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.

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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=d7WtduFy
cDY
• Living planet the open ocean

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