Download Zoology - Chapter 11 Pseudocoelomate Body Plan

Zoology - Chapter 11 Pseudocoelomate Body Plan
The aschelminths are ________ phyla grouped for convenience. Most have a well-defined _________________, a constant
number of _________ ___________ or nuclei , protonephridia, and a ______________ digestive system with a welldeveloped ______________. _________ organs are developed for _______ exchange or circulation. A __________ that may
be _____________ covers the body. Only longitudinal muscles are often present in the ________ _________. Most
aschelminths are __________________ and freshwater animals.
Phylum Rotifera
The rotifers get their name from the characteristic ciliated organ, the _______________ around lobes on their head. The
corona functions in ___________________ and food gathering. Rotifers are ____________ animals that are abundant in
freshwater habitats; a few are _____________. There are around __________ thousand species. Rotifers are usually
______________, free-swimming animals, some may form colonies. Characteristics of the phylum Rotifera include:
1. Triploblastic, ________________, unsegmented, pseudocoelomate 2. _____________ digestive system, regionally
specialized 3. Anterior end often has a _____________ organ called a corona 4. Posterior end with toes and ___________
glands 5. Well-developed ______________ 6. Protonephredia with ___________ cells 7. ____________ generally reduced in
number or absent; parthenogenesis common.
External Features
An epidermally secreted ______________ covers a rotifer’s external surface. In many species, the cuticle thickens to form an
encasement called a __________ that provides protection. The head contains the corona, ______________, sensory organs,
and __________. The trunk is the ________________ part of the rotifer that is elongated and saclike. The _________ occurs
dorsally on the posterior trunk. The posterior narrow portion is called the __________ that has _______ toes.
Feeding and Digestive System
Most rotifers feed on small ______________________ and suspended organic matter. The coronal cilia create a __________
of water that brings food particles to the ____________. The pharynx contains a unique structure called the __________
which is a muscular organ that _________ food. From the mastax the food passes through a short ciliated esophagus to the
ciliated _____________. Complete extracellular _____________ and __________________ of food occur in the stomach. In
some species a short ciliated ________________ extends posteriorly and becomes a cloacal _________________, which
receives water from the protonephredia and ____________ from the ovaries, as well as digestive ______________.
Other Organs Protonephredia that empty into the cloacal bladder function in _____________________. The nervous system
is composed of ___________ lateral nerves and a ganglion _________________ on the dorsal surface of the mastax.
Reproduction and Development
Some rotifers reproduce ________________, and a few types by parthenogenesis. In one class, the females produce
_____________ eggs that must be fertilized to develop into either males or females. In another class, all females are
parthenogentic and produce ____________ eggs that hatch into diploid __________________. The third class produces
________ different types of eggs. ______________, mixed or blended; thin-shelled eggs are produced by __________, are
diploid, cannot be fertilized and develop directly into amictic females. Thin-shelled, mitic eggs are ____________. If the
mictic egg is not fertilized, it develops parthenogentically into a _____________; if fertilized, mictic eggs secrete a thick
heavy shell and become _________________ or resting winter eggs. Dormant eggs always hatch with melting _________
and spring ____________ into amictic females.
Phylum Kinorhyncha
Kinorhynchs are small, elongate, bilaterally symmetrical worms found only in ___________ environments, where they live
in _________ and sand. They have no external ___________ or locomotor appendages, they _____________ with their
snouts. The body surface of the kinorhyncha does _______ have cilia and is composed of ______ or _______ units called
_____________. Zonite 1 contains the __________, mouth, spines, and oral cone. Zonite 2 contains the neck, spines called
_____________ and plates called _____________. The head can be _____________ into the neck. The trunk consist of the
____________ remaining zonites and ends with the __________. The body wall consists of a __________, epidermis, and
two pairs of muscles. The pseudocolelom is __________ and contains ___________ cells. A ________________ digestive
system is present consisting of _____________, buccal cavity, muscular pharynx, esophagus, stomach, intestine, and ______.
