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Chapter 15
The Animal Kingdom
Chapter Outlines
Introduction
Life Cycle of Animals
Characteristics of Animals
Economic Importance of Animals
Classification of Animals
Introduction
The scientific study of animals is called Zoology (Gr. zoon, “animal,” logos, “study of”).
It’s a subdivision of biology (Gr. bios, “life”), the study of all life forms on Earth. In this part of
the course, you will study the diversity of animals and how animals function, live, reproduce,
and interact with their environment. The study of zoology helps not only to understand animals
in general, but also to understand our own bodies and lives. Every educated person should have
at least a modest grasp of how the human body functions to live a better life. The study of
zoology is also important to prepare some students for a medical, veterinary, or other health-care
career, either in clinical practice or as researchers on diseases of humans or other animals.
Specialties in zoology include entomology (study of insects), parasitology (parasites), pathology
(diseases), orniothology (birds), mammalogy (mammals), ichthyology (fishes), herpetology
(amphibians and reptiles), protozoology (protozoa), acarology (ticks and mites), arachnology
(spiders), malacology (mollusks), and many others.
Life Cycle of Animals
Animals produce heterogametes (egg and sperm) and follow the diplontic life cycle in
which the adult is always diploid (2n). In this life cycle, gametic meiosis occurs in the sex organs
of males and females and produces haploid (n) gametes, sperm in males and eggs in females. The
two haploid gametes join to form a diploid zygote. The zygote divides by mitosis (cleavage) and
goes through a unique pattern of embryonic development. The zygote becomes a ball of cells
called the morula, then a hollow ball of cells called the blastula. The blastula forms an opening
called the blastopore, and becomes the gastrula. The subsequent growth and movement of the
cells of the gastrula produce the digestive system (gut). The details of embryonic development
differ widely from one phylum of animals to another. The embryo becomes the fetus, and the
fetus grows into the adult.
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Characteristics of Animals
Animals (Domain Eukarya, Kingdom Animalia) are believed to have evolved from
multicellular ancestral protists about 700 million years ago. Animals are diverse in form. Out of
the 10 million known animal species, 95% lack a backbone and are called invertebrates; and only
42,500 species have a backbone and are referred to as vertebrates. The animal kingdom includes
35 phyla, most of which occur in the sea. Far fewer phyla occur in fresh water and fewer still
occur on land.
All animals are multicellular eukaryotic heterotrophs that obtain their food by ingestion.
In most animals, ingestion of food is followed by digestion in an internal cavity. Their cells lack
cell walls and they typically store their carbohydrate reserves as glycogen. Animals are able to
move from place to place in search for food and mates. The body of an animal contains many
types of specialized cells that show division of labor. With the exception of sponges (phylum
Porifera), animal cells are organized into structural and functional units called tissues. Two types
of tissues, muscle tissue and nervous tissue, are unique to animals. These tissues are responsible
for movement and impulse conduction, respectively. Animal cells are surrounded by
extracellular matrix (ECM), a gel of polysaccharides and fibrous proteins that fill the interstitial
space between individual cells in a tissue. The ECM gives animal cells a shape and provides
support and anchorage for cells, segregates tissues from one another, and regulates intercellular
communication. Also animal cells have unique intercellular junctions: tight junctions, gap
junctions, and desmosomes.
All animals, with the exception of sponges, have a definite body shape and symmetry.
Sponges lack any definite symmetry, and are described as asymmetrical. Some of the simplest
animals exhibit radial symmetry, a body design in which the parts of the body are arranged
around a central axis in such a way that any plane passing through the central axis divides the
organism into halves that are mirror images. Animals with radial symmetry are included in the
phylum Cnidaria (hydra, jellyfish, sea anemone, and corals). The bodies of all other animals are
marked by bilateral symmetry, a body design in which the body has a right and a left half that are
mirror images of each other. Bilaterally symmetrical animals can only be bisected into equal
halves in one plane (the sagittal plane). Animals with bilateral symmetry have dorsal (top) and
ventral (bottom) ends, and anterior (front) and posterior (back) sides.
Bilateral symmetry has many advantages. The need for forward motion has caused the
anterior and posterior ends of animals to develop differently, and the left and right sides to be
the same. This unique form of body organization allows parts of the body to evolve in different
ways, permitting different organs to be located in different parts of the body. Animals with
bilateral symmetry move from place to place more efficiently than animals with radial
symmetry, which, in general, lead a sessile or passively floating existence. Bilaterally
symmetrical animals are therefore more efficient in seeking food and sexual mates and avoiding
predators. Animals with bilateral symmetry include the flatworms (Phylum Platyhelminthes),
roundworms (Phylum Nematoda), molluscs (Phylum Mollusca), annelids (Phylum Annelida),
arthropods (Phylum Arthropoda), echinoderms (Phylum Echinodermata), and chordates
(Phylum Chordata).
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During early embryonic development, animals produce three body layers: ectoderm,
mesoderm, and endoderm. Cnidarians produce only ectoderm and endoderm, and are called
diploblastic. All bilaterally symmetrical animals produce all three body layers, and are called
triploblastic.
The kingdom Animalia is divided into two subkingdoms: Parazoa and Eumetazoa.
Animals with no true tissues and lack a definite symmetry are included in the subkingdom
Parazoa. This group includes only the sponges (phylum Porifera). The rest of the animals have
cells organized into tissues and have definite body symmetry. These animals are included in the
subkingdom Eumetazoa. Animals in this subkingdom are divided into two groups based on type
of symmetry: Radiata have radial symmetry, and Bilateria have bilateral symmetry.
Bilaterally symmetrical animals produce three body layers, and are called triploblastic.
They also have dorsal (top) and ventral (bottom) sides, and anterior (front) and posterior (back)
ends. These animals are divided into three groups based on their body cavities: acoelomates,
pseudocoelomates, and coelomates. Acoelomates have a sac body plan and no body cavity.
These animals include the flatworms (phylum Platyhelminthes). The pseudocoelomates have a
body cavity, called pseudocoel, located between the mesoderm and the endoderm. The
pseudocoel is not completely lined by tissue derived from the mesoderm. In these animals, the
pseudocoel separates the mesoderm from the endoderm, limiting developmental interactions
between these body tissues. The pseudocoel, however, serves as a hydrostatic skeleton – one
that gains its rigidity from being filled with fluid under pressure. The animal’s muscles can
work against this “skeleton,” thus making the movements of pseudocoelomates far more
efficient that those of the acoelomates. Pseudocoelomates include the roundworms (phylum
Nematoda). The tube-within-a-tube body plan first appeared in the roundworms. Coelomates
have a true coelom, a fluid-filled body cavity that develops entirely within the mesoderm. The
true coelom first appeared in the molluscs (phylum Mollusca). In these animals, the gut is
suspended within the coelom; and a layer of epithelial cells, called the peritoneum, entirely
derived from the mesoderm surrounds the coelom. Coelomates are divided into protostomes
and deuterostomes based on embryonic development. In protostomes (molluscs, annelids, and
arthropods), the first embryonic opening, called the blastopore, becomes the mouth (protostome
development). In deuterostomes (echinoderms and chordates), the blastopore becomes the anus
and a second opening becomes the moth (deuterostome development).
During the evolution of bilateral symmetry, structures that were important to the
organism in monitoring its environment came to be grouped at the anterior end. Nerve cells,
which constitute the nervous system, became grouped around the anterior end of the body and
functioned to transmit impulses from the anterior sense organs to the rest of the nervous system.
This trend ultimately led to the evolution of a definite head and brain area, a process called
cephalization. Some animals have gangilia; others have brains.
A circulatory system is a network of vessels that carries fluid to different parts of the
body. Primitive invertebrates (sponges, cnidarians, flatworms and roundworms) have no
circulatory system. Animals with a circulatory system have either an open circulatory system or
a closed circulatory system. The circulating fluid, or blood, carries nutrients and oxygen to the
tissues and removes waste and carbon dioxide. Blood is usually pushed through the circulatory
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system by contractions of one or more muscular hearts. In the open circulatory system, the
blood passes from vessels into sinuses, mixes with the body fluid, and then re-enters the vessels
later in another location. In the closed circulatory system, the blood is contained in closed
vessels and is separate from the body fluid. Molluscs and arthropods have open circulatory
systems, while annelids, echinoderms and chordates have closed circulatory system.
