Transcript Chapter 18 The Fishes Zoology

Chapter 18 The Fishes
Zoology
Mrs. Fleming
Evolutionary perspective
• Water covers over 70% of the earth.
• It is believed by some that life began in
the water.
• Water is an essential element to all life,
land and water life.
• Fish dominate the watery environments
and are the ancestors of all other
members of the subphylum Vertebrata.
Relationships
• Fish belong along with the chordates
in the group called the Craniata. The
name describes the skull that
surrounds the brain, organs, eyes,
and inner ear.
• It is believed that fish started out in
the marine environments (salt water)
and then adapted to the freshwater
environments.
Subphylum Vertebrata
• Breaks down into 6 categories (classes)
• Class Cephalospidomophi
• Class Gnathostomata
• Class Placoderm
• Class Chondrichthyes
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Subclass Actinopterygii
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Subclass Sarcopterygii
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The tetrapods
The placoderms were small fish, usually
only a few inches long. The mouth of
these fish was interesting because as
the lower jaw moved down the head
shield moved up, thus giving a wide
gape. They had no teeth, instead using
a bony plate as a biting surface.
Fish Body Parts
Fish Fins
Start of day 2
Locomotion page 285
• Swimming is less energetic
that humans running.
• Fish are streamlined shaped
and have mucoid secretions
that lubricate its body
surface to reduce friction
between the fish and the
water.
Locomotion continued
• Fish move through the water
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using their fins and body wall
to push against the
surrounding water.
Muscles are arranged in a
side ways W pattern.
Because they extend
posteriorly and anteriorly in a
zigzag fashion the
contraction of each muscle
bundle can affect a large
portion of the body wall.
Body wall on both sides
of the fish.
Nutrition and Digestive System
• The first fish were probably
filter feeders and scavengers.
However fish nutrition
dramatically changed with the
evolution of jaws.
• Most modern fish are predators
and spend most of their time
searching for food.
• Prey varies greatly.
Nutrition and Digestive System
• Some feed on vertebrates, larva,
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plankton, other fish.
Teeth capture and hold prey, some
teeth are modified for crushing the
shells of mollusks or the
exoskeletons of arthropods.
Another method of eating is by
using gill rakers that trap plankton
while the fish swim. Basically they
swim with their mouth open and
everything goes through their gills.
Teeth
Digestive system
• Similar to other vertebrates.
• Has a stomach that stores meals
• Small intestine is primary site for enzyme
secretions and food digestions. Some have
a spiral valve in their intestine and others
have out pockets of the intestine called
pyloric ceca, both of these parts increase
absorption and secretory substances.
Digestive System
Circulation and Gas Exchange
• All vertebrates have a closed
circulatory system where the
heart pumps blood with red
blood cells containing
hemoglobin through a series
of arteries, capillaries, and
veins.
• The typical fish's circulation is
a single circuit: heart-gillsbody-heart
Circulation and Gas Exchange
• The fish heart proper is two-chambered,
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consisting of an upper atrium and a lower
ventricle.
Amphibians, basically, have a three-chambered
heart, two atria and one ventricle;
Reptiles have a three- or four-chambered
heart; and
Mammals and birds have a four-chambered
heart consisting of two atria and two
ventricles.
Comparison
• Amphibian Heart
Mammal Heart
Comparison
Circulation and Gas Exchange
• The fish heart, however, has two accessory
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chambers, and all four chambers are contained
within a single pericardial sac.
One accessory chamber is the thin-walled sinus
venosus, which collects blood and leads into the
atrium;
the other accessory chamber is the conus
arteriosus, an enlargement of the main artery
leading out of the ventricle.
In some fishes, such as sharks, the conus
arteriosus is muscular and pumps blood in the
manner of the ventricle.
Start of Day 3: Reproduction
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Most fishes are egg-layers, but many bear living young.
Live-bearing fishes may be ovoviviparous, in which the
eggs essentially simply hatch within the female, or
viviparous, in which the unborn young are supplied
nourishment through the mother's tissues.
In some ovulation (or release of the egg) and birth occur
at the same time.
In some viviparous fishes the walls of the egg follicle
are in intimate contact with the embryo, supplying it
with nourishment. In the viviparous sharks, a part of the
oviduct, or egg channel, is developed into a uterus,
where the modified yolk sacs of the young are closely
joined to pockets within the uterus.
Fish Eggs
Reproduction
• In live-bearing fishes and in some egg-
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layers, fertilization occurs internally, and
methods have been evolved for introducing
the sperm into the female's body.
In sharks the pelvic fins of the male are
modified into intromittent organs called
myxoptergia, and in the male topminnows
the anal fin is modified into a similarfunctioning intromittent organ called the
gonopodium.
Know that fins are used in the deliverance
of sperm into the female fish.
Stopped here on April 24
Reproduction
• At least three modes of reproduction-•
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heterosexual, hermaphroditic, and
parthenogenetic--are found in fishes.
