Transcript Biology\Fish Unit

Chordates and Fish Unit
Learning Target Objectives:
•Distinguish between the 3 major chordate divisions and
between classes of chordates/fish, listing examples of
each.
•Compare and contrast features of organisms that make
them unique or help place them in a particular class.
•Identify body structures (anatomy) and functions
(physiology) for each type of vertebrate.
•Differentiate between types of births: oviparous,
ovoviviparous, and viviparous.
Vocabulary:
Notochord * gill slits * tunicate * lancelet *
vertebrate * endoskeleton * axial skeleton *
appendicular skeleton * ectothermic * endothermic
* cloaca * lateral lines * spiracles * olfactory
sacs * viviparous * oviparous * ovoviviparous *
rays * operculum * caudal fin * dorsal fin * anal
fin * pelvic fins * pectoral fins * pharynx * liver
* pancreas * villi * atrium * ventricle * arteries
* capillaries * veins * gills * kidneys * bladder
* osmoregulation * optic * olfactory * cerebrum
* cerebellum * medulla oblongata * swim bladder
* external fertilization * milt
Kingdom: Animalia
Phylum: Chordata
At some time in their lives, all chordates show the following characteristics:
1)
2)
3)
A notochord – a dorsal rodlike, internal supporting structure (found
only in the embryonic stage of vertebrates, later it’s replaced by a
backbone)
A dorsal, hollow nerve cord
Pharyngeal pouches, or gill slits
3 Subphyla:
1)
Tunicates (Subphylum Urochordata)
- soft-bodied
- marine (saltwater)
- larva resemble tadpoles, adults are sessile & lose notochord &
nerve cord
- filter feeders
Ex: Sea squirts
2) Lancelets (Subphylum Cephalochordata)
- Live in shallow warm, marine water
- poor swimmers, usually stay mostly buried in sand
- Adults show all 3 chordate characteristics
- Filter feeders
3) Vertebrates (Subphylum Vertebrata)
- Spinal column of bones (vertebrae) in the advanced stages (beyond
embryo) (spinal column of cartilage in sharks)
- Endoskeleton grows with organism
- Spinal column surrounds dorsal nerve cord
- Dorsal nerve cord swells into a brain at anterior end (cephalization) &
is protected by a skull, or cranium
- Axial skeleton (backbone & skull)
- Appendicular skeleton – formed where appendages (fins, arms, etc.)
join axial skeleton
Vertebrates (continued)
- Heart with 2 to 4 chambers, closed circulatory system, hemoglobin
- Coelom contains heart, etc.
Vertebrates may be either:
1) ectothermic – body temperature varies with environment
(a.k.a. “cold-blooded”)
ecto = outside therm = heat
2) endothermic – fairly constant body temperature (warm-blooded)
endo=inside therm = heat
----------------- Cloaca – a common chamber where the reproductive tract, excretory
system, and/or digestive system empty. Therefore only 1 opening is
needed to the external world. This is common in vertebrates.
Figure 30–1 The Generalized Structure
of a Chordate
Section 30-1
Notochord
Muscle segments
Tail
Hollow
nerve cord
Anus
Mouth
Pharyngeal pouches
Chordate Cladogram
Section 30-1
Mammals
Birds
Amphibians
Fishes
Nonvertebrate
chordates
Invertebrate ancestor
Reptiles
Fish
Subphylum: Vertebrata (have backbones)
3 Classes:
1) Class Agnatha
round, “jawless” mouths
No scales, slimy skin
Notochord present in adults
eel-like shape
Cartilaginous skeleton
Unpaired fins
Ex: lamprey
Lamprey are parasites, drink blood, have no stomach, sucker mouth
with teeth, a problem in the Great Lakes, lay eggs in streams –
take 3 to 7 years to mature
2) Class Chondrichthyes
- Cartilaginous skeleton, NO bones except in jaws on occasion
- Paired fins
- Good sense of smell
- Lateral lines detect vibrations & chemicals
- Gill slits
- Placoid scales (spiny, like sandpaper) – don’t overlap like fish scales
from other classes of fish
- Exs. Include: Rays, Skates, & Sharks
- All have a 2 chambered heart
Rays & Skates
- Flattened body
- Wing-like pectoral fin
- Spiracles- openings on top of head let water in for gills
- Eat mostly mollusks and crustaceans
- Some have poisonous or electrical tails
Sharks:
- Flattened wing-like pectoral fins
- Rows of rotating replacement teeth
- Water entering nostrils does NOT flow to gills, it passes
through olfactory sacs used to detect smells. (Because our
nostrils are connected to our lungs, we can’t use them for
smell under water.)