Body segmentation, the subdivision of the body into segments, is one of the key
transitions in animal body plan. Segmented bodies first appeared in the annelids (phylum
Annelida). In some adult arthropods (phylum Arthropoda), the segments are fused, but
segmentation is usually apparent in their embryological development. In vertebrates, the
backbone and muscular areas are segmented. Jointed appendages first appeared in the
arthropods. Deuterostome development and endoskeleton first appeared in the echinoderms
(phylum Echinodermata). The notochord, nerve cord, pharyngeal pouches, postanal tail, and
vertebrae first appeared in the chordates (phylum Chordata).
Animals have evolved various ways of feeding: herbivores, carnivores, filter feeders,
detritus feeders, and parasites. Some animals respire through their skin, while large active
animals have respiratory systems. While some aquatic animals can function without an internal
transport system, many complex animals have evolved a circulatory system to carry oxygen,
nutrients, and waste products to and from cells. Small aquatic animals depend on diffusion to
carry harmful metabolic waste, such as ammonia, from their tissues into the surrounding water.
Larger animals have excretory systems to remove poisonous metabolic wastes.
Animals have nerve cells that hook up to form a nervous system. Sense organs, such as
eyes and ears, gather information from the surrounding environment by responding to light,
sound, temperature, and other stimuli. The brain processes the information and regulates how
the animal responds.
Animals must keep watch on their surroundings to find food and sex mates, and to avoid
predators. While some animals are sessile, most animals are motile. To move, most animals use
muscles that generate force by contracting. In the most successful groups of animals muscles
work together with a skeleton. Insects and their relatives have exoskeletons, while echinoderms,
amphibians, reptiles, birds, and mammals have endoskeletons.
Some animals switch back and forth between asexual and sexual reproduction. Many
animals that reproduce sexually have a diplontic life cycle and bear their young alive. Other
animals lay eggs.
Economic Importance of Animals
Many marine animals live on, in, and under sponges. Sponges are also involved in many
symbiotic relationships with organisms other than animals. Some sponges contain symbiotic
bacteria, cyanobacteria, or algae. Sponges interact with red algae and corals to make and
maintain coral reefs. Sponges are an important part of the diets of certain snails, starfish, and
fish. Since ancient times, humans used the soft skeletons of certain sponges for bathing. Many
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chemicals produced by sponges for defense are found to be powerful antibiotics that can be used
to fight diseases caused by bacteria and fungi. Other chemicals obtained from sponges act
against viruses almost as well as antibiotics fight bacteria. A compound taken from a Caribbean
sponge may be useful against leukemia and herpes viruses. Another compound may help fight
certain forms of arthritis. Still other sponge chemicals may be effective against the bacteria that
cause strep throat and those that become resistant to penicillin.
Cnidarians form symbiotic relationships with many fish, shrimps, and other animals.
Coral form reefs in which many fascinating animals live. Coral reefs provide home for fish and
other edible animals, as well as for organisms that produce valuable shells, pearls, and other
products. Reefs also protect land from much of the action of waves and protect shorelines. Some
cnidarians are used in medical research. Some chemicals produced by corals may provide us
with anti-cancer drugs. The nerve toxins produced in cnidarian nematocysts help scientists better
understand nerve-cell function.
Mollusks feed on plants, prey on animals, and “clean up” their surroundings by eating
detritus. Some mollusks are hosts to symbiotic algae or to parasites; others are themselves
parasites. In addition, mollusks are an important source of food for many organisms, including
humans. Because filter-feeding bivalves concentrate dangerous pollutants and microorganisms in
their tissues, careful checks of bivalves can warn biologists and public health officials of health
problems long before scientists can detect these dangers in the open water. Mollusks also serve
as subjects in biological research. Some current investigations are based on the observation that
snails and other mollusks never seem to develop any form of cancer. If scientists can determine
what protects the cells of these animals from cancer, they will gain valuable insights into how to
fight cancer in humans. Land slugs and snails are plant eaters that can do much damage to
gardens and crops. The bivalves called shipworms are sometimes described as the termites of the
sea. They cause millions of dollars worth of damage to wooden boats and docks every year.
Clams and oysters are filter feeders and thus gather and concentrate particles floating in the
water, including bacteria, viruses, and the toxic protists that cause red tides. Eating bivalves that
contain high concentrations of pathogens, toxins, or pollutants can result in sickness or even
death.
Earthworms help aerate the soil and recycle nutrients. Leeches were used in the past for
bloodletting. Nowadays leeches are used to remove excess blood from body parts reattached by
microsurgery. The chemicals in leech saliva (anticoagulants) prevent blood from clotting,
dissolve existing blood clots, expand blood vessels, loosen the connections between cells, and
anesthetize the area of the bite. Researchers are currently developing medicines based on these
chemicals. These new medicines may soon be used to clear clogged up blood vessels and to treat
a variety of circulatory-system diseases. Small polychaetes and their larvae are members of the
ocean plankton, where they are food for fish, crabs, and lobsters.
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Arthropods, especially insects, compete with humans for food of every kind. Insects play
a major role in the pollination of certain crop plants. Insects cause billions of dollars of damage
to crops, before and after harvest. Insects are by far the most important herbivores in all
terrestrial ecosystems. Diseases spread by insects cause enormous financial damage each year
and strike every kind of domesticated plant and animal, as well as human beings. Some spiders
are used to produce silk for commerce. Some spiders have bites that are poisonous to humans
and other large mammals. Many crustaceans, such as lobsters, crayfish, and crabs are edible.
Echinoderms are efficient scavengers of decaying matter on the seafloor. Some of them,
especially sea urchins and sea cucumbers are considered delicacies in some countries. Some
echinoderms produce toxins that could be used as anticancer agents.
The vertebrates in the phylum Chordata are our main source of meat. These include all
types of fish, birds, and mammals. We also get milk, eggs, and other food items from animals.
We also use animals’ skins for clothes and shoes. We use animals to do work and plough the
soil. We also use animals in research.
Classification of Animals
Historically, evolutionary biologists used to classify animals based on general features of
body structure. More recently, biologists modified their approach due to a wealth of genetic data.
The animal kingdom (Kingdom Animalia) is divided into two subkingdoms, Parazoa and
Eumetazoa. The subkingdom Parazoa includes the phylum Porifera (animals with no tissues and
no body symmetry). The rest of the animals are included in the subkingdom Eumetazoa (animals
with tissues and body symmetry). This subkingdom is divided into two subgroups, Radiata
(animals with radial symmetry) and Bilateria (animals with bilateral symmetry). The subgroup
Radiata includes the phylum Cnidaria. The rest of the animal phyla are included in the subgroup
Bilateria. This subgroup includes the acoelomates, the pseudocoelomates and the coelomates.
The acoelomates are included in the two phylum Platyhelminthes, the pseudocoelomates are
included in the phylum Nematoda, and the coelomates are included in the rest of the animal
phyla. These animals include the protostomes and the deuterostomes. The protostomes are
included in the phyla Mollusca, Annelida and Arthropoda; and the deuterostomes in the phyla
Echinodermata and Chordata. The phylum Chordata is divided into three subphyla: Urochordata,
Cephalochordata, and Vertebrata. Animals in the subphylum Vertebrata are included in eight
classes: Myxini (jawless fish - hagfishes), Cephalaspidomorphi (Jawless fish – lampreys),
Chondrichthyes (cartilagenous fish – sharks, rays), Osteichthyes (bony fish – piranha), Amphibia
(amphibians - frog, salamander), Reptilia (reptiles - snakes, lizards, turtles, alligators), Aves
(birds – chicken), and Mammalia (mammals - monotremes, marsupials, placentals).
