Animal Kingdom IV

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Animal Kingdom IV
Echinoderm Through Fish
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Echinoderms Back to the Future

• Echinoderms (which means spiny skin) are a return
  to radial symmetry with a twist.
• The appendages are usually in multiples of 5
  instead of 7 or 9.
• Includes about 6000 living species.
• All species are marine.
• starfish, brittle stars, sea urchins, sand
  dollars, and sea cucumbers.

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Echinoderm Skeleton

• Echinoderms are among the most unique of all
  animal phyla.
• The skeleton is made of calcium.
• It is composed of many ossicles (in humans these
  are small bones in the ear).
• Echinoderm skeletons are composed of calcium
  carbonate and several proteins.
• Ossicles are not solid, but have a sponge-like
  microstructure called stereom that is unique to
  the phylum.

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Echinoderm Skeleton

• Morphologically, echinoderm ossicles are a true
  endoskeleton.
• They are produced by mesenchymal cells and are
  usually covered by epidermis.
• Functionally, however, the majority of ossicles
  act more like an exoskeleton.
• The ossicles lie just under the epidermis and
  enclose most other tissues in a flexible but
  tough covering.

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Water Vascular System

• Echinoderms have a unique water vascular system.
• This system may have evolved from tentacle
  systems like the Cnidaria.

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Water Vascular System

• On the ventral side of echinoderms, there are
  hundreds of tiny feet usually arranged into
  several rows on each ray.
• These are called tube feet, or podia, and are
  filled with sea water.
• The water vascular system within the body of the
  animal is also filled with sea water.
• By expanding and contracting chambers within the
  water vascular system, the echinoderm can force
  water into certain tube feet to extend them.

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Echinoderm Water Vascular System
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Echinoderm Locomotion

• Echinoderms have muscles in the tube feet.
• By expanding and retracting the right tube feet
  in the proper order, the creature can walk.
• Many echinoderms can also form suckers on the
  ends of their tube feet.
• These suckers can be used to capture and hold
  prey, or to hold onto rocks in a swift current or
  tide.

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Nervous System

• Echinoderms have a primitive nervous system like
  Cnidarians.
• Most of the sensory neurons are located at the
  ends of podia (tube feet).

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Chordata

• http//school.nettrekker.com/redirecter/?link_id1
  37969

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Chordata Classification

• Kingdom Animalia
• Phylum Chordata
• Important classes to remember
• Fish can be broken down into 3 class
• Class Agnatha Jawless includes hagfish and
  lampreys
• Class Chrondrichthyes Fish whose skeleton is
  made of cartilage such as sharks, rays and skates
  
• Class Osteichthyes Fish whose skeleton is
  composed mostly of bone such as bass, perch,
  catfish, and flounder
• Class Amphibia Amphibians salamanders, newts,
  frogs and toads
• Class Reptilia Snakes, lizards, crocodiles,
  aligators, turtles and tortoises
• Class Mammalia
• Monotremes Subclass Prototheria Order
  Monotremata
• Marsupials
• Placentals

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Chordata Classification

• Class Amphibia Amphibians salamanders, newts,
  frogs and toads
• Class Reptilia Snakes, lizards, crocodiles,
  aligators, turtles and tortoises
• Class Mammalia
• Monotremes Subclass Prototheria Order
  Monotremata includes platypus and echidna
• Marsupials Subclass Metatheria these are pouched
  mammals includes kangaroos, opossums, wallabies,
  wombats, koalas
• Placentals Subclass Eutharia includes deer,
  bats, whales, rabbits, groundhogs, elephants,
  monkeys, humans

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Chordate Diversity

• The phylum chordata is extremely diverse and
  includes both tunicates (sea squirts) and humans!
• 4 characteristics define a chordate
• The notochord (dorsal stiffening rod)
• A hollow dorsal nerve cord
• Pharyngeal gills
• A post anal tail that includes the notochord and
  nerve cord.

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Your Relative The Sea Squirt

• The most primitive chordates are the
  unichordatatunicates (sea squirts).
• The chordate characteristics can be observed only
  by examining the entire life cycle.

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Your Relative The Sea Squirt

• The adult feeds using a pharyngeal basket, a
  type of pharyngeal gill formed into a mesh-like
  basket.
• Tunicates have an unusual heart which pumps by
  wringing out. It also reverses direction
  periodically.

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Your Relative The Sea Squirt

• Tunicates are usually hermaphroditic, often
  casting eggs and sperm directly into the sea.
• After fertilization, the zygote develops into a
  tadpole larva.
• This swimming larva shows the remaining three
  chordate characters - notochord, dorsal nerve
  cord and post-anal tail.

