Zoology Mid Term Material

Subphylum Urochordata (Tunicata)

"tail-chordates", or commonly called tunicates, include about 1600 species that live in all seas from near shoreline to great great depths. a) Most are sessile (sedentary) as adults, although some are free living

Atriopore

(see #49, Atrium) equivalent to the excurrent siphon of tunicates

Radial cleavage is usually accompanied by several characteristics including: the blastopore becoming the anus, the coelom forming via schizocoely, and the cleavage being regulative?

FALSE

Taxonomy

The science of grouping and naming organisms is?

Extracellular Space

The space surrounding or outside the body's cells is the?

Segmented trunk musculature

1 of the additional characteristics (above and beyond the basic diagnostic chordate characteristics) that the amphioxus has, which include hepatic cecum, a diverticulum that resembles a vertebrate pancreas in secreting digestive enzymes and the liver storing glycogen is segmented trunk musculature and the basic circulatory plan of vertebrates.

List 3 groups of adaptations that guided vertebrate evolution, and explain how each has contributed to the success of vertebrates.

1) Increased speed and mobility resulting from modification of the skeleton and muscles. 2)When vertebrae shifted from filter feeding to active predation new sensory organs motor skills and integrative controls became essential for location and capture of larger prey. endoskeleton permits almost unlimited body size. 3) For the increased speed it developed a postanal tail for movement. The more advanced sensory organs are a brain/ganglion. And they developed a notochord as well.

Physiology Upgrade

2 additional digestive glands, the liver and pancreas, enabled vertebrates to manage the increased amount of food digested. A ventral 3 chambered heart consisting of a sinus venosus, atrium and ventricles and erythrocytes with hemoglobin-enhanced transportation of nutrients, gases and other substances.

Notochord

A rod-like, semirigid body of fluid engorged cells enclosed by a fibrous sheath which extends, in most cases, the length of the body just ventral to the central nervous system A flexible, rod-like structure, extending the length of the body. 1) It is the 1st part of the endoskeleton to appear in the embryo 2) It is a hydrostatic organ, but unlike nematodes, which contain fluid in a single, large cavity, the fluid in a notochord is contained within cells or in tiny compartments between cells. 3) Muscles attach to the notochord, and because it can bend laterally without shortening, it permits undulatory movements of the body. 4) In amphioxus and jawless vertebrates the notochord persist throughout life In most vertebrates the notochord is replaced by vertebrae.

Ocellus

A sense organ that is anterior and unpaired. It's an apparent homologous to parts of the vertebrate brain despite the fact it is not enlarged to the size and capacity of the typical vertebrate brain.

Dorsal tubular nerve cord

A single cord that is dorsal to the digestive tract and is a tube. The anterior end becomes enlarged to form the brain in vertebrates.

Tunic

A, usually, tough non-living structure that surrounds the animal and contains cellulose. a)As adults tunicates are highly specialized chordates, for in most species only the larval form, which resembles a microscopic tadpole, bears all of the chordate hallmarks.

Hepatic cecum

After food is trapped in mucus secreted by the endostyle, and then moved by cilia to the gut... here the smallest food particles are separated from the mucus and passed into the hepatic cecum, where they are phagocytized (The process of engulfing and ingestion of particles by the cell or a phagocyte (e.g. macrophage) to form a phagosome (or food vacuole), which in turn fuse with lysosome and become phagolysosome where the engulfed material is eventually digested or degraded and either released extracellularly via exocytosis, or released intracellularly to undergo further processing.) and digested intracellularly.

Gnathostomes

All jawed vertebrates, rater extinct or living a) A monophyletic group; presence of jaws is a derived character state shared by ALL jawed fishes and tetrapods b) An additional feature characteristic of ALL gnathostomes is the presence of paired pectoral and pelvic appendages in the form of fins or limbs c) However, pectoral fins appear in the fossil record before pelvic fins do, suggesting a more complex evolutionary scenario

What is the currently favored explanation for the evolution of vertebrate jaws?

Ample evidence suggests that jaws arose through modifications of the first or second serially repeated cartilaginous gill arches.

Anapsids

Another group of ostracoderms.... Were more streamlined than other ostracoderms. a) However all ostracoderms became extinct by the end of the devonian period.

Ostracoderms

Armored, jawless fishes, which were until recently the earliest known vertebrate fossils. Ostrakon = shell, derma = skin... They were armored with bone in their dermis and lacked paired fins (that later fishes found so important for stability.

Name 5 characteristics shared by all chordates, and explain the primary function of each.

