Fish, Amphibians, Reptiles
Chordates
• Four characteristics present at some stages of
their development
– Notochord- extends along upper part of body for
support
– Postnatal tail- muscular structure at end of
developing chordates
– Nerve cord- develops into the brain and spinal
cord
– Pharyngeal pouches- found in region between
mouth and digestive tube
Vertebrates
• Have all chordate characteristics but
additionally
• Have endoskeleton, and part of it is stack of
vertebrae and cartilage
• Either cold blooded ectotherms or warmblooded endotherms
Fish
• Ectotherms with streamline shape, muscular
tail, fins, and scales
• Exchange carbon dioxide and oxygen through
gills
• Reproduce sexually, either external or internal
fertilization
Types of Fish
cartilaginous
• Skeletons made of cartilage,
movable jaws with well
developed teeth, and tiny
scales that make their skin
feel like fine sandpaper
Bony fish
• Skeletons of bone
• Swim bladder that inflates
or deflates
• About 95% of all fish
Amphibians
• Ectotherms that engage in hibernation in cold
weather and estivation in hot weather
• Some breathe through skin, others have small
lungs
• Need water for reproduction because eggs
fertilized externally
• Most go through metamorphosis
• Frogs, toads, newts, salamanders
Reptiles
• Ectotherms with thick, dry, waterproof skin
covered with scales.
• Breathe with lungs
• Internal fertilization and lay eggs with shells.
– Amniotic egg provides a complete environment
for embryo’s development
Three Reptile Groups
• Lizards and snakes have jaws that unhinge so
they can swallow their prey whole
• Turtles have two part shell made of hard, bony
plates that protects against predators
• Crocodilians are lizard shaped with large, deep
scales on their backs
– Crocodiles have narrow head with triangular shaped
snout while alligators have broad head with rounded
snout. Gavials have slender snout with large bump on
the end
– Among few reptiles that care for young
Birds
• All have feathers and scales and lay eggs
• Bird eggs
– Shell made of calcium carbonate
– Clutch- group of eggs laid by female bird
– Parent incubates egg to keep warm until it hatches
Flight Adaptations
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Lightweight, strong skeleton
Wings
Feathers
Strong flight muscles
Efficient respiratory system
Well-developed senses
Bird Features
• Bones are hollow to be lighter
• Feathers
– Contour feathers give birds their coloring and
smooth shape. Used for flight
– Down feathers provide birds with an insulating
layer to keep them warm
– Preening is a process where birds rub oil on its
feathers to condition them
Wings
• Move up down, back
forth
• Shape provides upward
push called lift for flight
• Also can be used for
swimming and balance
Importance
• Food source, pets, pest control, flower
pollinators, seed dispersers
• Evolved from reptiles
– Archaeopteryx oldest bird fossil found
Mammals
• Have hair and produce milk for young
• Skin and glands
– Skin produces fur or hair, horns, claws, nails, or hooves
– Mammary glands make milk for feeding young
– Oil, sweat, scent glands, too
• Hair
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Keeps mammals warm
Whiskers help animals sense their environment
Blubber- how animals with no hair keep warm
Quills and spines are modified hairs that protect animals
from predators
Teeth
• Incisors, premolars,
canines, and molars
• Omnivores have all
types of teeth
• Carnivores have large
canine teeth for eating
meat
• Herbivores have
premolar and molar
teeth to eat plants
Reproduction
• All mammals produce sexually
• Most mammals give birth to live young
• Young feed on milk while learning survival
skills
Types of Mammals
• Monotremes- lay eggs and have no nipples on
mammary glands
• Marsupials- give birth to immature young that
usually feed and develop in mother’s pouch
• Placentals- develop embryos inside mother’s
uterus
– Gestation period- amount of time embryo develops in
the uterus
– Placenta- organ inside uterus, absorbs oxygen and
food from mother’s blood
– Umbilical cord- how embryos connect to placenta
Monotremes
Marsupials
Placental
Mammal Importance
• Carnivores control populations of grazing
animals
• Mammals pollinate flowers and distribute
seeds
• First developed around 65 million years ago
when dinosaurs become extinct