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MARINE BIOLOGY LABORATORY
Objectives:
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To appreciate the changes in animal body plans that have occurred throughout the
evolution of the Animal Kingdom;
To be able to recognize representatives of the major phyla of the Animal Kingdom.
There are millions of different species (kinds) of living organisms on the earth. Living
organisms come in many different forms: everything from single-celled bacteria to seaweeds to
large whales. This diversity of living things is overwhelming. However, all living things must
solve the same basic problems: they must acquire food for energy, exchange gases (oxygen and
carbon dioxide) with their environment, get rid of waste products, develop, grow and reproduce.
How they solve these problems, and the structures that they have in their bodies to accomplish
all of this, varies from one type of organism to the next.
This lab is designed to introduce you to the large diversity of living things that occupy marine
habitats. You will start by observing “simpler” organisms and move on to observing more and
more complex body plans. As you observe these organisms, think about their basic body plan
and how it accomplishes each of the tasks detailed in the preceding paragraph. Think about how
each organism’s body is similar or differs from the other organisms that you observe.
I.
PRIMARY PRODUCERS
a. Phytoplankton
We will start with organisms that are single-celled. This means that their entire body is
made up of just one cell. Phytoplankton is the name of a group of microscopic, single-celled
algae that are found drifting around in the ocean. Algae are photosynthetic organisms that have
chlorophyll and are classified in the Kingdom Protista. Large, macroscopic algae are known as
seaweeds. All algae require light, carbon dioxide, water and nutrients just as plants do. We will
observe some examples of phytoplankton today in lab. There are many different types of
phytoplankton; the two most common groups are diatoms and dinoflagellates.
Diatoms are the most abundant form and there are thousands of different species of
diatoms. Diatoms have a glass-like shell made of silica which gives them their iridescent
appearance when they are viewed under a light microscope. Diatoms also store a drop of oil
under their shell which makes them more buoyant so they do not sink away from well-lit surface
waters. Diatoms come in a variety of shapes. Some species have extensions of the shell which
also help slow their sinking rates and some species form chains of cells as they divide and
reproduce.
Dinoflagellates are a group of Protists which have two whip-like tails called flagella.
Most dinoflagellates are photosynthetic and are part of the plankton. Some species are
responsible for the harmful algal blooms known as “red tide” or “brown tide” but many species
are harmless, such as Ceratium which you will view today in lab.
Ceratium shown at left from algaebase.org
Melosira, a diatom, shown at right, may grow together in long colonial chains from
http://www.ucmp.berkeley.edu/chromista/diatoms/diatomlh.html
Procedure:
Examine the prepared slides of phytoplankton that are available in lab. There is one slide
of a common type of dinoflagellate called Ceratium and one slide that has many different types
of diatoms on the single slide. Note the variety of shapes and sizes. Sketch a few representative
organisms from each slide below and then answer the question.
Drawing of Diatoms
Drawing of Ceratium (a dinoflagellate)
Describe the difference between diatoms and dinoflagellates.
b. Seaweed
Seaweeds are also algae but they are multicellular, meaning that there body is made up of many
cells. Seaweeds are large and photosynthesize like plants but they are not true plants. Most
plants live on land and must suck up water and nutrients from the soil using roots.
Seaweeds live in aquatic habitats. Which part or parts of their body do you think they can use to
absorb water and nutrients?
Look at the seaweeds on display. Some seaweeds have structures that look like roots at their
base (also see photo above). If this structure is not being used to absorb water, what do you
think is its function?
Observe the seaweeds on display. Describe their color. What do you think gives them these
different colors?
II. ZOOPLANKTON
Plankton refers to small organisms that drift or swim weakly, going where the ocean
currents carry them. They are unable to move consistently against waves or current flow.
Phytoplankton, as you have already seen, are plankton that can photosynthesize, and thus are
“plant-like”. Zooplankton is the name given to heterotrophic plankton, meaning that they cannot
make their own food and must consume other organisms. Zooplankton are the most abundant
consumers of phytoplankton in the ocean and thus are an important link in the food web.
Zooplankton is a very diverse group, with nearly every type of animal represented. Many
organisms produce larvae that complete their early development as part of the zooplankton. The
most abundant type of zooplankton is a group of tiny animals called copepods. Copepods are
crustaceans and are related to shrimp, crabs and lobsters.
Procedure:
Observe the slides of various zooplankton that have been set up under the microscopes.
Sketch each slide that you view in the boxes below and write the name of the zooplankton
underneath your sketch.
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Many of the zooplankton that you observed have spines and spikes protruding from their body.
What do you think these are used for?
(Larger) “ANIMALS:”
I Sponges
Observe the sponges on display. What you are seeing is what is left of the sponge after the living
cells have died. Sponges are animals. They have the simplest body plan of all the animals but
they are animals nonetheless.
What characteristics do you think make this organism an animal?
Sponges are unique among the animals in that they have no tissues (such as nervous tissue,
muscle tissue, etc.) or organs in their bodies.
Based on what you see when you observe the sponges. How do you think they eat?