Chordates share five distinct characteristics that separate them from all other phyla, 1.) a notochord, 2.) dorsal tubular nerve cord, 3.) pharyngeal pouches or slits, 4.) endostyle, and 5.) postanal tail. 1) NOTOCHORD functions to hold muscles that are attached to it because it can bend laterally without shortening, it permits undulatory (wave-like motions that propel an organism forward) movements of the body. 2) DORSAL TUBULAR NERVE CORD functions to form the brain from the anterior end. It passes through protective neural arches of the vertebrae, and the brain is surrounded by a bony or cartilaginous cranium. 3) PHARYNGEAL POUCHES AND SLITS function to assist the pharynx in its function. The pharynx originally evolved for filter-feeding (still used among protochordates). Early fishes adapted even further to form a capillary network within their pharynx to allow efficient transfer of gas between blood and the water outside. This later formed internal gills within fishes. 4) ENDOSTYLE (in the pharyngeal floor) secretes mucus that traps small food particles brought into the pharyngeal cavity. Some cells in the endostyle secrete iodinated proteins, these cells are homologous to the thyroid gland of adult lampreys and all other vertebrates. 5) POSTANAL TAIL functions to provide more motility by propulsion of water, this function is increased later in fish with fins. The human tail is only recognizable as a vestige, but other adult mammals (mostly) have waggable tails.

Blood vessels penetrate the epithelium providing oxygen and nutrients?

FALSE

In the name of the white oak, Quercus alba, Quercus is the species name?

FALSE

Linnaeus used similarities in structure to determine relationships among organisms?

FALSE

Organisms that are similar in structure and form and successfully reproduce among themselves belong to the same family?

FALSE

Heterostracans

Heteros = different, ostrakon = shell.... A group of ostracoderms.... The swimming movements of this early group must have been imprecise, although sufficient to propel them along the ocean floor where they searched for food.

Which of the following is the proper way to type the scientific name for humans?

Homo sapiens (each word has to be underlined independently)

Neural spines

In most vertebrates, disclike centra replace the notochord, and dorsal projections called the neural spines are present, which provide more area for attachment of segmented muscles.

GENUS & species (G is cap but s is not)

In the Linnaean system of scientific nomenclature, a single species is identified by a binomial, which consists of the following;

What is the phylogenetic position of Haikouella, and what evidence supports its placement there?

It has been hypothesized as the sister taxon of vertebrates (craniates). It has earned this distinction because it has several characters that define it as a chordate: a notochord, pharynx, and dorsal nerve cord. Like vertebrates, its fossils show pharyngeal muscles and enlarged brain. Its position as a sister taxon of vertebrates is not widely accepted as it lacks diagnostic vertebrate traits such as a cranium, an ear, and a distinct telecephalon.

Explain why it is necessary to know the life history of a tunicate to understand why tunicates are chordates.

It is necessary to know the life history of tunicates to understand why tunicates are chordates because we can learn about the origin of vertebrates and better our knowledge of the world around us. As adults, tunicates are highly specialized chordates, for in most species only the larval form, which resembles a microscopic tadpole, bears all the chordate hallmarks.

Endostyle

It's derivative, the thyroid gland, occur in all chordates but in no other animals. a) The endostyle in the pharyngeal floor, secretes mucus that traps small food particles brought into the pharyngeal cavity b) Some cells in the endostyle secrete iodinated proteins (check T3/T4). c) Feeding depends on formation of a mucous net that is secreted by a glandular groove... the endostyle.... Located along the mid-ventral side along the ventral side of the pharynx.

Agnathans

Jawless vertebrates a) Defined simply and principally by the absence of jaws, a character that is not unique to jawless fishes bc jaws are lacking in vertebrate ancestors.... Therefore, agnatha is paraphyletic

Appendicularia

Known as larvacea in some classifications. Contain tiny, pelagic creatures shaped like a bent tadpole. The name larvacea refers to their resemblance to the larval stage of other tunicates. a) They feed by a method unique in the entre animal world.... Each builds a delicate house, a transparent hollow sphere of mucous interlaced with filters and passages through which water enters. Tiny phytoplankton and bacteria trapped on a feeding filter inside the house are drawn into the animal's mouth through a straw-like tube. b)When the filters become clogged with waste, which happens about every 4 hours, the appendicularian abandons its house and builds a new house, a process taking only a few minutes

Conodonts

Kono = cone, dont = tooth.... Fossils were found to be phosphatized tooth like elements, myomeres, notochord, and paired eye and otic capsules conodonts clearly belong to the vertebrate clade.... Although their exact position is unclear.

