Name: __________________________________ Date: _____________________ Block: ____
Chesapeake Bay Exploration (Day 2)
This packet includes various concepts learned in the Ecology unit that can be applied to the Chesapeake Bay. All
together (Day 1 and Day 2), it will be counted as a quiz grade. Late packets will be docked 10 points per day
Biotic Factors (continued): Shells
Part A: Oyster
Oysters are soft-bodied animals that have two hard,
protective shells (a bivalve). They spend their entire
lives in one underwater location. The shape of the
oyster's shells varies, depending mostly upon how
crowded they are in the oyster bed.
Anatomy: The two hard, rough-textured shells are
attached by a muscular hinge (the adductor muscles)
at the narrow end. The shell is generated by the
mantle, a thin layer of tissue separating the shell from
the soft body. When an oyster is threatened, it closes
its shells, using the very strong adductor muscle.
Oysters draw in water through their gills, and extract
oxygen and filter out floating algae (which they use
for food). An oyster changes its sex during its life; it
starts out as a male and often ends as a female. The
largest oysters are up to 3 feet (1 m) long, but most are a few inches long.
Pearls: Pearls are sometimes found in oysters. When a grain of sand (or other irritating substance) gets
stuck between the oyster's mantle and shell, the oyster secrets nacre. This shiny substance coats the grain
of sand, and over the years, forms a lustrous pearl.
Predators of the Oyster: Many animals eat oysters, including whelks, sea stars, and people.
Questions:
1. What do we call an organism that has a two-part shell?
2. Name the muscular hinge that attaches the two parts of an oyster shell.
3. In 2 complete sentences, describe the process of pearl formation.
Observations: Obtain an oyster shell from the bucket. Follow the directions below to make
observations about your oyster shell.
1. Describe the texture and shape of the oyster shell.
2. Describe the inner surface of the shell.
Part B: Clam
Clams are animals that burrow under the sea floor. They are
bivalves, mollusks that have two shells that protect a soft body.
There are over 15,000 different species of clams worldwide. The
biggest clam is the Giant Clam, Tridacna gigas; it is up to 4.8 feet
(1.5 m) long and weighs up to 550 pounds (250 kg). Most clams
are only a few inches long.
Anatomy and Diet: Clams come in many colors, including shades
of brown, red-brown, yellow, cream, etc. The two shells are
attached by a muscular hinge (the adductor muscle). When a clam
is threatened, most clams will pull their soft body into into the
shells and close the shells tightly for protection. The foot is used
to burrow into the sand. Clams use their tube-like siphon to draw
in water, from which they extract oxygen and filter plankton (tiny
plants that they eat).
Predators of the Clam: Many animals eat clams, including eels, sea stars, whelks, and people
Questions:
1. What do clams do when threatened?
2. How do clams accomplish gas exchange and feeding? What body structure is involved
Observations:
1. Describe the texture and shape of the clam shell.
2. Identify two similarities and two differences between the clam shell and the oyster shell.
Part C: Scallop
Scallops are bivalves; they have two hard shells and a soft body. They are benthic animals; they spend
most of their time on the sea bottom. Scallops mostly stay in underwater grass beds on a soft, shallow sea
floor. Scallops use jet propulsion to move; they quickly open and close their shells, squirting the water
out of the shells, moving in spurts. These invertebrate animals have a life span of about 1 1/2 years.
Anatomy: The two hard shells (also called valves) are attached by a muscular hinge called the adductor
muscle The Bay Scallop is about 3 inches (8 cm) in diameter; other scallops can reach 8 inches (20 cm)
in diameter. The shell is secreted by the mantle, which is a thin sheet of tissue located between the shell
and the body. Scallops have many primitive eyes; they can only sense changed in light and motion,
helping them to detect predators.
Diet: Scallops eat microscopic food, like algae and plankton that floats through the water.
Predators of the Scallop: Many animals eat scallops, including sea stars, crabs, and people.
