Download BIOLOGY NOTES: THE ANIMAL KINGDOM I. Overview of the

BIOLOGY NOTES: THE ANIMAL KINGDOM
I. Overview of the Animal Kingdom
A. Animals with backbones are vertebrates; those without a backbone are invertebrates.
B. General Characteristics of Animals
1. Most animals are multicellular, heterotrophic, diploid, have tissues that are arranged into organs and
organ systems, and are motile at some point in their life cycle.
2. Animal life cycles include a period of embryonic development; germ tissue layers (ectoderm, endoderm,
and in most species, mesoderm) give rise to adult organs.
C. BODY PLANS
1. Body Symmetry and Cephalization
a. Animals show either radial (round) or bilateral (right and left sides) symmetry.
b. Cephalization means having a definite head end, usually with feeding and sensory features.
2. Type of Gut
a. The place where food is digested is the gut; some are saclike with one opening: a mouth.
b. "Complete" (one-way) digestive tracts have two openings (mouth and anus) for continuous food
processing, often through specialized regions.
3. Body Cavities
a. A coelom (lined with peritoneum) is a space between the gut and body wall that allows internal
organs to expand and operate freely.
b. Some animals (sponges, cnidarians, flatworms) do not have a coelom (acoelomate) but instead
are packed
solidly with tissue between the gut and body wall.
c. Others, such as roundworms, have a
(pseudocoelom,) not lined with peritoneum.
4. Segmentation
a. A segmented animal is composed of repeating body units (somites).
b. The segments may be grouped and modified for specialized tasks, as for example in insects.
THE INVERTEBRATES
I. Sponges (Phylum Porifera)
A. Sponges are mostly marine animals of widely varying size and shape.
B. Sponges have an asymmetric body with no true tissues, no organs.
1. Flattened cells cover the exterior.
2. Collar cells line the interior chambers.
a. By means of their beating flagella, these cells move large volumes of water in
through body pores and out through the large osculum at the top of the body.
b. They also trap suspended food particles in their microvilli collars and transfer
the food to amoeba-like cells in the matrix.
3. Between the two layers of cells there is a semifluid matrix with spicuoles for
support.
C. Sponges reproduce sexually and asexually.
1. Sperm are released into the surrounding water to be picked up by a nearby
sponge and directed to the egg within the matrix.
2. The zygote develops into a free-swimming larva.
3. Asexually, sponges reproduce by fragmentation and gemmules: a spore like collection of sponge cells
that can survive until living conditions improve.
II. Cnidarians (Phylum Cnidaria)
A. This phylum includes the hydrozoans Hydra and Obelia (class Hydrozoa), jellyfishes (class
Scyphozoa), and corals and sea anemones (class Anthozoa).
B. There are two body forms:
1. The medusa resembles an umbrella and floats like a tentacle-fringed bell in the water; oral
arms surround the central mouth.
2. The polyp is tubelike and is usually attached to some substrate; it may be solitary or part of
a colony.
C. The digestive cavity is saclike (only a mouth) and can accommodate prey
larger than the cnidarian itself.
D. Cnidarians have two tissue layers.
1. An outer epidermis covers the body, and an inner endodermis lines the
digestive cavity.
a. A nerve net running through both layers coordinates the animal's
response to stimuli.
b. Some jellyfishes also have sensory cells.
2. A jellylike mesoglea lies between the outer and inner body layers.
a. Jellyfishes have abundant mesoglea helpful in providing buoyancy and in swimming.
b. Polyps have little mesoglea but use the water in their guts as a hydrostatic skeleton.
3. Unique stinging devices called nematocysts can discharge threads to capture prey.
E. Corals (colonial organisms) secrete calcareous structures that accumulate to form
huge reefs.
F. The life cycle of a cnidarian may have a polyp and medusa stage, or it may have
just the polyp.
1. The medusa is usually the sexual form with either epidermal or gastrodermal
gonads.
2. The zygote develops into a swimming larva called a planula.
3. Polyps reproduce by asexual budding.
III. Comb Jellies (Phylum Ctenophora)
A. Their name is derived from the eight rows of cilia that resemble the teeth of a hair comb.
1. The cilia beat in waves for propulsion.
2. In addition, two long tentacles coated with toxins extend from the body for gathering prey.
B. Although closely related to cnidarians, ctenophorans lack nematocysts and have slightly
more advanced tissues.
