wat

er, t

erre

stri

alA

qu

atic

an

d

Ter

rest

rial

T

erre

stri

al, o

n p

lan

ts, s

ton

e an

d t

he

gro

un

dT

erre

stri

al, d

ecay

ing

wo

od

Ho

w n

utr

ien

ts

are

ob

tain

ed

*

Ass

oci

ati

on

s*M

yco

rrh

izae

on

ro

ots

of

pla

nts

. Ass

oci

ated

wit

h s

om

e in

sect

s. S

om

e ex

ist

as l

ich

ens.

Myc

orr

hiz

ae o

n r

oo

ts o

f p

lan

ts. S

om

e ex

ist

as l

ich

ens.

Myc

orr

hiz

ae o

n r

oo

ts o

f p

lan

ts.

Clo

se a

sso

ciat

ion

bet

wee

n

fun

gal

hyp

hae

an

d g

reen

alg

ae

or

cyan

ob

acte

rial

cel

ls.

No

ne

Sp

ore

s*H

aplo

idH

aplo

idH

aplo

id a

nd

Dik

aryo

tic

zy

gosp

ore

Hap

loid

Hap

loid

Sex

ua

l

rep

rod

uc

tio

n*

Dra

win

gs

Bas

idia

wit

h _

__

_#

of

B

asid

iosp

ore

s

Asc

us

wit

h _

__

_#

of

Asc

osp

ore

sS

po

ran

gia

wit

h N

sp

ore

s

Zyg

osp

ore

s (n

+ n

)B

asid

ia o

r A

scu

s—d

raw

on

e o

r th

e o

ther

typ

e se

en i

n l

ab f

or

lich

ens

Sp

ora

ng

ia w

ith

n s

po

res

or

dra

w r

egu

lar

gro

wth

hab

it

Str

uc

ture

wh

ere

m

eio

sis

tak

es

pla

ce*

Na

me

of

fru

itin

g b

od

y*

Use

sF

oo

d, i

llic

it d

rugs

, pig

men

ts,

enzy

mes

use

d i

n p

aper

pro

-d

uct

ion

, bio

rem

edia

tio

n

Dec

om

po

sers

of

live

an

d d

ead

p

lan

t m

ater

ial,

use

d i

n b

read

an

d a

lco

ho

l p

rod

uct

ion

Bio

-co

ntr

ol

of

inse

ct p

ests

, fo

od

pro

du

ctio

n (

chee

ses.

..)F

oo

d f

or

som

e an

imal

s, u

sed

as

po

llu

tio

n i

nd

icat

or

Gen

eral

dec

om

po

siti

on

Dra

win

g

*Ch

arac

ters

th

at c

an b

e u

sed

as

defi

nit

ive

char

acte

rist

ics

in c

on

stru

ctin

g yo

ur

key

s fo

r th

ese

fun

gal

gro

up

s.

NO

TE

: B

e su

re t

o c

hec

k t

he

mat

eria

l o

n t

he

lab

ora

tory

tab

les

to h

elp

yo

u fi

ll i

n t

he

bla

nk

sp

aces

.


119


3. Before constructing your dichotomous key, review the characters you filled in

your chart with your class. As a table, construct a dichotomous key in the space

below for the five groups studied. Appendix F contains some pictures of these

fungi and fungal related groups.

Your dichotomous key:


120



121


Activity Three: Familiarity with the Invertebrates

BACKGROUNDAs you try to assess similarities and differences among the invertebrate groups

(Table 7-2), try to become familiar with common representatives of each group. Also,

realize that it is very difficult to determine relationships among invertebrate organ-

isms. It is obvious from invertebrate diversity that many “evolutionary designs” were

tried and ended in extinction. Extant groups or living representatives have diverged

very far from the main line, or, more aptly, main lines, of animal evolution.

Table 7-2. Invertebrate phyla

INVERTEBRATES

Annelida Arthropoda Cnidaria

Echinodermata Mollusca Platyhelminthes

Porifera Nematoda

For example, sponges (Porifera) are very primitive in construction; they are in some

sense relics of the transition from a colony level of construction to a tissue level of

construction. Yet sponges typically have a type of highly specialized cells, the col-

lar cells, rarely found outside their group. These cells display cell recognition and

immune responses more typical of groups known from the fossil record to be more

advanced with regard to body construction, possessing tissue layers, organ systems,

etc. Sponges are also sessile (nonmotile), and all evidence points to a motile ances-

tor for most invertebrate groups.

