chapter 24 animals ii: the chordates (sections 24.1 - 24.3)
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Chapter 24 Animals II: The Chordates (Sections 24.1 - 24.3). 24.1 Windows on the Past. Fossils are physical evidence of changes that led to modern animal diversity Radiometric dating assigns fossils to places in time - PowerPoint PPT PresentationTRANSCRIPT
Albia Dugger • Miami Dade College
Cecie StarrChristine EversLisa Starr
www.cengage.com/biology/starr
Chapter 24 Animals II: The Chordates
(Sections 24.1 - 24.3)
24.1 Windows on the Past
• Fossils are physical evidence of changes that led to modern animal diversity
• Radiometric dating assigns fossils to places in time
• Structure, biochemistry, and genetic makeup of living organisms provide information about branchings
Transition Fossils
• Fossils reveal that birds evolved from feathered dinosaurs, and that some early birds had a bony tail and teeth
24.2 The Chordate Heritage
• Chordates are distinguished by their embryonic traits
• Chordates include vertebrates and two lineages of marine invertebrates
• chordate • Animal with an embryo that has a notochord,
dorsal nerve cord, pharyngeal gill slits, and a tail that extends beyond the anus
Chordate Characteristics
• Four features define chordate embryos: • a notochord• a dorsal hollow nerve cord• a pharynx with gill slits• a muscular tail extending past the anus
• These features may or may not persist in adults
Key Terms
• notochord • A rod of stiff but flexible connective tissue that runs
the length of the body in chordate larvae or embryos and supports it
Invertebrate Chordates
• Invertebrate chordates include lancelets and tunicates
• lancelet • Invertebrate chordate that has a fishlike shape and retains
the defining chordate traits into adulthood
• tunicate • Invertebrate chordate that loses its defining
chordate traits during the transition to adulthood
Lancelets
• Gill slits filter food particles out of the water and also function in gas exchange
Fig 24.1a, p. 378
Lancelets
Fig 24.1a, p. 378
anus
tail extends past anus
eyespot
notochord
dorsal nerve cord
pharynx with gill slits
Lancelets
Fig 24.1b, p. 378
Lancelets
ANIMATION: Lancelet body plan
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Tunicates
• Larvae swim about briefly, then undergo metamorphosis
• Adults retain only the pharynx with gill slits
• Adults feed by drawing water in through an oral opening, past gill slits, then expels it through a second opening
Larval and Adult Tunicates.
Fig 24.2, p. 378
pharynx with gill slits
A
C
1 cm
Larval and Adult Tunicates
Fig 24.2a, p. 378
Larval and Adult Tunicates
Fig 24.2c, p. 378
Larval and Adult Tunicates
ANIMATION: Tunicate body plan
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Overview of Chordate Evolution
• Craniates are chordates with a braincase of cartilage or bone
• Most craniates are vertebrates
• craniate • Chordate with a braincase
• vertebrate • Animal with a backbone
Chordate Evolution (cont.)
• Vertebrae and other skeletal elements are components of the vertebrate endoskeleton
• Jaws evolved from bony parts that supported gill slits of early jawless fishes
• endoskeleton • Internal skeleton made up of hardened components
such as bones
Chordate Evolution (cont.)
