1. Ch 25 Vertebrate Diversity 25.1 Vertebrate Origins
Chordates share four features at some stage of development.
notochord
hollow nerve cord
pharyngeal slits
tail
Most chordates lose some or all of these characteristics in adulthood.

2. An endoskeleton allows vertebrates to grow to large sizes.
internal
made of bone or cartilage
An endoskeleton can be divided into four parts
braincase (cranium)
Vertebrae
Bones
gill arches (in fish and some amphibians)

3. There are seven classes of vertebrates.
Agnatha are jawless fish.
Cartilaginous and bony fish are characterized by the presence of jaws.
Amphibians are characterized by the presence of four limbs.
Reptiles, birds, and mammals are characterized by the presence of an amnion.
Birds are characterized by the presence of feathers.
Mammals are characterized by the presence of hair.

5. Tunicates may be the closest relatives to vertebrates.
The first recognizable vertebrates were jawless fish.
Two groups of jawless fish still exist today.
Lampreys
hagfish

6. 25.2 Fish Diversity Dominant verts are fish Have gills and paired fins
Fish use specialized organs called gills to breathe underwater.
sheets of thick, frilly tissue filled with capillaries
take in dissolved oxygen from water, release carbon dioxide
water
flow

7. Fins are surfaces that project from a fish’s body.
Countercurrent flow is the opposite movement of water against the flow of blood in the fish’s gills.
Fins are surfaces that project from a fish’s body.
keep fish stable
redirect water around fish as it swims
help fish maneuver in water
All fish have a lateral line system.
sensory system
sensitive to small changes in water movement

8. Jaws developed from gill arches located around the pharynx.
Jaws gave vertebrates a huge advantage as predators.
Cartilaginous fish and bony fish are still in existence.
Cartilaginous fish have skeletons made of cartilage.

9. Cartilaginous fish include the Holocephali and Elasmobranchs.
Holocephali include ratfish, a small group of deep-sea fish.
Elasmobranchs include sharks, rays, and skates.

10. Bony fish have skeletons made of bone.
operculum protects a bony fish’s gills
movements of operculum help bony fish move water over gills

11. 25.3 A closer look at boney fishes
Ray-finned fish have fins supported by a fan-shaped array of bones.
embedded in a thin layer of skin and connective tissue
light, collapsible, and easy to move
Ray-finned fish have a variety of body plans.
long torpedo-shaped bodies (barracuda)

12. Ray-finned fish have a variety of body plans.
flattened bodies (plaice)
elaborate camouflage (sea dragon)
A swim bladder helps a fish float higher or lower in the water.

13. Some ray-finned fish have both lungs and gills.
can breathe air and survive out of water for several hours at a time
example: bichir found in West Africa
Lobe-fins are paired pectoral and pelvic fins that are round in shape.
not as maneuverable as ray-fins
able to support weight

14. Only seven species of lobe-finned fish exist today.
Coelacanths
lungfish

15. 25.4 Amphibians Tetrapods are vertebrates that have four limbs.
Vertebrates that lack four limbs evolved from limbed ancestors.
Amphibians are animals that can live both on land and in water.

16. A number of adaptations allow amphibians to live on land.
large shoulder and hip bones
mobile, muscular tongue
middle ear
breathe through skin or with gills or lungs

17. Amphibians use many strategies to keep their eggs wet.
lay eggs directly in water
lay eggs on moist ground
wrap eggs in leaves
brood eggs in pockets on the female’s back
Tadpoles are aquatic larvae of frogs.
During metamorphosis, tadpoles develop into their adult form.
Not all amphibians undergo metamorphosis.

18. Amphibians are divided into 3 groups
Salamanders have a long body, four walking limbs, and a tail.
There are over 300 species of salamanders.
Frogs are the largest amphibian group and include toads.
There are over 3000 species of frogs.
Glands in the skin of frogs and toads contain poisons that help to protect them from predators.
Caecilians are legless, burrowing, tropical amphibians.
There are 160 species of caecilians.

19. 25.5 Vertebrates on land
Reptiles, birds, and mammals are adapted for life on land.
Amniotes are specialized to maintain moisture.
An amniote develops inside a thin, tough, membranous sac as an embryo or fetus.
Amnion Protects and surrounds the embryo

20. Several characteristics help amniotes prevent water loss.
keratin forms a hydrophobic layer
larger size of kidneys and intestines increases water absorption
The amniotic egg is an almost completely waterproof container.
prevents embryo from drying out as it develops
each egg represents a large investment of energy

21. Not all amniotes lay eggs.
reptiles such as garter snakes retain their eggs
most mammals develop inside the mother’s reproductive tract
The placenta is a membranous organ that develops in female mammals during pregnancy.
lines the uterine wall and partially envelops the fetus
carries nutrients from mother to embryo and removes wastes