1. List and briefly describe the four primary
chordate phylum characteristics.
2. List the three subphyla in the phylum Chordata,
name representatives of each, and define their habitats in general.
3. Describe the two unique features of the
vertebrates, or craniates, which have enabled them to become the predominant
group of large animals.
4. Describe the characteristics of the hypothetical
first chordate, the habitat in which its evolution is thought to have occurred,
and the reasoning upon which this is based.
5. List the characteristics of present day
tunicates which are similar to the hypothetical first chordate.
6. List the characteristics which make Amphioxus
seem like a reasonable candidate for an ancestor to the vertebrates.
7. List the characteristics which make it seem
unlikely that Amphioxus was actually the ancestral chordate from which the
vertebrates evolved.
8. Name and describe the characteristics of
the present day animal whose life cycle may indicate a more probable ancestor
of the first fish.
9. Contrast the basic body plans of chordates
and non-chordates (e.g. insects)
10. Describe the anatomy, feeding and respiration
of a sea squirt.
11. Outline the life cycle of a typical tunicate
12. Briefly describe the anatomy, habitat and
ecological niche of Amphioxus.
13. Diagram a generalized vertebrate, showing
the location of the nerve cord, notochord and vertebrae; heart, gills and
lungs; digestive tract and accessory organs; and kidneys and gonads.
14. List the seven classes of vertebrates and
give examples and main distinguishing characteristics of each.
15. List and describe four major advances displayed
by the subphylum vertebrata over previously studied groups.
16. Define neotony and its applications to
evolutionary perspectives of the chordates.
Resources: Text: Animal Diversity, Chapter
15
Internet Resources:
http://www.ucmp.berkeley.edu/chordata/
http://nsm.fullerton.edu/~lamberts/ascidian/
http://orion1.paisley.ac.uk/courses/Tatner/biomedia/units/chor5.htm
http://www.mhhe.com/hickmanad4e
Phylum Chordata
4 MAJOR PHYLUM CHARACTERISTICS:
1. Notochord- supportive rod
that extends most of the length of the body and
into tail; dorsal to body cavity
-connective tissue sheath that encloses
cells, each of which has large fluid filled
vacuole; gives notochord turgidity
(prevents compression along anterior/posterior
axis)
-flexible to allow lateral bending (swimming)
-in most adult vertebrates is replaced by cartilage or bone
2. Pharyngeal gill slits
-series of openings in pharyngeal region
between digestive tract and outside body.
-in some chordates, have become:
*gill pouches (gills never break
to outside)
*earliest chordates used them for
filter feeding
*some (fishes) have developed gills
in pharyngeal pouches for gas exchange
*gill slits of higher vertebrates are mainly embryonic
3. Tubular nerve cord
-single, dorsal; anterior end enlarged
into brain
-largely responsible for chordate
success
-nerve cord runs along longitudinal
axis, dorsal to notochord
-this central nervous system associated
w/development of complex systems for
sensory perception, integration
and motor responses
4. Post anal tail
-generally supported by notochord or
vertebral column
-provides method of locomotion in
aquatic chordates
-present in humans as coccyx; in most
other mammals as wagging tail.
PHYLUM CHORDATA
-marine, freshwater and terrestrial habitats
-4 phylum characteristics all present at some time in chordate life history
SubPhylum Urochordata
-notochord, nerve cord, postanal tail only in free swimming larva
-adults sessile, occasionally
planktonic
-marine; sea squirt (tunicates)
SubPhylum Cephalochordata
-body laterally compressed and transparent
(fish like)
-all four chordate characteristics
persist throughout lifetime
-Amphioxus
SubPhylum Vertebrata
-notochord, nerve cord, postanal
tail and gill slits at least present in embryonic stages
*vertebrae surround nerve cord and serve as primary axial support
*skeleton modified anteriorally into skull for protection of brain
*features have enabled them to become predominate group of large animals
Classes: Chondrichthyes-
sharks, skates, rays
Osteichthyes-
bony fish
Amphibia
Reptilia
Aves- birds
Mammalia-
you and me!!
SUBPHYLUM UROCHORDATA- sea squirts (tunicates), marine
-sessile as adults, either solitary or colonial (2 of 3 classes are planktonic as adults)
-sessile adults attach to solid substrates
-unattached end has 2 siphons that circulate
sea water through body (oral ---> water in;
atrial ---> water out)
-body wall called tunic, quite tough,
secreted by epidermis, composed of protein, salts
and cellulose
-some tissues (ex. blood vessels, blood
cells) are incorporated into tunic
-rootlike extensions of tunic (stolon) anchor
tunicate to substrate or connect individuals
-larval form has all four chordate characteristics,
tadpole like larva
(swims around before attaching and
undergoing metamorphosis to adult)
-adults retain only pharyngeal gill slits, function in feeding and gas exchange
-monoecious, self-fertilization occurs
but cross fertilization is the rule
SUBPHYLUM CEPHALOCHORDATA- lanclets (Amphioxus) ~45 species
-marine, slender, laterally compressed,
transparent, benthic (sandy)
-adults retain all four chordate characs.
(chordate ancestor??)
-despite streamlined form are weak swimmers,
spend most time in filter feeding position
(buried w/anterior out)
-unlike other chordates, notochord cells
are muscular, allowing some contraction (adaptation
for burrowing)
-filter feeders; water over gills of
pharynx, food collected on gill bars, mucus secretions
moved by cilia to intestine. Digestion
intracellular by phagocytosis
-no true heart, blood propelled by contractile waves (peristaltic) in walls of major vessels.
-blood contains amoeboid cells but lack
RBCs and hemoglobin
-dioecious, fertilization external
SUBPHYLUM VERTEBRATA- extremely successful and large group
*two additional characteristics not shared
with other chordates
1. spinal column of vertebrae
2. a skull to protect brain
-much more complex
GENERAL CHARACTERISTICS:
-outer epidermis varied (skin, scales,
hair, etc) inner dermis of connective tissue
-advanced musculature
-ventral, pumping heart, circulatory
system closed w/red and white blood cells and
hemoglobin
-eucoelomate
-kidneys for excretion
-endocrine system of ductless glands
throughout body
-dioecious w/widely varied strategies.
Usually involves large expenditure of energy
MAJOR ADVANCES OVER PREVIOUS GROUPS:
1. Living endoskeleton- internal
supportive structure unlike invertebrate exoskeleton
-endoskeleton grows with body, provides unlimited size potential
-skull and rib cage provide protection of vulnerable organs
2. Pharynx and efficient respiration
-filter feeding apparatus replaced w/buccal pump
-internal gill ---> (lung)
allow much greater extraction of oxygen from water or
atmosphere
3. Advanced nervous system
-most responsible for functional
and structural advancement
-sessile filter feeders --->
predators brought about advancement in sensory and
motor organs
-brain enclosed in case; sensory
organs
4. Paired limbs
pectoral limbs (upper/anterior body)
"arms"
pelvic limbs (lower/posterior body) "legs"
-began as swimming fins and stablizer
---> became walking legs
-jointed appendages allow for greater
motions and manipulations
**Evolutionary relationships between 3 chordate phyla are speculative
-life style of urochordates suggests
relationship to early echinoderms, suggesting an
ancestral line through the echinoderms
-evolution of motile chordates from
attached ancestors may have involved tadpode-like
larva
(Neotony)- larval individuals
became capable of reproduction
Therefore skip adult stages,
eventually became different line (amphibians)
-could have led to small fishlike chordates