Advanced Biology

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Advanced Biology

• Chapter 35 Sponges, Cnidarian, and Ctenophores

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Chapter 35 Sponges, Cnidarian, and Ctenophores

• 35-1 Sponges (Porifera)
• 35-2 Cnidarians and Ctenophores

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35-1 Sponges

• Classification
• Body Plan
• Feeding and Digestion
• Reproduction

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Classification

• Sponges simple aquatic animals that make up the
  phylum Porifera
• Clearly represent the transition from unicellular
  to multicellular life
• No gastrula stage
• Exhibit less cell specialization than most other
  animals
• No true tissues or organs

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Classification

• About 10,000 species
• Early biologists thought sponges were plants.
  Sessile

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Body Plan

• Body wall 2 layers of cells separated by a
  jellylike substance and surrounds a hollow
  cylinder that is closed at the bottom and open at
  the top.
• Collar cells
• Line the interior of the body cylinder
• Beating flagella draw water into the sponge
  through pores in the body wall.
• Osculum the opening at the top of a sponge
  through which water leaves the body cylinder

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Body Plan
Spongin

• Simple skeleton
• Spongin protein fibers that support the body
• Spicules tiny, hard particles of calcium
  carbonate or silicon dioxide. Often shaped like
  spikes
• Some sponges have a combination of spongin and
  spicules.
• Sponges are divided into three classes based on
  differences in composition of the skeleton

Spicules
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Feeding and Digestion

• Filter Feeding feed by screening food out of the
  water that the collar cells pump through their
  body.
• Food bacteria, protozoans, unicellular algae,
  bits of organic matter

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Feeding and Digestion

• Food that is collected is engulfed and digested
  by collar cells.
• Nutrients pass from collar cells to amebocytes,
  cells that crawl about within the body wall to
  deliver food to the rest of the body
• CO2 and other wastes diffuse into water passing
  through the sponge and flows out through the
  osculum.

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Asexual Reproduction

• Form small buds that break off and live
  separately
• Gemmules internal buds produced by some
  freshwater sponges during droughts or cold
  weather. Food-filled ball of amebocytes
  surrounded by a protective coat made of organic
  material and spicules
• Regeneration re-grow missing parts. A small
  piece can regenerate a complete new sponge.

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Gemmule
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Sexual Reproduction

• Sperm released into the water by one sponge
  enters the pores of another sponge.
• Collar cells engulf the sperm and transfer them
  to amebocytes which carry the sperm to an egg.
• The fertilized egg develops into a larva

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• Flagella on larvas surface enable it to leave
  parent sponge, swim, and be carried by currents,
  settle and attach to an object.
• Cells reorganize to form an adult sponge.
• Some species have separate sexes but most species
  are hermaphrodites. Increases chances of
  successful fertilization if all individuals can
  produce eggs... Self-fertilization is rare.

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Smoking sponge Some colonies are known to
simultaneously mass produce gametes within a
limited time period.
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35-2 Cnidaria and Ctenophora

• General Characteristics
• Structure and Function of Cnidarians
• Class Hydrazoa
• Class Scyphozoa
• Class Anthozoa
• Phylum Ctenophora

Frilled Anemone
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General Characteristics

• Radially symmetrical invertebrates
• Somewhat more complex then sponges (Porifera).
  Have tissues and a few simple organs
• Aquatic, live in the ocean

Lined Anemone
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Structure of Cnidarians

• Body shape
• Polyp vase-shaped. Specialized for a sessile
  existence
• Medusa bell-shaped. Specialized for swimming

Burrowing Anemone
Polyp
Medusa
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• Two cell layers
• Epidermis outer layer
• Gastrodermis inner layer
• Mesoglea jellylike material between layers
• Gastrovascular cavity hollow center of the body.
  Single opening for mouth
• Tentacles numerous flexible extensions
  surrounding the mouth

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Feeding and Defense

• Cnidocytes specialized cells used for defense
  and capturing prey. Usually concentrated in the
  dermis especially the tentacles.
• Nematocyst organelle in cnidocyte that has a
  long filament coiled up inside it.

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• When object brushes against trigger on
  cnidocyte the nematocyst inside it pushes out of
  the cell with great force.
• Some have sharp tips and spines that inject
  poison.
• Some have filaments that adhere by wrapping
  around objects.

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Tentacles

• Capture small animals with nematocysts and
  paralyze them with poison injection
• Tentacles push the prey into the gastrovascular
  cavity through the mouth.

Hydra
Lionsmane jellyfish eating another jellyfish
Fish caught in tentacles
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Tentacles

• Enzymes in the gastrovascular cavity break up the
  prey. Cells lining cavity absorb nutrients.
• Undigested food and waste expelled through the
  mouth.