A pair of protonephredia are in _______________.
Phylum Nematoda
Nematodes or _________________ are some of the most _____________________ animals on earth. There are some _____
billion in every acre of fertile garden soil. Zoologists estimate that the number of roundworm species ranges from
__________ to _____________. Roundworms feed on practically every source of ______________ matter. They range in
size from __________ to several ___________. Many nematodes are ______________ of plants and animals; most of the
others are free-living in marine, freshwater, or soil habitats. Some nematodes play an important role in ________________
nutrients in soils and sediment bottoms. Characteristics of nematodes include: 1. Tripoblastic, ______________, vermiform,
unsegmented, pseudocoelomate 2. Body __________ in cross section and covered by a layered elastic ___________; molting
usually accompanies growth in juveniles 3. _____________ digestive tract; mouth usually surrounded by lips bearing sense
organs 4. Most with unique excretory system comprised of one or two __________ cells or a set of collecting tubules 5. Body
wall has only ______________________ muscles.
External Features
A typical nematode body is _________________, elongate, cylindrical, and _______________ at both ends. Much of the
success of nematodes is due to their outer, noncellular, collagenous _______________ that is continuous with the foregut,
hindgut, sense organs, and parts of the _____________ reproductive system. The cuticle maintains internal ____________
pressure, provides mechanical protection, and in parasitic species of nematodes, resists _______________ by the host. The
cuticle is usually _______________ four times during maturation.
Internal Features
The nematode pseudocoelom is a spacious ______________-_________ cavity that contains the _______________ organs
and forms a hydrostatic skeleton. All nematodes are _____________ because the body muscles contracting against the
pseudocoelomic fluid generate an equal outward force in all directions.
Feeding and the Digestive System
Depending on the __________________, nematodes are capable of feeding on a wide variety of foods; they may be
__________________, herbivores, omnivores, or _________________ that consume decomposing organisms, or parasitic
species that feed on blood and tissues fluids of their hosts
Other Organ Systems
Nematodes accomplish osmoregulation and ________________ of nitrogenous waste products with ___________ unique
systems. The ______________ system is in aquatic species and consists of ventral gland cells, called ____________. Each
gland absorbs wastes from the pseudocoelom and ___________ them to the outside through an excretory pore. Parasitic
nematodes have a more ____________ system, called the tubular system, that develops from the renette system. The renettes
unite to form a large ____________, which opens to the outside via an ______________ _________. The nervous system
consists of an anterior _________ _________. Nerves extend anteriorly and posteriorly.
Reproduction and Development
Most nematodes are _______________ and dimorphic, with the _____________ being smaller than the ____________. The
long coiled ________________ lie free in the pseudocoelom. The females system consists of a pair of convoluted
______________. The male system consists of a single ____________, which is continuous with a vas deferens that
eventually expands into a _________________ ___________________. After copulation, hydrostatic forces in the
pseudocoelom move each fertilized ________ to the gonopore. External factors such as _________________ and moisture
influence the development and hatching of the _________.
Some Important Nematode Parasites of Humans
Parasitic nematodes show a number of evolutionary ____________________ to their way of life. These include a high
reproductive potential, life cycles that _____________ the likelihood of transmission from one ________ to another, an
____________-resistant cuticle, resistant eggs, and encysted larvae.
Ascaris lumbricoides: The Giant Intestinal Roundworm of Humans
As many as _____________ million people worldwide may be infected with Ascaris. Adult Ascaris live in the _________
____________ of humans. They produce large numbers of ___________ that exit with the feces. A first-stage larva develops
_____________ in the egg, ______________, and matures into a second-stage larva, the infective stage. When a human
_______________ embryonated eggs, they hatch in the ________________. The larva penetrate the intestinal ________ and
are carried via the circulation to the ______________. They molt ____________ in the lungs, migrate up the trachea, and are
swallowed. The worms attain sexual maturity in the intestine, mate, and begin ____________ production.