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Meet the Lancelet

• Lancelets live in shallow tropical sandy-bottom
  environments.
• They stick their heads out of the sand and feed
  somewhat like a tunicate.
• Cilia-driven currents suck water into the mouth
  and across the pharyngeal gills.
• The lancelet has a strong supportive notochord,
  and angled muscles along the body used for brief
  periods of swimming, such as when the animal is
  dislodged from the sand.

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Fish

• Any of a large group of cold-blooded, finned
  aquatic vertebrates.
• Fish are generally scaled and respire by passing
  water over gills.

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Gills

• What do fish breathe?
• All fish have gills
• The water surrounding a fish contains a small
  percentage of dissolved oxygen.
• The fish must use a special system for
  concentrating the oxygen in the water to meet
  their physiological needs.

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Gills

• In the gills, the blood picks up oxygen from the
  surrounding water and leaves the gills in
  arteries, which go to the body.
• If fish breathe oxygen, why cant they survive in
  the air?
• Its because the gills collapse without the water
  to provide support.

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Fish Circulation

• Fish have a two chambered, closed system, heart.
• The fish heart only pumps blood in one direction.
  
• The blood enters the heart through a vein and
  exits through a vein on its way to the gills.
• In the gills, the blood picks up oxygen from the
  surrounding water and leaves the gills in
  arteries, which go to the body.
• The oxygen is used in the body and goes back to
  the heart.

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Cold-Blooded

• There is really no such thing as a cold or warm
  blooded animal.
• The popular term cold-blooded means having an
  average body temperature lower than that of the
  surroundings.
• Warm-blooded is the opposite.

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Cold-Blooded

• Scientists have more technical terms
• Endothermic Generating internal heat to moderate
  body temperature, e.g., modern birds and mammals.
  
• Ectothermic Relying on the environment and
  behavior to regulate body temperature, e.g.,
  typical reptiles.
• Homeothermic Maintaining a constant internal
  body temperature, e.g., modern mammals and birds.

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Fish Scale

• Scales provide protection.
• Most, but not all, fish have scales.

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Fish Fin

• All fish have fins
• Fins are not much more than sheets of skin that
  hang from the fish.
• They offer a fish stability when jetting through
  the water.
• Throughout evolution, some fins have evolved into
  protective devices like spines, or into a bait
  decoy that lures the prey closer.

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Fish Egg

• The eggs of fish and amphibians are jellylike.
• Fish eggs are fertilized externally, typically
  with the male inseminating the eggs after the
  female lays them.
• These eggs do not have a shell and would dry out
  in the air.

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Fish Egg

• Usually the mother does not provide any
  nourishment to the larvae outside of the egg.
• In certain instances, the most physically-develope
  d offspring will devour its smaller siblings for
  further nutrition while still within the mother's
  body.

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Fish Larvae

• Nearly all bony fishes, especially marine ones,
  have a larval stage which is morphologically very
  different from the adult.
• In general, these larvae live in different places
  than the adult, have different behaviors, eat
  different foods and have different predators.
• During this larval phase, the tiny fish develops
  from little more than an egg with a tail to a
  miniature adult.

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Jawless Fish (Agnatha)

• Hagfishes and lampreys
• The first vertebrates

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Hagfish

• Hagfish (slime-eels) are probably an evolutionary
  intermediate between lancelets and fish.
• Hagfishes are generally deep-water marine
  scavengers.

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Hagfish

• Slime-eels burrow into the mud, sticking their
  heads out until they detect waterborne odors of
  food such as decaying flesh.
• Then they travel along the odor gradient until
  they find their food, whereupon they use a
  rasping tongue to burrow into the flesh.
• When threatened or attacked, hagfish have the
  ability to secrete a skin-derived compound that
  immediately swells into a large ball of slime.

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Fish With Jaws

• The fish evolved in two directions
• One line acquired a cartilaginous skeleton
  leading to one of the most successful and ancient
  group of fishes, the sharks and rays.
• Another ancestral line developed calcified bones
  and spines.

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Lung Evolution

• Contrary to the old idea that swim bladders gave
  rise to lungs--new evidence indicates exactly the
  opposite -- primitive lungs evolved first as a
  supplement to gill-breathing.
• These primitive lungs became the swim bladder.

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Why Fish Evolved For Land

• Around 400 million years ago a combination of
  conditions allowed previously uninhabitable land
  to be colonized by plants, insects and other
  invertebrates.
• Key among these conditions was the diminishing
  intensity of ultraviolet light due to the
  developing ozone layer.
• Most likely, the invasion of land by chordates
  was linked, at least in part to the availability
  of prolific, essentially untapped, food resources
  (mostly insects).

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Mudskipper--Water to Land

• The mudskipper provides an excellent model for
  the movement of chordates from water to land over
  400 million years ago.
• Mudskippers live in mangrove swamps where they
  feed both in water and on the land.
• They move about by walking with their pectoral
  and pelvic fins.