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Biology - Animals Vertebrates

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    Study Guide Biology – Animals: Vertebrates 1. Vertebrates Animals can be grouped in a simple way based on one key feature: whether or not they have a backbone. Using this idea, scientists divide all animals into invertebrates and vertebrates . 1.1 Invertebrates vs. Vertebrates • Invertebrates are animals without a backbone . • Vertebrates are animals with a backbone . Most animals on Earth are invertebrates. They appear in every major animal group , including a large group called the Chordata . 1.2 What Is the Phylum Chordata? The phylum Chordata includes animals that share three important features at some stage of their life: 1. A notochord (a flexible supporting rod) 2. A hollow nerve cord 3. Gill slits Not all chordates are vertebrates. However, vertebrates belong to this phylum . 1.3 Vertebrates: The Subphylum Vertebrata Within the phylum Chordata, animals that develop a backbone are placed in a smaller group called the subphylum Vertebrata . • There are more than 40,000 living vertebrate species . • Vertebrates include the largest animals ever to live on Earth .

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    Study Guide ○ Dinosaurs were vertebrates. ○ The blue whale , the largest animal alive today, is also a vertebrate. 1.4 Major Groups of Vertebrates Vertebrates are divided into several major classes. These include: • Fishes • Amphibians • Reptiles • Birds • Mammals Each group has its own unique traits, but all share the defining feature of a backbone. 2. Quiz Animals Vertebrates 1. Question How many living species of vertebrates are there? Answer Choices • 120,000 • 200,000 • 60,000 Correct Answer 60,000 Why This Is Correct

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    Study Guide Scientists estimate that there are about 60,000 living species of vertebrates on Earth today. These include fish, amphibians, reptiles, birds, and mammals. This number reflects currently known and classified species. 3. Fishes Fishes are animals that live in water. Their bodies are streamlined , which means they are shaped to reduce resistance as they swim. Most fishes also have a strong, functional tail , helping them move quickly and smoothly through water. To breathe, fishes usually use gills , which allow them to take oxygen from water. A few species also have lungs that work alongside gills, giving them extra help with breathing. 3.1 Jawless Fishes: Agnatha One group of fishes is called Agnatha , which means “without jaws.” • These fishes do not have jaws . • Examples include lampreys and hagfishes . • They feed in a unique way by sucking blood and other body fluids from their prey, usually other fishes. These jawless fishes represent some of the simplest fish body plans still alive today.

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    Study Guide 3. 2 Early Jawed Fishes: Placodermi (Extinct) Another group of fishes is the Placodermi . • Placoderms are extinct , meaning they no longer exist. • They are important because they were the earliest known fishes with jaws . • They lived mostly in freshwater and stayed near the bottom. • Their bodies had a partly bony internal skeleton and hard, armored plates on the outside. Placoderms helped set the stage for more advanced fishes that came later. 3. 3 Cartilaginous Fishes: Chondrichthyes The class Chondrichthyes includes fishes with skeletons made entirely of cartilage , not bone. • This group includes sharks, skates, and rays . • They breathe through several vertical gill openings located on both sides of the throat. • Cartilage makes their bodies lighter and more flexible than those with bony skeletons. 3. 4 Bony Fishes: Osteichthyes Most fishes we recognize today belong to the class Osteichthyes , or bony fishes .

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    Study Guide • They have bony skeletons . • They live in both saltwater (such as tuna, mackerel, and herring) and freshwater (such as trout, striped bass, and goldfish). • Bony fishes became especially successful during the Devonian Period , often called the Age of Fishes . These fishes have: • Gills for breathing • Fleshy pectoral and pelvic fins for movement and balance 3. 5 Ray - Finned Fishes and the Swim Bladder The most common bony fishes today are ray - finned fishes . • They have a special organ called a swim bladder . • The swim bladder is a gas - filled sac near the gut. • It helps the fish control buoyancy , allowing it to float at different depths without much effort. 4. Quiz Fishes 1. Question What trait defines the class of fish called Agnatha ? Answer Choices • bony • jawless • lungs Correct Answer jawless

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    Study Guide Why This Is Correct The class Agnatha includes fish that do not have jaws . In fact, the word Agnatha literally means “without jaws.” These fish also lack paired fins and include animals such as lampreys and hagfish. 2. Question What trait defines the class of fish called Chondrichthyes ? Answer Choices • armored plates • cartilaginous • swim bladder Correct Answer cartilaginous Why This Is Correct Fish in the class Chondrichthyes have skeletons made of cartilage rather than bone . This flexible but strong material gives the group its name, which means “cartilage fish.” Sharks, rays, and skates are examples of cartilaginous fish. 3. Question What trait defines the class of fish called Osteichthyes ? Answer Choices • bony • cartilaginous • jawless Correct Answer bony

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    Study Guide Why This Is Correct Fish in the class Osteichthyes have bony skeletons , which is the defining feature of this group. The name Osteichthyes means “bony fish.” Most modern fish, such as salmon and goldfish, belong to this class. 5. Amphibians Amphibians are special animals because they can live both in water and on land . Their name reflects this dual lifestyle. They belong to the class Amphibia and play an important role in showing how life first moved from water onto land. 5.1 Where Amphibians Came From Scientists believe amphibians evolved from lobe - finned fishes about 370 million years ago . This transition was important because air contains more oxygen than water , making breathing on land more efficient. A key fossil discovery helped explain this change. In 2006, scientists discovered a fossil called Tiktaalik . It is considered a remarkable transitional form between fish and early land animals (tetrapods). Tiktaalik showed a mix of features: • Like a fish, it had fins and gills • Unlike most fish, it had a neck, shoulders, ribs , and fin bones arranged like a limb (humerus, radius, ulna, and wrist bones) These traits show the early steps toward animals walking on land. 5.2 Modern Amphibians Today, amphibians include: • Frogs • Toads

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