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• Nerve net diffuse web of interconnected nerve
  cells
• In many cnidarians the nerve net is distributed
  uniformly throughout (no brain or control center)
• In some medusa forms nerve cells are clustered
  in rings around the edge of the bell-shaped body

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• Nerve net enables response to specific stimuli in
  environment, But stimuli anywhere on the body
  causes signal to be sent through nerve net in all
  directions and contract entire body
• Nerve net also coordinates the complex activities
  of the body that are necessary for feeding and
  traveling through the environment. (movement of
  tentacles, rhythmic contractions of body for
  propulsion of medusae)

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Classification

• Hydrozoa (hydrozoans)some species live as
  polyps, some as medusae, some alternate between
  forms.
• Scyphozoa (scyphozoans) most of lives as medusae
• Anthozoa (anthozoans) live only as polyps.

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Class Hydrozoa

• 3,700 species. Most live as colonial organisms in
  oceans
• Examples
• Obelia
• Portuguese Man-of-War
• Hydra

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Obelia

• Many polyps attached to branched stalks. Some
  function in food gathering, others specialize in
  reproduction.

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Portuguese Man-of-War (Physalia)

• Exists as a colony of medusae and polyps.
• Gas-filled float keeps colony at surface
• Polyps specialized for feeding, digestion, or
  sexual reproduction.
• Tentacles 20m long dangle from the feeding polyps
  and carry large number of cnidocytes.
• Preys mostly on small fish but cnidocytes
  poisonous/fatal to humans

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Magnified view of tentacle
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Hydra

• Not typical hydrozoans. Exist only as polyps, not
  colonial, and live in fresh water.
• Range in size from 1-4cm in length
• Most white or brown, some appear green because of
  symbiotic relationship with algae living in their
  gastrodermis

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Two cell layers
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• Found in quiet ponds, lakes, streams. Attach to
  rocks or water plants by means of sticky
  secretion by cells at base.
• Can leave one location and move to another by
  secreting bubbles at base causing it to float to
  surface or can move by somersaulting motion
• Reproduce asexually during warm weather by
  budding on side of body.

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Hydra budding
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• Sexual reproduction in the fall.
• Sperm and egg produced by meiosis along the body
  wall in swellings called ovaries and testes.
• Some species are hermaphroditic
• Sperm released into water, those that reach
  ovaries can fertilize egg cells.
• A hard covering protects the embryo through the
  winter. Embryos hatch in spring and develop into
  a new hydra.

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Class Scyphozoa

• Cup animals. Medusa is the dominant form of the
  life cycle.
• 200 species. Commonly known as jellyfish
• Cup sizes range from 2cm to 4m. Some have
  tentacles several meters long

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• Pulsating motions of the cup propel it through
  water.
• Some have poisonous nematocysts that can cause
  pain/death in humans.
• Aurelia life cycle Figure 35-9 p700

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Class Anthozoa

• Flower animals
• 6,100 marine species.
• Examples
• Sea Anemones
• Corals

Anthozoa Colony
Capnella Soft Coral
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Sea Anemones

• Polyps commonly found along coastal areas.
• Feed on fishes and other animals.
• Some have symbiotic relationship with Clownfish.
• Share food and protect each other from predators.
  
• Movements of clownfish prevents sediment from
  burying the anemone. Anemone does not fire its
  nematocysts when clownfish touches its tentacles.

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Jewel Anemone
Striped Sea Anemone
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Corals

• Small polyps usually live in colonies.
• Cements its calcium carbonate skeleton to the
  skeletons of adjoining polyps in the colony.
• When they die, hardened skeletons remain and
  serve as foundation for new polyps. Build up to
  form coral reefs. Only the top layer is living.

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Coral Reefs

• Provide food and shelter for an enormous and
  colorful variety of fishes and invertebrates.
• Coral reefs are restricted to ocean with in 30 N
  or S of equator. Only warm, shallow, clear water.
  

Coral skeleton
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Coral Reefs

• Photosynthetic algae live symbiotically inside
  coral cells.
• Corals depend on algae to provide oxygen and to
  speed up accumulation of calcium from the sea
  water.
• Algae depend on corals to supply vital nutrients.

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Northern Star Coral
Polyps withdrawn
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• (The Phylum Cnidaria was once called
  Coelenterata, which also included the Ctenophora,
  or "comb jellies" or "sea gooseberries". Animals
  in the new Phylum Ctenophora do not have stinging
  cells. )

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Phylum Ctenophora

• 100 species. Resemble jellyfish. Often called
  comb jellies
• Ctenophoa means comb holder and refers to the 8
  comblike rows of cilia that run along the outside
  of the animal.

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Bloodybelly
Lobed Comb Jelly
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• Differ from jellyfish and other cnidarians
• Move through water by beating cilia rather than
  pulsating
• Most do not have cnidocytes. Have cells called
  colloblasts which secrete a sticky substance that
  binds to their prey.
• Apical organs sensory structures at one end of
  their body enables it to sense its orientation in
  the water. Nerves running from the apical organ
  coordinate the beating of the cilia.

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• Most are hermaphroditic
• Bioluminescence production of light. Often
  observed in large swarms near surface at night.

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Ctenophora (comb jellies) superficially resemble
cnidaria but lack nematocysts and have a complete
gut. The name derives from the cilia-bearing
ctenes, which the animals use for locomotion.