DIVERSITY, CLASSIFICATION &

EVOLUTIONPART II

VERTEBRATE ZOOLOGY (VZ Lecture02 – Spring 2012 Althoff - reference PJH Chapters 1-2)

1 2

3

4Branchiostoma

Fig. 2-4 p4 PJH

Amphioxus-likenonvertebratechordate

Hypotheticalprimitive vertebrate

1 2

3

4

Basics of Vertebrate Design (reference Table 2.1 PJH)

No cranium Cranium Simple brain Tripartite brain No specialized sense organs Multicellular sense

(except photoreceptors) organs (eye, nose, inner ear) Poor distance sensation Improved distance (but sensitive skin) sensation; lateral line system No electroreceptionElectroreception in primitive form

FEATURE Generalized Nonvertebrate Primitive Vertebrate

A

HINDBRAIN MIDBRAIN FOREBRAIN

________________ BRAIN

Basics of Vertebrate Design (reference Table 2.1 PJH)

Gill arches for filter feeding Gill arches support (respiration by diffusion) gills used for

respiration Numerous gill slits & arches Few gill slits (6-10 (up to 100 per side) per side); gill filaments complex Pharynx not muscularized Pharynx muscularized (w/ exceptions)(specialized) Water moved through pharynx Water moved by and over gill arches by active muscular ciliary action pumping Gill arches made of collagen Gill arches made of mucoscleroproteins cartilage—allows elastic recoil & thus aids in pumping

FEATURE Generalized Nonvertebrate Primitive Vertebrate

B

Basics of Vertebrate Design (reference Table 2.1 PJH)

Gut not muscularized, food Gut muscularized, passage by ciliary action food moves by

peristalsis Digestion of food is intracellular; Digestion of food is Cells lining gut take in extracellular; individual food particles Enzymes poured

onto food in gut lumen No discrete liver and pancreas; Discrete liver and midgut cecum or diverticulumpancreatic tissue is probably homologous to both

FEATURE Generalized Nonvertebrate Primitive Vertebrate

C

Basics of Vertebrate Design (reference Table 2.1 PJH)

No true heart (ventral pumping Ventral pumping heart structure (vessels) 3-chambered

peristalsis No neural control of pumping Neural control of

pumping (excepthagfishes) Open circulatory system, minimal Closed circulatory capillary system system Blood not specifically involved Blood specifically in transport of O2 and CO2 involved in O2 & CO2 transport No red blood cells or respiratory Red blood cells with pigments hemoglobin

FEATURE Generalized Nonvertebrate Primitive Vertebrate

D

Basics of Vertebrate Design (reference Table 2.1 PJH)

No specialized kidney; coelum Specialized glomerular filtered by flame cells kidney; segmental structures along dorsal body wall Flame cells empty into atrium Empty to ‘outside” via then out atriopore archinephric ducts leading to cloaca Body fluid concentrations and Body fluids more dilute ionic composition = seaH20 than seawater

No kidney present to regulate Kidney regulates fluid volume, where nitrogen excretion occurs

FEATURE Generalized Nonvertebrate Primitive Vertebrate

E

FLAME CELL

GLOMERULARSTRUCTUREIN KIDNEY

Note: example here is of planaria (non-chordate)

Basics of Vertebrate Design (reference Table 2.1 PJH)

Notochord provides main support Notochord provides for body muscles main support for body muscles plus vertebral elements around nerve cord (except hagfishes)

Myomeres with simple V-shape Myomeres more complex W-shape

No lateral fins or medial fins Primitively, no lateral beside tail fin fins. Caudal fin

has dermal fin rays. No dorsal fins Dorsal fins present (except hagfishes)

FEATURE Generalized Nonvertebrate Primitive Vertebrate

F

AMPHIXOUS

LAMPREY

SHARK (DOGFISH)

BONY FISH (perch)Fig. 2-10 p33 PJH

Embryology& Germ Layers

• All animals except sponges (Porifera) form distinct tissue (germ) layers. For vertebrates, 3 germ layers form during embryonic development

• 3 layers: ectoderm, mesoderm, endoderm

• Each has enabled refinements in organ-systems

Fig. 2-5 p26 PJH

ECTODERM

ECTODERM

Pharyngula state of embryonic development

Gut endoderm

Germ Layers: ECTOderm

• forms superficial layers of skin in adults, linings of most anterior and most posterior parts of the digestive tract and the nervous system (including most of the sense organs…eyes and the ear

• How can it be the “ecto” layer if it lines much of the digestive tract?

Germ Layers: ENDOderm

• forms balance of digestive tract as well as lining of glands associated with the gut (i.e., pancreas, gall bladder, liver). Linings of most respiratory surfaces of vertebrate gills and lungs

Germ Layers: MESOderm

• The last of the 3 germ layers to appear during embryonic development

• Forms everything else:muscles

skeleton (including notochord)connective tissue

circulatory systemurogenital system

• Further along in development, mesodermforms the coelom (body cavity)

pleuroperitoneal & pericardial cavities… in gut the cavity is lined by mesenteries

Pharyngula Stage (Fig. 2-5, p26)

• In most vertebrates, the linings of the pharyngeal pouches result in 6 or more glandular structures including….

Lymphatic systemthymus glandparathyroid glandscarotid bodies

tonsils• During this stage, the embryo is a mix of

______________ and ___________________components

Pharyngula Stage and beyond

• Gives rise to _______________ (running from the head end to the tail end

• __________ eventually form:dermis of the skin

striated muscles of the body used in locomotion

portions of the skeleton (vert. column & back of head)

5 Tissue Types in ADULT vertebrates

• Epithelial

• Connective

• Vascular (blood)

• Muscular

• Nervous

Most of these tissue have, as fundamental component, the fibrous protein ________. Otherkey component fibrous proteins that may be present include _________ and _________.

Integument

• External covering of vertebrates

• Makes up ________ of body weight in most vertebrates…more in armored species

• Includes skin and deriatives (i.e., glands, scales, dermal armor, and hair)

• 3 layers: epidermis—outer layerdermis—middle “unique”

layer subcutaneous tissue layer (hypodermis)

Important Mineral

• Unique to vertebrates: type of mineral called ________________. A complex compound of ____ and ____.

• This mineral more resistant to acid than calcium carbonate (in mollusk shells)…an may explain how vertebrates can resist tissue damage when engaged in muscular activity that can release lactic acid into the blood

Mineralized tissues…

• Six types possible in vertebrates:________ (adults only, 99% of composition)________ (adults only, 90% of composition)_______ (adults only, ~ 50% of composition)_________ – not mineralized in most

vertebrates, sharks major exception_________—primitive verte. & today’s

fishes__________—bonelike, mostly found

only in mammals (fastens teeth tosockets)