1. Higher Chordata: Subphylum Vertebrata: The Fishes
Biology 11
Higher Chordata:
Subphylum Vertebrata:
The Fishes

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

3. 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

4. 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

5. 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

6. 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

7. 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

8. Lampreys - most are parasites

9. hagfish

10. 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

11. 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

12. 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

14. Hammerhead Shark
Tiger Shark

15. 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

16. 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)

17. 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)

18. 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)

19. 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

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

22. 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)

23. 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

25. End
Living planet the open ocean