The Vertebrate Genealogy Chapter 30. What is a chordate? There are 4 anatomical structures that...
-
Upload
bertram-parks -
Category
Documents
-
view
216 -
download
0
Transcript of The Vertebrate Genealogy Chapter 30. What is a chordate? There are 4 anatomical structures that...
The Vertebrate Genealogy
Chapter 30
What is a chordate?
There are 4 anatomical structures that appear during some point during the animal’s lifetime:1. Notochord – long flexible tube between the
gut and the nerve cord - becomes gelatinous material between vertebrae in humans
2. Dorsal, hollow nerve cord – becomes CNS 3. Pharyngeal slits
4. Muscular postanal tail – most chordates have a tail that extends beyond the anus
What is a chordate?
Survey of Vertebrate Classes
Fishes: Agnatha, Chondrichthyes, Osteichthyes
Tetrapods: Amphibia, Reptilia, Aves, Mammalia
Amniotes: Reptilia, Aves, Mammalia Have a shelled water-retaining egg
Class Agnatha
Sample organisms: Hagfishes, lampreys
Jawless vertebrates Feed by sucking blood
after clamping onto prey or by scavenging
Do not have paired appendages
Class Chondrichthyes
Sample organisms: sharks and rays
Cartilaginous fishes – have relatively flexible skeletons made of cartilage rather than bone
Most sharks are carnivorous and have acute senses
Class Osteichthyes Bony fishes
Have hard skeletons (due to ossification)
Sample organisms: perch, trout Breathe by drawing water over 4-5
pairs of gills covered by operculum (protective flap)
Most bony fishes are oviparous Females lays large numbers of
eggs, fertilization occurs externally
Class Osteichthyes
Class Amphibia The first vertebrates
(tetrapods) on land Amphibians must deposit
their shell-less eggs in water
Sample organisms: frogs & salamanders
Amphibian = “two lives” Tadpole – larval stage Metamorphosis occurs Frog – legs develop
Salamanders – have tails Frogs – do not have tails
The Amniotic Egg The amniotic egg is a
reproductive adaptation that allowed terrestrial vertebrates to complete their life cycles on land
The shell prevents the egg from drying out
4 layers of protection: Amnion – prevents
dehydration, cushions shocks Yolk Sac – stockpile of
nutrients Allantois – disposal sac for
certain metabolic wastes Chorion – gas exchange
Class Reptilia Sample organisms: lizards,
snakes, turtles, crocodiles Reptiles have scales made of
keratin that cover their skin Obtain oxygen with their lungs Fertilization occurs internally
Most reptiles lay amniotic eggs on land
Ectotherms – body temperature fluctuates with the environment
Class Aves
Birds are tetrapods with feathers
Their forelimbs are modified as wings
Sample organisms: owl, sparrow, penguin, eagles
Lay amniotic eggs Endothermic – regulate their
own body temps. Anatomy adapted for flight
Form & function
Class Mammalia Mammals have hair Endothermic Mammary glands that produce milk Most mammals are born, not hatched Three major groups:
Monotremes – lay eggs platypuses, echidnas
Marsupials – complete development in a maternal pouch Kangaroos, koalas, opossums
Placental mammals – complete development within the uterus, joined to the mother by the placenta Sheep, bats, elephants, humans
Paleoanthropology
Paleoanthropology is the study of human origins and evolution
Correcting misconceptions: “Let’s first dispose of the myth that our ancestors
were chimpanzees or any other modern apes. Chimpanzees and humans represent two divergent branches of the anthropoid tree that evolved from a common, less-specialized ancestor.”
Paleoanthropology 1974 – Ethiopia
“Lucy” is an Australopithecus skeleton
3.18 million years old Homo habilis
2.5 million years ago Enlargement of the human
brain Homo erectus
First hominid to migrate out of Africa into Asia and Europe
Taller than H. habilis and a larger brain capacity
Paleoanthropology
2 models of how Homo sapiens evolved
To think about…
“Of the many crises in the history of life, the impact of one species, Homo sapiens, is the latest and potentially the most devastating.”
- Neil Campbell, 4th ed.