• Evolutionary modifications allowed animals to move from water onto land:• Fins would evolved into limbs of tetrapods• A subset of tetrapods, amniotes produce eggs
that allow embryos to develop away from water
Key Terms
• tetrapod • Vertebrate with four legs, or a descendant thereof
• amniote • Vertebrate in which the embryo develops
surrounded by fluid enclosed by membranes inside the egg
Evolutionary Tree of Vertebrates
Fig 24.3, p. 379
Vertebrates Craniates Chordates Tetrapods Amniotes
ancestral chordate
Bony appendages
Amniote eggs
Swim bladder or lung(s)
Backbone
Tunicates Reptiles (with birds)Lancelets
Jaws
Four limbs
Cartilaginous fishesHagfishes Lampreys
Ray-finned fishes
Lobe-finned fishes
MammalsAmphibians
Braincase1
2
3
4
5
6
7
Evolutionary Tree of Vertebrates
Key Concepts
• Characteristics of Chordates • Four traits characterize chordate embryos: a
supporting rod (notochord), a dorsal nerve cord, a pharynx with gill slits in the wall, and a tail that extends past the anus
• Certain invertebrates and all vertebrates belong to this group
ANIMATION: Vertebrate Evolution
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24.3 The Fishes
• The number and diversity of fishes exceed those of all other vertebrate groups combined
• Fishes are divided into jawless and fishes with jaws
• Fishes with jaws are divided into cartilaginous fishes and bony fishes
Jawless Fishes
• The first fishes were jawless – two lineages survive – both have a cylindrical body, no fins or scales, and move with a wiggling motion
• hagfish • Jawless fish with a cranium (skull case) but no
backbone
• lamprey • Jawless vertebrates with a backbone of cartilage• Some are parasites of other fish
Two Modern Jawless Fishes• Hagfish • Parasitic lamprey
Fishes With Jaws
• Jawed fishes likely evolved from jawless ancestors when some gill supports became modified
• Jawed fishes typically have scales and paired fins
• Jawed fished are divided into the cartilaginous fishes and the bony fishes
Proposed Evolution of Jaws
Fig 24.5, p. 380
supporting structure for gill slits
jaw, derived from support structure
jaw
location of spiracle (modified gill slit)
jaw supportgill slits
Proposed Evolution of Jaws
jaw
location of spiracle (modified gill slit)
jaw supportjaw, derived from support structure
Fig 24.5, p. 380
supporting structure for gill slitsgill slits
Stepped Art
Proposed Evolution of Jaws
Cartilaginous Fishes (Chondrichthyes)• Cartilaginous fishes include sharks and rays
• Some sharks have rows of teeth, some are filter feeders
• Rays include filter feeders (mantas) and bottom feeders (stingrays)
• cartilaginous fish • Fish with a skeleton of cartilage• Gills are visible at the surface
Two Cartilaginous Fishes
Bony Fishes
• There are two lineages of bony fishes:
• Ray-finned fishes are the most diverse, including salmon, sardines, bass, swordfish, trout, tuna, halibut, carp, and cod
• Lobe-finned fishes include coelacanths and lungfishes
Key Terms
• bony fish • Fish with a lung or swim bladder and a skeleton
consisting largely of bone
• lobe-finned fish • Fish with fleshy fins that contain bones
• ray-finned fish • Fish with fins supported by thin rays derived from
skin; member of most diverse lineage of fishes
Bony-Fish Body Plan
• Aspects of the fish body plan adapt fish to life in water:• A swim bladder allows ray-finned fish to adjust its
buoyancy• Kidneys filter blood and adjust volume and solute
composition• Lungfishes have gills and one or two air-filled lungs
Body Plan of a Perch
Fig 24.7a, p. 381
liverintestine
ovary nerve cord
stomachanus gills
brain
heart
swim bladder kidney
Body Plan of a Perch
Ray-Finned Fish Diversity
ANIMATION: Bony fish body plan
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Lungfish: A Lobe-Finned Fish• Pelvic and pectoral fins are supported by bones
Fig 24.8, p. 381
pectoral finpelvic fin
Lungfish: A Lobe-Finned Fish
Key Concepts
• The Fishes • The first vertebrates were jawless fish• Most modern fishes have jaws • Sharks and their relatives are jawed fishes with a
cartilage skeleton • Ray-finned fishes and lobe-finned fishes are jawed
bony fishes • Ray-finned fishes are the most diverse vertebrate
group
ANIMATION: Jawless Fishes
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ANIMATION: Evolution of Jaws
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ANIMATION: Cartilaginous Fishes
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