Download CHAPTER 30 What is a chordate? An animal that has a dorsal

CHAPTER 30
What is a chordate? An animal that has a dorsal, hollow nerve cord, a notochord, pharyngeal pouches, and a tail that
extends beyond the anus. These characteristics are present during at least one stage of life.
Hollow nerve cord: runs along dorsal (back) of the body. Nerves branch from this cord to connect to internal organs,
muscles, and sense organs.
Notochord: Long supporting rod that runs through the body just below the nerve cord. Usually present only in embryos.
Pharyngeal pouches (gill slits): One pair in the throat region. Develop into gills in fish and amphibians.
Tail: Extends beyond the anus. Can contain muscle and bone and can be used for swimming.
In vertebrates, the dorsal hollow nerve cord is called the spinal cord. As the embryo develops, the front of the spinal cord
grows into a brain. The backbone, which replaces the notochord in most vertebrates, is made of individual segments
called vertebrae which support, enclose, and protect the spinal cord.
Nonvertebrate chordates do not have backbones. They are soft bodied marine animals.
-Subphylum Urochordata: Tunicates. Larval form has all chordate characteristics. Adult only has pharyngeal gill slits.
-Subphylum Cephalochordata: Lancelets. Have all chordate characteristics as an adult.
Fish are aquatic vertebrates in Subphylum Vertebrata- most have paired fins (movement), scales (protection), and gills
(respiration). Were the first vertebrates to evolve. Jaws (allowed for more varied food types) and paired fins (provided
more speed and accuracy of movement) were the most important evolutionary development.
Feeding: Every mode of feeding is found in fish. Herbivores, carnivores, omnivores, parasites, filter feeders, and
detritivores. Many have a fingered like structure called a pyloric cecum that is attached to the stomach and aids in
digestion.
Respiration: Most use gills. Gills are made up of many threadlike filaments, each containing a network of capillaries for
gas exchange. Bony fish have one gill opening. Sharks have many. Fish in oxygen poor areas have specialized organs
that act as lungs.
Circulation: Closed circulatory system. Most have a 4 chambered heart. Sinus venosus- thin walled sac that collects
blood from fishes veins before it flows into the atrium, a large muscular chamber that funnels blood into the ventricle,
which is the pumping portion of the heart that pumps blood to the bulbus arteriosus which connects to the aorta to send
blood to the gills.
Excretion: Nitrogenous waste= ammonia. Some diffuse across gills, others have kidneys. Kidneys also help control the
amount of water in a fish's body. Marine have a very concentrated urine, freshwater have a very dilute urine.
Movement: Contracting paired muscles along backbone to create a series of S shaped curves that move down the body,
and fins for direction and thrust. Bony fish have a gas filled swim bladder they can contract and relax to adjust buoyancy.
Response: Well developed nervous system and brain. Anterior end is olfactory bulbs for smell. Cerebrum which does all
voluntary responses in body. Optic lobe for sight. Cerebellum coordinates body movements. Medulla oblongata controls
internal organs. No ears, but "hear" vibrations (motion) via the lateral line.
Reproduction: Internal or external. Oviparous- eggs hatch outside the body. Ovoviviparous- eggs develop inside body and
have a yolk. live birth. Viviparous- Embryos do not have a yolk- get nourishment from mother's body and are born alive.
Groups of Fishes: 3 main groups- Jawless, cartilaginous, bony
-Jawless: Lamprey and hagfish. Lampreys are parasitic, sucking out tissues and body fluids of host. Hagfish feed on dead
and dying fish.
-Class Chondrichthyes- Cartilaginous skeleton. Sharks, skates, rays. Can be filter feeders or carnivorous. Carnivores can
replace their teeth- about 20,000 in a lifetime!
-Class Osteichthyes: Bony fish. Skeletons made of bone. Most have rayed fins- slender bony spines connected with a thin
layer of skin. Only 7 species do not have rayed fins. One is the coelacanth which have support bones in their fins- some
are jointed like in land vertebrates.
Amphibians- Class Amphibia. Vertebrate that lives in water as larvae (gills) and land as adult (lungs), has a moist skin, no
scales or claws. First amphibians probably resembled coelacanths. Could live on land because bones became stronger,
developed lungs with a protective bony sternum.
Feeding: Most larvae are filter feeders or herbivores. Most adults are carnivores. Digestive organs much like oursstomach, liver, pancreas, gall bladder, small/large intestines. At end of large intestines is a cavity called the cloaca where
feces, urine, and eggs/sperm leave the body.
Respiration: Larvae use skin and gills. Adults use lungs and/or skin.
Circulation: Closed, with a double loop- one for the lungs and skin and one for the rest of the body. 3 chambered heartleft atrium, right atrium, ventricle.
Excretion: Kidneys filter nitrogenous waste. Can be stored in a small bladder. Exits cloaca.
Movement: Larvae swim by wriggling tail. Adults have 4 limbs for jumping, crawling, or climbing.