Subphylum Cephalochordata

Lancelets, slender, laterally compressed, translucent animals 3 - 7 cm in length that inhabit sandy sediments of coastal waters around the world. a) The generic name is amphioxus or branchiostomata (branchia = gills, stoma = mouth) b) This subphylum is especially interesting bc it has the 5 distinctive characteristics of chordates in simple form.

Structural

Linnaeus used __________________ similarities to determine relationships among organisms?

Subneural gland

Located beneath the nerve ganglion and is connected by a duct to the pharynx.

Ascidiacea

May be solitary, colonial or compound a) Among the compound forms many individuals may share the same tunic. In some cases compound ascidians each member has its own incurrent siphon, but the excurrent opening is common to the group. (Just think about that for a minute)....

Offer a description of an adult tunicate that would identify it as a chordate, yet distinguish it from any other chordate group.

Of the 5 characteristics of chordates, adult sea squirts (ascidians) have only 2: 1) After metamorphosis an adult tunicate maintains pharyngeal slits and endostyle like chordates. However, an extremely odd feature exists in the cardiovascular system, found in no other chordate. The tunicate uses its heart to drive blood first in one direction for a few beats, then pauses, reverses the action, and drives the blood back in the opposite direction for a few beats. 2) Another remarkable feature of tunicates is the presence of strikingly high amounts of rare elements found in their blood, such as vanadium and niobium.

Osteostracans

Osteon = bone, ostrakon = shell.... Another group of ostracoderms.... Had paired pectoral fins, an innovation that improved swimming efficiency by controlling yaw (no), pitch (yes) and roll (head to shoulder)

Ventral aorta

Part of the closed circulatory system that is so complex for a simple chordate... BUT THERE IS NO HEART.... Blood is pumped forward in the ventral aorta by peristaltic contractions of the vessel wall, then passed upward through the branchial arteries (aortic arches) in the pharyngeal bars to paired dorsal aortas.

Distal

Parts farther from the midline of the body are?

Ectodermal placodes

Platelike epidermal thickenings that appear on either side of the neural tube. These give rise to the olfactory epithelium, lens of the eye, inner ear epithelium, some ganglia and cranial nerves, lateral line mechanoreceptors, and electroreceptors. a) ***Development of the vertebrate head and special sense organs was largely the result of 2 embryonic innovations present only in vertebrates... neural crest and ectodermal placodes***

Placoderms

Plax = plate, derm = skin... Heavily armored and were among the 1st jawed vertebrates a) Placoderms evolved a great variety of forms, some very large and grotesque in appearance. They were armored fish covered with diamond shaped scales or with large plates of bone b)Placoderms are thought to be the SISTER TAXON to all other gnathostomes.

Serving as reminder that most vertebrates have exoskeletons, this armor has been highly modified and can be seen as scales in later fish. What are some other keratinized structures derived from the epidermis, that are present in vertebrates today.

Scales, hair, feathers, claws, and horns.

Both sea squirts (urochordates) and lancelets (cephalochordates) are filter feeding organisms. Describe the filter feeding apparatus of a sea squirt and explain in what ways its mode of feeding is similar to and different from, that of amphioxus.

Sea squirts filter feed by formation of a mucous net this is secreted by a glandular groove. The endostyle located along the mid ventral side of the pharynx. Cilia on the gill bars of pharynx pull mucous into a sheet that spreads dorsally across the inner face of the pharynx. Food particles brought in the incurrent openings are trapped in the mucous net, which is worked into a rope and carried posteriorly by cilia into esophagus and stomach. It is similar to amphioxus because they both use a mucous net, and cilia . It is different because The food particles are separated from the mucous and passed to the hepatic cecum, where they are phagocytized and digested intracellularly.

Dorsal aortas

Structures that join posteriorly to become a single dorsal aorta. From there blood is distributed to the body tissues by microcirculation and then is collected in veins, which return it to the ventral aorta.

All types of epithelia are supported by an underlying basement membrane?

TRUE

Fat is also known as adipose tissue?

TRUE

Skeletal muscle is distinguished from smooth muscle in that the former (skeletal muscle) has striations?

TRUE

When organisms are classified within the same group, it can be assumed that they have a common phylogeny?

TRUE

Subphylum Vertebrata (Craniata)

The 3rd subphylum of chordates is the large and diverse vertebrata, which will be the subject of chapters 24 and 28. This monophyletic group shares the basic characteristics with the other 2 subphyla, BUT in addition it exhibits a number of novel characters that the others do NOT share. The alternate name of the subphylum, CRANIATA, more accurately describes the group bc all have a cranium ( bony or cartilaginous braincase) but some jawless fishes lack vertebrae.