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The following table represents a set of features that appeared in the nine major phyla in
the phylogenetic tree of the animal kingdom:
Sponges (Phylum Porifera):
Asymmetrical, no true tissues
Cnidarians (Phylum Cnidaria):
Radial symmetry, true tissues, diploblastic, sac
body plan, acoelomates
Flatworms (Phylum Platyhelminthes):
Organs and organ systems, bilateral symmetry,
triploblastic
Roundworms (Phylum Nematoda):
Pseudocoelom, tube-within-a-tube body plan
Molluscs (Phylum Mollusca):
True coelom, protostome development
Annelids (Phylum Annelida):
Body segmentation
Arthropods (Phylum Arthropoda):
Jointed appendages, exoskeleton
Echinoderms (Phylum Echinodermata):
Closed
circulatory
system,
development, endoskeleton
Chordates (Phylum Chordata):
Dorsal, hollow nerve cord; notochord; pharyngeal
slits; post-anal tail; vertebrae
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deuterostome
Selected glossary
Amniotic egg: the egg of reptiles and birds. It contains an amnion that encloses the embryo in a
watery environment; this allows the egg to be laid on dry land.
Anterior: the front, forward, or head end of an animal.
Asexual reproduction: reproduction that does not involve the fusion of haploid sex cells
(gametes). The parent body may divide and new parts regenerate, or a new, smaller individual
may be formed attached to the parent, to drop off when complete.
Bilateral symmetry: body plan in which only a single plane drawn through the central axis will
divide the body into mirror-image halves; half left and right sides.
Carnivorous: feeding on the bodies of other animals.
Cephalization: the increasing concentration over evolutionary time of sensory structures and
nerve ganglia at the anterior end of animals.
Chitin: a tough, flexible, nitrogen-containing polysaccharide that forms the cell walls of certain
fungi and the exoskeletons of arthropods.
Choanocytes (or collar cells): specialized flagellated cells lining the body cavity, or spongocoel,
of a sponge. The beating flagella of the many choanocytes create water current that draws water
in through the pores, through the sponge, and eventually out through the osculum. When a
choanocyte beats its flagellum, water is drawn through openings in its collar, where food
particles become trapped. The particles are then devoured by endocytosis.
Closed circulatory system: a type of circulatory system in which the blood is always enclosed
in the heart and vessels.
Coelom: a space or cavity within the body separating the body wall from the inner organs.
Compound eye: an image-forming eye consisting of numerous similar light-gathering and lightdetecting elements; common in arthropods.
Deuterostomes: (Greek, deuteros, “second,” and stoma, “mouth”) animals in which the egg
cleaves radially, and the blastopore, the first embryonic opening, becomes the anus, and the
mouth develops from a second pore that arises in the blastula later in development.
Deuterostomes include echinoderms and chordates.
Diploblastic: animals with two body layers, ectoderm and endoderm; include cnidarians
Dorsal: the top, back, or uppermost surface of an animal oriented with its head forward.
Endoskeleton: a supportive structure within the body; an internal skeleton that may be
nonliving, as in echinoderms and sponges, or living, as in vertebrates.
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Exoskeleton: an external, nonliving supporting structure; an external skeleton.
Flame cells: cells in flatworms specialized for excretion and fluid regulation. They enclose a
small chamber full of beating cilia, whose flickering appearance gives them their names.
Free-living: not parasitic.
Ganglion: an aggregation of neurons.
Gastrovascular cavity (GVC): a saclike opening in the bodies of cnidarians with a single
opening serving as both mouth and anus.
Germ layer: a tissue layer formed during early embryonic development.
Hemocoel: a blood cavity within the bodies of certain invertebrates in which blood bathes tissues
directly. A hemocoel is part of an open circulatory system.
Hermaphroditic: possessing both male and female sex organs. Some hermaphroditic animals
can fertilize themselves; others must exchange sex cells with a mate.
Hydrostatic skeleton: the use of fluid contained in body compartments to provide support for
the body and mass against which muscles can contract.
Invertebrate: a category of animals that never possess a vertebral column.
Lancelets: nonvertebrate chordates (subphylum Cephalochordata), have notochords but not
vertebrae. Most lancelets belong to the genus Branchiostoma, formerly called Amphioxus. In
lancelets, the notochord runs the entire length of the dorsal nerve cord and persists throughout
the animal’s life.
Larva: an immature form of an organism prior to metamorphosis into its adult form. The
caterpillars of moths and butterflies, and the maggots of flies, are larvae.
Mammary glands: milk-producing organs used by female mammals to nourish their young.
Mantle: an extension of the body wall in certain invertebrates, such as mollusks. It may secrete a
shell, protect the gills, and, as in cephalopods, aid in locomotion.
Marsupial: a type of mammals whose young are borne at an extremely immature stage and
undergo further development in a pouch while they remain attached to a mammary gland.
Includes kangaroos, opossums, and koalas.
Medusa: a bell-shaped, often free-swimming stage in the life cycle of many cnidarians, such as
jellyfish.
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Mesoglea: a middle, jellylike layer within the body wall of cnidarians. Cnidarians are
diploblastic because they lack mesoderm.
Metamorphosis: a dramatic change in body form during development, as seen in amphibians
(tadpole to frog) and insects (caterpillar to butterfly). In insects, there is complete
metamorphosis (egg, larva, pupa, and adult) and incomplete (simple) metamorphosis (egg,
nymph, adult).
Monotreme: a type of mammal that lays eggs, such as the platypus.
Nematocyst: a small but powerful “harpoon” located within cnidocytes, specialized stinging
cells located on tentacles and body surface of cnidarians. A nematocyst is a coiled, threadlike
tube propelled by osmotic pressure and is one of the fastest and most powerful processes in
nature. When a cnidocyte is disturbed, the nematocyst is discharged and its barbed filament is
used to spear prey or even to penetrate the hard shells of crustaceans.
Nerve cord: also called the spinal cord of vertebrates, a nervous structure lying along the dorsal
side of the body of chordates.
Notochord: a stiff but somewhat flexible, supportive rod found in all members of the phylum
Chordata at some stage of development.
Open circulatory system: a type of circulatory system in arthropods and mollusks in which the
blood is pumped through an open space, where it bathes the internal organs directly.
Organ: two or more tissues integrated to perform a specialized function, i.e., the kidney.
Organ System: two or more organs that work together to perform a specific function, e.g., the
digestive system.
Osculum: a relatively large opening in the sponge body through which water is expelled.
Parasite: an organism that lives in or on the body of another organism, causing it harm as a
result.
Pharynx: a portion of the digestive system between the mouth and the esophagus. In flatworms
it is developed as an extensible, muscular organ.
Placenta: a tissue rich in blood vessels that develops in the mammalian uterus during pregnancy.
Here nutrients and oxygen from maternal blood are exchanged for wastes from the developing
embryo.
Polyp: the sedentary, vase shaped stage in the life cycle of many cnidarians. Hydra and sea
anemones are examples.
Posterior: the tail, hindmost, or rear end of an animal.
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Protostomes: (Greek, protos, “first,” and stoma, “mouth”) animals in which the egg cleaves
spirally, and the blastopore becomes the mouth.
Pseudocoel: “false coelom”, a body cavity with a different embryological origin than a coelom,
but serving a similar function; found in roundworms.
Radial Symmetry: a body plan in which any plane drawn along a central axis will divide the
body into approximately mirror image halves. Cnidarians and many adult echinoderms show
radial symmetry.
Radula: a ribbon of tissue in the mouth of gastropod mollusks that bears numerous teeth on its
outer surface and is used to scrape and drag food into the mouth.
Segmentation: division of the body into repeated, often similar units.
Sessile: not free to move about, usually permanently attached to a surface.
Spicule: subunits of the endoskeleton of sponges made of protein, silica, or calcium carbonate.
Tentacle: an elongate, extensible projection of the body of cnidarians and cephalopod mollusks
that may be used for locomotion, grasping, stinging, and immobilizing prey.
Tissue: a group of similar cells that together carry out a specific function, e.g., muscle tissue.
Tracheae: a system of air tubes that branch within the body of insects and some arachnids,
carrying air close to every cell.
Triploblastic: animals with three body layers, ectoderm, mesoderm, and endoderm; include all
phyla higher than Cnidaria.
Tube feet: cylindrical extensions of the water-vascular system of echinoderms, used for
locomotion, grasping food, and respiration.
