Lab 10 Flashcards
Kingdom Animalia (Part 2)
- *3. Phylum Platyhelminthes** – flatworms
- *4. Phylum Annelida** – earthworms, marine worms, leeches
- *5. Phylum Mollusca **
a) Class Bivalvia – scallops, clams, oysters
b) Class Gastropoda – snails, slugs
c) Class Cephalopoda – octopuses, squid, cuttlefish, chambered nautilus
Class Bivalva
scallops, clams, oysters
Class Gastropoda
snails, slugs
Class Cephalopoda
octopuses, squid, cuttlefish, chambered nautilus
Commonalities between Phylum Platyhelminthes, Phylum Annelida, and Phylum Mollusca
- They are triploblastic.
- They are bilaterally symmetrical. (Thus, these animals are all called bilaterians!)
triploblastic
Triploblasty is a condition of the blastula in which there are three primary germ layers: the ectoderm, mesoderm, and endoderm. The germ layers form during gastrulation of the blastula. Additionally, the term may refer to any ovum in which the blastoderm splits into three layers.[1]
bilateral symmetry
Many animals have a body form that is symmetrical, meaning that it could be divided into matching halves by drawing a line down the center. In this respect, arthropods are built like humans are; the right half of an arthropod is a mirror image of its left half — this is called bilateral symmetry
cephalization
the evolutionary concentration of feeding and sensory
structures at one end of the body
bilateral symmetry and cephalization are closely associated
Thus, animals with bilateral symmetry generally have a very distinct head.
How is cephalization adaptive for motile animals?
there is an advantage in having the end that goes first, as the animal moves, fitted out with sense organs—on the premise that it is better to know where you are going than where you have been. Because a lot of computational power is needed to deal with sensory stimuli, the nervous system tends to be larger in the head as well. And finally, food can be captured more effectively if the mouth is also at the front of the body
Earthworm Body Plan (Tube-within-a-Tube)
Many bilateran animals have what kind of body organization?
Tube-within-a-tube (e.g. earthworm)
Inner tube/Outer tube
Inner Tube = gut/digestive system
Outer Tube = body wall
coelom
the fluid-filled space between the digestive tube and the outer body wall
function of ceolom
In addition to providing space for internal organs and
fluid for circulation of oxygen and nutrients, the coelom acts as a hydrostatic skeleton in some animals. The fluid-filled body cavity is pressurized (like a turgid water balloon). Muscle contraction against the pressurized coelom changes the body’s shape and generates movement.
Phylum platyhelminthes
flatworms
do flatworms have a coelom?
No, they are aceolomate (meaning they lack a ceolom). Solid tissue occupies the region between the gut and the body wall.
Acoelomates
Planaria
A free-living (i.e. not parasitic) flatworm
They live in streams, ponds, and moist terrestrial environments.
Planaria Movement
These soft bodied, ciliated flat worms move much like slugs in an undulating motion.
Planarians move by beating cilia on the ventral dermis, allowing them to glide along on a film of mucus. Some also may move by undulations of the whole body by the contractions of muscles built into the body membrane.[3]
Planaria - Structures
Identify the following structures and describe their function: head, eyespots, auricles (chemosensory
structures), gastrovascular cavity, pharynx (tube connecting the mouth to the gastrovascular cavity).
Function of a Planaria’s Head
(cephalization) where accumulation of nervous tissue and sensory structures occurs.
Function of a Planaria’s Eyespots
The eye spots are sensitive to light
Function of Planarian’s Auricles
There are two auricles (earlike projections) at the base of the head, which are sensitive to touch and the presence of certain chemicals.
Function of Planarian’s Gastrovacular Cavity
gastrovascular cavity. This structure branches throughout the body allowing nutrients from food to reach all extremities; this is where digestion occurs
The food enters the gastrovascular cavity through the pharynx located at the center of the planarian’s underside and is digested into feces and monomers.
The feces exit through the pharynx and the monomers are absorbed by the tissues from the gastrovascular cavity. The gastrovascular cavity is multiply-branched and so virtually all cells are near one of the branches. Not a true circulatory system - no blood or blood vessels.
Function of the Planarian’s Pharynx
The pharynx connects the mouth to the gastrovascular cavity.
a muscular tube through which the flatworm can suck food into its gastrovascular cavity. The opening into the pharynx could be considered the mouth, but since this animal has a two-way gut, that opening also must function as the anus.
Mouth on the ventral surface allows muscular pharynx to be extended and inserted into prey
Planarian’s pharynx part II
Mouth on the ventral
surface allows
muscular pharynx to
be extended and
inserted into prey
How is undigested food eliminated by the planaria?
Undigested food is eliminated out the
mouth and through the pharynx (just like in
phylum cnidaria)
Tapeworm specimen
long, whitish, worm
Taenia slides
Taenia is a tapeworm that lives in the gut of its host. At the anterior of its body, a scolex, which has barbs
and suckers, attaches the worm to the host’s intestinal lining. The long flat body absorbs nutrients, and
produces reproductive segments called proglottids. Mature proglottids are filled with fertilized eggs, and
they break off from the posterior end of the worm and are eliminated along with the host’s waste to
continue the life cycle.