The same can be said of the Cnidaria, whose typical representatives include hydra

and some jellyfish. Cnidarians basically consist of only two layers or tissue types. Yet

many biologists think they have become simpler in morphology as a group over time.

Sea anemones belong to this group and are more complex in structure than Hydra,

yet they are considered to be more primitive in regards to fossil records and new mo-

lecular data. There are also those that would argue that Cnidaria evolved as a group

from a more complex ancestor. We expect to see relationships change in the light of

new molecular data. Although there will always be a Cnidarian way of life, Cnidaria

may not always be a phylum as it is today. It may become part of another phylum or

even be broken up into several phyla as we learn more about the genetic makeup and

relatedness of all animals.

We have provided some important terminology below. Before you begin be sure you

understand these terms.

NOTE: You should review with your laboratory instructor any feature that you do

not understand.

INVERTEBRATE TERMINOLOGYSymmetry and cephalization: Adult symmetry is correlated with lifestyle. If the adult

is sessile (attached to a surface), radial symmetry is the general rule. Most self-mobile

animals are bilaterally symmetrical with the end that enters a new environment first


122


housing the “brain” and well-developed sensory structures. Why would this be advan-

tageous? This end is known as a head and is said to exhibit cephalization.

Coelom: A body cavity or space in addition to the gut/digestive system is termed

a coelom. There are various kinds of coeloms and taxonomists disagree as to the

affinities of the types and what type of cavity should even be considered a “true”

coelom. Many taxonomists feel that coeloms first arose as a hydrostatic skeleton:

volumes of fluid surrounded by muscles.

Once animals had a coelom, the coelom began to take on other functions, such as

transport of materials and housing expanding organ systems. This allowed the de-

velopment of animals larger than flatworms (Platyhelminthes). If the phylum you are

examining includes some relatively large organisms with bulkiness to their bodies

that can move efficiently, they probably have some type of coelom.

Segmentation: The origin of segmentation, like most trends in the animal kingdom,

is debatable. Segmentation allows animals to become larger by replication of the same

structures over and over again. Segmentation also allows for more precise localized

movement. The pressure differences that are caused in the coelom by contraction of

muscles in one segment can be somewhat isolated from other segments. Study the

diagram below (Figure 7-3) and watch earthworms move in the laboratory (Annelida).

In our simple demonstration of annelid movement, circular muscles contract, length-

ening a few segments. The back part of the animal is anchored by chaetae (stiff hairs

that can act as holdfasts; note the arrows in this figure). The animal then anchors

its front, releases the back, and as the original shape of the lengthened segments is

restored (usually by longitudinal muscles), the rear moves forward.

©Hayden-McNeil, LLC ©Hayden-McNeil, LLC

Circular muscles relax

Lengthdecreases

Chaetae

Lengthincreases

Circular muscles contract

Longitudinalmusclesrelax

Longitudinalmusclescontract

Direction of movement

Figure 7-3. Annelid Movement

Once a number of segments were present, different segments could become spe-

cialized for different functions. The most interesting case of segment specialization

involves some sessile, bottom-dwelling marine annelids. Segments develop that bear

reproductive structures, appendages for effective swimming, and even sensory or-

gans. Some of these segments may comprise “individuals” that separate and come to

the surface to mate in swarms. Note that in the Arthropoda not all the segments are


123


involved in locomotion. Some segments may form part of a well-defined head, where-

as other segments form an abdomen that houses reproductive and other organs.

Limbs and joints: Locomotion appendages, or limbs, allow a great deal of move-

ment from a minimum amount of muscular contraction. The bulk and weight of the

body moves in the forward direction while only the limbs are moved back and forth.

Jointed limbs provide a system of levers that allow precise placement of antagonistic

muscles, allowing great flexibility of movement.

Locomotion: How do most species in the group move? Sometimes there are several

modes employed. Larger flatworms move by muscular contractions as well as cilia.

Some groups, such as Echinodermata, a group that includes the sea stars, move by

small tube feet. Only Echinoderms move by using tube feet. Many Arthropods (and

Vertebrates seen last week) use muscles and jointed appendages or limbs to move.

We tend to focus on the muscles as organs of movement. But muscles alone cannot

move the body effectively. Muscles need energy to contract, but cannot return to their

relaxed position without an external force to return them to their original relaxed

length. In your body, your muscles are oriented around a movable or jointed skeleton

such that the contraction of one muscle brings about the relaxation of another.

