Vertebrate Evolution and Diversity

1
Vertebrate Evolution and Diversity

• This chapter focuses on the origin and
  characteristics of Phylum Chordata with emphasis
  on the subphylum Vertebrata and its classes. One
  version chordate evolution is presented in your
  book. Fossil evidence and hypothesis about human
  ancestry are described.
• http//www.royalsoc.ac.uk/international/tadpole.h
  tm

2
Vertebrate Evolution and Diversity
3
Invertebrate Chordates and the Origin of
Vertebrates

• There are four anatomical feature that
  characterize chordates, many of which only appear
  during embryonic development.

• Notochord
• Dorsal, hollow nerve chord
• Pharyngeal slits
• Tail

4
Invertebrate Chordates Provide Clues to the
Origin of Vertebrates

• There are two subphyla of invertebrate chordates
• Urochordata
• Cephalochordata
• They are simpler version of vertebrates.

5
Introduction to the Vertebrates

• Four things that differentiate the vertebrates
  are
• Neural crest
• Significant neuralization
• Vertebral column
• Closed circulatory system

6
Superclass Agnatha Jawless Vertebrates

• Two extant classes
• Class Myxini also called hagfishses, are marine
  bottom-dwelling scavengers they possess no
  vertebrae and have a skeleton made of cartilage

7

• 2. Class Cephalaspidomorphi also called
  lampreys, live in marine and freshwater their
  rasping mouth bore holes in the side of a fish
  and they live on the blood and tissue of the
  host a cartilaginous pipe surround the
  notochord lampreys lack skeleton-supported jaws

8
Superclass Gnathostomata The FishesSuperclass
Gnathostomata II The Tetrapods - Amphibians

• The jaws of vertebrates
• evolved form the
• modification of skeletal
• parts that had once
• supported the
• pharyngeal gill slits.

• The skull of a gnathostome, or jawed vertebrates
  (here a shark), are characterized by vertically
  biting jaws (red) consisting of the
  palatoquadrate dorsally and the Meckelian
  cartilage ventrally. The gill arches (green) are
  situated internally to the gill filaments, and
  the nasal capsules (blue) open to the exterior by
  means of paired nostrils.

9
Class Chondrichtyes

• Have flexible
• endoskeletons composed
• of cartilage possess
• streamlined bodies are
• denser than water and will sink if they stop
  swimming
• Examples sharks and rays

10
Class Osteichthyes

• Bony fishes, are most numerous of vertebrate
  groups Have an ossified skeleton, are covered in
  scales, have an operculum and posses a swim
  bladder
• Three main classes
• Ray-finned
• Lobe-finned
• Lungfishes

11
Class Amphibia

• The oldest class of tetrapods maintain close
  ties with water and rely on their skin for gas
  exchange with the environment some have legs and
  some do not

12
Class Amphibia continued

• Some have a larval stage, like frogs, with a dual
  (aquatic and terrestrial) life
• Their eggs lack a shell, and fertilization is
  external.
• They can exhibit complex social behavior

Poison Arrow frogs receive their name because
South American Indians use toxic alkaloids
contained in the skin of certain species to
poison the tips of their blowgun darts when
hunting animals for use in religious ceremonies.
Most members of this family are brilliantly
colored, presumably as a warning to predators.
This species, Dendrobates auratus, is common in
the tropical forests of Panama and Costa Rica.
Smithsonian Tropical Research Institute Photo by
Marcos A. Guerra. (c) 1991 Smithsonian
Institution
13
The Amniotes

• The clade of Amniotes consists of mammals, birds,
  and reptiles.
• The amniotic egg was an important evolutionary
  development, expanding success on land.

14
The Amniotes continued

• Amniotic eggs have a shell that retains water and
  thus can laid in a dry environment.
• Amniotic eggs have extraembryonic membranes that
  function in gas exchange, waste storage, and the
  transport of nutrients to the embryo.

15
The Reptiles

• Reptiles have scales, which are an adaptation for
  terrestrial living. They obtain oxygen through
  their lungs, not their skin. Reptiles are
  ectotherms.
• They lay eggs on land, and undergo internal
  fertilization.

16
The Reptiles continued

• Ancient reptiles included dinosaurs (which lived
  on land) and pterosaurs (flying reptiles).
• Modern reptiles consist of
• Testudines (turtles)
• Sphenodontia (tuataras)
• Squamata (lizards and snakes)
• Crocodilia (alligators and crocodiles)

17
The Birds

• Birds lay amniotic eggs and have scales on their
  legs both of which are vaguely reptilian.
  Birds began as flying reptiles.
• Birds are endotherms and maintain a warm,
  consistent body temperature. Feathers, and in
  some cases, a layer of fat insulate birds and
  help them maintain an internal temperature.

18
The Birds continued

• Most birds bodies are constructed for flight,
  with light, hollow bones, relatively few organs,
  wings and feathers. Flightless birds are called
  ratites, and birds that fly are called carinates.

19
The Birds continued

• Birds have a four-chambered heart and a high
  rate of metabolism, and they have larger brains
  (compared proportionally) than reptiles do.

20
The Mammals

• Most or all mammals share certain
  characteristics.
• Mammary glands
• Hair
• Endothermic
• Born (not hatched)
• Internal fertilization
• Proportionally larger brains
• Teeth

21
The Mammals Three Groups

• Montremes egg-laying mammals that have hair
  and produce milk platypus, spiny anteaters

22
The Mammals Three Groups

• Marsupials are born early in development and
  complete embryonic development in a marsupian
  (pouch) while nursing wombats, Tasmanian devils,
  kangaroos.

23
The Mammals Three Groups

• Placental mammals have a longer period of
  pregnancy complete their development in the
  uterus deer mice, moles, flying squirrels,
  wolverines

24
Primates and the Phylogeny of Homo sapiens

• Characteristics common to all primates include
  hands and feet that grasp large brains and short
  jaws forward-looking eyes flat nails
  well-developed parental care and complex social
  behavior

25
Primate Subgroups

• Prosimii lemurs, lorises, pottos, tarsiers
• Anthropoidea monkeys, apes, and humans

26
Primates and the Phylogeny of Homo sapiens

• Primate evolution provides a context for
  understanding human evolution and origins.
• Humanity is very young.
• Some features of human evolution include
• Increased brain volume
• Shortening of the jaw
• Reduced size differences between the sexes
• Changes in family structure