Vertebrates

1. Vertebrates Vertebrate Survey Anatomy and Physiology of Vertebrates

2. Vertebrate Evolution • Phylum Chordata is the group of animals with a notochord – a flexible, supporting structure along the back • Contains the invertebrate chordates, and Subphylum Vertebrata, which have evolved vertebral columns • Serves as site for muscle attachment, protects nerve cord

3. Trends in Vertebrate Evolution • Development of true bony jaws • Development of paired pectoral and pelvic limb girdles • Development of bones • Most vertebrates have two sets of appendages (arms and legs), a closed circulatory system with a ventral heart, and either gills or lungs for breathing

4. Class Agnatha • Jawless fish • Ex. Lampreys and hagfishes • Only living vertebrates without jaws • Parasites – survive by attaching themselves to other fish or aquatic animals, feeding on their blood and body fluids • Scavengers – eat decaying carcasses

5. Class Chondrichthyes • Cartilaginous fish • Ex. Sharks, skates, rays • Skeletons made of cartilage • Some are fearsome predators, other eat small fish, mollusks, or plankton

6. Class Osteichthyes • Bony fish • Contain half of all vertebrate species, all aquatic habitats • Ray-finned fish – sub-class containing almost all fish species – well-developed bone systems, specialized jaws with teeth • Lobe-finned fish – sub-class with lungs and gills, relatives of amphibians

7. Class Amphibia (amphibians) • Lay eggs in water and spend part of their life cycle there (gills) • As adults, live on land and breathe through lungs • Most have moist skin, as part of their respiration occurs through skin

8. Class Amphibia • Examples include: • Newts and salamanders (lay eggs in water, hatch into young that resemble adults – larvae have gills that disappear and are replaced by lungs as they grow) • Frogs and toads (eggs hatch in water as tadpoles, which look completely different from adults)

9. Class Reptilia (reptiles) • Fully terrestrial • Reproduce by internal fertilization – egg/sperm fuse within body of the female • Produce leathery eggs to prevent water loss • Dry scaly skin to retain moisture • Developed lungs

10. Class Reptilia • Order Chelonia – turtles and tortoises, protective shell of bony plates (long fossil record) • Order Crocodilia – crocodiles, alligators, caimans (long fossil record) • Order Squamata – lizards and snakes, most abundant group

11. Class Aves (Birds) • Only vertebrates with feathers • Used for flight and conservation of body heat • Lay eggs

12. Class Mammalia (mammals) • Named for presence of mammary glands, enable females to nourish young with milk • Have hair to retain body heat

13. Class Mammalia • Three groups: • Monotremes – egg-laying mammals like duck-billed platypus – have body hair/fur, lay leathery eggs • Marsupials – live young born very early in their development and continue to develop within marsupium – kangaroos, koalas, opossums • Placental mammals – largest group, names for placenta (organ that connects mother with developing embryo, allows for nutrient, gas, and waste exchange)

14. Support and Movement • All have an endoskeleton surrounded by muscles and skin • Vertebral column (backbone) is the main part of the skeleton • Adapting to life on land led to changes in limb positions • Amphibians had limbs that are horizontal while reptile limbs are vertical to support increased body mass

15. Feeding and Digestion • All food sources presented problems as vertebrates evolved • Meat is easy to digest, but must first be caught then cut up for swallowing • Plant matter is easy to find, but must be pulverized and shredded before swallowing, and cellulose is hard to digest

16. Feeding and Digestion • Adaptations are present in teeth • Meat requires teeth that hold, shred • Plants require teeth that grind/pulverize

17. Feeding and Digestion • Adaptations seen in digestive tracts • Meat digests easily, so carnivores have short digestive tracts that secrete enzymes to break down proteins • Plants need to be broken down slowly, so herbivores spend more time chewing/rechewing, and long digestive tracts full on bacteria help digest cellulose

