Echinoderms and Chordates - MCCC - West Windsor, NJnatalep/documents/powerpoint... · Echinoderms...
Transcript of Echinoderms and Chordates - MCCC - West Windsor, NJnatalep/documents/powerpoint... · Echinoderms...
Echinoderms and Chordates
Echinoderms
• Sea stars and most other echinoderms are slow-moving 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
Madreporite
Radial nerve
Gonads
Ampulla
Podium
Tube feet
Radial canal
Ring canal
Central disk
Digestive glands
• 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)
(c) A sea urchin (class Echinoidea)
(e) A sea cucumber (class Holothuroidea)
(b) A brittle star (class Ophiuroidea)
(d) A feather star (class Crinoidea)
(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
Dorsal, hollow nerve cord
Notochord
Tail
Cirri
Mouth
Pharyngeal slits
Digestive tract
Atrium
Atriopore
Segmental muscles
Anus
2 cm
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
Tunic
Water flow
Excurrent siphon
Atrium
An adult tunicate
Pharynx with slits Anus
Atrium
Excurrent siphon
Incurrent siphon to mouth
Dorsal, hollow nerve cord
Incurrent siphon
Excurrent siphon
Muscle segments
Notochord
Tail
Stomach
Intestine
Intestine
Esophagus
Stomach
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
Pelvic fins Pectoral fins
(c) Spotted ratfish (Hydrolagus colliei)
(a) Blacktip reef shark (Carcharhinus melanopterus)
(b) Southern stingray (Dasyatis americana)
• 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
Class Osteichthyes ---- Bony Fish
Fig. 34-16
Intestine
Adipose fin (characteristic of trout)
Cut edge of operculum
Swim bladder Caudal
fin
Lateral line
Urinary bladder Pelvic
fin
Anus
Dorsal fin
Spinal cord
Brain
Nostril
Gills
Kidney
Heart
Liver
Gonad
Anal fin
Stomach
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
(c) Mating adults
(a) Tadpole
(b) During metamorphosis
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)
(c) Wagler’s pit viper (Tropidolaemus wagleri)
(b) Australian thorny devil lizard (Moloch horridus)
(e) American alligator (Alligator mississippiensis)
(d) Eastern box turtle (Terrapene carolina carolina)
• 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
• 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 Birds
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