Tunicates: nonvertebrate chordates (subphylum Urochordata), have notochords but not vertebrae. The
tadpole like larvae of tunicates exhibit all of the basic features of chordates, while adult tunicates lack
notochord. Many adult tunicates secrete a tunic, a tough sac composed of cellulose.
Ventral: the lower, or underside of an animal whose head is oriented forward.
Vertebrate: an animal that possesses a vertebral column (subphylum Vertebrata). Vertebrates
are included in seven classes.
Water-vascular system: a system in echinoderms consisting of a series of canals through which
seawater is conducted and used to inflate tube feet for locomotion, grasping food, and
respiration.
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Review Questions
Multiple Choice Questions: Select the most appropriate answer or statement
1.
During the life cycle of animals, called diplontic life cycle, adults produce gametes by
meiosis. The gametes unite during fertilization and produce a diploid zygote. The zygote
grows into an embryo, the embryo becomes a fetus, the fetus grows into a baby, and the
baby grows into an adult. The type of meiosis that occurs during the diplontic life cycle is
called
A.
sporic
B.
mitotic
C.
zygotic
D.
gametic
E.
organismic
Answer: D
2.
Animals are multicellular heterotrophic eukaryotes that obtain their food by ingestion.
Although biologists have identified 1.3 million living species of animals, this number
may represent only 10-20% of the animals living today. The more than 35 living animal
phyla are believed to have evolved from a colonial protistan ancestor over 600 million
years ago. This common ancestor may have resembled modern choanoflagellates, protists
that are the closest living relatives of animals. All animal phyla contain only
invertebrates, animals without a backbone, except the phylum Chordata. This phylum is
mainly composed of vertebrates, which are animals with a backbone of bone or cartilage.
Although both animals and fungi are heterotrophs, animals obtain their nutrients by
A.
absorption
B.
photosynthesis
C.
consumption of living, rather than dead prey
D.
using exoenzymes to digest dead organisms and then absorb nutrients
E.
ingestion of food followed by enzymatic digestion in an internal cavity
Answer: E
3.
Although animals lack the structural support of cell walls, their bodies are held together
by structural proteins, the most abundant being collagen. In addition to collagen, which is
found mainly in extracellular matrices, animals have three unique types of intercellular
junctions (tight junctions, desmosomes, and gap junctions) that consist of other structural
proteins. Among animal cells are two specialized forms not seen in other multicellular
organisms: muscle cells and nerve cells. In most animals, these specialized cells are
organized into muscle tissue and nervous tissue, respectively, and are responsible for
movement and impulse conduction. Which of the following structures are unique to
animals?
A.
intercellular junctions (tight junctions, desmosomes, and gap junctions)
B.
collagen and other structural proteins
C.
muscle and nerve cells
D.
A and B are correct
E.
A, B, and C are correct
Answer: E
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4.
Most animals reproduce sexually, and the diploid stage usually dominates the life cycle.
In most animals, a small, flagellated sperm fertilizes a larger, nonmotile egg, forming a
diploid zygote. The zygote then undergoes cleavage, a succession of mitotic cell divisions
without cell growth between division cycles. Cleavage leads to the formation of a
multicellular solid ball stage called a morula, and then to a hollow ball stage called a
blastula. Following the blastula stage is the process of gastrulation, during which layers
of embryonic tissues that will develop into adult body parts are produced. The resulting
developmental stage is called a gastrula. Which of the following is a correct sequence of
early embryonic development in animals?
A.
zygote – gametes – morula – blastula – cleavage – gastrula
B.
gametes – cleavage – zygote – morula – gastrula – blastula
C.
gametes – zygote – cleavage – gastrula – blastula – morula
D.
gametes – zygote – cleavage – morula – blastula – gastrula
E.
gametes – cleavage – zygote – blastula – gastrula – morula
Answer: D
5.
Both animals and plants are multicellular eukaryotes. However, they differ in a number
of ways. Plants are autotrophs; animals are heterotrophs. Plants have cell walls that
provide structural support; animals lack strong cell walls and their bodies are held
together by structural proteins, including collagen. Animals have unique cell types and
tissues (muscle and nerve) and unique patterns of embryonic development, including the
multicellular blastula stage. Some animal cells have flagella; plant cells lack flagella.
Which of the following is a difference between animals and plants?
A.
animals obtain their food by ingestion; plants obtain their food by photosynthesis
B.
plants have cell walls; animals lack cell walls
C.
some animal cells have flagella; plant cells lack flagella
D.
animal cells have centrioles and lack chloroplasts; plant cells lack centrioles and
have chloroplasts
E.
all of these are correct
Answer: E
6.
Among the characteristics unique to animals is
A.
gastrulation
B.
muscle tissue
C.
nervous tissue
D.
heterotrophic nutrition by ingestion
E.
all of these are characteristics unique to animals
Answer: E
13
7.
Animals can be characterized by body plans. The major features of animal body plans
include symmetry, tissues, body cavities, and embryonic development. Animals can be
categorized as aymmetrical (absence of symmetry), radially symmetrical, or bilaterally
symmetrical. Bilaterally symmetrical animals exhibit cephalization. Some animals lack
true tissues while other animals develop tissues during embryonic development through
the process of gastrulation. Some animals have two body layers (ectoderm and
endoderm) and are called diploblastic, while other animals have three body layers
(ectoderm, mesoderm, and endoderm) and are called triploblastic. Triploblastic animals
have a sac body plan or a tube-within-a-tube body plan. They also are divided into
acoelomates (no body cavity), pseudocoelomates (false body cavity), or coelomates (true
body cavity) based on the type of body cavity they have. Based on certain embryonic
features, triploblastic animals are categorized as having protostome development or
deuterostome development. Which of the following is a major feature of animal body
plans?
A.
animals may lack any body symmetry or have radial or bilateral symmetry
B.
animal embryos form germ layers and may be diploblastic or triploblastic
C.
according to body cavity, triploblastic animals may be acoelomates,
pseudocoelomates, or coelomates
D.
triploblastic animals may have protostome development or deuterostome
development
E.
all of these are correct
Answer: E
8.
Bilateral symmetry in the animal kingdom is best correlated with
A.
ability to sense equally in all directions
B.
mobility and active predation and escape
C.
adaptation to terrestrial environments
D.
development of a true coelom
E.
the presence of a skeleton
Answer: B
9.
Acoelomates, such as flatworms, are characterized by
A.
a solid body without a cavity surrounding internal organs
B.
a coelom that is not completely lined with mesoderm
C.
deuterostome development
D.
the absence of mesoderm
E.
both A and B are correct
Answer: A
14
10.
Zoologists currently recognize 35 animal phyla. Most taxonomists agree on the following
major features of the animal phylogenetic tree:
a.
All animals share a common ancestor
b.
Sponges (phylum Porifera), the only animals without tissues and body symmetry,
are classified in the clade Parazoa.
c.
All animals other than sponges have tissues and body symmetry, and are
classified in the clade Eumetazoa.
d.
Few of the animals classified as Eumetazoa belong to the clade Radiata (phylum
Cnidaria, for example), and most eumetazoans belong to the clade Bilateria.
e.
Animals in the clade Bilateria are divided into acoelomates (lack coelom),
pseudocoelomates (have false coelom), and coelomates (have true coelom).
f.
Animals with true coelom (coelomates) are divided into the clades Protostomia
(protostome embryonic development) and Deuterostomia (deuterostome
embryonic development).
Which of the following combinations of phylum and description is incorrect?
A.
Echinodermata – bilateral symmetry, coelom forms from archenteron
B.
Porifera – coelomates, mouth forms from blastopore
C.
Nematoda – roundworms, pseudocoelomates
D.
Platyhelminthes – flatworms, acoelomates
E.
Cnidarians – radial symmetry, diploblastic
Answer: B
11.
Two body plans are observed in the animal kingdom: the sac plan and the tube-within-atube plan. Animals with a sac plan, such as cnidarians and flatworms, have an incomplete
digestive system. This type of digestive system has only one opening, which is used both
as an entrance for food and as an exit for undigested material. Animals with the tubewithin-a-tube plan, such as roundworms and insects, have a complete digestive system,
with a separate entrance for food and an exit for undigested material. Having two
openings allows specialization of parts to occur along the length of the tube. Which of the
following phyla includes animals with a sac body plan?