IV. Flatworms (Phylum Platyhelminthes)
A. This phylum includes the free-living turbellarians and the parasitic flukes and tapeworms.
B. Common features include: 3-branched gut (but none in tapeworms), bilateral symmetry, cephalization, no
coelom, and three germ tissue layers (mesoderm important in evolution of muscles and reproductive organs).
C. Turbellarians (planarians)
1. Pharynx tube extends to feed on whole small animals or to suck tissues from
dead or wounded prey.
2. Protonephridia, with flame cells, regulate body fluid volume and composition.
3. Asexual reproduction is by dividing of the body; sexually they are hermaphrodites, reproducing by crossfertilization.
D. Flukes (trematodes)
1. They are internal or external parasites of living vertebrate hosts.
2. Internal parasites require a primary host (such as a human) for sexual reproduction and an intermediate
host
(such as a snail) for development.
E. Tapeworms (cestodes)
1. They are intestinal parasites of vertebrates, where they absorb predigested nutrients (they have no
digestive
tract).
2. The body consists of an anterior scolex
proglottids, each of which possesses both male and female organs.
V. Roundworms (Phylum Nematoda)
A. Most are small and free-living, but some are parasitic on plants and animals (for
example,
hookworms in the human intestine). Parasitic nematodes often have a
complicated life cycle
involving primary and secondary hosts.
B. They are bilateral and possess a slender tapered body with one-way digestive tract in
a
pseudocoelom filled with fluid; a tough cuticle covers and protects the body
and longitudinal
muscles.
VI. The Coelomates: Two Main Evolutionary Roads
A.
1.
2.
B.
1.
2.
3.
C.
1.
2.
3.
Coelomate animals belong to two main groups:
Protostomes: molluscs, annelids, and arthropods.
Deuterostomes: echinoderms and chordates.
Protostomes are characterized by the following:
In the ball-shaped early embryo, the first indentation (blastopore) becomes the mouth.
The coelom forms from tissue at the sides of the gut near the blastopore.
Deuterostomes are characterized by the following:
The zygote divides symmetrically; this is called radial cleavage.
The blastopore becomes the anus; the mouth develops from a second opening.
The coelom forms from outpouchings of the gut wall.
VII. Annelids (Phylum Annelida)
A. Includes the segmented worms and share with Mollusca a larval form called a trochophore.
B. Earthworms bear few setae (oligochaetes); their habit of ingesting dirt particles while scavenging
for organic matter makes them valuable tillers of the soil.
C. Most leeches are aquatic or semiaquatic predators of invertebrates; others withdraw blood of
vertebrates by first making an incision with tiny jaws followed by a pumping action of the pharynx.
D. Polychaetes include wandering or tube-dwelling marine worms with tentacles, numerous setae, and
chitinous jaws.
E. These features are common to annelids:
1. Setae (bristles) project directly from the highly segmented body (except leeches) or are borne on fleshy
lobes
called parapodia.
2. The outer body surface is covered with a cuticle; internal partitions define individual coelomic chambers.
3. The digestive system is complete; the circulation is closed.
4. A ventral nerve cord runs the length of the body with a ganglion in each segment.
5. The coelomic chambers in conjunction with the circular muscles, longitudinal muscles, and setae
allow the
typical earthworm pattern of movement.
6. Paired nephridia (primitive excretory system) occur in nearly every segment.
VIII.
Molluscs (Phylum Mollusca)
A.
B. Features in common usually include a head, foot, shell(except nudibranchs), mantle (skirtlike
tissue covering the
body), ctenidia (gills), and a radula (a rasping tonguelike structure, absent in bivalves).
C. Chitons (Amphineura)
1. Chitons are marine molluscs with an oval body covered dorsally with eight movable plates and
ventrally by a large adhesive foot.
2. The radula is used to scrape small animals from the rocks along the seashore.
D. Gastropods (snails and slugs)
1. Literal meaning of belly foot
animal when it is crawling.
2. Most of the other organs are located in the spiraled or cone-shaped shell.
3. As the larvae develop, the internal organs undergo a unique twisting, or torsion, that places the
anus anteriorly near the mouth. Gastropods are hermaphrodites.
E. Bivalves (clams, scallops, oysters)
1. The shell of two parts encloses the body.
2. There is no recognizable head, but there is a large foot specialized for burrowing.
3. Water and suspended food are drawn in, and waste voided, through openings called siphons, by the
action of the cilia on the gills.
