Phylum
Chordata
Having a spinal CHORD
Subphylum Vertebrata
Vertebrata
Easily the most recognizable organisms to us. Vertebrata is a subphylum
of the phylum Chordata.
Vertebrata
-Vertebrates are without a doubt the most complex organisms on Earth.
-We may be outnumbered by arhtropods and molluscs, but we are far more complex,
intelligent, larger, and faster.
ALL organisms under the subphylum vertebrata contain the following characteristics:
1) Spinal cord that is protected by vertebrae.
2) Some form of a distinct head with a brain.
Vertebrata
-This subphylum can be further split into several other classes. We will only study 2 of them:
1) Chondrichthyes
2) Osteichthyes
Chondrichthyes
1) Bilateral Symmetry
Chondrichthyes
2) No operculum
-Sharks and rays have very exposed gills. There is no hard cover for them,
which is why you sometimes hear that the best way to fend off a shark is to hit
their gills.
Chondrichthyes
3) Lack a swim bladder
-This is one reason why sharks and rays must always be in motion
Chondrichthyes
4) Lack a true skeleton
-The majority of their body is cartilage (like the stuff in our noses and ears)
-The closest things they have to true bone are their teeth, jaw bones, skull, and
vertebrae. Even these are just calcified (hardened) cartilage.
Chondrichthyes
5) Placoid scales – hardened scales
-2 major purposes:
1) Improved streamlining
2) Self-defense
Chondrichthyes
-Sharks are not violent organisms. Of the 1,000 species of chondrichthyes, very
few have ever attacked humans. And even those attacks are rare.
http://dsc.discovery.com/videos/shark-week-bull-shark-bite.html
-They are almost always the top of the food chain, made to be ferocious hunters.
http://dsc.discovery.com/videos/best-of-shark-week-air-jaws-sharks-of-southafrica.html
http://dsc.discovery.com/videos/shark-week-anatomy-of-an-attack.html
-Sharks have an acute sense of smell. They can smell a drop of fish blood up to
mile away in the water.
http://dsc.discovery.com/videos/shark-week-mini-myths-bloody-taste-test.html
-Sharks also have tiny sensory organs called ampullae
of lorenzini
http://videos.howstuffworks.com/discovery/36697-ultimate-guide-to-sharksampullae-of-lorenzini-video.htm
SHARK WEEK MYTHBUSTERS
Osteichthyes
**Nearly half the world’s vertebrates are species of bony fish.
1) Bilateral Symmetry
Osteichthyes
2) Operculum (gill flap) – protective gill cover/aids in respiration.
This bony operculum opens and
closes with the mouth, causing a
pressure change.
This pressure change forces water
over the gills for respiration.
These types of fish do not always
need to be moving.
http://www.biotopics.co.uk/pot/animals/fishcy.html
Osteichthyes
3) All have swim bladder - buoyancy
INFLATED
**This bladder is filled
and drained in one of
two ways:
DEFLATED
1) Direct intake or
release of air at
surface of water.
2) Intake/release of
gases through blood
via respiration.
Osteichthyes
4) Have a true skeleton – “osteo”
The common name for this class is the “bony fish”, because they have true
bones and a complex skeletal structure.
5) Scales
Osteichthyes
-Serve purpose of
camouflage,
protection,
and possibly
energy efficiency.
Countercurrent Exchange
The flow of water over a fish’s gills is in the opposite direction of blood flow through
capillaries. This maximizes the intake of oxygen into the bloodstream from the water.
This ensures that the most oxygen rich water only contacts the most oxygen rich blood,
and the most oxygen deficient water only contacts the most oxygen deficient blood.
If it there was no countercurrent
exchange…..
WATER
100%
70%
50%
35%
15%
5%
0%
20%
40%
40%
40%
40%
BLOOD
% of oxygen is being shown, notice how
the blood never goes above 40% oxygen.
Osteichthyes
-Most bony fish are gape-limited predators (they can only eat what fits in their mouth),
however some have viscous teeth tear apart prey.
http://videos.howstuffworks.com/discovery/4592-barracuda-in-slow-motion-video.htm
-The lateral line of a fish is used to detect small movements or changes in water
flow. It is lined with sensory receptors directly connected to the spinal cord.
http://dsc.discovery.com/videos/wild-pacific-sea-lion-vs-fish.html
Other short clips on anatomy
http://www.britannica.com/EBchecked/topicart/208456/48248/Lateral-line-system-of-a-fish
candiru
cichlids
One trait they share:
Lateral Line
-A line of nerves that run up the side of the fish. These nerves are incredibly
sensitive to even the tiniest vibrations in the water.
-School fish move in unison due to a combination of vision and the senses received
through their lateral line.
School fish reactions using lateral line