Download Echinoderms and Chordates

Echinoderms and Chordates
Echinoderms
• Sea stars and most other echinoderms are slowmoving or sessile marine animals
• A thin epidermis covers an endoskeleton of hard
calcareous plates
• Echinoderms have a unique water vascular system,
a network of hydraulic canals branching into tube
feet that function in locomotion, feeding, and gas
exchange
• Males and females are usually separate, and sexual
reproduction is external
Fig. 33-39
Anus
Stomach
Spine
Gills
Central disk
Digestive glands
Madreporite
Radial
nerve
Ring
canal
Gonads
Ampulla
Podium
Radial canal
Tube
feet
• Living echinoderms are divided into six classes:
– Asteroidia (sea stars)
– Ophiuroidea (brittle stars)
– Echinoidea (sea urchins and sand dollars)
– Crinoidea (sea lilies and feather stars)
– Holothuroidea (sea cucumbers)
– Concentricycloidea (sea daisies)
Fig. 33-40
(a) A sea star (class Asteroidea)
(b) A brittle star (class Ophiuroidea)
(c) A sea urchin (class Echinoidea)
(d) A feather star (class Crinoidea)
(e) A sea cucumber (class Holothuroidea)
(f) A sea daisy (class Concentricycloidea)
Sea Stars
• Sea stars, class Asteroidea, have multiple arms
radiating from a central disk
• The undersurfaces of the arms bear tube feet, each
of which can act like a suction disk
• Sea stars can regrow lost arms
Fig. 33-40a
(a) A sea star (class Asteroidea)
Chordates
• Phylum Chordata consists of two subphyla of
invertebrates as well as hagfishes and vertebrates
• Chordates share many features of embryonic
development with echinoderms, but have evolved
separately for at least 500 million years
Chordates have a notochord and a
dorsal, hollow nerve cord
• Vertebrates are a subphylum within the phylum
Chordata
• Chordates are bilaterian animals that belong to the
clade of animals known as Deuterostomia
• Two groups of invertebrate deuterostomes, the
urochordates and cephalochordates, are more
closely related to vertebrates than to other
invertebrates
Derived Characters of Chordates
• All chordates share a set of derived characters
• Some species have some of these traits only during
embryonic development
• Four key characters of chordates:
– Notochord
– Dorsal, hollow nerve cord
– Pharyngeal slits or clefts
– Muscular, post-anal tail
Lancelets
• Lancelets (Cephalochordata) are named for their
bladelike shape
• They are marine suspension feeders that retain
characteristics of the chordate body plan as adults
Fig. 34-4
Cirri
2 cm
Mouth
Pharyngeal slits
Atrium
Notochord
Digestive tract
Atriopore
Dorsal, hollow
nerve cord
Segmental
muscles
Anus
Tail
Tunicates
• Tunicates (Urochordata) are more closely related to
other chordates than are lancelets
• They are marine suspension feeders commonly
called sea squirts
• As an adult, a tunicate draws in water through an
incurrent siphon, filtering food particles
Fig. 34-5
Incurrent
siphon
to mouth
Water flow
Dorsal, hollow
nerve cord
Excurrent
siphon
Atrium
Pharynx
with
slits
Tunic
Excurrent
siphon
Excurrent
siphon
Tail
Muscle
segments
Incurrent
siphon
Intestine
Anus
Intestine
Esophagus
Stomach
An adult tunicate
Notochord
Stomach
Atrium
Pharynx with slits
A tunicate larva
• Tunicates most resemble chordates during their
larval stage, which may last only a few minutes
Derived Characters of Vertebrates
• Vertebrates have the following derived characters:
– Vertebrae enclosing a spinal cord
– An elaborate skull
– Pectoral and pelvic appendages
Jawless fish- Class Agnatha
• Lampreys represent the oldest living lineage of
vertebrates
• They are jawless vertebrates inhabiting various
marine and freshwater habitats
• They have cartilaginous segments surrounding the
notochord and arching partly over the nerve cord
Fig. 34-10
Chondrichthyans (Sharks, Rays, and
Their Relatives)
• Chondrichthyans (Chondrichthyes) have a skeleton
composed primarily of cartilage
• The cartilaginous skeleton evolved secondarily from an
ancestral mineralized skeleton
• The largest and most diverse group of chondrichthyans
includes the sharks, rays, and skates
• Placoid dermal scales
• Lateral line sense vibrations
Fig. 34-15
Pectoral fins
Pelvic fins
(a) Blacktip reef shark (Carcharhinus
melanopterus)
(b) Southern stingray (Dasyatis americana)
(c) Spotted ratfish (Hydrolagus colliei)
Class Osteichthyes ---- Bony Fish
• Nearly all living osteichthyans have a bony
endoskeleton
• Aquatic osteichthyans are the vertebrates we
informally call fishes
• Most fishes breathe by drawing water over gills
protected by an operculum
• Fishes control their buoyancy with an air sac known
as a swim bladder
Fig. 34-16
Swim
bladder
Spinal cord
Dorsal fin
Brain
Adipose fin
(characteristic
of trout)
Nostril
Anal fin
Cut edge
of operculum
Liver
Gills
Heart
Kidney
Gonad
Stomach
Intestine
Lateral
line
Anus
Pelvic
fin
Urinary
bladder
Caudal
fin
Class Amphibia
• Amphibians (class Amphibia) are represented by
about 6,150 species
• Amphibian means “both ways of life,” referring to
the metamorphosis of an aquatic larva into a
terrestrial adult
• Most amphibians have moist skin that
complements the lungs in gas exchange
• Fertilization is external in most species, and the
eggs require a moist environment
Fig. 34-22
(a) Tadpole
(b) During
metamorphosis
(c) Mating adults
Class Reptilia
• The reptiles includes the tuataras, lizards, snakes,
turtles, crocodilians, birds, and the extinct
dinosaurs
• Reptiles have scales that create a waterproof
barrier
• They lay shelled eggs on land: amniotic eggs
Fig. 34-27
(a) Tuatara (Sphenodon punctatus)
(b) Australian thorny devil
lizard (Moloch horridus)
(c) Wagler’s pit viper
(Tropidolaemus wagleri)
(d) Eastern box turtle
(Terrapene carolina carolina)
(e) American alligator
(Alligator mississippiensis)
• Most reptiles are ectothermic, absorbing external
heat as the main source of body heat and
poikilothermic
• Birds are endothermic, capable of keeping the
body warm through metabolism and
homeothermic
Birds: Class Aves
• Almost every feature of their reptilian anatomy has
undergone modification in their adaptation to flight
Derived Characters of Birds
• Many characters of birds are adaptations that
facilitate flight
• The major adaptation is wings with keratin feathers
• Other adaptations include lack of a urinary bladder,
females with only one ovary, small gonads, and loss
of teeth
Derived Characters of Class Mammalia
• Mammals have
–
–
–
–
–
–
–
Mammary glands, which produce milk
Hair
A larger brain than other vertebrates of equivalent size
Differentiated teeth
Homeothermic endothermic
Most have placenta
Diaphragm separating abdominal and thoracic cavities
Monotremes
• Monotremes are a small group of egg-laying
mammals consisting of echidnas and the platypus
Marsupials
• Marsupials include oppossums, kangaroos, and
koalas
• The embryo develops within a placenta in the
mother’s uterus
• A marsupial is born very early in its development
• It completes its embryonic development while
nursing in a maternal pouch called a marsupium
Eutherians (Placental Mammals)
• Compared with marsupials, eutherians have a
longer period of pregnancy
• Young eutherians complete their embryonic
development within a uterus, joined to the mother
by the placenta