4. Scallops can clap their shells together to produce a jet of water that propels the animal forward.
F. Cephalopods (squids, octopuses, nautiluses, cuttlefish)
1. This group includes the largest invertebrates known; the giant squid can attain a length of 60+ feet.
2. The body is modified for a highly active predatory life-style; bilateral, it has tentacles and beaklike jaws.
3. They move by a type of jet propulsion caused by mantle contractions out the siphon.
4. To support greater activity, the circulatory system is a closed one; the nervous system is well developed
with a
large brain; the eyes form images; and learning and memory are possible.
IX. Arthropods (Phylum Arthropoda)
A. This is the largest phylum and is divided into four subphyla:
1. Trilobites: now extinct
2. Chelicerates: horseshoe crabs, spiders, scorpions, ticks, mites.
3. Crustaceans: copepods, crabs, lobsters, shrimps, barnacles.
4. Uniramians: centipedes, millipedes, insects.
B. Arthropod Adaptations
1. The Arthropod Exoskeleton
a. It is a combination of protein and chitin (plus calcium in crustaceans) that is flexible, lightweight, yet
protective.
b.
c. Exoskeletons restrict growth and so must be shed periodically (molting process).
2. Specialization of Segments
a. Body segments became more specialized, reduced in number, and grouped together.
b.
3.
a.
b.
4.
a.
b.
5.
a.
b.
6.
a.
b.
c.
C.
1.
In some lineages this has resulted in a head, thorax, and abdomen regions.
Jointed Appendages
Arthropod appendages are jointed.
Appendages became specialized for feeding, sensing, locomotion, sperm transfer, and spinning silk.
Respiratory Systems
Special tubes called tracheas supply oxygen directly to
body tissues.
This allows high metabolic rates and sustained activity, as
in flight.
Specialized Sensory Structures
The compound eye provides a wide angle of vision.
Many individual units allow motion perception.
Division of Labor in the Life Cycle
Larval stages concentrate on feeding and growth.
Adults specialize in dispersal and reproduction.
The process of change from larva to adult is called
metamorphosis.
Arachnida & relatives (spiders, scorpions, ticks, and mites)
Spiders are keen predators that trap insects in their webs produced as silk strands from the
abdomen.
2. Some mites are free-living, others are serious pests of plants and animals; ticks are
notorious
blood-suckers and disease-carriers.
3. The chelicerate body bears eight legs plus a pair of chelicerae (jaws) with venom
and a pair of pedipalps to
manipulate the food (or transfer
sperm!). Spiders have no antennae.
4. Unique respiratory organs called book lungs reside in an invagination of the
abdominal wall; they
greatly increase the surface area available for gas exchange.
D. Crustaceans (shrimps, crayfishes, crabs, pill bugs)
1. These are important components of food webs and serve as human food also.
2. The crustacean body is divided into about twenty segments each of which bears paired specialized
appendages including 2 pairs of antennae, mandibles, maxillae, grasping claws (chelipeds),
10 walking legs, swimmerets
and tail (telson).
3.
carapace.
E. Insects and Their Relatives
1. Millipedes and Centipedes
a. Both bear numerous paired legs along the elongated trunk.
b. Millipedes are cylindrical, slow-moving vegetarians.
c. Centipedes have a more flattened body, move rapidly, and prey on small
invertebrates using
their fangs and venom glands.
2. Insects
a. Their enormous success is due to their ability to exploit nature
metamorphosis, and the ability to disperse by flight.
b. The body is divided into three regions: head (sensory and feeding, with one pair of antennae), thorax
(locomotion by six legs, two pairs of wings), and abdomen.
c. The complete digestive tract is divided into three regions: foregut, midgut (digestion and absorption), and
hindgut (water reabsorption).
d. Unique Malpighian tubules process metabolic waste and aid in water retention.
X. Echinoderms (Phylum Echinodermata)
A. The name of this phylum refers to the spiny skin
urchins, brittle stars, and sea cucumbers.
B. Adults are radially symmetrical
C. The unique water-vascular system operates the tube feet by contracting the ampulla on each
one to achieve a suction useful in locomotion and prey capture. Modified tube feet called
pedicillaria
D. Sea stars can turn their stomachs inside out when feeding.
THE VERTEBRATES
I. On the Road to Vertebrates
A. Characteristics of the Chordates
1. The phylum Chordata consists of a majority of species that are vertebrates (with a backbone) and a
minority
that are invertebrate chordates.
2. All chordates, at some time in their lives, have four distinctive features:
a. A notochord is a long rod of stiffened tissue that supports the body; later it changes to bony units in
vertebrates.
b. A dorsal, tubular nerve cord lies above the notochord and gut.
c. Muscular pharyngeal gill slits are positioned at the entrance to the digestive tract.
d. A tail, or rudiment thereof, exists near the anus.
