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Sponges and Cnidarians

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Title: Sponges and Cnidarians


1
Sponges and Cnidarians
  • By Elina Shapiro and Gilbert Hernandez

2
Phylum Porifera (Sponges)
  • Porifera or sponges are the simplest animal in
    the animal kingdom. They have no tissues,
    muscles, nerves, or internal organs. Instead
    their cells perform actions that organs are
    supposed to. There are 5,000 species known to
    man including the vase sponge (Ircinia campana),
    the yellow sponge (Cleona celata), and the sea
    squirt (Didemnum molle).

3
Vase Sponge
Yellow Sponge
Common Sea Squirt
4
Evolution
  • Sponges are undoubtedly the first fossils
    recovered. They date all the way back to the
    Precambrian era.

5
Symmetry and Body Cavity
  • Sponges are asymmetrical and acoelomate.

6
Body Structure
  • Sponges have three body types asconoid,
    syconoid, and leuconoid
  • Asconoid- Are tube-shaped and have a central
    shaft called the spongocoel.
  • Syconoid- Similar to asconoids they have a
    tubular body but are more complex. These have
    collar-cell-lined radial canals that empty into
    the spongocoel. Water enters through canals and
    then filters through tiny holes called prosopyles
    into the radial canals. Food is there ingested by
    the collar cells. Syconoids usually dont form
    colonies like asconoids do. However, during their
    development syconoid sponges do pass through the
    asconoid stage.

7
Body Structure Cont.
  • Leuconoid- These dont have a spongocoel and
    instead have chambers that contain collar cells.
    The only way in or out is through canals.

8
Skeleton
  • A sponge skeleton is made up of calcium carbonate
    or silicon dioxide that are in the for of
    spicules (stiffened rods or spikes which are also
    used for defense). Some dont even have a
    skeleton.

9
Nutrition and Digestion
  • They feed by filtering food particles (sometimes
    bacteria) out of the water using choanocytes
    (collar cells). Choanocytes create the water
    currents by beating their flagella. Sponges dont
    have a real digestive system but they do use
    choanocytes to digest the food particles.

10
Transportation and Circulation
  • While in the larvae stage sponges float along by
    means of water currents. As adults they dont
    move at all (theyre sessil). A sponge has water
    flow in through its pores.

11
Respiration
  • Sponges dont have a respiratory system. They
    pump water all through their canals and extract
    oxygen from the water.

12
Water Balance and Excretion
  • Sponges beat the flagella of certain cells to
    pump water in or out. And they dont have
    excretory organs so wastes leaves with water.

13
Reproduction
  • Sponges can reproduce sexually and asexually.
  • Asexually- They reproduce by budding internally
    or externally. The new sponges are exactly like
    their parent.

14
Reproduction Cont.
  • Sexually- Even though sponges are hermaphroditic
    they dont fertilize their eggs with their own
    sperm (which would be asexual reproduction).
    Instead all the sponges of the same species
    release sperm on one night (usually the full
    moon) and fertilize each other in the water. The
    new sponges are different from either parent.

15
Nervous System
  • Sponges dont have a nervous system. They dont
    have nerve or sensory cells.

16
Classes
  • The three classes of sponges are
  • Calcarea
  • Hexactinellida
  • Demospongiae

17
Phylum Cnidaria
  • The Phylum Cnidaria has thousands of living
    species worldwide, which include hydroids,
    jellyfish like the Physalia physalis (the
    Portuguese Man of War), anemones, and corals.

18
The Portuguese man of war
19
Evolution
  • Cnidarians were one of the first recognized
    animal fossils. They can be dated back 550
    million years ago.
  • The first Cnidarians that were made of soft
    tissue only remain today in exceptional cases.
  • The first coral reefs date back 500 million years
    and structurally differ from the ones today.

20
Body Structure
  • Cnidarians can have one of two basic body types
    polypoid or medusoid
  • Polypoids- have tentacles and a mouths generally
    facing up and the other side connected to a
    colony of other creatures of the same
    species.They also have sturdy skeletons. A couple
    of examples of cnidarians with polypoid body
    structures would be corals and sea anemones.

21
Body Structure Cont.
  • Medusoids- this organism is basically
    upside-down, with the mouth and tentacles usually
    pointed down. These types of Cnidarians are
    generally free-swimmers like jellyfish.

22
Skeleton
  • Their endoskeleton is the mesoglea and their
    exoskeleton is made up of calcium carbonate and
    chitin.

23
Symmetry and Body Cavity
  • Cnidarians are radially symmetrical and they are
    acoelomate

24
Nutrition
  • Most Cnidarians feed on prey that come into
    contact with their tentacles. These usually
    include large protists, crabs, worms, fish, and
    even other cnidarians.
  • Others like coral live symbiotically with algae
    (dinoflagellates and even sometimes chlorophyta).
    They absorb the carbon dioxide produced by the
    Cnidarians, sunlight via photosynthesis and
    release oxygen, the algae produce carbohydrates
    which the Cnidarians use as a main food source.

25
Digestion and Excretion
  • Since Cnidarians dont have any organs the
    gastrovascular cavity serves as their stomach and
    anus. It ingests food and then secretes digestive
    enzymes which break the food down into small
    particles that are digested into the cells lining
    gut. And the waste is secreted out of where it
    came in.

26
Transportation and Circulation
  • The nerve net and nerves control the movement
    throughout their body. And Cnidarians have not
    true circulatory system.

27
Respiration
  • Cnidarians dont have a real respiratory system.
    Instead respiration takes place through diffusion
    of oxygen directly through their tissues without
    specialized organs like the trachea, lungs or
    even gills.

28
Water Balance
  • Cnidarians diffuse water through their tissue.

29
Reproduction
  • They can reproduce both sexually and asexually.
  • Asexual- Asexual larvae bud laterally from adult
    polypoid and develop into polypoids themselves.
    Budding is usually incomplete so colonies of
    identical polypoids tend to form.
  • Sexually- A key characteristic here is the
    alteration of generations. Which is when a
    asexually reproducing organism reproduces and has
    an organism that can reproduce sexually.

30
Reproduction Cont.
  • These grow to full maturity and then release the
    male and female gametes. Those then unite to form
    a zygote. This forms a spherical structure (the
    blastula) through cell division. The larvae then
    forms from the blastula. The larvae then swims
    until it finds a surface to attach to. Then it
    passes through metamorphasis to the polypoid
    stage.

31
Nervous System
  • Is a nerve net that has a network of nerve fibers
    that can communicate when they overlap.

32
Classes
  • The four classes of cnidarians are
  • Cubozoa (Medusoid)
  • Scythozoa (Medusoid)
  • Hydrozoa (Medusoid and Polypoid)
  • Anthozoa (Polypoid)

33
The End
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