18. Respiration (gas exchange) • Method/system depends on environment • Fish rely on gills for respiration • Amphibians have gills as tadpoles and poorly developed lungs as adults • No muscles to inflate/deflate lungs • Rely on diffusion through thin, moist skin

19. Respiration (gas exchange) • Reptiles are fully adapted to life on land and have more developed lungs that are divided into chambers to increase surface area • Reptiles also have muscles to inflate/deflate lungs

20. Respiration (gas exchange) • Mammals require higher rate of gas exchange because of higher metabolic rate • Most developed lungs • Bronchi (air tubes) enter lungs then branch to create more surface area, ending in alveoli

21. Respiration (gas exchange) • Alveoli are bubblelike structures surrounded in capillaries • Efficient at gas exchange, but inefficient because air must move in and out through the same passageway

22. Respiration (gas exchange) • Birds have highest requirements for lung efficiency because they fly • Have branched bronchi and alveoli like mammals, but also have air sacs within some bones • Air is pumped in one direction

23. Internal Transport • Closed circulatory systems • Two types: single-loop and double loop

24. Internal Transport • Single-loop circulatory systems are found in fish – blood is pumped from the heart to the gills where respiration takes place, then flows from the gills to the rest of the body, returning to the heart • Heart has two chambers – one atrium (receives) and one ventricle (pumps)

25. Internal Transport • Vertebrates with lungs have a double-loop circulatory system • First loop carries blood between the heart and lungs (pulmonary) • Second loop carries blood between the heart and the rest of the body (systemic)

26. Internal Transport • Amphibians and reptiles have a three-chambered heart – two atria and one ventricle • Birds and mammals have a four-chambered heart – two atria and two ventricles

27. Temperature Control • Vertebrates need to control their body temperature because chemical reactions operate differently at various temperatures • Need a way to heat the body, conserve that heat, and eliminate excess heat

28. Temperature Control • Fish, amphibians, and reptiles are ectothermic because they rely on interactions with their environment to control body temperature • Lay in sun to warm themselves, stay in shade or burrow to cool down

29. Temperature Control • Mammals and birds are endothermic because they generate heat in body tissues through chemical reactions in the body • Also have layers of fat and fur/feathers to conserve heat • Shivering generates more heat, panting or sweating dissipates heat

30. Excretion • Elimination of nitrogen-containing wastes linked to maintaining water balance • Aquatic vertebrates get rid of ammonia by diffusion (fish through gills, amphibians through skin) • They also have the beginnings of a kidney (primitive, gets more complex)

31. Excretion • Mammalian kidney most complex • Use the conversion to urea and uric acid and concentration to conserve water • Urea eliminated in urine, uric acid in solid waste

32. Response • All vertebrates are cephalized • Bundle of nerves and neural connections in head called the brain, and the long, thick collection of nerves running down the back is the spinal cord • Spinal cord protected by vertebral column

33. Response • Pairs of nerves run out between individual vertebrae to connect muscles, organs, and sensory receptors around the body • More complex behavior means more complex brain • All vertebrates have a cerebrum (thinking) and cerebellum (balance, coordination, movement)

34. Reproduction • All vertebrates reproduce sexually • Fish and amphibians have external fertilization • Female lays thousands of eggs in water, male deposits sperm • Young develop and hatch in water

35. Reproduction • Reptiles, birds, and mammals have internal fertilization (inside female) • Fewer eggs are produced • Developing embryo is nourished inside the egg by a yolk (food) and wrapped in membranes (called the amniotic egg) • Membranes bathe embryo in liquid and receive and store wastes

36. Reproduction • Amniotic egg also has a shell for protection and allows for gas exchange • Important step in evolution – no water necessary

37. Reproduction • How eggs are handled is different amongst vertebrates • Oviparous animals lay their eggs, and the embryo completes its development and hatches outside of the female’s body

38. Reproduction • Ovoviviparous animals keep their eggs inside the body until the embryo fully develops and hatches • Viviparous animals have eggs with very little yolk (if at all) because the female nourishes the embryo internally for a long period of time, and the young are born alive (do not hatch)