An introduction to animal diversity

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An introduction to animal diversity

• BY Carlos Paez

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OVERWIEW

• WE WILL BE LEARNING ABOUT THE ANIMAL KINGDOM THAT
  GOES BEYOND HUMANS AND WE WILL ALSO LEARN ABOUT
  ANIMAL DIVERSITY WHICH IS THE DIFFERENCE OR
  VARIETY OF ANIMALS.

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NUTRITIONAL MODE

• Animals differ from both plants and fungi in
  their mode of nutrition plants create food and
  unlike plants animals cannot construct all of
  their own organic molecules and so in most cases
  they ingest them either by eating other living
  organisms or by eating nonliving organic
  material.

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REPRODUCTION AND DEVELOPMENT

• Cleavage- a succession of mitotic cell divisions
  without cell growth between division cycles.
• Blastula-During the development of most animals
  cleavage leads to the formation of a
  multicellular stage known as this
• Gastrulation- in this process layers of embryonic
  tissues that will develop into adult body parts
  are produced.

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CONTINUATION

• Gastrula- after the gastrulation the resulting
  developmental stage is known as the gastrula.
• Larva- a sexually immature form of an animal that
  is morphologically distinct from the adult stage
• Metamorphosis- a resurgence of development that
  transforms the animal into an adult.

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NEOPROTEROZOIC ERA

• Despite the molecular data indicating a much
  earlier origin of animals the first generally
  accepted fossils of animals are only 575 million
  years old. These fossils are known collectively
  as the Ediacaran Fauna named for the Ediacara
  Hills of Australia where they first discovered
  the fossil in figure 32.5 and similar fossils
  have since been found on other continents

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PALEZOIC ERA

• Animal diversification appears to have
  accelerated dramatically between 542 and 525
  million years ago, early in the Cambrian period
  of the Paleozoic Era a phenomenon often referred
  to as the Cambrian Explosion. In strata formed
  before the explosion only a few animal phyla can
  be recognized.

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BODY PLANS AND GRADES

• One way in which zoologists categorize the
  diversity of animals is according to general
  features of morphology and development. A group
  of animal species that share the same level of
  organizational complexity is known as a grade
• The set of morphological and developmental traits
  that define a grade are generally integrated into
  a functional whole referred to as a body plan

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SYMMETRY

• Radial symmetry- is symmetry that radiates from
  the center and any imaginary slice through the
  central axes divides the object into mirror
  images.
• Bilateral symmetry- only one imaginary cut
  divides the object into mirror-image halves.

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BILATERAL ANIMALS

• Dorsal- the top side of a bilateral animal
• Ventral- the bottom side.
• Anterior- the head of the animal
• Posterior- is the tail of the animal

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TISSUES

• The germ layers form the various tissues and
  organs of the body and ECTODERM which is the germ
  layer covering the embryo which gives rise to the
  outer covering of the animal. The ENDODERM which
  is the intermost germ layer lines the developing
  digestive tube which is known as the archenteron
  and this gives rise to the lining of the
  digestive tract and also organs derived from it.

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CONTINUATION

• Animals that have only these two germ layers are
  said to be diploblastic which are usually jellies
  like jelly fish and coral.. A third layer is
  called a mesoderm which is between the endoderm
  and ectoderm these animals are known as
  triploblastic. In triploblasts the mesoderm forms
  the muscles and most of the other organs between
  the digestive tract and the outer covering of the
  animal.

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BODY CAVITIES

• Body cavities are fluid-filled space separating
  the digestive tract from the outer body wall. The
  body cavity is also known as the coelom the inner
  and outer layers of tissue that surround the
  cavity connect dorsally and ventrally and form
  structures called mesenteries that suspend the
  internal organs animals with a coelom are known
  as coelomates animals that have cavities made
  from blastocoels are known as pseudocoelomates.
  Animals who lack a coelom are known as
  acoelomates.

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PROTOSTOME AND DEUTEROSTOME DEVELOPMENT

• Based on certain features of early development
  many animals can be categorized as having one of
  two developmental modes protostome development
  and deuterostome development three features often
  distinguish these modes.

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CLEAVAGE

• A pattern in many animals with protostome
  development is a spiral cleavage in which the
  planes of cell divisions are diagonal to the
  vertical axis of the embryo. The determinate
  cleavage of some animals with this development
  pattern rigidly casts the developmental fate of
  each embryonic cell very early. A cell isolated
  at the four cell stage from a snail for example
  forms an inviable embryo that lacks many parts.

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CONTINUATION

• In contrast to the spiral cleavage pattern
  deuterostome development is predominantly
  characterized by radial cleavage. The cleavage
  planes are either parallel or perpendicular to
  the vertical axis of the egg. As seen in the
  eight-cell stage. Most animals with deuterostome
  development are further characterized by
  indeterminate cleavage meaning that each cell
  produced by the early cleavage divisions retains
  the capacity to develop into a complete embryo.

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COELOM FORATION

• As the archenteron forms in the protostome
  development initially solid masses of mesoderm
  split and form the coelomic cavity the pattern is
  known as schizocoelous development. In contrast
  formation of the body cavity in deuterostome
  development is described as enterocoelous.

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POINTS OF AGREEMENT

• The hypotheses agree on a number of major
  features of animal phylogeny.
• All animals share a common ancestor, sponges are
  basal animals, eumetzoa is a clade of animals
  with true tissues, most animal phyla belong to
  the clade Bilateria, vertebrates and some other
  phyla belong to the clade Deuterostomia

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DISAGREEMENT OF THE BILATERIANS

• While these two phylogenic hypotheses agree on
  the overall structure of the animal tree they
  also disagree on some significant points. The
  most important are the relationships among the
  bilaterians. The morphology based tree in figure
  32.10 divides the bilaterians into two clades
  deuterostomes and protostomes. The hypothesis
  assumes that these two developments reflect a
  genetic pattern. Within the protostomes the
  figure indicates that arthropods are grouped in
  annelids. Both groups have segmented bodies,
  earthworms which is an annelid and the underside
  of the tail of the lobster which is arthropod.

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ECDYSOZOANS

• In contrast several recent molecular studies as
  shown in figure 32.11 generally assign two sister
  taxa to the protostomes rather then one. Which
  are the ecdysozoans and the lophotrochozoans the
  ECD. include nematodes, arthropods and some other
  animals. These animals secrete external skeletons
  the crickets cover is an example. As the animal
  grows it molts squirming out of its old external
  skeleton and the having a new and larger one the
  shedding is known as ecdysis which is why this
  animal is classified as a ecdysozoans.

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LOPHOTROCHOZOA

• The name refers to two different structures
  observed in animals belonging to this clade. Some
  animals such as ectoprocts develop a structure
  called a lophophore which is a crown of tentacles
  that function in feeding. Which includes annelids
  and molluscs which go through a distinctive larva
  stage known as trochophore larva relating to the
  word lophotrochozoan

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EARLY EMBRONIC DEVELOPMENT
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EDIACARAN FOSSILS
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CAMBRIAN SEASCAPE
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RADIAL AND BILATERAL SYMMETRY
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BODY PLANS OF TRIPLOBLASTIC ANIMALS
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PROTOSTOME AND DEUTEROSTOME DEVELOPMENT
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HYPOTHESES OF ANIMAL PHYLOGENY
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ECDYSIS
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LOPHOTROCHOZOANS