Fishes: The First Vertebrates Chapter 16.1

Chordates Fish have backbones so they are vertebrates Just like us they are in the Phylum –Chordata Largest group of chordates -live in the sea floor (no backbone) -filter feeders (no backbone) Chordates Vertebrates LancelesTunicates

All Chordates At some point in every chordates life they will have 1.Tail-some only have a tail in embryo stage 2.Notochord-flexible rod that gives support that can be replaced by backbone 3.Nerve cord-runs along back with fluid and becomes the spinal cord in vertebrates 4.Pharyngeal Pouch-in all embryos, develop into gills or other parts

Characteristics of Vertebrates vertebrae gives the body support and protects the spinal cord well developed head protected by a skull Fish were the first vertebrates on earth Fossil evidence indicates that the appeared about 500 million years ago.

Warm Blooded vs. Cold Blooded Endotherms- animals that have a stable body temperature due to energy released by chemical reactions in their cells Examples: birds and mammals Ectotherms-animals that can’t control body temperature, rely on surrounding to stay warm Examples: amphibians, reptiles, and most fish

Characteristics of Fish 1. Swimming – Fishes will use fins to help move and have scales to protect their body and lower friction when swimming 2. Senses -Fishes have a brain, sense of vision, hearing and smell. Some have a lateral line with are sense organs that detect vibrations

Characteristics of Fish continued.. 3. Breathing -gills allow water to pass through. Oxygen enters the membranes of the gills to the blood and remove CO2 from the blood 4. Reproduction -external fertilization allows females to lay eggs in the water and males drop sperm over them. Some perform internal fertilization

5 Classes of fish 1.Armored Fish (EXTINCT) 2. Spiny Sharks (EXTINCT) 3. Jawless Fish 4. Cartilaginous Fish 5. Bony Fish

Jawless Fish Eel-like fishes with smooth, slimy skin and round mouths without jaws. Skeleton is cartilage with no backbone Eat dead fish on ocean floor with the help of a suction cup mouth Scavengers Lampreys Hagfish

Cartilaginous Fishes Body is made completely of cartilage Have a jaw and are strong swimmers Predators with strong sense of smell and site Store oil in liver to help them float, but need to keep moving to stay afloat Will suffocate if they don’t keep water moving over gills

Joke Break What lies at the bottom of the sea and shakes? A nervous wreck

Bony Fish 95% of all fish Range in size from 1 cm to 8.6 meters long Have a skeleton of bone and can rest in one place without swimming Swim bladder-balloonlike organ fills with oxygen and other gases to allow fish to float Two classifications 1.ray-finned-have fins with bones (trout, minnows, perch) 2.Lobe-finned-thick muscular fins (thought to be ancestors of amphibians, because they have air sacs that act as lungs)