Ch. 30 Loulousis
Is a seahorse a fish, amphibian, or reptile?
FISH
•Vertebral Column (Endoskeleton)
•Gills
•Single-loop circulation
•Kidneys Also share all the characteristics of chordates such as notochord, bilateral symmetry, coelomate, sense organs
Structures to help swim and sense environment: ◦ Endoskeletons
◦ Fins
◦ Swim bladders
◦ Lateral lines
◦ Shape
◦ Muscular tail
• Most fish have complete endoskeleton made of cartilage or bone
• Muscles attach for movement
• Fins are attached
Increase stability Some have paired fins to help turn, dive or climb ◦ Paired fins evolved into limbs and wings
Swim bladder ◦ Amount of gas regulates vertical position in water ◦ Sharks and stingrays don’t have swim bladders, use fat for buoyancy
Hard bony plates formed from skin
Can be tooth-like, diamond shaped, cone shaped, or round
Some fish (catfish) do not have scales
Shark scales are like teeth of other species
Annual growth rings in scales for some species can tell you age
•Eyes •Nostrils •Lips •Fins •Skin •Inner ears •Lateral line
•System of small canals in the skin, senses water vibrations by currents or pressure waves
•Directs their swim movements
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Fish get oxygen for cellular respiration from water
Gill- respiratory organ, made of rows of filaments
Located at the gill slit- rear of cheek
Use countercurrent flow to extract maximum amounts of oxygen
Single-loop blood circulation
Water passes over gills in one direction and blood flows in the other direction Allows oxygen to diffuse into the blood in gill capillaries Gills are efficient and extract up to 85% of the dissolved oxygen in the water
Blood leaves gills’ capillaries -> vessels in fish body -> heart •Heart is a simple chamber –pump, one atrium, one ventricle
What is the major respiratory organ of a fish?
◦ Gill (made up of gill filaments)
Why does a fish open and close its mouth as it swims?
◦ Movement pumps large amount of water over the gills and drives countercurrent flow
How does countercurrent flow increase the efficiency of a bony fish’s gills?
◦ Water passes in one direction over capillaries while blood flows in opposite direction. Allows oxygen to diffuse into the blood over the entire length of the capillaries.
Osmosis: causes net movement of water through membranes (like gills and skin) toward regions of higher ion concentration (less water)
Most vertebrates body is 2/3 water
Sea water has 3x the amount of ions than a fish body
•Marine Fish •Lose water to environment through osmosis •Fish must drink sea water and pump out excess ions through their gills
•Fresh Water Fish •Bodies have more ions than surrounding water, so tend to take in water through osmosis
•Filter water and waste from the blood •Excrete products as urine •Regulate concentration of substances in blood •Marine Fish
•Conserve water excrete small amount of urine (or waste)
•Freshwater Fish •Excrete most of their waste as urine, very little out gills
Kidneys are organs made up of nephrons ◦ Tubelike organs made up of thousands of nephrons
◦ Regulate the body’s salt and water balance and remove metabolic wastes from the blood
◦ Excess water and bodily wastes leave the kidneys in the form of urine
Marine fishes excrete small amounts of urine and rid their bodies of ammonia largely through their gills
Freshwater fishes excrete large amounts of dilute urine
Most reproduce sexually
External fertilization
Spawning ◦ Male and female release gametes into water and
eggs are fertilized
◦ Group spawning- Large number of eggs ensures some will survive
◦ Sharks, skates, and rays have internal fertilization produces larger offspring, less likely to be eaten
Why is maintaining water balance within the body a different process for freshwater versus marine fishes?
How is group spawning advantageous to fish?
3. Where does blood that enters chamber A come from?
4.Where does blood go when it leaves chamber B?
5.How do the walls of chamber B enable it o carry out its function?
1.Identify chambers A and B. 2.What is the function of chamber A? B?
3 classes
1.) Agnatha- Jawless fish
2.) Chondrichthyes- cartilaginous fish
3.) Osteichthyes- bony fish
Hagfishes and lampreys
Have cartilage skeletons
Strong fibrous connective tissue
Notochord in adulthood
Only modern vertebrates without a backbone!
◦ Swim with undulating movements
•Hagfish are scavengers and predators
•Eats dead body of animals on ocean floor
•Lampreys are parasitic •Uses circular suction-cuplike mouth to suck blood of host
Sharks, skates, rays, and ratfishes
Paired fins and jaws ◦ Jaws let animals grasp and crush prey
Cartilage skeletons strengthened
By calcium carbonate
•Living fossils- having changed little in hundreds of thousands of years •All are predators •Has triangular-shaped scales makes skin rough •Shark teeth are modified scales also triangular arranged in 6-10 rows
•System of tooth replacement ensures the teeth in use are always sharp and new
•Have flat bodies adapted for sea floor life •Rays are less than 1m long and skates are smaller
Class osteichthyes
Most numerous of all fishes
Have a skeleton made of bone and paired fins
Have teeth that are fixed onto the upper jaw
Have structural adaptations:
◦ Lateral lines
◦ Opercula
◦ Swim bladders
Lateral line system (1)
◦ Sensory system that extends along each side of a bony fish’s body
◦ Enables a fish to detect motionless objects by the movement of water deflected by that object
Helps a fish perceive its position in water
◦ Occurs by nerve impulses from ciliated sensory cells
Much like we hear music with our inner ear
Both use sensory cells with cilia to detect vibrations
Gill Cover (2)
◦ Operculum – hard plate that covers the gills on each side of the head
◦ Movement of the opercula and other muscles permit a fish to draw water over the gills, which allows them to take in oxygen
◦ Can move water over their gills while remaining stationary
Doesn’t have to swim to respire
Enables them to conserve energy
Swim Bladder (3) ◦ Keeps a fish from sinking
◦ Swim bladder is a special gas sac
By adjusting gas content of swim bladder, fish can regulate their buoyancy
As it fills, they rise and vice versa
◦ Early bony fish had swim bladder connected to throat
Gulped air to fill it
◦ Modern bony fish swim bladder does not have a direct passageway to mouth
Gas is exchanged between bloodstream and the swim bladder
**There are 2 groups of bony fishes
◦Ray-finned fishes
Yellow perch
◦Lobe-finned fishes
coelacanth
Vast majority of living fishes
Fins are supported by bony structures called rays
Teleosts – most advanced of the ray-finned bony fishes ◦ Highly mobile fins
◦ Very thin scales
◦ Completely symmetrical tails
◦ Includes 95% of all living fish species
Only 7 species survive today 1 species is coelacanth Other 6 are all lungfishes Have paired fins ◦ Each fine consists of a long, fleshly, muscular
structure supported by central core of bones ◦ Bones are connected by joints
like joints in the bones of your hand
◦ Bony rays are only found at the tips of each lobed fin
Scientists are still debating ancestry.. ◦ Used to believe ancestor was amphibian
Now they believe it is most likely a third type of lobe-finned fish now extinct