B. Chordate Classification
1. There are three subphyla: Urochordata, Cephalochordata, and
Vertebrata.
2. The vertebrates are divided into eight classes (one of which is extinct).
C. Invertebrate Chordates
1. Urochordates
a. Tunicates, or sea squirts, are marine organisms covered with a
gelatinous tunic.
1) The larval stage resembles a tadpole and has a notochord in the tail.
2) Metamorphosis to the adult results in a loss of the notochord and tail, a regression of the nerve cord,
and an expansion of the pharynx for filter feeding.
b. The adult is sessile, maintaining a constant flow of water through the body bringing in food particles
and
oxygen and carrying away wastes.
c. Perhaps vertebrates evolved from a tunicate-like ancestor whose larva became sexually functional.
2. Cephalochordates
a. Lancelets are small fishlike animals with tapered bodies; they lie buried in the sand filtering food from
the
stream of water passing through the pharynx.
b. Lancelets are a separate evolutionary branch but, compared to tunicates, are closer to the
vertebrates.
D. EVOLUTIONARY TRENDS AMONG VERTEBRATES
1. The single, continuous notochord was replaced by a column of separate, hardened vertebrae, parts of
which
became modified near the head to form jaws.
2. More complex sense organs and nervous systems began to arise in fishes.
3. The fins of fishes were the starting point for the legs, arms, and wings seen among higher vertebrates.
4. Gradually, there was less reliance on gills and more on lungs and the circulatory system (heart, blood
vessels), which work in connection.
II.
A.
1.
a.
b.
2.
Fishes (Agnatha, Chondrichthyes, Osteichthyes)
Ostracoderms
Among the earliest jawless fishes (Agnathans) were the Ostracoderms.
They were covered with hardened external plates but did not have a well-developed endoskeleton.
The lived on the ocean bottom where they were filter feeders.
The were gradually replaced by fishes with jaws, although a remnant lineage remains today in the form of
B.
1.
2.
3.
C.
1.
hagfishes and lampreys.
Placoderms
In these fishes, bony elements reinforced the notochord and pairs of fins stabilized the body.
As the Paleozoic drew to a close, Placoderms were replaced by cartilaginous and bony fishes.
Living Fishes
Present-day species have a powerful tail (caudal fin), dorsal, pectoral, pelvic and anal
fins to prevent rolling and to aide in turning, scales, and a lateral line for pressure
Fish
have a twochambered
heart and
are
primarily
ectotherms.
2.
Jawless Fishes
(Agnatha)
a.
Today
eellike with a
notochord and cartilaginous
skeletons.
b. Lampreys are parasitic on other fish, attaching to them with an oral, suckerlike disk.
c. Hagfishes
scavenge dead bodies.
3. Cartilaginous Fishes (Chondrichthyes)
a. They possess a streamlined body with a cartilaginous endoskeleton, multiple gill slits,
electrosensors
(dermal denticles,)
and use huge oily livers for buoyancy.
b. This group includes the sharks, skates, rays, and chimaeras.
1) Sharks are formidable predators with their powerful jaws and replaceable teeth.
2) Skates and rays have bodies that are compressed dorso-ventrally and have gill slits
3) Chimaeras are almost scaleless, live in the deep ocean, with a body resembling a rat.
4. Bony Fishes (Osteichthyes)
a. Most bony fishes are ray-finned fishes who can use their flexible fins to backup, hover, or turn on a dime.
1) The highly maneuverable fins are supported by rays that originate from the dermis. Most species have
swim bladder for buoyancy
2) The teleosts are a very successful group of advanced fishes occupying the reef and open ocean .
b. The lobe-finned fishes bear fleshy extensions on the body.
1) Arising during the Devonian, these fishes used their lobed fins to move
over land from one muddy pool to the next.
2) They, and their few modern descendants, are also equipped with lungs.
III. Amphibians (Amphibia)
A. Challenges of Life on Land
1. Life on land presented new challenges to the emerging amphibians.
a. Water availability was not reliable.
b. Air temperatures were variable, and air itself was not the strong supporting
medium that water was, but it was a richer source of oxygen.
c. New habitats, including vast arrays of plants, necessitated keener sensory input.
d. Fortunately, climate shifts in the Carboniferous provided an abundance of insects as food for the
amphibians.
