AP Biology
LECTURE NOTES: Chapter 34
Vertebrates
The animals called vertebrates get their name from vertebrae, the series of bones that make up the backbone. Chordates have a
notochord and a dorsal, hollow nerve cord. Vertebrates are a subphylum of 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 invertebrates. All chordates share a set of derived characters
although some species possess some of these traits only during embryonic development:
1.
2.
3.
4.
NOTOCHORD - The notochord Is a longitudinal, flexible rod
located between the digestive tube and the nerve cord. It provides
skeletal support throughout most of the length of a chordate. In
most vertebrates, a more complex, jointed skeleton develops and
the adult retains only remnants of the embryonic notochord.
DORSAL HOLLOW NERVE CORD - Develops from a plate
of ectoderm that rolls into a tube dorsal to the notochord.
Develops into the central nervous system: the brain and the spinal
cord.
PHARYNGEAL SLITS - In most chordates, grooves in the
pharynx called pharyngeal clefts develop into slits that open to the
outside of the body. These pharyngeal slits function as
suspension-feeding structures in many invertebrate chordates.
They are modified for gas exchange in aquatic vertebrates. They
develop into parts of the ear, head, and neck in terrestrial vertebrates
MUSCULAR, POST ANAL TAIL - Chordates have a tail extending posterior to the anus, although in many species it is
lost during embryonic development. The chordate tail contains skeletal elements and muscles and it provides much of the
propelling force in many aquatic species.
AP Biology
LECTURE NOTES: Chapter 34
Vertebrates
AP Biology
LECTURE NOTES: Chapter 34
Vertebrates
Adaptive Value of Cranium
Craniates are chordates that have a head. The origin of a head opened up a completely new way of feeding for
chordates: active predation.
• Craniates share some common characteristics: a skull, brain, eyes, and other sensory organs
Adaptive Value of Lateral Line System in Sharks
• The lateral line system is a row of microscopic organs sensitive to changes in the surrounding water
pressure – enables animal to detect minor vibrations.
Modes of Internal Fertilization
 Some species are oviparous (lay eggs that hatch outside mother’s body)
 Some species are ovoviviparous (retain fertilized eggs in oviduct – embryos are nourished by yolk and
develop into young that are born after hatching in the uterus)
 Some species are viviparous (young develop within the uterus – receive nutrients via placenta)
Adaptive Value of Swim Bladder in Fishes
• The swim bladder is an air sac that helps control the buoyancy of the fish. The transfer of gases between
the swim bladder and the blood varies the inflation of the bladder and adjusts the density of the fish.
• So…as opposed to sharks, fishes can conserve energy by remaining motionless.
Adaptive Value of Amniotic Egg
• Amniotes are named for the major derived character of the clade, the amniotic egg
– Amniotic eggs contain specialized membranes that protect the embryo (leathery shell) – the shell
prevents desiccation of the embryo
– The amniotic egg removes the need to return to water for reproduction – the embryonic
membrane allows for gas and waste exchange; food supplies are stored in yolk; and the amnion
protects the embryo in a fluid filled cavity from mechanical shock
– In amniotes, there is more efficient reproduction with internal fertilization – fewer gametes
required
– New hatchlings are more fully developed in amniotes
Adaptive Value of WaterProofed Skin in Reptiles
• Reptiles have several adaptations for terrestrial living not generally found in amphibians:
– Scales containing keratin waterproof the skin – helping prevent dehydration in dry air.
– This adaptation permits life on terrestrial habitats and provides mechanical and chemical
protection of the body
– They have well-developed lungs so they are better able to exchange gases with their atmosphere
(air instead of water)
Groups of Mammals
Monotremes: egg-laying mammals that have hair and produce milk (Ex. platypuses).
Marsupials: complete embryonic development in pouch. (Ex. kangaroos).
Eutherians: placental mammals that have longer period of pregnancy and complete development in uterus.