Study #3: Test 3: Fishes

Question 1

Traits of Vertebrata

Answer 1

1. Largest, most diverse group of chordates
2. Bony vertebrae (endoskeleton) completely replaces notochord
3. All (xc jawless) have vertebral column
4. Anterior end of nerve cord develops into 3 part brain
5. Body plan: head, trunk, post-anal tail
6. Two pairs of appendages (most)
7. Many paired structures: kidneys, gonads, etc.
8. Closed circulatory with heart

Question 2

Theory of Vertebrate evolution: Walter Garstang 1928

Answer 2

Paedomorphosis: evolutionary retention of juvenile traits in adult body.
Theory that a tunicate tadpole larvae failed to become a sessile adult (mutated?), leading to a free-swimming adult
Recent molecular evidence supports a free-swimming ancestor

Question 3

Jawless fish

Answer 3

Ostracoderms: earliest known fossil vertebrates; died off 360 MYA
Gave rise to modern jawless fish: Agnatha (hagfish and lampreys)

Question 4

Super Class Agnatha: jawless fish

Answer 4

Hag fish and lampreys
LACK:
jaws 
scales
paired fins
bony skeleton

Question 5

Class Myxini: Hagfishes

Answer 5

1. Brain enclosed in fibrous sheath
2. No vertebrae
3. Possess notochord
4. 4 pr of sensory tentacles surround mouth, but blind
5. Slime covers body
6. Burrow into mud on marine bottom and feed on dead animals

Question 6

Class Petromyzontida: lampreys

Answer 6

1. True vertebrates: nerve cord surrounded by vertebrae
2. Suckerlike mouth with teeth
3. Adults attach to prey, rasp away scales and feed on their blood

Question 7

Lamprey problem in Great Lakes

Answer 7

1. 1829 a canal was built between between Great Lakes and Atlantic
2. By 1940, lampreys had invaded fisheries causing damage
3. 1950, lake trout fishery collapsed along with other important species
4. Problem still exists today

Question 8

Fishes

Answer 8

1. Oldest, most diverse Vertebrata (>25K species ie most vertebrates are fish)
2. Aquatic; gill breathing
3. Ectothermic (body head from environment)
4. Paired appendages (pectoral-anterior & pelvic-posterior fins)
5. Scales to reduce drag during swimming
6. Jawed

Question 9

Evolution of jaws

Answer 9

Evolved from anterior pharyngeal arches.
Allowed > efficient gill ventilation
Allowed > capture and ingestion of many different foods.
Same genes involved in development of bones supporting gills, also form the jaw.

Question 10

Class Chondrichthyes: Cartilaginous Fishes

Answer 10

1. Endoskeleton cartilaginous
2. Tough skin with scales
3. Teeth are modified scales
4. Ventral mouth, no gill cover
5. No swim bladder to regulate buoyancy

Question 11

Subclasses of Chondrichthyes

Answer 11

Eslasmobranchii: sharks (predators), skates and rays (bottom feeders)
Holocephali: chimaeras (ratfish, ghostfish) no teeth and upper jaw fused to cranium

Question 12

Adv of bony endoskeleton

Answer 12

1. grows with body permitting unlimited body size
2. living tissue
3. Scaffold for muscle attachment
4. Bone:
   stores phosphorous & calcium
   necessary strength for life on land
   Protection (skull)
   Blood cell formation in marrow

Question 13

Class Osteichthyes: Bony fishes

Answer 13

1. Bony Skeleton
2. Bony operculum covers gill opening
3. Swim bladder or lungs for buoyancy
4. Examples: lobed-finned fishes (sarcopterygii)
   and ray finned fishes (actinopterygii)

Question 14

SIGNIFICANCE OF Subclass Sarcopterygii: Lobe-finned fishes

Answer 14

lungs for gas exchange allows survival out of water
Paired fins used to “walk” along bottom (ancestors to tetrapods)
Muscular lobes attached with their fins
Only 3 extant genera

Question 15

Subclass actinopterygii

Answer 15

Most living fishes belong to this group.
Also called Modern bony fishes or teleosts
Fins lack muscular lobes
Swim bladder for buoyancy

Question 16

Traits that make fish so successful

Answer 16

1. Streamlined shape and mucus secretions reduce friction during swimming
2. Paired fins and zigzag bands of muscles provide strong propulsion
3. Can pump large volumes of water with muscles in mouth (swim with mouths open) to extract low amount of O2 present in water

Question 17

Gas exchange across gills

Answer 17

Very efficient using countercurrent exchange method

Question 18

Swim bladder

Answer 18

Gas filled chambers regulates buoyancy.
Gas comes from blood.
Light body tissues and lift from fins also help with buoyancy

Question 19

Osmoregulation

Answer 19

Freshwater problem: osmotic uptake of water; loss of ions; do not drink water; kidneys designed to reabsorb ions, leading to dilute urine
Saltwater problem: must fight water loss
Drink water
Kidneys designed to reabsorb water, leads to salty urine

Question 20

Elasmobranchs

Answer 20

Convert nitrogenous waste to urea and store it in tissues;

This reduces water loss because it is iso-osmotic with the seawater

Question 21

Diadromous fishes

Answer 21

Migrate between freshwater and marine environments

NEED GILLS WHICH CAN DO BOTH

Question 22

Sensory capabilities of fishes

Answer 22

Well developed:
vision
smell
vibration reception (lateral line)
electroreception (ampullae of lorenzini)

Question 23

Reproduction of fishes

Answer 23

1. Internal fertilization, parental care
2. Oviparous: eggs dev outside female, nourished by stored yolk
3. Oviviparous: embryos develop in a modifed oviduct of female, nourished by stored yolk
4. Viviparous: embryo develops inside female, nourished coming directly from her

Question 24

What makes sharks good predators?

Answer 24

***Highly developed senses: can perceive tiny changes in electricity around them; make them skillful hunters
Cartilaginous skeletons: strong and flexible
Replaceable teeth
5-7 gill slits on each side of body
No swim bladder so can cruise bottom for long periods of time