Transcript The Vertebrate Genealogy

The Vertebrate
Genealogy
Chapter 30
What is a chordate?
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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
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Fishes: Agnatha, Chondrichthyes,
Osteichthyes
Tetrapods: Amphibia, Reptilia, Aves,
Mammalia
Amniotes: Reptilia, Aves, Mammalia
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Have a shelled water-retaining egg
Class Agnatha
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Sample organisms:
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Hagfishes, lampreys
Jawless vertebrates
Feed by sucking blood
after clamping onto
prey or by scavenging
Do not have paired
appendages
Class Chondrichthyes
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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
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Bony fishes
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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
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Females lays large numbers of
eggs, fertilization occurs externally
Class Osteichthyes
Class Amphibia
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The first vertebrates
(tetrapods) on land
Amphibians must deposit
their shell-less eggs in
water
Sample organisms: frogs &
salamanders
Amphibian = “two lives”
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Tadpole – larval stage
Metamorphosis occurs
Frog – legs develop
Salamanders – have tails
Frogs – do not have tails
The Amniotic Egg
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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:
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Amnion – prevents
dehydration, cushions shocks
Yolk Sac – stockpile of
nutrients
Allantois – disposal sac for
certain metabolic wastes
Chorion – gas exchange
Class Reptilia
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Sample organisms: lizards,
snakes, turtles, crocodiles
Reptiles have scales made of
keratin that cover their skin
Obtain oxygen with their lungs
Fertilization occurs internally
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Most reptiles lay amniotic eggs
on land
Ectotherms – body
temperature fluctuates with the
environment
Class Aves
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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
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Form & function
Class Mammalia
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Mammals have hair
Endothermic
Mammary glands that produce milk
Most mammals are born, not hatched
Three major groups:
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Monotremes – lay eggs
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Marsupials – complete development
in a maternal pouch
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platypuses, echidnas
Kangaroos, koalas, opossums
Placental mammals – complete
development within the uterus, joined
to the mother by the placenta
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Sheep, bats, elephants, humans
Paleoanthropology
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Paleoanthropology is the study of human
origins and evolution
Correcting misconceptions:
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“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
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1974 – Ethiopia
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Homo habilis
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“Lucy” is an
Australopithecus skeleton
3.18 million years old
2.5 million years ago
Enlargement of the human
brain
Homo erectus
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First hominid to migrate out
of Africa into Asia and
Europe
Taller than H. habilis and a
larger brain capacity
Paleoanthropology
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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.