Questions
1. Describe the habitat of a scallop.
2. How do scallops move?
Observations:
1. Describe the shape and texture of the scallop shell.
3. How is the scallop shell different from the clam shell? (Identify two differences)
Diagrams:
In the three boxes below, draw the following three shells: oyster, clam, and scallop
http://www.enchantedlearning.com/subjects/invertebrates/bivalve/Bivalves.shtm
Biotic Factors: Organisms
Part A: Crayfish
Use the information on Pages 747 to 749 of your textbook to fill-in the background information below:
Crayfish are crustaceans that live in ________________________. They are related to the
_____________________ because they both have ten feet. Organisms with ten feet are called
_______________________. Crayfish bodies are divided into two main sections, the
_______________________ and the ______________________. The cephalothorax is further divided
into the ______________________ and ____________________. Each body region is further
segmented, and the final abdominal segment is called the ________________. Different segments are
associated with different appendages (Ex: walking legs, antennae).
Crayfish use _______ for respiration. These respiratory structures extend from the ____________
______ into a chamber under the ______________, a hard covering on the back side of the crayfish.
Using the information on Page 748 of your book, fill in the functions for each type of appendage found in
crayfish. Also, observe the appendages on your crayfish specimen and describe their location/
appearance in the chart below.
Appendage Type
Mandible
Maxilliped
Cheliped
Walking Leg
Swimmeret
Uropod
Function
Location/ Appearance
Label the diagram below with the following terms: antenna, cheliped, mandible, walking legs,
swimmerets, telson, uropod,
Part B: Yellow Perch
Use the information on Page 807-808 of your textbook to fill in the blanks in the paragraph below.
The yellow perch belongs to the major fish group Osteichthyes—the bony fishes. The bony fishes are
characterized by three main features: ______________, _________________________________, and
____________________. There are two main types of bony fish, the
_________________________________ and the ____________________________________________.
The external anatomy of a yellow perch is characterized by three main regions, the ________________,
__________________, and __________________. In the head region, perch poses a bony covering to
protect their _____________, which are used in gas exchange.
Perch have five types of fins: ________________, ____________________, ______________________,
and _____________________.
Using Figure 41-8 on Page 808 of your textbook, label the following structures in the diagram
below:
Anterior Dorsal Fin
Posterior Dorsal Fin
Pelvic Fin
Anal Fin
Pectoral Fin
Lateral Line
Operculum
Caudal Fin
Use the Fin information found on Page 808 to fill in the functions for each fin type in the table below.
Also, observe the fins on your perch specimen, and record your observations about each fin’s
shape/appearance in the table. You must comment on whether each fin has spines (bony/rigid fin
supports) or rays (bony/flexible fin supports)
Fin Name
Function
Location
Spines vs. Rays
Use forceps to remove ONE scale from your fish. Observe the scales under the hand lens. See the
figure at the top of the next page for a diagram of basic scale structure
Count the growth ridges on your scale to tell the age of your fish. (Hint: each ridge represents one
year's growth.) Dispose of your scale in the designated bag provided by the teacher.
How old was your fish when it died?__________________________________
Choose two of the 5 labeled structures in the dissected perch and record their function (using
Pages 809-812) and observations of their appearance in the table below.
Structure
Function
Observations
Part C: Sea Urchin
Use the information on Page 807-808 of your textbook to fill in the blanks in the paragraph below.
Sea urchins belong to Class __________________, which means “spine-like.” Sea urchins poses a
rigid endoskeleton called a _____________ to protect their internal organs. Additionally, they
have special adaptations for living on sea bottom. Sea urchins use ____________________ for
movement. They possess teeth and a muscle system, which form a complex, jaw-like feeding
apparatus called ________________________ .
In the sea urchin, the most prominent structures are the coiled intestines, gonads (sex organs), and
Aristotle’s Lantern. The teacher will label these structures in the sea urchin specimen. Using the
table below, make observations about each of these structures.
Structure
Intestines
Observations
Gonads
Aristotle’s Lantern
In the box below, draw a picture of Aristotle’s Lantern.
Part D: Sea Star
Use the information on Page 785-786 of your textbook to fill in the blanks in the paragraph below.
Sea stars (AKA starfish) belong to class ____________________, meaning “star-like.” Sea stars
typically have ____ arms that extend from a central region. There are two body surfaces on the sea star
body plan. The _________ surface is where the mouth is located, and the opposite surface is called the
_________ surface.
Sea star bodies are generally covered with short ______. They also have ____________________ to
keep the body surface free of foreign objects. Additionally, sea stars have a _____________
______________ _______________, which is a series of canals to circulate water throughout the body.
This system is used in feeding, respiration, and movement.
Follow the procedure below to dissect your sea star. Your teacher will tell you what dissecting
materials you will need and discuss safety precautions. At points in this lab, your directions will
tell you to circle or underline certain structures. You may also be asked to give observations about
certain body structures.
