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.

Biology 11
Higher Chordata:
Subphylum Vertebrata:
The Fishes
Higher Chordata Objectives: Vertebrata
• Describe the 3 Classes and an example
• Anatomy of a ray finned fish
Subphylum Vertebrata
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
• have cartilaginous skeleton
• no vertebral column
• only vertebrates to retain notochord through all
stages of their life
Lampreys - most are parasites
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
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
• have tough, leathery skin that is covered with PLACOID
• 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
Tiger Shark
- Rounded
- Thicker heavier tails
- No spines on tail
- Thorns on tail and back
- Elongated nose
- Smaller
- Lay eggs
- 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
• 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
• 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
– 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
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
• Have a two
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
• Living planet the open ocean

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