Tripartite brain

The anterior end of the nerve cord that has become enlarged and contains a forebrain, midbrain and hindbrain and is protected by a cartilaginous or bony cranium. a) Paired special organs designed for distance reception evolved. These included eyes with lenses and inverted retinas; i) pressure receptors, such as paired inner ears designed for equilibrium and sound reception, ii) chemical receptors including taste and exquisitely sensitive olfactory organs; lateral line receptors for detecting water vibrations; and iii) electroreceptors for electrical currents that signal prey.

Atrium

The area where filtered water 1st passes, then leaves the body by an atriopore.

Thaliacea

The cylindrical or lemon shaped body is typically surrounded by bands of circular muscle with incurrent and excurrent siphons at opposite ends. Water pumped through the body by muscular contraction (rather than by cilia as ascidians) is used for locomotion by a sort of jet propulsion.

Paedomorphosis

The evolutionary retention of juvenile or larval traits in the adult body. As Walter Garstang postulated regarding the larval form of tunicates. a) Paedomorphosis is a well-known phenomenon in several different animal groups (amphibians)

What characteristics shared by the 3 deuterostome phyla indicate a monophyletic group of interrelated animals?

The following characteristics are shared by the three deuterostome phyla and indicate they represent a monophyletic group of interrelated animals: 1.) Radial cleavage, 2.) An anus derived from the first embryonic opening (blastopore), 3.) A mouth derived from an opening of secondary origin and 4.) A coelom formed by fusion of enterocoelous pouches.

What characteristics shared by the 3 deuterostome phyla indicate a monophyletic group of interrelated animals?

The following characteristics are shared by the three deuterostome phyla and indicate they represent a monophyletic group of interrelated animals: 1.) Radial cleavage 2.) An anus derived from the first embryonic opening (blastopore) 3.) A mouth derived from an opening of secondary origin 4.) A coelom formed by fusion of enterocoelous pouches.

Distinguish between ostracoderms and placoderms. What important evolutionary characters first appeared in each group? What are conodonts?

The major difference between ostracoderms and placoderms is that ostracoderms are jawless and the placoderms were jawed vertebrates, and were among the first jawed vertebrates. Conodonts are extinct vertebrates that were extremely challenging to identify. They are small and tooth-like, and have all of the characteristics of vertebrates. They are important in understanding the origin of vertebrates.

Cladistics

The method used to construct a hypothetical evolutionary tree is?

Muscular

The most abundant tissue type in the body of mammals is?

Spinal nerve roots

The nervous system is centered around a hollow nerve cord lying above the notochord.... Pairs of spinal nerve roots emerge at each trunk myomeric (muscle) segment.

Pharyngeal pouches or slits

The slits are openings that lead from the pharyngeal cavity to the outside. a) They are formed by inpocketing of the outside ectoderm (pharyngeal grooves) and evagination, or outpocketing, of the endodermal lining of the pharynx (pharyngeal pouches) b) function to assist the pharynx in its function. The pharynx originally evolved for filter-feeding (still used among protochordates). Early fishes adapted even further to form a capillary network within their pharynx to allow efficient transfer of gas between blood and the water outside. This later formed internal gills within fishes.

In debating the question of chordate origins, zoologists eventually agreed that chordates must have evolved within deuterostome assemblage rather than from protostome group as earlier argued. What embryological evidences support this view?

Their morphological similarities weren't homologous, meaning that they did not derive from the same ancestor, they were only analogous. In the early 20th century this point was further expressed as the group Deuterostomia includes the echinoderms, hemichordates, and chordates which all have similar embryological features as well as shared gene sequences that clearly separate chordates from Protostomia and establish it's monophyly Furthermore, as stated in question #1, in development, deuterostomes, including chordates, all form radial cleavage and the blastopore goes on to form the anus, and a second forms the mouth. The coelom forms by outpocketing and they have a regulative embryo.

Explain how a cladistic classification for the vertebrates produces important regroupings of the traditional vertebrate taxa (refer to Fig. 23.2). Why are agnatha and reptilia, as traditionally recognized, inconsistent with cladistic principles?

They are subdivided into Agnatha, vertebrates lacking jaws OR Gnathostomata, vertebrates having jaws. They are then classified by either Amniota, vertebrates whose embryos develop within a fluid-filled sac (amnion) OR Anamniota, vertebrates lacking development in the amnion. a) From Gnathstomata, it can be further divided into Pisces, which are jawed vertebrates with appendages, if any at all, in the form of fins AND Tetrapoda, which are jawed vertebrates with appendages, if any at all, in the form of limbs. Agnatha and Reptilia are inconsistent with these principles because they are paraphyletic, meaning that they don't contain all the descendants of the most recent common ancestor. Cladistics uses monophyletic groupings which contain all the descendants of the most recent common ancestor.