A. External Anatomy
Figure 1: Dorsal (top) side of Sea star
1.
2.
Figure 2: Ventral (bottom) side of Sea star
Place your sea star in the dissecting tray so that the dorsal surface faces upward.
Examine the animal’s top surface. Locate the central disc and the five arms, or rays that extend from the
central disc. Circle the central disc in the figure above.
3.
Locate the madreporite plate. It is a round, structure that looks almost like a wart. The madreporite plate is a sievelike structure, which regulates the movement of water in and out of the water vascular system. Place a box
around the madreporite in the figure above.
4.
Note that many spines are scattered over the surface of the arms and the central disc. These spines
are attached to the plates of the sea star skeleton just under the skin. These plates are called ossicles.
5.
Turn the sea star over to its oral side. Locate the mouth and the five ambulacral grooves that extend
from the mouth along the middle of each ray. Draw a triangle around the mouth and shade-in the ambulacral
groove.
B. Internal Anatomy
At a point about one inch from the tip of any of the rays, force the point of a sharp scissors or scalpel through the
upper surface of the sea star. To expose the internal organs cut the skin as shown in Figure 3. Carefully pull back and
remove the skin. Make sure you are cutting on the top side of the sea star!
1. The Digestive System.
Note that most of the space in the ray is taken up by two highly branched digestive glands (pyloric ceca) which
secrete digestive juices. Circle these in the figure below. A duct in each arm connects the pyloric cecum back to its
connection with the stomach, which consists of a lobed lower cardiac region and an upper pyloric region. During feeding
the cardiac region and an upper pyloric region are used. The cardiac region of the stomach is exerted (extended) through
the mouth. The food is partially digested and then passed into the pyloric region, which empties into the anus where the
waste products of digestion are discharged to the outside.
Figure 3: Internal Anatomy of the Sea Star
1.
Carefully cut a ring around the madreporite plate, and use your scissors to cut off the tip of any ONE arm except for
the two arms right next to the madreporite plate.
2.
Starting at the end of the arm with its tip cut off, use your scissors to remove the remaining skin/skeleton from the
top of the arm and from the central disc. This will expose the sea star’s internal organs, including the digestive
gland (AKA pyloric cecum), a large gland with two branches that fills most of the arm. Draw and label the digestive
gland on the outline of the sea star pictured below.
List 3 meaningful, scientific observations of the pyloric ceca in the
box below:
3.
Turn your sea star over and locate the mouth. The mouth is attached
to the pouch-like stomach, which can be seen through the opening
you have cut in the top surface. Draw and label the mouth and stomach on the blank sea star pictured above.
3. The Water Vascular System
The water vascular system of the sea star consists of a series of seawater filled ducts that function in locomotion
and feeding. To study this system, it will be necessary to carefully remove the reproductive organs and the remaining parts
of the digestive system, the stomach and anus. Be careful not to damage the sieve plate. After careful dissection, locate
the following parts of the water vascular system.
Water enters this system through the madreporite plate, which is connected, to a circular ring canal by the stone
canal. The water is then distributed to the radial canals that pass into each of the rays. Lining the ridge through which each
radial canal passes is a double row of bulb-like structures called ampullae. These are connected to the tube feet that
project from the ambulacral groove on the undersurface of each ray. Water from the radial canal collects in the ampullae.
Contraction of the ampullae causes the tube feet to elongate as water is forced into them. Expansion of the ampulla results
in shortening the tube feet. Thus, through the use of small suction discs at the end of each tube foot and the alternate
expansion and contraction of the ampullae, the starfish is able to move.
1.
Carefully remove the remaining parts of the
digestive system (including the stomach). This
will expose the water vascular system.
2.
Study your sea star. Use the Figure to the right to
find each of the structures of the water vascular
system that is underlined in the above
paragraph. Be sure to circle structures
(NOT THE LABELS) as well.
3.
Trace the pathway that seawater takes from the
madreporite plate to the tube feet.
Mark this pathway using short dashed lines on
the figure above.
4.
After completing the dissection, dispose of your
sea star to your teacher’s instructions.
Conclusion: In a well-written 5-7 sentence paragraph, discuss what you learned from today’s lab.
Make sure to include information about the shells and dissected organisms. Note: points WILL be taken
off for paragraphs that are not 5-7 sentences. Points will also be deducted for not including all required
information.