Biology 112
 A chordate is an animal with the following
four features:
 A hollow nerve cord that runs along the
back of the body
 A notochord is a support rod that runs
just below the nerve cord
 Pharyngeal pouches are paired
structures in the throat
 A tail that extends beyond the anus
 Most chordates are vertebrates
 Most have a backbone made up of
vertebrae
 The backbone replaces the notochord
and supports and protects the spinal
cord
 It also gives muscles a place to attach
 Tunicates
 Ocean-living filter feeders
 Have no notochord or tail
 As larva, they possess all the
characteristics of chordates
 Lancelets
 Small, fish-like animals
 Adults possess all four characteristics
 Have a definite head region
 Aquatic vertebrates
 Most have paired fins, scales and gills
 Jaws and paired fins marked an evolutionary turning
point for fish
 Jaws improved defense and expanded food choices
 Paired fins improved controlled movement
 In order to survive in water, special adaptations
include:
 Various modes of feeding
 Specialized structures for gas exchange
 Paired fins for locomotion
 May be herbivores,
carnivores, parasites,
filter feeders, or detritus
feeders
 One fish may feed in
many different ways,
depending on the food
available
 Most fish breathe with gills
 Gills have many tiny blood
vessels that provide a large
surface area for gas
exchange
 Fish pull water into their
mouths
 Water moves over the gills
and out of the body
through openings in the
sides of the pharnyx
 Fish have a closed
circulation system
 It pumps blood in a loop
from its heart to gills to
the body and then back
to the heart
 The heart consists of two
chambers: an atrium and
a ventricle
 Most fish get rid of
wastes as ammonia
 Some diffuse wastes
through the gills into the
water
 Others remove wastes
from the blood through
the kidneys
 Kidneys help control the
amount of water in their
bodies
 Well developed with a




brain housing several parts
Cerebrum responsible for
smell
Cerebellum coordinates
movement
Medulla oblongata
controls internal organs
A lateral line system
senses currents and
vibrations in the water
 Most move by
contracting muscles on
either side of the
backbone
 Fins pull the fish forward
and help it steer
 Many have a gas-filled
organ called a swim
bladder that prevents its
from sinking
 Eggs may be fertilized internally or externally
 Oviparous fish
 Lay eggs
 Eggs develop and hatch outside the mother’s body
 Ovoviviparous fish
 Develop eggs inside the mother
 Egg provides food to the young while inside mother
 Young are born alive
 Viviparous fish
 Mother provides food to the young while inside mother
 Young are born alive
 Jawless fish




Lampreys and hagfish
Bodies are supported by a notochord
Do not have true teeth or jaws
Parasites and scavengers
 Cartilaginous fish
 Sharks, rays and skates
 Have a skeleton made of cartilage
 Most have tooth-like scales covering their bodies
 Bony fish
 Skeletons made of bone
 Most are ray-finned fishes
 Fins have thin, bony spines that are joined by a thin layer of
skin
 Vertebrates that live mostly in aquatic environments as
a larva and on land as an adult
 As adults, breath with lungs, have moist skin that
contains mucous glands and lack scales and claws
 In order for amphibians to adapt to living on land,
from an evolutionary standpoint:
 Bones became stronger
 Lungs and breathing tubes developed
 The breastbone (sternum) developed a bony shield to
support organs
 As larvae, they are filter feeders or herbivores; adults






are carnivores
Gas exchange occurs through skin and gills (larvae)
and lungs (adults)
Adults have three heart chambers; circulation is a
double loop system
Kidneys remove wastes from blood
Eggs are laid in water and then the male fertilizes
them
Eggs hatch into larvae, called tadpoles
They have good vision and can sense sound vibrations
 Salamanders
 Long bodies, four legs and long tails
 Frogs and Toads
 Do not have tails and can jump
 Frogs live close to water, toads live in moist wooded
areas
 Caecilians
 Do not have legs
 Live in water or burrow in moist soil