Comparative Anatomy Test 1 Review

Describe the ideas of Richard Owens

• argued that all vertebrates share a common structural plan, which he called the archetype

• developed the modern idea of homology— structures in different animals that share the same underlying design, even if their functions differ

Describe Preadaptation

A trait that originally evolved for one function but later turned out to be useful for a different function

Describe the notochord

• elastic, but largely incompressible rod that provides structural rigidity with a fluid core enclosed within a fibrous sheath

• allows for lateral undulation following opposing muscle contraction

• absent in mature form of chordates, a scaffold that forms the vertebral column is formed during development

Describe pharyngeal slits

• form pockets or openings in the body wall that allow for respiration or aid in feeding

Describe the endostyle or thyroid gland

• associated with filter feeding, but also involved in iodine metabolism

Describe the dorsal or tubular nerve cord

• formed by invagination of the neural plate derived from the ectoderm

• surrounds the neurocoele, a fluid-filled central canal

Describe the postanal tail

• posterior elongation of the body past the anus

• major implications for locomotion, and generally a wide range of adaptations

Subgroups of Protochordates

• Hemichordates

• Urochordates

• Cephalochordates

Subgroups of Hemichordates

• Enteropneusta

• Pterobranchia

Describe Enteropneusta

• primarily live in mucous-lined tunnels

• body plan is divided into three regions: proboscis, collar, and trunk

• Epibranchial ridge → endostyle

• Stomochord

• Pharyngeal slits divided by tongue bar

Describe Pterobranchia

• engage in filter feeding

• collar branches into tentacles

• tubular nerve cord is absent

Describe the parts of cephalochordates

• Buccal cirrus: prevents larger particle from entering the oral hood

• Hatschek’s pit: secretes mucous help collect food particles that enter

• Atriopore: filtered water exists

• Endostyle: collects iodine

• Midgut cecum: forerunner of liver, pancreas

Subgroups of Urochordates

• Tunicata

• Larvacea

• Thaliacea

Describe Larvacea

• modified tunicates retain larval characteristics

• believed to play an important role in carbon cycling

• three-part feeding system that is called the house

  • screen

  • filter

  • gelatinous matrix

Describe Thaliacea

• “salps”, filter-feeding urochordates

• free-floating and pelagic

• often form colonial aggregations

What is the major hypothesis that states chordates arise from echinoderms?

Auricularian Hypothesis

Describe the Auricularian Hypothesis

• echinoderm chordate relationship based on the Auricularian larvae of holothurians

• idea that with lengthening and enlarging of certain features, you get a chordate

What are the major signaling proteins for bilaterian dorsoventral axis?

• Bone morphogenic protein (BMP)- dorsal surface

• Chordin- ventral surface

Describe dorsoventral inversion

• BMP and Chordin are reversed in deuterostomes

What are the two vertebrate innovations and their description?

• Vertebral column

  • comprised of vertebrae

  • cartilaginous discs

  • consists of:

    • centrum

    • neural arch

    • hemal arch

  • remnants of notochord persist as nucleus pulposus

• Head

  • clustering of specialized sensory structures

  • varies but underpinned by presence of neural crest and placodes

What are the earliest vertebrate fossils called?

• Haikouella

• Yunnanozoon

Subgroups of Elasmobranchii

• Selachimorpha

• Batoidea

• Rajidae

Subgroups of Actinopterygii

• Chondrosteans

• Holosteans

• Teleosts

Subgroups of Sarcopterygii

• Dipnoi

• Actinistia

Describe different tetrapod transitional forms

• Eusthenopteron

• Tiktaalik

• Acanthostega

• Ichthyostega

Subgroups of Gnathostomes

• Placodermi

• Chondrichthyes

• Teleostomi

Subgroups of Teleostomi

• Acanthodii

• Osteichthyes

Describe Osteichthyes

• A higher degree of ossification

• swim bladder to control buoyancy and expand their ecological potential

• bony operculum and fin strengthened by lepidotrichia

Subgroups of Osteichthyes

• Actinopterygii

• Sacropterygii

Chiridium

muscular limbs with well defined digits — characterizes tetrapods

Labyrinthodonts

paraphyletic group of early tetrapods

Subgroups of Lissamphia

• Urodela

• Saleinta

• Apoda (Gymnophobia)

Describe Urodela

• salamnaders and newts

• lack external ears and temporal notch

Describe Salientia

• well developed tympanum

• saltatorial locomotion

Describe Lepospondyls

• radiation of amphibians

• well-defined complex vertebrate with three elements

Subgroups of Sauropsides

• Mesosaurs

• Parareptilia

• Euroreptilia

What is the only surviving parareptilia?

• Testudines

Subgroups of Eureptilia

• Lepidosauromorpha

• Archosauromorpha

• Ichytopterygia

• Nothosaurs

• Plesiosaurs

Describe Lepidosauria

• snakes, lizards (squamata) and tuataras (rhynchocephalia)

• extinct Eosuchia are the basal members

Characteristics of Archosauromorpha

• antiorbial fenestra

• bipedalism

Describe Aves

• high derived of saurishian, tehropod dinosaur adpated for flight

• exhibit a furcula (wish bone) and fused sternum

• feathers, high modified scales, evolved before flight

Subgroups of Synapids

• Pelycosaures

• Therapsids

• Mammals

Example of Pelycosauria

• Dimetrodon

Describe Therapsid

• cynodonts were successful

• experienced major reduction in body size

• presence of turbinates

Describe Mammalia

• mammary glands derived from sebaceous glands

• pelage (hair)

