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: Rays: Thicker heavier tails No spines on tail 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=d7WtduFycDY Living planet the open ocean