II Cnidaria
Jellyfish, anemones and coral all belong to the group of animals known as Cnidarians. Observe
the preserved jellyfish and live anemone. What characteristics do these animals have in
common?
Now view the coral that is on display. Coral are also Cnidarians. What you are observing is not
living coral, but the calcareous skeleton that is built by the living coral. The coral animals
themselves are dead and not present in the pieces of coral on display. In life, a piece of coral
consists of thousands of coral polyps that look similar in body plan to the live anemones on
display. Notice the many holes or impressions on the coral pieces; these would each be the home
to a coral polyp when the coral is alive.
Cnidarians have a mouth that is located in the middle of the ring of tentacles. This mouth leads
to a sac-like gut where food is digested and transported to all the cells of the body. Undigested
material is then spit back out the mouth. They have no circulatory system and a primitive
nervous system called a nerve net.
Use the probe to touch the tentacles of one of the anemones. Describe what happens:
Allow the anemone to relax and open again. Now touch a different tentacle on the other side of
the animal. Was the reaction different? Explain what this tells you about its nervous system:
III. Arthropods: Crustaceans
Crabs are Crustaceans, which are a subgroup within the phylum Arthropoda. This group also
includes the lobsters, shrimp and the copepods. All arthropods have jointed appendages. They
also have an exoskeleton, made of chitin, which must be periodically molted so the crab can
grow. Crabs and lobsters have 10 legs. The 1st pair of legs in the blue crab has the pinchers or
chelae. Sketch one of the chela of the blue claw crab in the space below:
What structures do you notice on the chelae?
What do you think is their function?
Compare the chelae of the blue crab to that of the spider crab. Which crab should you be more
fearsome of?
The next three pairs are walking legs. Carefully observe the last pair of legs on the blue crab
and the spider crab. Describe the difference and explain what this tells you about how the crabs
move.
The abdomen of crabs is tucked underneath the body. Turn the crab over and view the abdomen
on the ventral side. Crabs can be easily sexed externally. Females have a large, rounded
abdomen, while males have a small, slender one. Pull back the abdomen. On the male, you will
see to thin extensions. These are used to guide the sperm into the female during copulation. In
females, the feather-like pleopods are located under the abdomen. Females will fertilize the
eggs internally and then arrange them on the pleopods. The eggs will be carried around by the
female until the larvae are ready to hatch. The larvae will hatch out and develop in the water as
part of the plankton. A few weeks later it will settle down to the bottom and metamorphose into
a juvenile crab.
There is also a horseshoe crab on display. Horseshoe crabs are Arthropods but are more closely
relate to spiders and ticks than they are to the true crabs, like the blue and rock crabs. Look on
the underside of the horseshoe crab, on the abdomen are a series of flaps. These are the opercula
that cover the gills which are called book gills on horseshoe crabs. Pull up on one of the
opercula to view the actual gills.
Describe some differences between the horseshoe crab and the other crabs on display:
IV. Molluscs:
Bivalves
Mussels, scallops, oysters and clams are bivalve molluscs. These animals are enclosed in two
shells that are hinged together. The shell, which is secreted by the mantle, serves to protect the
animal. These animals are in the same phylum (PHYLUM MOLLUSCA) as the snails, slugs,
octopuses, squids. Bivalves are suspension feeders; they eat by filtering tiny particles from the
water. Cilia (tiny hairs) located on the gills draw water into the body of the animal through a
siphon. Particles of food settle on the gills and are swept toward the mouth by the beating of the
cilia. Food is then swallowed by the mouth and passes to the stomach. The gills also function in
gas exchange. Oxygen dissolved in the water diffuses into the circulatory system of the clam
across the gills. Mussels and clams also have a muscular foot. In clams, the foot is used to
burrow into the ground. In mussels, near the foot there is a byssal gland that secretes byssal
threads. These sticky threads serve to anchor the mussel in place. Clams and mussels have
similar body plans. The foot of a clam is typically larger than the mussel’s and there are no
byssal glands or threads in clams.
Procedure:
Using the model, ands preserved clam as guides. Sketch what the inside of a clam looks
like and label the following structures: shell, mantle, gills, foot, muscles and siphons.
There are several bivalve shells on display. Choose four and sketch them below. Use the
available field guides to identify the animal that the shell belongs to and write it below your
sketch.
Squid:
The squid is also a mollusk. It is in a different subgroup than the clam and the mussel, known as
the Cephalopods. Cephalopods, unlike their bivalve cousins, are active predators and their
bodies are adapted to this purpose.
Carefully observe the squid and list below several differences between the squid and the
bivalves, like the clam.
In the middle of the tentacles is the mouth. Pull the tentacles apart and observe the mouth.
What structure do you see inside the mouth and what do you think it is used for?
Why do you think squid have no shell?
The thick “skin” found on the outside of the body is called the mantle. Within the mantle cavity
are their paired gills. Find the gills on the squid. Squid will draw water into the mantle around
the head to bathe the gills in water. They can then use their muscles to seal off this opening
around the head and forcefully expel the water through their funnel (siphon). Locate the funnel
on the squid and describe how you think it can be used to help the squid swim.
