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