our first focus…fish in your own words, describe what makes a fish a fish
TRANSCRIPT
Our first focus…FISH
In your own words, describe what makes a fish a fish.
What Is A Fish?Definition: aquatic
vertebrates that are characterized by scales, fins, and gills
Have a cranium (skull)
Lack limbs or digits
Types of Fish3 main groups of
fishes:Jawless fish
Ex: hagfish
Cartilaginous fish Ex: sharks
Bony fish Ex: puffer fish
Thinking about the three types of fish, draw a cladogram with how they could be classified. Explain why you chose it.
Evolution of FishesJawless fishes with heavy
armor (bony plates)Then came the fishes
with jaws (an important evolutionary innovation!)
Then came paired appendages (pectoral and pelvic fins)
Then came the cartilaginous and bony fishes
Jawless Fish (Agnatha)Lampreys
Filter feeders as larvae, parasites as adults
Head is a round sucking disk with a mouth in the middle
HagfishWorm-like bodies with 4-6
short tentacles around the mouth
Only a light-detecting region, no eyes
They use a toothed tongue to scrape holes into dead or dying fish for food
They secrete tons of slime
http://www.youtube.com/watch?v=bqk0mnMgwUQ
Cartilaginous Fish (Chondricthyes)
Chondros means cartilage, icthyes means fishToothlike projections all over their cartilaginous
skin (act like scales and aide in swimming)Multiple rows of teethA typical shark may go through 20,000 teeth in
one lifetime!
Bony Fishes (Osteichthyes)~40% of all vertebrates are bony fishes
What are the 3 big questions we want to think about for every group of animals we are going to be discussing.
How do they Reproduce?Most are oviparous (egg layers)
with external fertilizationSome have internal fertilization
and lay fertile eggs (sharks)Varied parental care (from non-
existent to utmost importance)Some fish are ovoviviparous
(young develop inside the mother’s body but are not nourished directly by the mother’s body)
Still others are viviparous (species that bear living young and have unborn young that are nourished directly by the mother’s body)
How do they eat: FeedingVariety of feeding
mechanismsHerbivorescarnivores parasitesfilter feedersdetritus feeders
Many fish do more than one
DigestionFood goes from the mouth to the esophagus,
to the stomach where it is broken downIn some fish, the broken down food can go to
fingerlike pouches at the point where the stomach and the intestines meet called pyloric ceca
Any other undigested food gets passed through the anus as waste
ExcretionFish excrete nitrogenous waste in the form
of ammonia through gills and kidneysOsmoregulation:
Freshwater fish
Saltwater fish
How do they Survive:Respiration
Most breathe with gills
Gills contain many capillaries, allowing for maximum exchange of O2 and CO2
Dissolved gasses are sometimes stored in a swim bladder, a sac that lies on top of the body cavity and is used for buoyancy
How do they survive:Internal Transport
Closed circulatory systemTwo-chambered heart (atrium, ventricle)
ExExplain how blood and gas exchange within a fishes circulatory system.
How do they Survive:Response
Well-developed nervous system organized around a brain
Spinal cord (hollow dorsal nerve cord) lies behind the brain and may be protected by a vertebral column
Chemoreceptors and electrical detectors may aid in strong sensory perception in some fish