A.
Platyhelminthes
B.
Echinodermata
C.
Arthropoda
D.
Chordata
E.
Mollusca
Answer: A
12.
Which of the following clade of the animal kingdom encompasses all the other clades in
the list?
A.
Deuterostomia
B.
Protostomia
C.
Eumetazoa
D.
Bilateria
E.
Radiata
Answer: C
15
13.
The distinction between sponges (clade Parazoa) and other animal phyla (clade
Eumetazoa) is based on the absence versus the presence of
A.
true tissues
B.
body symmetry
C.
body segmentation
D.
a complete digestive tract
E.
both A and B are correct distinctions
Answer: E
14.
Invertebrates, animals without a backbone, account for 95% of known animal species and
all but one of the 35 animal phyla that have been described. The only phylum that
includes vertebrates, animals with a backbone made of bone or cartilage, is Chordata.
Some members of the phylum Chordata are also invertebrates. Invertebrate animals
occupy almost every habitat on Earth, from the scalding water released by deep-sea
hydrothermal vents to the rocky, frozen ground of Antarctica. Which of the following
animals are not considered invertebrates?
A.
sponges
B.
cnidarians
C.
flatworms
D.
mammals
E.
echinoderms
Answer: D
15.
Sponges (clade Parazoa, phylum Porifera) are sedentary suspension feeders that live in
both fresh and marine waters. Water, with suspended food particles, is drawn through the
numerous body pores into a central cavity, the spongocoel, and then flows out of the
sponge through a larger opening called the osculum. Unlike eumetazoans (clade
Eumetazoa), sponges lack both true tissues and body symmetry. However, sponges have
several specialized cell types. Choanocytes are feeding cells with flagella that create a
current that draws water and suspended food in through the porocytes. Amoebocytes
transport nutrients to other cells and produce spicules. Which of the following
combinations of cell type and function in sponges is correct?
A.
amoebocytes – transport nutrients and produce material for spicules
B.
choanocytes – feeding cells with flagella that create current to draw water and
suspended food
C.
porocytes – form channels through which water and suspended food enter the
body of the sponge
D.
only A and B are correct
E.
A, B, and C are correct
Answer: E
16
16.
Sponges are sessile suspension (filter) feeders. They are the only animals in which
digestion occurs within cells. The flagella of choanocytes (collar cells) draw water
through their collars, which trap food particles. The suspended food particles are engulfed
by phagocytosis and digested, either by choanocytes or by amoebocytes. The
amoebocytes also act as a circulatory device to transport nutrients from cell to cell. The
constant flow of water passing through a sponge also carries oxygen and allows for the
removal of wastes. The movement of suspended food particles through the body of a
sponge would follow what path?
A.
osculum – choanocyte – amoebocyte – spongocoel – porocyte
B.
porocyte – spongocoel – amoebocyte – choanocyte – osculum
C.
porocyte – choanocyte – amoebocyte – spongocoel – osculum
D.
porocyte – choanocyte – spongocoel – amoebocyte – osculum
E.
porocyte – choanocyte – amoebocyte – osculum – spongocoel
Answer: C
17.
The body of a sponge consists of two layers of cells separated by a gelatinous region, the
mesohyl. Wandering through the mesohyl are cells called amoebocytes, named after their
use of pseudopodia. Amoebocytes have many functions. They take up food from the
water and from choanocytes, digest it, and carry nutrients to other cells. They also
manufacture spicules and other skeletal fibers. During sexual reproduction, both
choanocytes and amoebocytes produce gametes. Which of the following is not a function
of sponge amoebocytes?
A.
act as circulatory devices to transport nutrients from cell to cell
B.
use their flagella to draw water and suspended food particles
C.
take up food from water and from choanocytes and digest it
D.
produce gametes during sexual reproduction
E.
manufacture skeletal fibers such as spicules
Answer: B
18.
Generally, sponges are classified according to their skeletons. Amoebocytes manufacture
tough skeletal fibers within the mesohyl. In some groups of sponges, these fibers are
sharp spicules made from calcium carbonate or silica. Spicules are needle-shaped
structures with one to six rays. The sponge Schypha has spicules with three rays. Other
sponges produce more flexible fibers composed of a collagen protein called spongin.
These pliant skeletons are used as bath sponges. Which of the following statements is
correct concerning spicules?
A.
spicules are needle-shaped structures with one to six rays
B.
spicules are composed of calcium carbonate or silica
C.
spicules are used in classifying sponges
D.
both A and B are correct
E.
A, B, and C are correct
Answer: E
17
19.
Sponges can reproduce both sexually and asexually. Asexual reproduction is by
fragmentation (regeneration) or budding. During sexual reproduction, cross fertilization
is the rule. Most sponges are hermaphrodites and each individual produces both sperm
and eggs. Gametes arise from choanocytes or amoebocytes. Eggs reside in the mesohyl,
but sperm are carried out of the sponge by the water current. Cross fertilization results
from some of the sperm being drawn into neighboring individuals. Fertilization occurs in
the mesohyl, where the zygotes develop into flagellated, swimming larvae that disperse
from the parent sponge. Upon settling on a suitable substrate, a larva develops into a
sessile adult. Which of the following statements is not correct concerning reproduction
and development in sponges?
A.
sponges reproduce asexually by budding and fragmentation and sexually by cross
fertilization
B.
cross fertilization occurs in the mesohyl where the zygotes develop into
flagellated larvae
C.
upon settling on a suitable substrate, a larva develops into a sessile adult
D.
generally, sponges are classified according to their reproduction
E.
almost all sponges exhibit sequential hermaphroditism
Answer: D
20.
Sponges produce a variety of antibiotics and other defensive compounds that hold
promise for fighting human diseases. Researchers have recently found a compound called
cribrostatin in marine sponges that kill penicillin-resistant strains of the bacterium
Streptococcus. Other compounds derived from sponges have promise as anti-cancer
agents. Some sponges with pliant skeletons are used as bath sponges. Today, however,
most commercial “sponges” are synthetic. Which of the following is a commercial use of
sponges?
A.
antibiotics
B.
bath sponge
C.
anti-cancer agents
D.
A and B are correct
E.
A, B, and C are correct
Answer: E
21.
Many chemicals produced by sponges for defense are found to be powerful antibiotics.
Other chemicals produced by sponges act against viruses almost as well as antibiotics
fight bacteria. A compound taken from a Caribbean sponge may be useful against
leukemia and herpes viruses. Another sponge chemical may help fight certain forms of
arthritis. Still other chemicals produced by sponges may be effective against the bacteria
that cause strep throat and those that become resistant to penicillin. Which of the
following statement is not correct about the use of sponge chemicals in medicine?
A.
treatment of arthritis
B.
treatment of HIV/AIDS
C.
production of antibiotics
D.
production of antiviral drugs
E.
treatment of leukemia and herpes
Answer: B
18
22.
Cnidarians (clade Radiata, phylum Cnidaria) have a tissue level of organization and are
radially symmetrical. They have a sac body plan and a gastrovascular cavity (GVC).
Cnidarians exist as polyps and/or medusae. The term cnidaria is derived from the
presence of specialized stinging cells called cnidocytes which contain nematocysts for
trapping prey or injecting paralyzing toxins as a defense mechanism. Cnidarians are
diploblastic because they have bodies with two germ layers (ectoderm and endoderm).
This ancient group of invertebrates contains some of nature’s most bizarre and beautiful
creatures, including jellyfishes, Portuguese man-of-war, sea anemones, hydra, and corals.
Although a diverse group, all cnidarians are characterized by having all of the following
except
A.
sac body plan and gastrovascular cavity
B.
cnidocytes with nematocysts
C.
diploblastic bodies
D.
radial symmetry
E.
organs
Answer: E
23.
