Biology 11 Higher Chordata Subphylum Vertebrata The Fishes

Biology 11 Higher Chordata: Subphylum Vertebrata: The Fishes

Higher Chordata Objectives: Vertebrata • Describe the 3 Classes and an example animal • Anatomy of a ray finned fish

Subphylum Vertebrata Characteristics: 1. Endoskeleton of bone or cartilage which surround the dorsal nerve cord (a backbone or vertebral column) 2. Notochord absent or reduced in adult 3. Pronounced cephalization 4. A closed circulatory system

Characteristics of All Fish • 1. breathe using gills • 2. have 2 chambered hearts (and closed circulatory system • 3. reproduce sexually • 4. highly developed sensory system

Characteristics of All Fish • 1. breathe using gills • as a fish takes water in through its mouth, water passes over the gills & then out through slits at the side of the fish • 2. have 2 chambered hearts • One chamber receives oxygen-poor blood from the body tissues • The other chamber pumps blood directly to the capillaries of the gills, where oxygen is picked up & carbon dioxide released • 3. reproduce sexually • Fertilization & development is external in MOST fishes • Eggs & sperm can be released directly into the water, or deposited in more protected areas • 4. highly developed sensory systems • Have eyes that allow them to see objects & contrasts between light & dark in the water, but the amount of vision varies among fishes

Class Agnatha Jawless fishes • Much more dominant in the early oceans where they were mud suckers or filter feeders – no articulating jaws • Represented today by Lamprey and Hagfish

Class Agnatha • Evolved gills to improve oxygen uptake and thus increased activity levels • No paired appendages • have smooth, scaleless skin & long cylindrical body • have cartilaginous skeleton • no vertebral column • only vertebrates to retain notochord through all stages of their life

Lampreys - most are parasites

hagfish

Class Chondrichthyes Cartilagenous Fishes • Skeleton is made of cartilage not bone (secondarily evolved) • Evolved articulating jaws by modification of anterior two pairs of gill slits • Have no operculum or air bladder • Very streamlined body with paired fins for steering

Class Chondrichthyes • Have well developed senses, especially smell • have a lateral line system that enables them to sense objects and changes in their environment – is a line of fluid-filled canals running along the sides of a fish that enable it to detect movement and vibrations in the water • Can sense electric currents in water • Are almost all predators • Developed internal fertilization and carry eggs internally (no nutritional connection) as young must swim when born • They are: sharks, skates, and rays

Sharks • have tough, leathery skin that is covered with PLACOID SCALES • mouth is lined with 6 -20 rows of sharp teeth which continuously form and move forward to replace lost or worn teeth • swim continuously – they are denser than water – suffocate if water not moving over gills • large, oily liver that can make up nearly 20% of its total body weight – liver oil is lighter than water and gives sharks buoyancy

Hammerhead Shark Tiger Shark

Skates: - Rounded shape - Thicker heavier tails - No spines on tail - Thorns on tail and back - Elongated nose - Smaller - Lay eggs Rays: - Kite shaped - Thin barbed tails - Spines on tail - No thorns on tail and back - Larger - Give birth to live young

Class Osteichthyes (bony fishes) • There are two main groups of fish seen today: 1. Ray finned fish: • true fish with ray finned appendages • Evolved in fresh water then moved back to the oceans • Most common fish today (salmon, trout etc)

Class Osteichthyes 2. Lung fish and Lobe-finned fish • These two fish evolved in fresh water at a time when periodic and severe droughts occurred • Lung fish seen today in Africa and South America • Use crude lungs to gulp air to assist gills (usually live in stagnant water)

Class Osteichthyes (bony fishes) • Have a calcified skeleton (bones!!) • Well developed system for motility (ray finned fish) – use their paired pectoral and pelvic fins to steer, brake, move up and down, and even swim backwards – air bladder – a thin-walled sac in the abdominal cavity filled with gas dissolved gases in the blood diffuse into & out of the swim bladder • as the bladder fills up, the fish rises and when it deflates, the fish sinks • Have an operculum (covering over gills)

• skin is covered with thin, round scales, called CYCLOID SCALES, which overlap like shingles (can determine age by counting rings of scales • mucus covers scales giving the fish a slimy surface • Unlike sharks, can pump water through their gills even when motionless

Class Osteichthyes 1. Circulatory System • Have a two chambered heart that pumps blood to the gills then the rest of the body

Class Osteichthyes 2. Response/nervous system • vertebrate brain and well developed senses • Eyes that detect light/dark • have two pairs of nostrils as well as chemical receptors scattered over their head and body. – Smell usually gives fish their first clues about food, mates, and enemies • Lateral line that enables them to sense objects and changes in their environment (vibrations)

Class Osteichthyes 3. Reproduction • Have external fertilization and little if any post natal care • Young are born able to swim and feed and must fend for themselves 4. Excretory System • Have a dorsal kidney that excretes mainly ammonia as nitrogen waste

• End • http: //www. youtube. com/watch? v=d 7 Wtdu. F yc. DY • Living planet the open ocean