• vibrissae (whiskers(

• lower jaw comprised only of dentary bones

• joint between dentary and squamosal bone

• three inner ear bone

Extinct mammals

• heterodont dentition

• specialized tooth function implies endothermy

• haramyoids

Subgroups of Mammalia

• Monotremes

• Therians

  • Metatheria

  • Eutheria

Parts of a fertilized egg

• Cortical granules activate fertilization

• Vitelline members is known as zone pellucida in mammals

• perivitelline space opens between vitelline membrane and plasma membrane

• surrounding ovarian/follicle is corona radiata

Licithotrophic

embryos draw nutrients from the yolk

Matrotrophic

embryos draw nutrients from alternative sources

Amphixuous eggs are …

microlecithal

Cleave across amia and hagfish, condrichythians and teleosts is….

amia: holoblastic

hagfish, etc.: meroblastic

What forms during blastulation for reptiles

epiblast formed from blastodermA , along with supporting hypoblast

• prominent yolk at vegetal pole promotes meroblastic cleavage

What is the blastula called in mammals

blastocyst

Egg/ yolk amount for monotremes, marsupials, eutherians

• monotremes: macrolecithal

• marsupials form a thin shelled egg which is shed at the end of gestation

• eutheriaans are microlecithal

Process of gastrulation

•Epiboly-Cells spread across outer surface as unit

•Involution-Cells turn inward and spread across internal surface

•Invagination-A wall of cells folds inward

•Delamination-Sheets of cells split into parallel layers

•Ingression-Surface cells migrate to interior of embryo

Which coelomic cavity is found in the epimere, mesomere, and lateral plate respectively?

•Myocoel within the epimere

•Nephrocoel within the mesomere

•Coelom within the lateral plate

What are the two process that form the coelom and mesoderm

•Enterocoely-interior cavity contained within the mesoderm when it first pinches off

•Schizocoely-forms first as a solid sheet then splits into the open cavity within

Describe Primary and Secondary neuralation

•Primary neurulation-Surface ectoderm thickens into neural plate on future dorsal surface along anterior-posterior axis

•Neural crest cells form from ectodermal folds

•Secondary Neurulation-Neurocoel forms via cavitation from solid rod of ectodermal cells called neural keel

What does gastrulation begin with?

thickened region on the epiblast called the primitive streak, which will become the posterior portion of the embryo

Following neurulation what three important events are completed?

• polarity is established

• germ layers have been fully established

• germ layers are position to interact during organogenesis

What are the four different tissues during histogenesis

• connective tissue

• epithelial tissue

• muscle tissue

• nervous tissue

Describe epithelial tissue

• tightly formed with little EXM between, with one side sitting upon a basal layer comprised of two layers of distinct origin

  • basal lamina (derived from epithial)

  • reticular lamina (derived from connective tissue)

• surface, which faces lumen (i.e. external environment)

• Apical surface often contains cilia to facilitate exchange and interaction with lumen environment

Grandular epithelium

•Cells specialized for secretion are glands, and glands with ducts that collect and carry away the product are exocrine glands

•Specifically, where the product is carried away by the circulatory systems, they are endocrine glands

•May be multicellular or unicellular, and simple or compound (referring to the number of ducts)

Connective Tissue

•Incredibly diverse in terms of structure and function, including: bone, cartilage, fibrous connective tissue, adipose tissue, and blood

Special connective tissue is

Cartilage

•Myeloid tissue located in bone is hemopoietic (i.e. forms blood cells)

•Cartilage is made of chondroitin sulfate and collagenous or elastic proteins and comes in a few varieties

•Hyaline (becomes bone)

•Fibrocartilage (intervertebral disks, etc.)

•Elastic cartilage (ear and epiglottis)

Endochondral bone development

•Referred to as “replacement bones” because it is built on a cartilage scaffold

•Calcium salts entomb chondrocytes, which die and are subsequently replaced with innervated marrow

•In mammals epiphyseal plates in metaphyseal region ossify completely, arresting growth

Intramembranous bone development

•Forms from mesodermal cells (mesenchyme) with no cartilage precursor

•A few flavors:

•Dermal bone: Forms directly by ossification of the mesenchyme

•Sesamoid bones: Form directly within tendons

Joints

•Where separate bone or cartilage elements make contact

•Synovial joints (diathrosis) permit liberal movement, synathrosis suggest joints permit little movement

•Synostosis: direct connection between bone

•Synchondrosis: connection between cartilage (often termed symphyses e.g. pubic symphysis)

Neural crest and ectodermal placodes

•Neural crest cells break away before complete closure of the neural folds

•Placodes arise more or less in tandem, and similarly disperse to form a variety of structures

Amnion

•a fluid-filled sac around the embryo, providing a protective cushion and maintaining a stable environment.

Yolk Sac

•In early development, it supplies nutrients to the embryo. In mammals, it also contributes to the formation of the digestive tract and the first blood cells.

Chorion

•This outer membrane facilitates gas exchange and, in mammals, contributes to the formation of the placenta, which connects the embryo to the mother’s blood supply.

Allantois

It helps in waste removal and gas exchange. In mammals, it also forms part of the umbilical cord and contributes to the development of the urinary bladder

Heterochrony

•Describes the timing of developmental changes relative to ancestral or related lineages

•In some cases, juvenile or larval traits are retained for longer periods, termed paedomorphosis

•In others, adult characteristics are exaggerated or occur earlier than usual, termed peramorphosis

Hypermorphosis

when ontogeny is longer and offset late such that allometric growth continues beyond normal endpoint

Acceleration

•character grows faster during ontogeny than normal pace compared to ancestor

Predisplacement

onset of character development is ealier

Types of Peramorphosis

• Hypermorphosis

• Acceleration

• Predisplacement

Types of Paedomorphosis

• Progenesis

• Neoteny

• Postdisplacement

Progenesis

growth stops at a relatively earlier age

Neoteny

features grow at a slower rate

Postdisplacement

features appears relatively late in development