Characteristics of Principle Animal Phyla

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Characteristics of Principle Animal Phyla
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Porifera

• The phylum Porifera includes the sponges
• Sponges are the simplest of all animals
• Sponges lack true tissues and organs
• Sponges are filter feeders. This means that food
  passes into its open body cavity, specialized
  collar cells with flagella trap food and pass it
  to amoebocytes that digest it and carry nutrients
  to other cells

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Porifera

• Sponges reproduce asexually by budding, however
  they do have male and female gametes and are
  capable of sexual reproduction
• Sponges are very good at regeneration
• Adult sponges are sessile and do not display
  symmetry
• Based on DNA evidence sponges evolved from
  complex protists
• There are over 9000 species of sponges

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Cnidarians

• Some of the most common cnidarians are jellyfish,
  hydra and sea anemones
• All cnidarians demonstrate radial symmetry, there
  body parts project from a central axis and have
  stinking cells
• Most stinging cells are called cnidocytes they
  are contained within a capsule
• One type of capsule is called a nematocyst which
  contains a single poisonous barb

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Cnidarians

• All cnidarians have a mouth that leads to a
  gastrovascular cavity. This single structure
  provides a mechanism for both digestion and
  distribution of nutrients
• Cnidarians have very primitive nerve nets that
  function like simple brains

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Cnidarians

• Cnidarians exist in two different forms at
  different times of their lives. They either exist
  as the non-reproductive polyp phase or the
  reproductive medusa stage (commonly called
  jellyfish)

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What do these have in common?
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What do these have in common?
They are both called Portuguese-Man-O-War
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Platyhelminthes

• Flatworm are a common member of this phylum
• Flatworms are the simplest form of animals that
  demonstrate bilateral symmetry
• Flatworms are the simplest animals to contain all
  three tissue layers (endoderm, mesoderm, and
  ectoderm)
• Flatworms have a digestive tract with a single
  common opening for food and waste

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Platyhelminthes

• There are over 20,000 species of flatworms
• Many such as planaria are free-living and
  non-parasitic
• Some such as flukes and tapeworms are parasites
  are parasites both cause severe and lasting
  damage to their hosts

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Platyhelminthes

• Flatworms are acoelomates this means that they
  do not have any body cavities (they are solid)

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Nematodes

• Nematodes are commonly called round worms
• Roundworms are the first animals to have a
  complete digestive tract with a mouth and anus
• Food travels in only one direction
  (unidirectional)
• The digestive tract is specialized by region

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Nematodes

• Roundworms are among the most abundant and
  diverse of all species on Earth
• Humans are host to at least 50 different species
  of round worm parasites, such as hookworms,
  threadworms, and pinworms
• Trichinosis is caused by eating undercooked pork
  containing trichinella spiralis

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Nematodes

• Roundworms have a pseudocoelum. This means that
  they have a fluid filled body cavity in direct
  contact with the digestive tract

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Annelids

• Annelids are commonly called segmented worms
• The word annelid means little ring
• Annelids are the first animals to have a closed
  circulatory system. This means that the blood
  remains closed within vessels and wastes diffuse
  in and out through vessel walls

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Annelids

• Annelids have bilateral symmetry and all three
  types of body tissue
• Annelids (and all the advanced animals) contain a
  coelom. This is large open cavity, completely
  lined with mesoderm

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Acoelomates, Pseudocoelom, and Coelom
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Mollusks

• Mollusks show diverse variations built around a
  common body form
• Mollusks include snails, slugs, oysters, clams,
  octopi and squid
• All mollusks have a muscular mass called a foot
  and a multifunctional structure called a mantle

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Mollusks

• The foot serves in locomotion
• The mantle is an outgrowth of the body that
  drapes over the animal. The mantle produces the
  shell, helps with respiration, waste removal and
  sensory reception
• The mantle houses the gills in aquatic mollusks

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Mollusks

• Another body feature unique to mollusks is the
  the rasping organ called the radula
• The radula is often used as a type of tooth or
  drill to smash into the shells of other mollusks
• All mollusks have a coelom with three open
  chambers
• Most mollusks have an open circulatory system
  that includes a heart that pumps blood into
  vessels that open into the chambers that are
  directly bathed by it

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Mollusks

• Diversity in Mollusks
• - Gastropods
• - make up the largest group of mollusks
• - Most have a single spiral shell
• - Most gastropods live in marine
  environments. Land snails and slugs live
  on land

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Mollusks

• Bivalves
• - Include clams, mussels, oysters and scallops
• - Bivalves have hinged shells with two halves
• - They all live in fresh or marine environments

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Mollusks

• Cephalopods (head and foot)
• - The cephalopods contain the squids and the
  octupi
• - They are faster and more agile than either
  the bivalves or gastropods
• - Some (like the nautilus) have external shells,
  most have small internal shells

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Bivalves
Gastropods
Cephalopods
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Echinoderms

• Echinoderms include the sea stars, sea urchins,
  and sea cucumbers
• Echinoderms lack body segments and exhibit radial
  symmetry
• Echinoderms have a hard internal skeleton called
  an endoskeleton
• Echinoderms have a water vascular system that
  branches into tube-feet used for locomotion,
  feeding and respiration

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Echinoderms

• Sea stars have a very high capacity for
  regeneration
• Sea cucumbers are actually capable of
  regenerating internal organs
• Larval echinoderms show bilateral symmetry, yet
  they have radial symmetry as adults They start
  out more advanced and become more primitive

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Various echinoderms
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