Enterbius vermicularis: The Human Pinworm
________________ are the most common roundworm _______________ in the US. Adult pinworms become establishes in
the lower region of the ______________ intestine. At night, gravid ____________ migrate out of the rectum to the perianal
area, where they deposit eggs containing a first-stage larva and then _________. When humans ingest these eggs, the eggs
_______________. The larva molt _________ times in the ____________ intestine and migrate to the ___________
intestine. Adults mate, and ____________ soon begin egg production.
Necator americanus: The New World Hookworm
The American Hookworm is found in the ____________ US. The adults live in the ___________ intestine, where they hold
onto the intestinal wall with ___________ and feed on blood and tissue fluids. Females may produce ___________ eggs
daily which pass out of the body in the feces. An egg hatches on warm moist soil and releases a small juvenile. It molts and
becomes the _________________ filariform. Humans become infected when the filariform penetrates the skin, usually
between the __________. The larva burrows through the ____________ to reach the ___________________ system.
Trichinella spiralis: The Porkworm
Adult trichinella live in the mucosa of the ___________ intestine of humans and other carnivores and omnivores. In the
intestine, adult ____________ give birth to young larvae that then enter the ___________________ system and are carried to
the skeletal muscles of the same host. The young larva encyst in the _______________ muscles and remain infective for
many years. The disease the nematode causes is called _______________. Another host must ingest infective ________ to
continue the life cycle. Humans most often become infected by eating improperly cooked ____________. Once ingested, the
larvae encyst in the _______________ and make their way to the ________________ intestine, where they molt __________
times and develop into adults.
Wuchereria spp: The Filarial Worms
In tropical countries, over _________ million humans are infected with filarial worms. These elongated threadlike nematodes
live in the _______________ system, where they block the _______________. Because lymphatic vessels return tissue fluids
to the circulatory system, when the filarial nematodes block these vessels, fluids and connective tissue tend to accumulate in
_________________ tissues. This fluid and connective tissue accumulation causes the ________________ of various
appendages, a condition called _____________________________. Another filarial worm very common in the US is a
parasite of __________. Since the adult worms live in the _______________ and large arteries of the lungs, the infection is
called _______________ disease.
Phylum Nematomorpha
Nematomorphs are a small group of elongate worms commonly called either ___________________ worms or Gordian
worms. The nematomorph body is extremely long and _______________________ and has no distinct __________. The
adults are free-living and the juveniles are ________________ in arthropods The nervous system contains an anterior
_____________ ___________ and a ventral cord. There is no _______________ system, they absorb nutrients across the
body wall. They have _______________ sexes; two long ___________________ extend extend the length of the body.
Phylum Acanthocephala
Adult acanthocephalans are endoparasites in the _________________ tract of vertebrates, especially ____________. _____
Hosts are required to complete the life cycle. These worms are known as the the _________-__________ worms because of
their spiny proboscis, which is retractable and provides a way to ___________ to the host’s intestines. ___________ are
larger than males.
Phylum Loricifera
The phylum Loricifera is a recently described animal phylum, with its first members being identified in __________.
Loriciferans live in ___________ between ____________ gravel. It is a small, bilaterally symmetrical worm with a
_____________ __________ called an introvert, a ____________, and an abdomen surrounded by a lorica or ____________
plate. Loriciferans can ___________ both the introvert and thorax into the anterior end of the lorica.
Phylum Priapulida
The pirapulids are a small group of _____________ worms found in ___________ waters. They live buried in the _______
and ______________ of the seafloor, where they feed on small annelids and other invertebrates. They have a cylindrical
body and it ranges in length from ______mm to _______cm. They have a thin _________ and a straight ___________ tract
suspended in the pseudocoelom. The nervous system consist of a _______ ________ and a single midventral _________
_____________.