Postanal tail

Together with somatic musculature (muscle derived from mesodermal somites, including most skeletal (voluntary) muscle.... Distinct from viscera or visceral (involuntary) muscle of autonomic innervation)) and the stiffening notochord, provides the motility that larval tunicates and amphioxus need for their free swimming existence. a) As a structure added to the body behind the end of the digestive tract, the tail clearly has evolved specifically for propulsion in water. b) The tail is evident in humans only as a vestige (a series of fused vertebrae at the end of the spinal column)

Sister Groups

Two Different monophyletic groups that share common ancestry with each other more recently than either does with other taxa are known as?

Acanthodians

Were characterized by large, anteriorly set eyes and fins with large spines and are included in a clade that underwent a great diversification to form the bony fishes that dominate the waters of the world today.

Nerve ganglion

What the nervous system is restricted to and the plexus of nerves that lie on the dorsal side of the pharynx

Sagittal

Which body plane divides the body into right and left "mirror" halves?

Cardiac

Which type of muscle makes up the heart?

Amphioxus long has been of interest to zoologists searching for a vertebrate ancestor. Explain why amphioxus captured such interest and how it is different from the hypothesized most recent common ancestor of all vertebrates.

Zoologists are interested in the Amphioxus because no other chordate shows the basic diagnostic chordate characteristics as clearly as it does. In addition to this, it shares some characteristics of the vertebrate plan such as the 1.) hepatic cecum 2.) diverticulum (which resembles the vertebrate pancreas by its digestive enzyme secretion and liver in storing glycogen). It also contains a: 3.) Segmented trunk musculature, and 4.) The basic circulatory plan of vertebrates, the closed circulatory system that is complex for such a simple chordate.. However, it is different than vertebrates because protochordates are less active and smaller than the earliest vertebrates. Their skeletal structures were modified and muscles were created with the purpose of increased speed and mobility. In addition to this, they were more readily designed for high metabolic rates.

Amphioxus long has been of interest to zoologists searching for a vertebrate ancestor. Explain why amphioxus captured such interest and how it is different from the hypothesized most recent common ancestor of all vertebrates.

Zoologists are interested in the Amphioxus because no other chordate shows the basic diagnostic chordate characteristics as clearly as it does. In addition to this, it shares some characteristics of the vertebrate plan such as the 1.) hepatic cecum, 2.) diverticulum (which resembles the vertebrate pancreas by its digestive enzyme secretion and liver in storing glycogen). It also contains a 3.) Segmented trunk musculature, and 4.) The basic circulatory plan of vertebrates, the closed circulatory system that is complex for such a simple chordate.. However, it is different than vertebrates because protochordates are less active and smaller than the earliest vertebrates. Their skeletal structures were modified and muscles were created with the purpose of increased speed and mobility. In addition to this, they were more readily designed for high metabolic rates.

Neural crest

a population of ectodermal cells lying along the length of the embryonic neural tube, contributes to the formation of many different structures, including most of the cranium, the pharyngeal skeleton, tooth dentine, some cranial nerves, ganglia, some endocrine glands, and schwann cells. In addition the neural crest regulates the development of adjacent tissue, such as tooth enamel and pharyngeal muscles (branchiomeres).

What characteristics are found in an ammocoete larva that are lacking in amphioxus and homologous to those of vertebrates? - Ammocoete is the freshwater larval stage of the lamprey (jawless fish).

a) Chambered heart b) Tripartite brain c) Paired special sense organs derived, in part from placodes d) Pituitary gland e) Distinct kidneys f) They also have a true liver, replacing the hepatic ceum of amphioxus g) Gallbladder h) Pancreatic tissue (but no distinct pancreatic gland) i) Only 7 pairs of pharyngeal pouches/slits instead of a numerous amount in amphioxus j) Gill filaments bearing secondary lamellae much like the more extensive gills typical of bony fishes k) AMMOCOETES display the most ancestral condition for these characteristics of any living vertebrate

Excurrent siphon

a.k.a. Atrial siphon, marks the dorsal side of the body. Water passes through the slits and into an atrial cavity and out through this excurrent siphon

Incurrent siphon

a.k.a. Oral siphon, corresponds to the anterior end of the body. a) Water enters the incurrent siphon passes into a ciliated Pharynx that is minutely perforated by slits to form an elaborate basketwork