Flatworms (clade Bilateria, phylum Platyhelminthes) have a sac body plan, three germ
layers (triploblastic), and the organ and organ system level of organization. They are
bilaterally symmetrical, and cephalization does occur. Animals with bilateral symmetry
have dorsal (top) and ventral (bottom) portions of the body, and anterior (front) and
posterior (back) ends. Flatworms include turbellarians (planaria), trematodes (flukes), and
cestodes (tapeworms). All flukes (such as Schistosoma) and all tapeworms (such as
Taenia) are parasitic flatworms, while all turbellarians (such as Dugesia) are free-living.
Flatworms are acoelomates because they lack body cavity. Which of the following is an
advantage of bilateral symmetry?
A.
cephalization, concentration of sensory equipment on the anterior end of the body
C.
more efficient in seeking food, sexual mates, and avoiding predators
B.
more efficient movement from one place to another
D.
both A and B are correct
E.
A, B, and C are correct
Answer: E
Roundworms or nematodes (phylum Nematoda) and rotifers (phylum Rotifera) are
pseudocoelomates with a tube-within-a-tube body plan. Nematodes have developed a
variety of life styles from free-living to parasitic. Some nematodes cause great
agricultural damage. One species, Caenorhabditis elegans, a free-living nematode, is a
model animal in genetics and developmental biology. Several parasitic nematodes,
including pinworms, hookworms, filarial worms, Trichinella, Wuchereria, and Ascaris,
infect humans and other animals. Which of the following is not a characteristic of
nematodes?
A.
pseudocoel
B.
triploblastic
C.
organ systems
D.
segmented bodies
E.
tube-within-a-tube body plan
Answer: D
24.
19
25.
Several parasitic nematodes infect humans and other animals. Which of the following
combinations of nematode and infection is incorrect?
A.
Trichinella spiralis – trichinosis
B.
Ascaris lumbricoides – taeniasis
C.
Necator americanus – hookworm
D.
Enterobius vermicularis – pinworm
E.
Wuchereria bancrofti – elephantiasis
Answer: B
26.
The evolution of efficient organ systems within the animal body depended upon a body
cavity for supporting organs, distributing materials, and fostering complex developmental
interactions. The presence of a body cavity between the gut and the outer body wall
allows the expansion of the digestive tract and more food intake. Another advantage of a
body cavity is that it allows contact between the mesoderm and the endoderm, so that
primary induction can occur during embryonic development. The body cavity also
provides space within which the gonads (ovaries and tests) can expand, allowing the
accumulation of large numbers of gametes (eggs and sperm). Bilaterally symmetrical
animals are divided into three groups based on their kinds of body cavities: acoelomates
(no body cavity), pseudocoelomates (false body cavity located between the mesoderm
and endoderm), and coelomates (fluid-filled body cavity that develops entirely within the
mesoderm). Which of the following is not an advantage of a body cavity?
A.
provides space within which the gonads (ovary and testis) can expand
B.
allows primary induction to occur during embryonic development
C.
allows the expansion of the digestive tract and more food intake
D.
protects and cushions internal organs
E.
allows more efficient predation
Answer: E
27.
In animals with a true coelom (coelomates), the gut is suspended within the coelom; and
a layer of epithelial cells entirely derived from the mesoderm surrounds the coelom. The
portion of the epithelium that lines the outer wall of the coelom is called the parietal
peritoneum, and the portion that surrounds the internal organs suspended within the
cavity is called the visceral peritoneum. The presence of a coelom enables the digestive
system and the body wall to move independently and allows organs to become more
complex. Coelomic fluid can assist respiration, circulation, and excretion, and also serves
as a hydrostatic skeleton. Coelomates are included in the phyla Mollusca, Annelida,
Arthropoda, Echinodermata, and Chordata. Which of the following animal phyla does not
include coelomates?
A.
Echinodermata
B.
Arthropoda
C.
Nematoda
D.
Chordata
E.
Annelida
Answer: C
20
28.
29.
The development of a body cavity poses a problemcirculation. This problem is solved in
pseudocoelomates (nematodes and rotifers) by churning the fluid within the body cavity,
and in coelomates (mollusks, annelids, arthropods, echinoderms, and chordates) by the
development of a circulatory system. A circulatory system is a network of vessels that
carry fluids to parts of the body. The circulating fluid, or blood, carries nutrients and
oxygen to the tissues and removes wastes and carbon dioxide. Blood is usually pushed
through the circulatory system by contractions of one or more muscular hearts. In an
open circulatory system, the blood passes from vessels into sinuses, mixes with the body
fluid, and then re-enters the vessels later in another location. In a closed circulatory
system, the blood remains within a completely closed system of vessels and hearts, and
never comes in direct contact with the cells. Molluscs (except squids), insects, and
crustaceans have open circulatory systems, while annelids, echinoderms and chordates
have closed circulatory systems. Which of the following is an advantage of a circulatory
system?
A.
transport of nutrients, gases, hormones, and antibodies; and removal of wastes
B.
maintenance of sufficient blood pressure for a large body
C.
control of fluid volume and pH
D.
regulation of blood temperature
E.
all of theses are correct
Answer: E
Animals with a true coelom (coelomates) are divided into two clades based on their
embryonic development. The two clades differ in cleavage, fate of blastopore, and
coelom formation. In the coelomates included in the clade Protostomia, cleavage is spiral,
the first embryonic opening (the blastopore) develops into the mouth, and the coelom is a
schizocoelom. In the coelomates included in the clade Deuterostomia, cleavage is radial,
the blastopore becomes the anus and a second opening becomes the mouth, and the
coelom is an enterocoelom. Animals with protostome development are classified in the
phyla Mollusca, Annelida and Arthropoda; and animals with deuterostome development
are included in the phyla Echinodermata and Chordata. According to recent molecular
data, flatworms and roundworms are considered protostomes, although they are not
coelomates. Which of the following is not a correct difference between protostomes and
deuterostomes?
A.
cleavage is spiral in protostomes and is radial in deuterostomes
B.
protostomes are acoelomates and deuterostomes are coelomates
C.
coelom is a schizocoelom in protostomes and an enterocoelom in deuterostomes
D.
blastopore is associated with mouth in protostomes and with anus in deuterostome
E.
protostomes include flatworms, nematodes, mollusks, annelids and arthropods;
and deuterostomes include echinoderms and chordates
Answer: B
21
30.
Mollusks (phylum Mollusca) are bilateral, soft-bodied, coelomate animals. Mollusks are
the only animals that form a mantle over the body mass. Those with a head have tentacles
and eyes, but not all have a head. Many have shells and a food-rasping organ called
radula. Mollusks include gastropods, chitons, bivalves, and cephalopods. With 90,000
species, including snails, slugs, nudibranchs, and limpets, the gastropods are by far the
largest group. Torsion, a process unique to gastropods, puts the anus near the mouth.
Which of the following statements is correct about gastropods?
A.
they experience torsion during embryonic development
B.
they are by far the largest group among the mollusks
C.
they include snails and sea slugs
D.
both A and B are correct
E.
A, B, and C are correct
Answer: E
31.
Cone snails, such as Conus magnus and C. geographicus, are predatory mollusks that live
in the sea. They produce paralytic secretions called conotoxins that subdue small prey.
Conotoxins bind to channel proteins of cell membranes and shut them down. Any species
of cone snail can make 100 to 300 different conotoxins, each with a specific molecular
target. This makes cone snails potential sources of many new drugs. A synthetic version
of a conotoxin secreted by C. magnus may shut down the neural pathway that gives rise
to sensations of pain. C. geophraphicus secretes a toxin that one day might help
epileptics. What is the economical importance of cone snails?
A.
cone snails subdue small prey with paralytic secretions
B.
cone snails can impale fish with a harpoon-like device
C.
cone snails are a potential source of many new drugs
D.
cone snail shells are used to make jewelry
E.
cone snails are a tasty treat
Answer: C
32.
Molluscs (phylum Mollusca) are a diverse group of animals (over 110,000 species) that
includes snails and slugs, oysters and clams, and octopuses and squids. Although most
mollusks are marine, some inhabit fresh water, and there are snails and slugs that live on
land. Molluscs are soft animals (Latin molluscus, soft), but most are protected by a hard
shell made of calcium carbonate. Slugs, squids, and octopuses have a reduced internal
shell or have lost their shell completely during their evolution. Despite their apparent
differences, all mollusks are coelomates with protostome development, and have a body
with three main parts: a foot, a visceral mass, and a mantle. Another feature often present
in mollusks is a rasping, tongue like radula, an organ that bears many rows of teeth and is
used to obtain food. Which of the following is not a characteristic of most mollusks?
