From Biol301

Contents 1 Early Vertebrate Evolution 1.1 1. Large Brain 1.2 2. Internal Skeleton 1.3 3. Rapid Movement 1.4 4. Large Size 2 Focus on Fish 2.1 1. Jawless Vertebrates (agnatha) 2.2 2. Jawed Vertebrates 2.2.1 Two (2) major groups 2.2.1.1 1. The Class Chondrichthyes 2.2.1.2 2. The Class Osteichthyes 2.2.1.2.1 Three groups of boney fish 2.2.1.3 Problem with Boney Fish 3 Problems with Existing Rank Taxonomy 3.1 Solutions

Early Vertebrate Evolution

• Features that came later in some vertebrates include lungs, teeth, eggs, etc.
• Four (4) key features evolved in early vertebrates

1. Large Brain

• Necessary to sense environ and move quickly
• All vertebrates are bilaterally symmetrical with an increased concentration of nervous tissue at the anterior end.

2. Internal Skeleton

• Can grow without having to molt
• Supports larger weight

3. Rapid Movement

• Facilitated by fixed attachment of muscles (to the skeleton)

4. Large Size

• Supported by internal skeleton
• Vertebrates could grow more quickly because they could move to food sources instead of filter feeding (waiting for food to float by).

Focus on Fish

• Vertebrates have two (2) superclasses, and therefore fish can be broken down by which vertebrate superclass they belong to.

1. Jawless Vertebrates (agnatha)

• Includes lampreys (suck blood), hagfish, etc.

2. Jawed Vertebrates

• Includes shark, salmon, humans
• Can injest large food particles.
• Jaws evolved from gill supports.

Two (2) major groups

1. The Class Chondrichthyes

• Chond = cartilage, ichthyes = fish.
• Includes sharks and reyes
• Cartilage skeleton (a secondary loss of bone, meaning they had cartilage, then bone, then evolved away from bone again)
• Only 750 extant species known.
• Well developed sensory system (smell, eyesight, lateral line, etc.)

2. The Class Osteichthyes

• Known as boney fish.
• About 30k extant species
• Operculum = gill cover that allows stationary position.
• Have well developed color vision
  • Note coral reef fishes

Three groups of boney fish

1. Ray Finned Fish

• Most of the fish we know
• Salmon, rockfish, goldfish

2. Lobe Finned Fish

• One or two extant species
• In genus Coelacanth
• Live deep in the ocean around Southern Africa and Indonesia
• Lobes are thick and muscular which is a preadaptation for life on land.

3. Lung Fish

• Found around South America and Africa
• Fewere than 100 species known.

Problem with Boney Fish

• No trait to unite the group.
• Osteichthyes is paraphyletic.

Problems with Existing Rank Taxonomy

1. Many traditional groups are paraphyletic (especially in the vertebrates).
2. Rank levels are not equivalent across the group.
3. We need more than eight (8) ranks.

Solutions

• Throw out the ranks and just name all the monophyletic groups.

• video....