2. Regardless of the extent of their success on land, amphibians must return to the water to reproduce.
B. Existing Amphibians
1. Several characteristics are common:
a. All have bony endoskeletons and usually four legs.
b. Most shed their eggs into water, which is also home to a free-swimming larval stage.
c. Depending on their habitat, amphibians can respire by use of gills, lungs, skin, and
pharyngeal lining.
d. They have thin, moist skin which sometimes has glands that produce toxins.
2. Salamanders
a. When they walk, the body bends from side to side, much like a fish moving through
water.
b. Adults may retain larval features including gills and tail.
c. Some larvae may become sexually mature but not reach a true adult stage.
3. Frogs and Toads
a. These animals are distinctive with their long hindlimbs capable of responding to
powerful muscles.
b. Their success on land is due in part to: the excellent prey-grasping capability of the
tongue attached at the front of the mouth; the closed circulation with one route to the lungs
and another to the body systems (some mixing of blood of varying oxygen content in the ventricle
of the three-chambered heart).
IV. Reptiles (Reptilia)
A. The Rise of Reptiles
1. Modification of limb bones, teeth, and jaw bones
allowed greater exploitation of the insect life
emerging in the Late Carboniferous.
2. The most critical adaptation was internal fertilization followed by the laying of the shelled
amniote egg; this freed the animals from reliance on water environments.
3. Development in cerebral cortex permitted greater
integration of sensory and motor response.
B. Existing Reptiles
1. Living reptiles have a scaly skin that is resistant to drying; they breathe
by lungs and regulate body temperature by behavioral and physiological means (Poikilotherms).
2. Turtles
a. The distinctive shell offers protection while conserving water and body heat.
b. Turtles lay their eggs on land, where, for some turtles, environmental temperature will
determine whether the embryo will develop into a male or a
female.
3. Lizards and Snakes
a. Most lizards are small-bodied insect eaters; their most usual
b. Snakes are limbless but retain vestiges of hind limbs; they are
4. Tuataras
a. Although they resemble lizards, they are evolutionarily more ancient, have a
third eye hibernate 6 months and live to 150+ years.
b. They have no male copulatory organ.
c. Only two species remain today; they live on islands off the shore of New Zealand.
5. Crocodilians
a. Crocodiles and alligators all live in or near water.
b. The body plan includes a long snout; body temperature is regulated behaviorally
(ectothermic).
c. The heart's ventricle is divided into right and left
chambers
V. Birds (Aves)
A. Birds apparently evolved from dinosaurs during
the
Jurassic.
1. The oldest known bird (Archaeopteryx)
resembled reptiles in limb bones and other features.
2. Birds still resemble reptiles: horny beaks, scaly
legs,
and hard-shelled eggs.
B. The body plan of birds is unique: The body is
covered with feathers
1. Digestive system has a crop (for storage) and gizzard (for grinding).
2. Construction meets the requirements of flight: low weight and high power.
a. Hollow bones in flying birds are lightweight; penguins are solid for strength against water.
b. Powerful muscles are attached at strategic places on the bones for maximum leverage.
c. Four-chambered heart, and lungs are 98% efficient in O2 uptake because of "flow-through" air-sac design.
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VI. Mammals (Mammalia)
A. Mammals originated in the Carboniferous when synapsid reptiles diverged from lineages that led
ultimately to modern reptiles and birds.
B. Modern mammals are characterized by the following:
1. Milk-secreting glands nourish the young.
2. Hair covers at least part of the body (whales are an exception).
3. Dentition is extensive and specialized to meet dietary habits.
4. Body heat is regulated by metabolism (endothermic).
5. Brain capacity is increased, allowing more capacity for memory, learning, and conscious thought.
C. Egg-Laying Mammals (Monotremes)
1. The platypus and spiny anteater survive today in Australia.
2. They differ from other mammals in these ways:
a. They are practically toothless.
b. Metabolic rates are lower.
c. They lay eggs but suckle their young.
D. Pouched Mammals (Marsupials)
1. The young are born tiny, blind, and hairless but find their
way to the mother's pouch
2. Most of the marsupials are in Australia, but the opossum thrives in North America.
E. Placental Mammals
1. Representatives of this group are found in virtually every aquatic and terrestrial
environment.
2. The young are nourished within the mother's uterus by the placenta: a composite of
maternal and fetal tissue.
a. It is the organ of exchange of nutrients, gases, wastes, viruses and antibodies
between the maternal blood and the fetal blood (no cells pass between them.)
b. Placental nourishment is more efficient than nourishment of the pouched animals.
where th