A.
segmented bodies
B.
protostome development
C.
a rasping, tongue like radula
D.
foot, visceral mass and mantle
E.
soft body protected by a hard shell
Answer: A
22
33.
Molluscs are divided into four groups: Chitons; gastropods (snails and slugs); bivalves
(clams, mussels, scallops, and oysters); and cephalopods (squids, octopuses, and
cuttlefish). Chitons are marine mollusks with a shell divided into eight dorsal plates,
radula, and no head. Land snails have a coiled shell; a flat, long, muscular foot; and a
head region. The mantle in the brown garden snail (Helix aspersa) becomes a lung. Sea
slugs lost their shells during their evolution. In clams, such as Anodonta, the body is
protected by a heavy shell. Clams are filter feeders with a hatchet-shaped foot that allows
them to burrow slowly in sand and mud. Squids, such as Loligo, have a closed circulatory
system and a well-developed nervous system with cephalization. They are active
predators in deep oceans. Which of the following statements is a correct difference
between snails and crayfish?
A.
snails have a broad foot, and crayfish have jointed appendages
B.
snails are hermaphrodites, and crayfish have separate sexes
C.
snails are bivalves, and crayfish are chelicerate crustaceans
D.
snails are terrestrial, and crayfish are aquatic
E.
all of these
Answer: E
34.
Which of the following statements is incorrect?
A.
squids have a closed circulatory system and cephalization
B.
in the brown garden snail, the mantle becomes a lung
C.
Clams are filter feeders with a hatchet-shaped foot
D.
Squids are cephalopods in the phylum Arthropoda
E.
Snails are gastropods in the phylum Mollusca
Answer: D
35.
In an open circulatory system of arthropods, blood (usually called hemolymph) spends
much of its time flowing freely within body cavities (called sinuses or hemocoel) where it
makes direct contact with all internal tissues and organs. A dorsal blood vessel is the
major structural component of the circulatory system. It runs longitudinally through the
thorax and abdomen. In the abdomen, the dorsal blood vessel is called the heart. It is
divided into chambers that are separated by valves (ostia) to ensure one-way flow of
hemolymph. Insect hemolymph does not contain hemoglobin or red blood cells. Oxygen
is delivered by the tracheal system, not the circulatory system. Which of the following is
a difference between the circulatory system of insects and humans?
A.
insects have open circulatory system and humans have closed circulatory system
B.
in insects, oxygen is delivered by the tracheal system, not the circulatory system
C.
hemolymph does not contain hemoglobin or red blood cells like blood
D.
insects have hemolymph and humans have blood
E.
all of these are correct
Answer: E
23
36.
Segmentation, the subdivision of the body into segments, is one of the key transitions in
animal body plan. Segmented bodies first appeared in the annelids (phylum Annelida). In
some adult arthropods the segments are fused, but segmentation is usually apparent in
their embryonic development. In vertebrates, the backbone and muscular areas are
segmented. Two advantages result from early embryonic segmentation: (1) In segmented
animals, such as annelids, each segment may go on to develop a more or less complete
set of adult organ systems. Damage to any one segment need not be fatal to the
individual, since the other segments duplicate that segment’s function. (2) Locomotion is
far more effective when individual segments can move independently because the animal
as a whole has more flexibility of movement. Which of the following animals does not
have a segmented body?
A.
Asterias, phylum Echinodermata
B.
Romalea, phylum Arthropoda
C.
Lumbricus, phylum Annelida
D.
Loligo, phylum Mollusca
E.
Rana, phylum Chordata
Answer: D
37.
Annelids (phylum Annelida) are segmented worms. They include earthworms, leeches,
and marine worms. Segmentation and the tube-within-a-tube body plan have led to
increased specialization of the digestive tract in annelids. The digestive system includes a
large pharynx, a long esophagus, a stomach, a long intestine, and accessory glands.
Annelids have an extensive closed circulatory system with dorsal and ventral blood
vessels that run the length of the body and branch to every segment. They also possess
muscular aortic arches called “hearts” that propel blood through the vessels. The nervous
system consists of a brain connected to a ventral solid nerve cord, with a ganglion in each
segment. Cephalization is apparent in some annelids, but not in earthworms. The
excretory system consists of paired nephridia, which are coiled tubules in each segment
that collect waste material from the coelom and excrete it through openings in the body
wall. Earthworms are hermaphroditic and have no larval stage. Which of the following is
not a characteristic of annelids?
A.
body segmentation
B.
jointed appendages
C.
closed circulatory system
D.
tube-within-a-tube body plan
E.
hermaphroditic with no larval stage
Answer: B
24
38.
The earthworm Lumbricus (phylum Annelida) has a closed circulatory system with five
pairs of hearts. In a closed circulatory system, the blood is contained in vessels and hearts
and is therefore distinct from fluid in the body cavity. The dorsal and ventral blood
vessels of the earthworm are linked by segmental pairs of vessels. The dorsal vessel and
the five pairs of hearts that circle the esophagus are muscular and pump blood through
the circulatory system. Which of the following is an incorrect match between an animal
and its circulatory system?
A.
sea star (Echinodermata) – open system
B.
earthworm (Annelida) – closed system
C.
insect (Arthropoda) – open system
D.
squid (Mollusca) – closed system
E.
frog (Chordata) – closed system
Answer: A
39.
Body segmentation is a synapomorphy that first appeared in the annelids (phylum
Annelida). The earthworm Lumbricus terrestris is a segmented, terrestrial annelid; while
the pork tapeworm Taenia solium is a non-segmented, parasitic flatworm. Which of the
following is an advantage of body segmentation?
A.
in segmented animals, each segment may go on to develop a more or less
complete set of adult organ systems. Damage to any one segment need not be
fatal to the individual, since the other segments duplicate that segment’s function
B.
in segmented animals, locomotion is far more effective when individual segments
can move independently because the animal as a whole has more flexibility of
movement
C.
segmentation leads to increased specialization of the digestive tract,
excretory system, circulatory system, and nervous system
D.
both A and B are correct
E.
A, B, and C are correct
Answer: E
40.
The medicinal leech Hirudo medicinalis is an annelid used in a number of medical
applications, including plastic surgery and reconstructive surgery for severed digits.
Leeches are still used in many parts of the world in blood-letting. Leeches are
bloodsuckers that attach themselves to open wounds. The medicinal leech can even cut
through tissue. Leeches are able to keep blood flowing and prevent clotting by means of a
substance in their saliva known as hirudin, a powerful anticoagulant. Which of the
following is not correct concerning medicinal leeches?
A.
they use a powerful anticoagulant, called hirudin, to keep blood flowing and to
prevent clotting
B.
they are internal parasites used to treat high blood pressure
C.
they are used in plastic surgery and reconstructive surgery for severed digits
D.
in many parts of the world they are still used in blood-letting
E.
they are bloodsuckers that attach themselves to open wounds and cut through
tissue
Answer: B
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41.
Arthropods (phylum Arthropoda) are segmented animals with protostome development,
exoskeleton composed primarily of chitin, jointed appendages, open circulatory system,
and a well-developed nervous system. This is the most successful and largest group of
animals with over a million known species. The phylum Arthropoda is divided into four
subphyla: Hexapoda (insects), Cheliceriformes (spiders, scorpions, ticks, mites,
horseshoe crabs), Myriapoda (millipedes and centipedes), and Crustacea (crayfish, crabs,
lobster, shrimps, barnacles). Which of the following is not a characteristic of arthropods?
A.
jointed appendages
B.
protostome development
C.
closed circulatory system
D.
segmentation is modified for specialization of body regions
E.
well-developed nervous system with brain and a ventral nerve cord
Answer: C
42.
Which of the following statements about arthropods is mis-matched?
A.
grasshoppers – Hexapoda
B.
centipedes – Myriapoda
C.
butterflies – Crustacea
D.
spiders – Cheliceriformes
E.
crayfish – Crustacea
Answer: C
43.