Response: Well developed nervous system. Nictitating membrane (like a thin lid) keeps eye moist and protected.
Tympanic membranes for sound. Many have a lateral line system.
Reproduction: External fertilization. Eggs are laid in water and encased in a sticky jelly to keep predators from being able
to grab them. Hatch into tadpoles which undergo metamorphosis to adult, land dwelling form.
Groups of Amphibians:
-Order Urodela: Salamanders.
-Order Anura: Frogs & Toads. Frogs have longer legs for jumping and live near water. Toads have shorter legs for hopping
and can even live in deserts.
-Order Apoda- Caecilians. No legs and have fishlike scales.
Amphibian extinctions are occurring worldwide- even in pristine habitats. Possibly due to decreasing habitat, depletion of
the ozone layer, acid rain, water pollution, fungal infections, introduced aquatic predators, and increasing human
population.
CHAPTER 31
Reptiles: Class Reptilia. Lizards, Snakes, Turtles, Crocodiles, Alligators. Vertebrates with dry, scaly skin, lungs, and
terrestrial eggs. Most can live entire life out of water. Scaly, tough skin can not grow, must be shed.
Success on land= Well developed lungs, a double loop circulatory system, water conserving excretory system, strong
limbs, internal fertilization, and shelled, terrestrial eggs. Also, the ability to control body temperature. Reptiles are
ectotherms and rely on behavior to maintain body temperature. Lay in sun to warm up, shade/water to cool down.
Feeding: Herbivores are carnivores. Herbivores have very long digestive tracts to break down plant fibers. Snakes can
dislocate their jaws to eat prey much larger than their mouths and swallow it whole. Chameleons have a sticky tongue to
catch insects.
Respiration: Can not exchange gases through skin. Have very spongy lungs with lots of surface area. Crocodiles have
flaps to separate mouth from nasal passages so they can breathe thru their nostrils with mouth open.
Circulation: Double loop. Two atria with one or two ventricles (most have 1). Crocodiles/Alligators have most well
developed heart with 2 ventricles- like in birds and mammals.
Excretion: Urine produced in kidneys. Have a cloaca. Urine is either ammonia (aquatic) or uric acid (terrestrial). Uric acid
is highly concentrated and look like a pasty white solid. Conserves water.
Response: Those active during day have complex eyes and can see color well. Many snakes have good sense of smell.
Some have sensory organs on roof of mouth to detect chemicals when they flick their tongue. Simple ears.
Movement: Reptiles with legs can walk, run, burrow, swim, or climb.
Reproduction: Internal fertilization. Most are oviparous. Eggs have a shell with leathery membranes to protect it from
drying out. This is called an amniotic egg- named after one of the 4 membranes that surround the embryo. The other 3 are
the yolk sac (nourishment), chorion (gas exchange), and allantois (stores waste). This type of egg is one of the most
important adaptations to life on land.
Groups of Reptiles:
-Order Squamata: Lizards and Snakes. Most lizards have legs, clawed toes, external ears, and moveable eyelids. Snakes
have lost legs. Some produce venom.
-Order Crocodilia: Crocodiles and alligators. Very protective of young. Only live in tropics and subtropics. Crocodiles can
be in salt or fresh water- others only in fresh.
-Order Testudines: Turtles and Tortoises. Turtles are aquatic, tortoises are terrestrial. Shell built into skeleton and has 2
parts...dorsal= carapace, ventral= plastron. Backbone forms the center of the carapace.
Birds- Class Aves. Reptilelike animals that maintain a constant internal body temperature(endotherm). Outer covering of
feathers, two legs covered with scales, front limbs modified into wings. The most important characteristic that separates
birds from other animals is feathers- made of protein, help bird fly and stay warm.
-Feeding: Beaks are adapted to the type of food the bird eats. Highly developed digestive system. Have a crop to store
and moisten food. Some birds use the crop to create food that is regurgitated to feed babies. Insect/seed eaters have a
gizzard to grind up food. Many species put gravel in their gizzard to assist with grinding.
Respiration: Have unique respiration system- air is regulated in and out of the lungs by air sacs and breathing tubes,
making sure the lungs are only exposed to oxygen rich air. This one way flow helps birds maintain a high metabolism
needed for warmth and flight, and so they can breathe in high altitudes.
-Circulation: 4 chambered heart with 2 separate loops.
-Excretion: Similar to reptiles- uric acid.
-Response: Well developed brain and sense organs. Cerebrum controls flight, nesting, care of young, mating. Cerebellum
controls precise movements. Medulla oblongata coordinates body processes (heartbeat). Taste and smell not well
developed.
Movement: Vast majority fly. Airspaces in bones make them very lightweight.
Reproduction: Internal fertilization. Have amniotic eggs with hard outer shells. Chicks have a small tooth on the end of the
bill to break through the shell.
Groups of birds: Over 30 different orders! Largest are the passerines, or perching birds, with over 5000 species.