Class Reptilia
Reptiles lay eggs on land covered by a shell.
They have internal fertilization ( the male deposits sperm inside the female).
Their dry skin is hardened with keratin ( the same protein in hair, fingernails and a bird's beak).
Reptiles typically have a 3 chambered heart, except 4 chambers in crocodilians.
They have efficient lungs ( use negative pressure to fill lungs ). Reptiles have good sense organs : eyes, internal ears ( detect vibrations ), smell ( Jacobsons organs in snakes ),
pit vipers detect infra-red (heat).
Skulls : Anapsid ( no temporal openings ) eg turtles or Diapsid ( two temporal openings ) eg snakes.
Many turtle species are endangered, mainly due to over-harvesting:
Sea turtle
Order : Squamata (Snakes)
Less than 15% are venomous. Snakes evolved from tetrapods ( some still have a pelvis ). Fossil. Streamlined body : ovaries and kidneys lined up behind each other.
Male snakes have two penises.
Some such as sea snakes and boas are viviparous ( give birth to live young).
Order: Crocodilia ( crocodiles & alligators ).
They have a 4 chambered heart.
They have the most acid stomach of any animal to digest bone etc.
Integumentary sense organs ( ISO ) on skin detect pressure in water. Palatal valve keeps water out of the lungs when submerged.
Communicate using sound.
Communication
eg Alligator
Class Aves ( birds )
Evolved about 150 million years ago from reptiles (so they evolved more recently than mammals). Internal fertilization.
Birds have a Diapsid skull (two temporal openings).
They have feathers for flying and insulation. Light weight for flying:
hollow bones, no teeth, reduced number of internal organs eg only one ovary. Birds have a four chambered heart.
Very efficient lungs : air sacs keep air flowing in one direction through the lungs. Excellent sense organs especially the eyes.
Endothermic (warm blooded) so eat energy rich foods: seeds, insects, fruit etc. Good parental care of young, complex behavior.
Song eg Pandion ( osprey ).
Class Mammalia
Mammals evolved almost 200 million years ago, and although most of the early mammals were small (the size of rats), some were larger and preyed on small dinosaurs. Early mammals
Mammals, like birds, are endothermic ( hair for insulation ). They have a Synapsid skull (one temporal opening ).
Internal fertilization.
Subclass Prototheria ( monotremes )
Monotremes lay eggs.
Monotremes.
They feed their young on milk (but have no mammary gland or breast). Found only in New Guinea and Australia.
eg Platypus
Subclass Metatheria ( marsupials )
They give birth to undeveloped young and raise the young in a pouch ( marsupium ).
Thylacine
Marsupials evolved in the southern hemisphere (Australia and South America), but some have spread to North America.
eg Didelphis ( possum ).
Subclass Eutheria ( placental mammals )
Young develop in the womb, fed through the placenta.
Found worldwide.
Orders of placental mammals
Carnivora : carnivores,
long canine teeth, short digestive tract.
eg bears, cats, dogs, wolf ( Canis ).
Cetacea : Whales and dolphins: marine, intelligent, streamlined body.They have
front flippers, and no rear limbs ( but have a pelvis).
Right whales breed near Jacksonville.
Whales are either toothed whales, or baleen whales.
Whales communicate over long distances with sound.
eg Humpback whale ( Megaptera ).
Chiroptera : bats.
Flying, feed on insects or fruit.
Most use echolocation.
A change in a single gene allowed bats to grow wings. News
eg Seminole bat ( Lasiurus ).
Sirenia : slow moving aquatic herbivores.
Florida manatee
eg sea cows, manatees ( Trichechus ).
Primates :
The order Primates includes monkeys, apes and humans.
Oldest fossils about 60 million years ago.
Primates have binocular vision, opposable thumb ( for climbing ), large brain, usually one birth at a time.
Prosimians (the oldest primates ) include lemurs.
Lemurs
American monkeys ( prehensile tails, nostrils to the side ) separated from African monkeys ( nostrils open down ) about 40 million years ago.
Audio
Humans are most closely related to African apes.
Humans, chimps and gorillas separated about 6 million years ago.
Human evolution
The oldest human fossils are roughly 6 to 7 million years ago.
Fossil. Later (roughly 4 million to 2 million years ago) the genus Australopithecus evolved. It was only found in Africa, slightly larger than a modern chimp, but walked on two legs.
The genus Homo evolved about 2 million years ago. Homo habilis : used stone tools, was about 5ft tall, had a small brain, only found in Africa.
Homo habilis
Homo erectus : used tools and fire, roughly 6 ft tall, larger brain, spread from Africa to Asia and Europe.
Homo erectus. Modern humans and Homo erectus may have come into contact in Asia. Louse study
Homo neanderthalensis : largest brain of any human, buried their dead. They were hunters, living mainly on large mammals. They cooked their food.
DNA studies show that Neanderthals and Homo sapiens did not interbreed, even though they lived in the same areas.
DNA study.
In 2004 skeletons of a new species of human were found on Flores, Indonesia. They were smaller than pygmies, but hunted large mammals and cooked their food.
Homo floresiensis
Homo sapiens : spread worldwide, the only surviving human species.
skull Modern humans all come from a small population who moved out of Africa less than 100,000 years ago:
When humans faced extinction
Early humans were "hunter-gatherers" - in other words they hunted animals and collected fruit, berries and shellfish. Humans did not start growing crops until about 10,000 years ago.
Summary of Human evolution
Age of fossils
(Years ago) | Genus | Species | Location | Comments |
|---|
| 4 million to 2 million | Australopithecus | afarensis | Africa | Small brain, no tools, bipedal |
| 2.5 million to 1.5 million | Homo | habilis | Africa | Larger brain, tools, 4.5ft tall |
| 2.3 million to 30,000 | Homo | erectus | Africa, Asia, Europe | Used fire, 6ft tall |
| 130,000 to 30,000 | Homo | neanderthalensis | Africa, Asia, Europe | Largest brain, buried their dead |
| 100,000 to 12,000 | Homo | floresiensis | Flores island, Indonesia | Height 3ft, hunted, used fire |
| 150,000 to Present | Homo | sapiens | Worldwide | Only human to reach America |
Note that from about 100,000 years ago to 30,000 years ago, there were four different species of human on the planet.
Last edited November 2008 by David Byres, dbyres@fccj.edu