In the most common form, heterosexual
reproduction, there are separate male and
female parents, but even here there is
considerable variation.
In some live-bearing fishes, the female is able to
store sperm for up to 8 or even 10 months, and
this sperm is used to fertilize new batches of
eggs as they develop. In some cases, a female
may carry sperm from several males at once.
• In hermaphroditic reproduction, a
single fish is both male and female,
produces both eggs and sperm
(either at the same time or at
different times), and mates with
other similar hermaphroditic fishes.
External self-fertilization occurs in one
hermaphroditic fish, which sheds egg
and sperm simultaneously. In
another, internal self-fertilization may
occur. In certain fishes there is a time
sequence of hermaphroditism, young
fishes reversing their sex as they
grow older.
Reproduction
• In parthenogenetic reproduction,
unfertilized eggs develop into embryos.
This is known to exist in at least one fish
species, Poecilia formosa, of the Amazon
River; however, even though development
proceeds without fertilization in some of
these females, mating with a male is still
required to stimulate egg development.
• Parental care also shows great diversity.
• Some fishes, like the Atlantic herring,
form huge schools of males and females
and freely shed their eggs and sperm
(milt), and then abandon the eggs.
• Other fishes build nests and care for both
the eggs and newly hatched young.
Others have evolved methods of carrying
the eggs with them, commonly in their
mouths, but also in gill cavities or in
special pouches on the body.
Mutton Snapper
Plankton
Bay anchovie
Silver Perch
Diseases
Signs of Disease
• Clamped fins (fins are held abnormally close to body)
• The fish refuses its usual food for more than 2 days.
• There are visible spots, lesions, or white patches on the
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fish.
The fish gasps at the surface of the water.
The fish floats, sinks, whirls, or swims sideways.
The fish shimmies (moves from side to side without
going forward).
A normally active fish is still.
A normally still fish is very active.
The fish suddenly bloats up, and it's not due to eggs or
young.
The fish is scratching against tank decorations.
Live Birth of a Killer
Whale
Another live birth
Baby is
alive and
well.
Swim Bladders and Lungs
• Do fish have lungs? Sort of???
• The Indian climbing fish is an example of a fish that has
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pneumatic sacs.
These are ducts that connect to the esophagus or
antoher part of the digestive tract.
They swallow air and it gets trapped in these sacs.
Then gas excahnage occurs across the vascular surfaces.
So the climbing fish that spends most of its time on land
can still breath so to speak with a strange form of lung.
Buoyancy Regulation
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Buoyancy= how things can or do stay a float.
Humans can because of their lungs and body makeup.
Fish do this in one of four ways.
1. incorporate low density compounds into their tissues
livers are saturated with buoyant oils
• 2. use fins for lift
• 3. reduction of heavy tissues, bones are less dense and
cartilage is only slightly heavier than water
• 4. use of a swim bladder
Swim Bladder
• A fish regulates buoyancy by controlling
the volume of gas in its swim bladder.
• Fish gulp in air at the waters surface and
forces air into their swim bladder.
• The blood also can exchange gas into the
swim bladder and out of it to help
maintain buoyancy.
Nervous System
• Consists of the brain and spinal column.
• Have sensory receptors for touch, temperature,
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hearing, vision, olfaction, balance, equilibrium,
detecting water movements.
Fish have no eye lids
Lenses are round which means that they must
move them backwards and forwards to focus.
Receptors for equilibrium, balance, and hearing
are in the inner ear.
Nervous System
• How do fish hear?
• They have no middle or outer ear, so they
hear from vibrations in the water that
strike the fish and are amplified by the
swim bladder and sent to the skull.
• The lateral-line system is in the epidermis
and it is a series of canals with sensory
receptors.
Electric Fish
• All organisms produce a weak electrical
field from the activities of nerves and
muscles.
• Electroreception: is the detection of the
electrical fields that a fish generates.
• Over 500 species of fish can do this.
• Some fish can also generate electrical
current.
Electric Fish
• Muscles near the caudal fin are modified into
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organs that produce a continuous electrical
discharge.
Current spreads between the head and the tail.
The most well known is the electric eel.
The organs for producing the electric current are
in the trunk. They can produce in excess of 500
volts.
Can stun or kill prey.
Stop here
• Main Types of Litter
• Type of Litter Percentage
• Fast Food Waste(33%)
• Paper(29%)
• Aluminum(28%)
• Glass(6%)
• Plastic(2%)
• Other(2%)
• Source: Missouri Department of
Transportation (MoDOT) survey of AdoptA-Highway volunteers - 1994
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How long does it take to decompose?
ObjectDecomposition Time
Styrofoam container> 1 million years
Plastic jug1 million years
Aluminum can200-500 years
Disposable diaper550 years
Tinned can90 years
Leather shoe45 years
Wool sock1 year
Paper bag1 month
Banana peel3-4 weeks