They have an ink sac and ink gland that produces a dark fluid that can be expelled to confuse
predators. They also have many chromatophores, or pigment cells, that allow them to rapidly
change color. This feature can be used to communicate or to blend into the environment. They
have very well-developed, image-forming eyes and complex nervous systems that allow them to
be efficient hunters.
V Echinoderms
Sea Stars, Sea Urchins and Sea Cucumbers are all found within the phylum Echinodermata. This
phylum is characterized by having “spiny skin” on the exterior of the animals and an
endoskeleton (on the inside of the body). How is this different than Arthropod or Mollusca
organisms?
Sea Star:
Feel the “skin” and describe what it feels like:
Sketch the basic “shape” in the space below:
Look at the top, or “dorsal side,” of the sea star for a small dot-like structure called a
madroporite. This organ is unique only to Echinoderms and allows water to circulate through the
body (as part of the “water vascular system.”). Locate this organ. What do you think its use is?
Sea Urchin:
Does this organism look different than the sea star?
They are in the same “phylum,” what characteristics do you think they share?
Observe the sea urchins under a dissecting microscope, besides the spines, sketch the structures
that you see moving:
What do you think these structures are used for?
VI. VERTEBRATES- Fish
Fishes are vertebrates (animals with backbones) that live in water and have gills for
breathing and fins for swimming. The most primitive fish have no jaw; that is they have no
hinged bones that allow their mouths to bit down. Sharks, skates and rays belong to another
class of fish called the Chondrichthyes (cartilagenous fish); these fish have jaws and skeletons
made entirely out of cartilage. Bony fish have a skeleton made of bone and belong to the Class
Osteichthyes. Fish use their gills to breathe. Water is drawn in through the mouth and passes
across the gills, where oxygen is taken in and carbon dioxide is released, and the water then
passes back out to the external environment through gill slits.
Jawless Fish – Lamprey
Notice the gill slits of the lamprey. How many slits are there?
Make a sketch of the mouth of the lamprey.
Lamprey are parasitic and feed by attaching themselves to the sides of other fish. Based on your
observations of the mouth, describe how you think lamprey feed.
Cartilaginous Fish –sharks & skates
Like lampreys, sharks and skates have skeletons made of cartilage, not bone. The cartilaginous
fish, unlike the lampreys, have a jaw and can bite. Notice that the gill slits of shark are visible on
the side of the animal’s throat. How many gill slits does the dogfish shark have? ________
Look on the belly side of the skate. How many gill slits are present? ________
Scientists believe that the bones that make up the jaw of cartilaginous fish evolved from the
bones that supported the first two gills of their ancestors.
Why are skates flat and sharks torpedo shaped?
Fish breathe by water entering their mouth, going into their throat, passing over the gills and out
the gill slits. Notice where the mouth of the skate and shark are located. What would happen to
the gills if the fish breathed this way when they were resting on the bottom of the ocean?
Observe the shark and the skate and locate a hole found behind the eyes; this is called the
spiracle. Pass a probe through the spiracle while holding the mouth open. Where does the
spiracle lead?
Based on your observations, how do you think the spiracle aids in breathing?
Bony Fish
There are more species of bony fish than there are species of all other vertebrates combined. A
protective covering called the operculum covers the gills of bony fish. The operculum can move
and help pump water across the gills.
Locate the operculum of the fish on display. Pull back the operculum to reveal the gills of the
fish. Each gill is supported by a bone called the gill arch. Find the gill arches. Each gill arch
has protrusions on it called gill rakers. Based on their location, what do you think gill rakers are
used for?
Fish eat a wide variety of prey and their teeth and mouths have evolved to specialize on various
prey types. Some fish have large mouths that open wide to gulp large prey; others have small
mouths suited for choosing small prey. Observe the mouths of each of the fish on display,
describe the mouth and guess what you think the fish eats:
1) Fish name_____________________
Description of the mouth:
I think this fish eats…
2) Fish name_____________________
Description of the mouth:
I think this fish eats…
3)Fish name_____________________
Description of the mouth:
I think this fish eats…
Bony fish come in a large variety of shapes and sizes. There are long, eel-like fish, short, fat fish
like a puffer fish, stream-lined fish like a bass, and odd-shaped fish like the seahorse. The shape
of a fish can tell you a lot about the way a fish moves. Some fish have evolved body-shapes that
make them efficient long-distance swimmers while others are more adapted to maneuvering.
Observe 3 of the fish on display. Pay attention to the overall shape of its body and the position
and shape of its fins. In the space below, describe what type of movement (accelerating,
cruising, maneuvering, etc.) you think the fish is best at and describe the characteristics of the
fish’s body that led you to this conclusion.
1)Fish name_____________________
The type of movement the fish is best at:________________
Explain why you think this…
2)Fish name_____________________
The type of movement the fish is best at:________________
Explain why you think this…
3)Fish name_____________________
The type of movement the fish is best at:________________
Explain why you think this…