1. Fish

2. Fish evolution

3. What is a Fish? •aquatic vertebrates •most have paired fins - movement
•most have scales - protection
•gills – gas exchange

4. Internal Anatomy

5. Fish
Respiration – fish breathe using gills. They take in water through their mouth and it exits through the gill slits on the side of the head. As it does, it passes over the gills. The water (with oxygen) passes from front to back while blood in capillaries travels from back to front. This is called countercurrent flow and makes respiration more efficient.

6. Fish
Circulation – occurs in a single loop with a 2 chambered heart.

7. Fish Excretion – Most fish produce ammonia as waste.
Gills & kidneys remove waste.
Marine Fish – lose water by osmosis. Their kidneys concentrate waste a & return as much water as possible.
Freshwater fish – have water continuously entering their bodies. Their kidneys pump out diluted urine.
Some fish move from fresh to salt water by adjusting
their kidney function.

8. Fish
Movement –
•Most fish use alternately contracting paired sets of muscles.
•Bony fish use swim bladders to maintain buoyancy because they are more dense than water.

9. Fish Response – Cerebrum – controls smell processes
Cerebellum – coordinates body movements
Medulla oblongata – controls functions of internal organs

10. Fish Response – Lateral line system – sensitive
receptors, down the body, for
detecting currents &
vibrations in the water.
Some fish (sharks & catfish) have evolved organs to detect electrical fields generated by other fish!

11. Fish Reproduction
There are species of fish that reproduce using internal fertilization, and species of fish that reproduce using external fertilization.
Fish can reproduce in one of 3 ways depending on the species:
Oviparous – egg laying fish. Young hatch from eggs outside the mother’s body (Salmon)
Ovoviviparous – eggs form and hatch inside the mother – young are born live – along with egg shells (Guppies)
Viviparous – young develop in the mother’s body – they are nourished by her – and born live (Some species of sharks)

12. Fish Evolution of Fish – Evolution of jaws & paired fins
1st vertebrates to evolve
First fish appeared during the Cambrian Period
-jawless
-armor made of bony plates
Devonian Period “Age of Fishes” – 500 mya
-many with no armor
-ancestors to modern hagfish & lamprey

13. Jaws evolved from skeletal rods in the gill
Fish
Jaws evolved from skeletal rods in the gill
slits of fish.

14. Jawless Fish Hagfish •(formerly) class Myxini •scavengers
•secrete slime
•six hearts
Lamprey
•(formerly) class Cephalaspidomorphi
•filter-feeders as larvae
•parasitic as adults
•sucking disk

15. (cartilaginous fishes)
Class Chondrichthyes
(cartilaginous fishes)

16. Chrondrichthyes •Jaws •Fins •Cartilage skeleton •Placoid scales
•Ectothermic
•Two-chambered heart
•Several gills slits
•Most live in salt water
•Ex: sharks, skates, rays, chimaera, sawfish, etc.

17. Cartilaginous Fish
Shark parts!

18. Class Osteichthyes
Bony Fish

19. Osteichthyes Bony endoskeleton Swim bladder Paired fins 2 groups
1.) Ray-finned fishes
most living species
2.) Lobe-finned fishes
lungfish & coelacanth
Ex: salmon, perch, sturgeon, tuna, goldfish, eel, etc.

20. Fish
Coelacanth
Lungfish – primitive lungs allow it to breath through it’s
mouth during droughts

21. Ecology of Fishes Anadromous – a type of behavior
in which an organism lives in the
ocean but migrates to freshwater
to breed.
Catadromous - a type of
behavior in which an
organism lives in freshwater
but migrates to the ocean