- Internal fertilization with 3 birth possibilities:
1) Viviparous – young develop in mother & are born alive.
Embryo is nourished through a placenta (like humans).
2) Oviparous – slimy eggs are laid shortly after fertilization.
3) Ovoviviparous – eggs remain inside mother,
embryo is nourished by the egg yolk. After
hatching in mom, young are born live.
3) Class Osteichthyes (Bony Fish)
a) Lobe-finned fish have fleshy base to fins/tail; almost
extinct Example: Coelocanth
b) Lungfish have lungs to breathe in air AND gills for
breathing in water.
c) Ray-finned fish
- Rays = long bones that support fins.
- Scales overlap each other
Examples within this group: eels, seahorses & most all
other fish
Fish Anatomy (structure)
Operculum – hard covering over gills at back of head region.
Water enters mouth, flows over gills, exits
out back of operculum.
Fins:
Caudal fin – tail fin, moves side-to-side
Dorsal Fins (usually 2) – are on top of fish’s back; the front fin
is the anterior dorsal fin, the back fin is the posterior dorsal
fin (posterior dorsal fin has rays-other fin has spines)
Anal fin – on ventral surface (helps keep fish upright and
moving in straight line)
Pelvic fins (paired) – found behind (“posterior to”) & below
(“ventral to”) the pectoral fins
Pectoral fins (paired) – located on sides of body just posterior
to the operculum
Internal Anatomy:
Digestive system: Mouth  pharynx (throat cavity) 
esophagus  stomach  intestine  anus
Liver – makes/secretes bile (aids digestion, especially of
fats) (gallbladder stores bile)
Pancreas – secretes insulin (regulates blood sugar) and
digestive enzymes
Villi – projections of the intestinal wall that increase surface
area for better nutrient absorption
Figure 30–11 The Anatomy of a Fish
Section 30-2
Kidney
Pyloric
cecum
Stomach
Vertebra
Muscle
Esophagus
Swim
bladder
Brain
Spinal Gills
cord
Mouth
Operculum
Urinary
bladder
Heart
Anus
Reproductive
organ
Pancreas
Intestine
Gallbladder
Liver
Circulatory System
2 heart chambers:
1)
Atrium – receives blood from body
2)
Ventricle – pumps blood to body
Arteries carry blood from heart to gills & other body organs. This blood
is high in oxygen after leaving the gills so it is bright red.
Capillaries – small blood vessels where oxygen is exchanged with
carbon dioxide (CO2). (Oxygen is taken in and carbon dioxide is
released by cells back into the bloodstream)
Veins – carry blood from organs back to heart
Excretory System (removes liquid & nitrogenous waste)
Gills release nitrogen wastes in the form of ammonia (Gills
are also part of the respiratory system)
Kidneys concentrate liquid nitrogenous wastes in urea,
then pass it to the bladder where it’s stored until release,
passing to a cloaca (combination of urinary tract just
before urogenital opening) and out an opening behind
the anus.
Gills & kidneys also release excess salt or water for fish
osmoregulation.
Ventral view:
Pectoral fin
pelvic fin anus urogenital opening
anal fin
Nervous System
Brain & spinal cord
Brain = 5 paired lobes:
- optic lobes – largest lobes, located toward middle of brain, receive
impulses from eyes (sight)
- olfactory lobes – furthest anterior lobes, used for smell
- cerebrum – just anterior to optic lobes, center for instinct &
intelligence
- cerebellum – just posterior to optic lobes, used for muscle
coordination
cerebrum
- medulla oblongata – controls internal organs
Swim Bladder – thin walled sac filled with air to control the
fish’s depth in water. Not present in sharks!
Reproductive System
- External fertilization usually; some fish, such as guppies
& mollies, bear live young & fertilization is internal.
- Separate sexes
- Male testes produce sperm (milt)
- Female ovaries produce eggs
- Sperm & eggs are released through urogenital opening
during external fertilization