Vertebrate Evolution

Question 1

Chordates (Chephalochordata): Notochord

Answer 1

Early spinal cord provides skeletal support and a structure/axis for muscle attatchment

–> crucial for more complex, coordinated movement (swimming)

Question 2

Urochordata (Tunicates):
Tunic (made of cellulose)

Answer 2

Thick protective layer that covers the body.

–> protection against predators/environmental hazards
–> support - helps maintain shape & structure imp. for sessile adult stage
–> supports structure of siphons for suspension feeding mechanism

Question 3

Basal Vertebrates:
Vertebral column no Jaw

Answer 3

Bones that line + protect spinal cord, structural support

–> better muscle attachment to bone allows for more active lifestyles

Question 4

Early Vertebrate innovations

Answer 4

Dental elements: barbed hooks in mouth

Soft bodied, lacking jaws, cartilage skeleton

Larger eyes for locating prey

Question 5

Gnathostomes (Sharks):
Jaws/mineralised skeletons

Answer 5

Modified skeletal rods: JAWS.
- Allowed predation of larger more armoured prey

• Enhanced Respiration (dont need to constantly move to breathe)
• Enlarged forebrain (better sense of smell and sight)

–> signif. changed ecological interactions (created food chain)

Question 6

Osteichthyes: Ray-finned fish
Bony Endoskeleton + Lung Derivatives

Answer 6

Bony endoskeleton
- stronger, more rigid then cartilage (more muscle leverage)
–> stronger movement/increased mobility

Swim Bladder (controlled buoyancy)
–> conserve energy by not having to swim constantly

Question 7

Lobe-fins (Quadrupeds):
Precursors to limbs

Answer 7

–> structural basis for evolution of limbs crucial for terrestrial locomotion

Question 8

Tetrapods (Amphibia):
Limbs with digits

Answer 8

For terrestrial movement, enable life on land.

–> Take advantage of new environmental niche (more resources, terrestrial plants)

–> temporarily escape large marine predators (remained as aquatic life stages occur in water)

Question 9

Amniotes (Amniotic Egg):

Answer 9

Lay amniotic eggs (in water needs to stay moist): Allowing development on land

–> hard shell provides protection and prevents dehydration in hot arid environments

–> able to develop more in the egg

–> rib cages help ventilate lungs

Question 10

Reptilia (Reptiles):

Answer 10

Scaly skin (keratin): armour and decreased water loss

Internal fertilisation: ensures eggs are safe during early development

More effective limbs for movement on land, some even adapted for flight

Question 11

Mammalia (Mammals):

Answer 11

• Mammary glands: produced milk that could nourish young

–> prolonged care of young enhances survival.

• Endothermy: generate heat metabolically allowing for habitat flexibility
• Inner ear bones (hearing sensitivity)
• Heterodonty (differentiated teeth for larger diet range)