Vertebrate Life Lab 10 - PDF

Vertebrate Life THE HISTORY OF LIFE L AB L AB 10 Early vertebrates Vertebrates are a group of living species with spinal column and back bone. One of the most significant evolutionary events that occurred on Earth was the transition from water-dwelling fish to terrestrial tetrapods. Lobe-finned fis...

Vertebrate Life THE HISTORY OF LIFE L AB L AB 10 Early vertebrates Vertebrates are a group of living species with spinal column and back bone. One of the most significant evolutionary events that occurred on Earth was the transition from water-dwelling fish to terrestrial tetrapods. Lobe-finned fish possessed lungs as well as gills, so the fish could survive through drought and lobed fins which allowed travel onto land During the Devonian the first terrestrial vertebrates the amphibians occur. These later gave rise to the reptiles. During the early stages of evolution, amphibians underwent a number of evolutionary trends to improve their fitness for living on land. Bones became larger and sturdier, skull reduced in size, and legs strengthened. Skull Types The most important characteristic for distinguishing one type of early reptile from another is the structure of the bones in the temple region of the skull, behind the eye. A. Anapsids have the skull solidly encased in bone, with no opening at the rear of the side, and are the most primitive. B. Synapsids posses a single temporal opening low on the side of the skull (they are extinct, but this is the group from which mammals evolved). C. Euryapsids have a single opening high D. Diapsids (ruling reptiles)had two openings, one above the other, separated by a bony connection (Dinosaurs of the Mesozoic, most living reptiles). Bone types 1. Flat bones: Skull, jaw, shoulder blade, and hip 2. Short bones: vertebrae, heel bone, wrist bones 3. Long bones: Arms and legs Dental formulas Some animals have different types of teeth and configurations to their teeth. Mammals have teeth of different sizes and shapes allowing teeth to be specialized for different tasks. These include: ◦ Incisors (I) ◦ Canine teeth (C) ◦ Premolars (P or PM) Human dental formula ◦ Molars (M) I-2, C-1, PM-2, M-3 Because the jaw is bilaterally symmetrical, only one half of the jaw is described Evolution of Humans Sub-species of ancestral Homo