TYPE OF SKELETONS Early skeletons were probably hydrostatic skeletons. In hydrostatic skeletons,

the contraction of one part of the muscular system sets up a pressure in the fluid-

filled body cavity (coelom) to relax other muscles or parts of the system. Refer back

to the discussion on segmentation. There are two types of rigid skeletal systems:

an exoskeleton (external) and an endoskeleton (internal). Exoskeletons have an

advantage in the strength to weight ratio. For a given quantity of skeletal material,

a thin tubular exoskeleton is far stronger than a solid, rod-like endoskeleton. This

explains the evolutionary advantage of small animals like insects. Exoskeletons also

support and protect soft internal organs and add a protective coating that prevents

desiccation. In order to grow large, animals with an exoskeleton must molt (shed

and regrow a new exoskeleton). Larger animals with exoskeletons would also require

larger muscles that are bulkier and harder to construct (if they are to remain flex-

ible at the joints). At some point/size it will become difficult to construct such large

exoskeletons. Endoskeletons provide internal rigidity and easier growth in size. Soft

body tissues and organs can grow along with an endoskeleton.

PROCEDURE

1. Fill in the comparative table (Table 7-3) on major characters for the phyla pre-

sented in this laboratory. Most of the characters can be recorded as “present”/“not

present” or as “yes”/“no.” Remember, in addition to the suggested characters you

may use other characters that are found in the specimens you have been observing.

2. After filling out Table 7-3, your lab instructor will provide an unknown organism

which you will have to place in one of the invertebrate groups using a dichoto-

mous key.


124


Tab

le 7

-3.

Co

mp

ari

son

s a

mo

ng

inve

rte

bra

te g

rou

ps

CHAR

ACTE

RPO

RIFE

RACN

IDAR

IAPL

ATYH

ELM

INTH

ESN

EMAT

ODA

ANN

ELID

AM

OLLU

SCA

ECH

INOD

ERM

ATA

ARTH

ROPO

DA

Co

mm

on

exa

mp

les

(nam

es)

Tru

e co

elo

m

Seg

men

tati

on

Sym

met

ry*

Cep

hal

izat

ion

Lim

bs/

app

end

ages

Join

ted

lim

bs

Lo

com

oti

on

Rig

id s

kel

eto

n

pre

sen

ce

Exo

- o

r

En

do

skel

eto

n

(rig

id)*

Dra

win

g:

Incl

ud

e as

man

y o

f

the

abo

ve c

har

acte

r-

isti

cs a

s p

oss

ible

in

you

r d

raw

ing

*In

dic

ate

the

spec

ific

nam

e o

f th

e o

bse

rved

ch

arac

ter.

NO

TE

: B

e su

re t

o c

hec

k t

he

mat

eria

l o

n t

he

lab

ora

tory

tab

les

to h

elp

yo

u fi

ll i

n t

he

bla

nk

sp

aces

.


[Questions]125


Name Lab/Section

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

Phylogeny Review1. Compare the fungal life cycle to that of plants (think of last week, Unit 6). How

are fungal and plant life cycles similar? How are they different?

2. If you were to construct a key for a local mushroom collector, how would your

key for fungi differ from the key constructed in the laboratory? What characters

of their biology would not be apparent to the mushroom collector?

3. Slime molds were at one time considered fungi. What character(s) do they share

with fungi? What character(s) do they exhibit that link them to other groups?

What are these other groups?

4. Why do you suppose lichens were included in a laboratory on fungi?


126


5. If you were to describe a “typical” animal based on sheer numbers and diversity,

it would most likely be an invertebrate. After examining all of the animals in lab

today what type of invertebrate/phyla would you consider “typical”? Would this

vary in different communities or habitats? Give some examples.

6. Define the term coelom. Why are coeloms important?

7. What types of locomotion did you observe for animals in this laboratory? Com-

pare and contrast the efficiency of cilia, hydrostatic skeletons, hard skeletons,

and jointed appendages used by animals as they get larger or exploit different

environments.

8. What are some phyla that contain important parasites of man or his domestic

animals? You will look at these relationships in greater detail in a later laboratory.

9. Give examples of pivotal roles played by fungi and invertebrates in ecosystems.


Laboratory - WolfWare WordPress Projects

Documents

Transcript of Laboratory - WolfWare WordPress Projects