Scolex of Taenia
The worm’s scolex (“head”) attaches to the intestine of the definitive host. In some species, the scolex is dominated by bothria, or “sucking grooves” that function like suction cups. Other species have hooks and suckers that aid in attachment.
Proglottids of Taenia
The body is composed of successive segments (proglottids). The sum of the proglottids is called a strobila, which is thin, and resembles a strip of tape. From this is derived the common name “tapeworm”. Like some other flatworms, cestodes use flame cells (protonephridia), located in the proglottids, for excretion. Mature proglottids are released from the tapeworm’s posterior end and leave the host in feces.
Because each proglottid contains the male and female reproductive structures, they can reproduce independently.
Once anchored to the host’s intestinal wall, the tapeworm absorbs nutrients through its skin as the food being digested by the host flows past it and it begins to grow a long tail, with each segment containing an independent digestive system and reproductive tract. Older segments are pushed toward the tip of the tail as new segments are produced by the neckpiece. By the time a segment has reached the end of the tail, only the reproductive tract is left. It then drops off, carrying the tapeworm eggs to the next host, since, by that point, the proglottid is, in essence, a sac of eggs.
What type of digestive system do tapeworms have?
Incomplete.
Tapeworms have no digestive systems as adults, which makes sense for an animal that already absorbs several materials through its surface and lives inside an intestine.
Phylum Annelida
segmented worms
(earthworms, marine worms, and leeches)
clitellum
The smooth, saddle-like structure near the middle of the earthworm’s body is called the clitellum, and it
functions in earthworm reproduction.
The Clitellum is actually used to secrete a sticky fluid which forms a sac for its eggs.
Identify the following structures and know their
function: prostomium
Prostomium - Some species of earthworms have a tongue-like lobe above the mouth called prostomium. The prostomium is actually a sensory device. Earthworms do not have a nose, eyes, ears, or hands to gather sensory information about their environment. Instead, they depend on their prostomium and sensory receptors in their skin to “feel” their way through the soil.
Earthworm: circular muscles and longitudinal muscles
Earthworm’s internal anatomy (cross-section)
Tube-within-a-tube anatomy (earthworm)
Typhosole (earthworm)
In earthworms, it is a dorsal flap of the intestine that runs along most of its length, effectively forming a tube within a tube, and increasing the absorption area by that of its inner surface. Its function is to increase intestine surface area for more efficient absorption of digested nutrients.
Marine worms (polychaetes)
Leeches
Suckers on Leeches
Function: leeches all have an anterior (oral) sucker formed from the first six segments of their body, which is used to connect to a host for feeding. It also releases an anaesthetic to prevent the host from feeling pain while it sucks blood. They use a combination of mucus and suction (caused by concentric muscles in those six segments) to stay attached and secrete an anti-clotting enzyme, hirudin, into the host’s blood stream. The medicinal leech (Hirudo medicinalis) has two suckers, one at each end, called the anterior and posterior sucker. The posterior is mainly used for leverage while the anterior sucker, consisting of the jaw and teeth, is where the feeding takes place.
Features of Mollusks
Like annelids, mollusks have a
coelom and a complete digestive system. Mollusks are also soft-bodied; however, most possess a protective
exoskeleton, a shell, made of calcium carbonate.
The general mollusk body plan consists of three basic parts (as illustrated in this snail diagram)…
- visceral mass – sack containing internal organs
- foot – muscular structure for locomotion
- mantle – thin tissue layer that secretes the shell
Gastropa (snails, slugs) Foot
Identify the foot and exoskeleton
Function: The Foot - a large part of a snail’s body can be seen extended outside of the shell, when the snail is crawling around. This body part is flattened at the belly side (ventrally) to form a flat crawling sole and mainly is used for locomotion.
Exoskeleton: The gastropod shell is an external skeleton or exoskeleton, which serves not only for muscle attachment, but also for protection from predators and from mechanical damage. In land snails, in some freshwater snails and in intertidalmarine snails, the shell is also an essential protection against the sun, and against drying out.
Radula
Gastropods have a feeding-structure called a radula, which is located inside the mouth and covered with small, chitinous teeth.
Adductor muscles of Bivalves
The adductor muscles are the main muscular system in bivalve
Adductor muscles leave noticeable scars or marks on the interior of the shell’s valves. (the white part)
Adductor muscle scars (bivalves)
External Anatomy of a Clam
Identify the following structures
associated with external anatomy:
hinge, umbo, left valve, right valve
Internal Anatomy of a Clam
Identify the following structures associated with internal anatomy and know their function:
- anterior adductor muscle
- posterior adductor muscle
- mantle
- foot
- visceral mass,
- incurrent & excurrent siphons
- gills (ctenidia)
Arms and Tentacles of Cephalopods
Arms are shorter,
Tentacles are longer
Animal Lineage: Protosomes
