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lab
ora
tory
7
7 LaboratoryS
alto
v/S
hutt
erst
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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
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115
Laboratory 7 A Survey of the Invertebrates and Fungi and Construction of a Dichotomous Key
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
Laboratory 7 A Survey of the Invertebrates and Fungi and Construction of a Dichotomous Key
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
Laboratory 7 A Survey of the Invertebrates and Fungi and Construction of a Dichotomous Key
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.
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118
Laboratory 7 A Survey of the Invertebrates and Fungi and Construction of a Dichotomous Key
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
.
NOT FOR DISTRIBUTION - FOR INSTRUCTORS USE ONLY
119
Laboratory 7 A Survey of the Invertebrates and Fungi and Construction of a Dichotomous Key
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:
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120
Laboratory 7 A Survey of the Invertebrates and Fungi and Construction of a Dichotomous Key
NOT FOR DISTRIBUTION - FOR INSTRUCTORS USE ONLY
121
Laboratory 7 A Survey of the Invertebrates and Fungi and Construction of a Dichotomous Key
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
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122
Laboratory 7 A Survey of the Invertebrates and Fungi and Construction of a Dichotomous Key
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
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123
Laboratory 7 A Survey of the Invertebrates and Fungi and Construction of a Dichotomous Key
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.
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124
Laboratory 7 A Survey of the Invertebrates and Fungi and Construction of a Dichotomous Key
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
.
NOT FOR DISTRIBUTION - FOR INSTRUCTORS USE ONLY
[Questions]125
Laboratory 7 A Survey of the Invertebrates and Fungi and Construction of a Dichotomous Key
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?
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126
Laboratory 7 A Survey of the Invertebrates and Fungi and Construction of a Dichotomous Key
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.
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