Most insects (subphylum Hexapoda) molt (shed their exoskeleton) several times between
hatching and adulthood. In most cases growth and development involve metamorphosis,
or a dramatic change in form. Butterflies and other insects undergo complete
metamorphosis (adult, egg, larva, pupa, adult); whereas grasshoppers and other insects
undergo incomplete metamorphosis (adult, egg, nymph, adult). Other adaptations that
enable insects to thrive on land are the exoskeleton, which allows terrestrial species to
retain water and supports their bodies on land; and wings, which allow insects to disperse
quickly to new habitats and to find food and mates. Which of the following is an
adaptation that enables insects to thrive on land?
A.
wings
B.
exoskeleton
C.
metamorphosis
D.
A and B are correct
E.
A, B, and C are correct
Answer: E
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44.
Arthropods, especially insects, compete with humans for food of every kind, cause
billions of dollars of damage to agricultural and horticultural crops before and after
harvest, and play a major role in pollinating many crop plants. Diseases spread by insects
cause enormous financial damage each year and strike every kind of domesticated plant
and animal, as well as human beings. Some spiders are used to produce silk for
commerce, and bees produce honey. Many crustaceans, such as lobsters, crayfish, and
crabs are edible. Arthropods are important for humans because they
A.
play a major role in pollinating food crops
B.
cause many human, animal, and plant disease
C.
cause serious damage to food crops before and after harvest
D.
some of them produce useful products such as honey and silk
E.
all of these are correct
Answer: E
45.
Echinoderms (phylum Echinodermata) are marine animals with a well-developed coelom,
deuterostome development, radial symmetry as adults and bilateral symmetry as larvae,
and a unique water vascular system ending in tube feet used for locomotion and feeding.
A spiny skin covers an endoskeleton of hard calcareous plates. Echinoderms do not have
a complex respiratory, excretory, or circulatory system. Fluids within the coelomic cavity
and the water vascular system carry out many of these functions. Sea stars (starfish) are
five-armed, mobile predators. They are the most familiar echinoderms. Which of the
following characteristics first appeared in the echinoderms?
A.
endoskeleton
B.
deuterostome development
C.
complex closed circulatory system
D.
both A and B are correct
E.
A, B, and C are correct
Answer: D
46.
The water vascular system in echinoderms
A.
moves water through the animal’s body during suspension or filter feeding
B.
functions as a circulatory system that distributes nutrients to body cells
C.
is analogous to the closed vascular system of annelids
D.
functions in locomotion, feeding, and gas exchange
E.
all of these are correct
Answer: D
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47.
Chordates (Phylum Chordata) are deuterostome coelomates with notochord; dorsal,
hollow nerve cord; pharyngeal slits or clefts; and muscular post-anal tail. Although most
chordates are vertebrates, lancelets, tunicates (sea squirts), and hagfishes are
invertebrates. Vertebrate chordates include lampreys, cartilaginous fish, bony fish,
amphibians, reptiles, birds, and mammals. In these animals, the embryonic notochord is
replaced by a vertebral column composed of individual vertebrae. Which of the following
characteristics first appeared in chordates?
A.
dorsal, hollow nerve cord
B.
notochord and vertebrae
C.
pharyngeal slits or clefts
D.
muscular post-anal tail
E.
all of these are correct
Answer: E
48.
Which of the following features makes vertebrates well adapted for an active lifestyle?
A.
endoskeleton with vertebral column
B.
high degree of cephalization
C.
closed circulatory system
D.
paired appendages
E.
all of these
Answer: E
True/False Questions
49.
The only animals that lack tissues are the sponges, which are included in the phylum
Porifera.
Answer: True
50.
Sponges are radially symmetrical animals.
Answer: False
51.
The tube-within-a-tube body plan first appeared in the flatworms.
Answer: False
52.
Both annelids and arthropods have closed circulatory systems.
Answer: False
53.
Pseudocoelomates, such as roundworms, have a coelom incompletely lined by mesoderm
because the coelom develops between the mesoderm and endoderm.
Answer: True
54.
The true coelom first appeared in the mollusks.
Answer: True
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55.
Coelomate animals are divided into protostomes and deuterostomes based on embryonic
development.
Answer: True
56.
In deuterostomes, which include the echinoderms and the chordates, the first embryonic
opening, the blastopore, becomes the anus, and a second opening becomes the mouth.
Answer: True
57.
Protostomes include mollusks, annelids, arthropods, and echinoderms.
Answer: False
58.
Body segmentation first appeared in the arthropods.
Answer: False
59.
The only animal phyla which include deuterostome coelomates are Echinodermata and
Chordata.
Answer: True
60.
The phylum Chordata includes both invertebrates and vertebrates.
Answer: True
61.
The distinction between animal heterotrophy and fungal heterotrophy is that animals
obtain their food by ingestion while fungi obtain their food by absorption.
Answer: True
Invertebrate chordates include lancelets, tunicates, and hagfishes.
Answer: False
62.
63.
All vertebrate chordates have a vertebral column made of bone or cartilage.
Answer: True
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Concept Questions and Answers
64.
Both plants and animals are multicellular eukaryotes. Identify four ways in which
plants and animals differ.
Plants are autotrophs; animals are heterotrophs. Plants have cell walls that provide
structural support; animals lack strong cell walls (their bodies are held together by
structural proteins, including collagen). Animals have unique cell types and tissues
(muscle and nerve) and unique patterns of development, including the multicellular
blastula stage.
65.
Describe how sponges feed.
The flagella of choanocytes draw water by their collars, which trap food particles. The
particles are engulfed by phagocytosis and digested, either by choanocytes or by
amoebocytes.
66.
Explain how changes in water currents can affect sponge reproduction.
Sponges release their sperm into the surrounding water; changes in current direction will
affect the odds that the sperm will be drawn into neighboring individuals.
67.
Describe the structure and function of the stinging cells for which cnidarians are
named.
Cnidarian stinging cells (cnidocytes) function in defense and prey capture. They contain
capsule-like organelles (cnidae), which in turn contain inverted threads called
nematocysts. The nematocysts either inject or stick to and entangle small prey.
68.
Explain how tapeworms can survive without a coelom, a mouth, a digestive system,
or an excretory system.
Tapeworms can absorb food from their environment and release ammonia into their
environment through their body surface because their body is very flat.
69.
Why would it be risky to order pork chops “rare” in a restaurant?
Incomplete cooking does not kill nematodes, such as Trichinella, and other parasites that
might be present in the meat.
70.
Would it be reasonable to call phylum Arthropoda the most successful animal
phylum? Explain your answer.
Yes. Two thirds of all known animal species are arthropods, which are found in nearly all
habitats of the biosphere.
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71.
Humans are chordates, yet they lack most of the main derived characters of
chordates. Explain.
In humans, characteristics of chordates are present only in the embryo. The notochord
becomes disks between the vertebrae, the tail is almost completely lost, and the
pharyngeal clefts develop into various adult structures.
72.
Describe two adaptations that enabled insects to thrive on land.
The arthropod exoskeleton, which had already evolved in the ocean, allowed terrestrial
species to retain water and support their bodies on land. Wings allowed insects to
disperse quickly to new habitats and to find food and mates.
73.
Contrast monotremes, marsupials, and eutherians in terms of how they bear young.
Monotremes lay eggs. Marsupials give birth to very small live young that remain attached
to the mother in a pouch. Eutherians (placentals) give birth to more developed live young.
74.
Identify at least five derived traits of primates.
Hands and feet adapted to grasping, flat nails, large brains, forward-looking eyes on a flat
face, parental care, and mobile big toe and thumb.
75.
List the eight classes of vertebrates and name an animal in each.
Myxini – the hagfish Eptatretus goliath
Chephalaspidomorphi – the lamprey Petromyzon marinus
Chondrichthyes – cartilaginous fish, the Manta ray Manta birostris
Osteichthyes – bony fish, the piranha Pygocentrus nattereri
Amphibia – amphibians, the frog Rana pipiens
Reptilia – reptiles, the coral snake Micrurus fulvirus
Aves – birds, the pelican Pelicanus occidentalis
Mammalia – mammals, humans Homo sapiens
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