1) Vertebrates evolved from early chordates like tunicates and lancelets. Fossils show the progression of vertebrate evolution over time. 2) Chordates are defined by four key features - a dorsal nerve cord, notochord, pharyngeal slits, and postanal tail. These features are present in vertebrate embryos and some persist in adults. 3) Vertebrates are classified into groups like fish, amphibians, reptiles, birds, and mammals based on shared characteristics.

1. ORIGEN
AND
CLASSIFICATION OF
VERTEBRATES
Essam Eldin Abdelhady Salama

2. Origen of vertebrates
• The efforts of vertebrate paleontologists to discover
countless fossils.
• These fossils tell us where the living vertebrates had come
from
• They show us views of the different areas of the worlds

3. Con.
• Vertebrates are a
minor twig on
the ‘Universal
Tree of Life’.

4. Con.
• Molecular studies through the 1990s showed that previous
conceptions of the tree were wrong, and that the
fundamental splits in the tree of life were all among Bacteria,
separating the two major groups Bacteria and Archaea.
• Modern studies confirm that a major clade within Metazoa,
the animals, is supported by both morphological and
molecular evidence.

5. Con.
• The familiar plants, animals and fungi are part of Eukaryotes,
the major group characterized by complex cells with a
nucleus,
• Examination of living animals;
• The vertebrates are members of a larger group, termed the
Phylum Chordata, and their closest living relatives
• Vertebrates are all the animals with backbones, the fishes,
amphibians, reptiles, birds, and mammals.

6. Classification

8. PHYLUM CHORDATA
• PHYLUM CHORDATA
• Subphylum I. Urochordata or Tunicata, the tunicates or sea squirts.
Subphylum II. Cephalochordata or Acranla, Amphioxus and its allies:
Subphylum III. Vertebrata or Craniata, all chordates with an
endoskeleton of cartilage or bone or a combination of these.

9. Vertebrate Classification
• All animals are consumers; that means that they do not
make their own food. They need to eat other living things in
order to survive.
• Animals that eat meat are carnivores (kahr-nuh-vohrs).
• Some animals only eat plants. They are herbivores (hur-buh-
vohr).
• Some animals eat both plants and animals. They are
omnivores (om-nuh-vawrs).

10. CHORDATES
• Four features characterize the chordates and have played an
important role in the evolution of the phylum
• 1. A single, hollow nerve cord runs just beneath the dorsal
surface of the animal. In vertebrates, the dorsal nerve cord
differentiates into the brain and spinal cord.

11. • 2. A flexible rod, the notochord, forms on the dorsal side of
the primitive gut in the early embryo and is present at some
developmental stage in all chordates.
• The notochord is located just below the nerve cord. The
notochord may persist throughout the life cycle of some
chordates or be displaced during embryological
development as in most vertebrates by the vertebral column
that forms around the nerve cord.

12. Con.
• 3. Pharyngeal slits connect the pharynx, a muscular tube
that links the mouth cavity and the esophagus, with the
outside. In terrestrial vertebrates, the slits do not actually
connect to the outside and are better termed pharyngeal
pouches. Pharyngeal pouches are present in the embryos of
all vertebrates. They become slits, open to the outside in
animals with gills, but disappear in those lacking gills. The
presence of these structures in all vertebrate embryos
provides evidence to their aquatic ancestry.

13. • 4. Chordates have a postanal tail that extends beyond the
anus, at least during their embryonic development. Nearly all
other animals have a terminal anus.

14. • All chordates have all four of these characteristics at some
time in their lives. For example, humans have pharyngeal
slits, a dorsal nerve cord, and a notochord as embryos.
• As adults, the nerve cord remains while the notochord is
replaced by the vertebral column and all but one pair of
pharyngeal slits are lost. This remaining pair forms the
Eustachian tubes that connect the throat to the middle ear.

15. Nonvertebrate chordates have a notochord but no backbone
Tunicates
The tunicates (subphylum
Urochordata) are a group of
about 1250 species of marine
animals.
Most of them are sessile as
adults, the larvae having a
notochord and nerve cord.

16. Con.
The adults exhibit neither a
major body cavity nor visible
signs of segmentation.
The pharynx is lined with
numerous cilia, and the animals
obtain their food by ciliary
action. The cilia beat, drawing a
stream of water into the
pharynx, where microscopic
food particles are trapped in a
mucous sheet

17. Lancelets (Amphioxus)
Lancelets are scale less, fishlike
marine chordates a few centimeters
long that occur widely in shallow
water, partly buried, throughout the
oceans of the world.
The notochord runs the entire length
of the dorsal nerve cord and persists
throughout the animal’s life.

18. Con.
Lancelets have many more
pharyngeal gill slits
Lancelets feed on microscopic
plankton, using a current created by
beating cilia that lines the oral hood,
pharynx, and gill slits, they provide
an exit for the water and are an
adaptation for filter feeding.