vertebrates vertebrate survey anatomy and physiology of vertebrates
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Vertebrates
Vertebrate SurveyAnatomy and Physiology of
Vertebrates
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
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
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
Class Chondrichthyes
Cartilaginous fish Ex. Sharks, skates, rays Skeletons made of cartilage Some are fearsome predators, other
eat small fish, mollusks, or plankton
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
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
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)
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
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
Class Aves (Birds)
Only vertebrates with feathers Used for flight and conservation of
body heat Lay eggs
Class Mammalia (mammals)
Named for presence of mammary glands, enable females to nourish young with milk
Have hair to retain body heat
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)
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
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
Feeding and Digestion
Adaptations are present in teeth Meat requires teeth that hold, shred Plants require teeth that
grind/pulverize
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
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
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
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
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
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
Internal Transport
Closed circulatory systems Two types: single-loop and double
loop
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)
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)
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
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
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
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
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)
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
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
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)
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
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
Reproduction
Amniotic egg also has a shell for protection and allows for gas exchange
Important step in evolution – no water necessary
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
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)