Transitions between land and water

Question 1

what is it that organisms use to enhance their performance

Answer 1

adaptations such as in swimming = flippers, blubber, stream line body plan

Question 2

give some examples of aquatic tetrapods which went back to the sea and what are the differences between them

Answer 2

whales
penguins
crocodiles
turtles

= different levels of aquaticness such as orcas spending all the time in water vs penguins only going in water to feed and turtles only on land to lay eggs

= therefore all have different adaptations for the different levels of aquaticness

Question 3

in the evolution of aquatic tetrapods what is the number of times they went from land to sea

Answer 3

27 total

amphibians = 1 (extinct species)
reptiles = 9 extinct species and 5 extant = 14
birds = 1 extinct species 3 extant = 4
mammals = 2 extinct species and 5 extant = 7

Question 4

what are some explanations for such frequent returns to the sea

Answer 4

Mass extinctions
tectonic restructuring of ocean systems
climatic changes

Question 5

outline how mass extinctions lead to such frequent returns of tetrapods to the sea

Answer 5

= mass extinctions create alot of opportunities due to the opening of ecological niches when species go extinct
= this allows speciation events to occur as a result of niche availability and species moving into these niches due to lack of competition

Question 6

outline how mass tectonic restructuring lead to such frequent returns of tetrapods to the sea

Answer 6

creates new ocean environments such as inner seas which can be inhabited by new species due to new resource availability

Question 7

outline how climatic change has lead to such frequent returns of tetrapods to the sea

Answer 7

often occurs during times of warming due to the creation of new opportunities as a result of increasing sea levels = new environments

can also occur as a result of cooling temperatures as cooler temps increase productivity in oceans

Question 8

give some examples of ancient aquatic tetrapods

Answer 8

Mesosaur = around 300 ma
ichthyosaur = around 250 ma
sauroptygeria = around 252 ma
mosasur = around 100 ma

Question 9

what is a secondary adaptations

Answer 9

refers to a characteristic or trait that an organism develops as a result of an initial adaptation to a specific environment or condition. Essentially, it’s a subsequent evolutionary modification that complements or enhances the primary adaptation.

= aquired after clades move to land then returned to sea

Question 10

give some examples of secondary adaptations of aquatic life

Answer 10

flippers and a flattened body = turtles
paddle like tail, permable skin = sea snake
smooth surfcaes and streamline body = penguin

Question 11

what are the differences between terrestrial and aquatic environments that aquatic tetrapods have to adapt to

Answer 11

water creates more drag then air
animals need to move in the water
= creates the aquatic problem

Question 12

outline the aquatic problem in terms of movement in water

Answer 12

1) resistance
2) 2D vs3D
3) density and viscosity
4) buoyancy
5) pressure

Question 13

to allow movement in water species have adapted to be either appendicular or axial swimmers- what is the difference?

Answer 13

App = movement of just appendages such as flippers e.g. in the plesiosaur

axial = movment of the tails and necks - propulsion at the start of the tail (caringiform), propulsion orginiating in the neck (anguiliform)

more efficient movement need to increase the SA to increase propulsion hence webbed feet or flippers

Question 14

how has the aquatic problem of moving from a 2D to a 3D environment been overcome

Answer 14

needs to maintain stability in the water- does this using a dorsal fin and/or a flattened body
a larger dorsal fin will be more fast than a flattened body
= trade off = big dorsal fin = more stable but easier to spot by predators

Question 15

how has the aquatic problem of water density and viscosity been overcome

Answer 15

As the body moves, it disturbs the water molecules forcing the water to flow around
- water enters empty space creating turbulence and creating a sucking down force
DENSITY causes drag
VISCOSITY causes resistance of flow and more friction
= slows the animal down

= has been overcome by adapting a streamlined (torpedo shaped) and smooth surface body plan to minimise water disturbance

Question 16

what is a benefit of water for aquatic tetrapods

Answer 16

provides more support therefore species can have a bigger body plan

Question 17

how has the aquatic problem of buoyancy been overcome

Answer 17

aquatic tetrapods have lungs which causes them to float, in order to overcome this they must achieve neutral buoyancy

Pachyostosis = refers to a condition where bones become unusually thickened or denser than normal (swelling) which weighs the animal down

osteosclerosis = increased mineral deposition in their bones which increases weight

Gastrolithis = added weight such as crocs which eat and hold rocks in their stomach

Question 18

how has the aquatic problem of water pressure been overcome

Answer 18

for every 10m of water depth pressure increases by one atmosphere which causes compression of the gas in spp lungs overcomes this by
1) filling and expanding lungs on the surface before diving
2) during decent the lower lung collapses as the body compresses from the pressure of the water. upper lungs are supported by cartilage which maintains its shape for acent

= FLEXIBLE RIBS AND COLLAPSED LUNGS

Question 19

how has the aquatic problem of breathing air been overcome

Answer 19

aquatic tetrapods dont breathe alot of oxygen therefore have to tolerate high levels of lactic acid in their bodies
over come by
- rapid breathes = empty and refill lungs in seconds
- efficient o2 exchange (90% vs 20% in humans)
- o2 storage in blood instead of lungs to maintain muscle actvity
- slow heart rate for diving
- blood flow to non-essential areas is reduced

Question 20

how has the aquatic problem of salt water been overcome

Answer 20

have to drink salt water and excrete salt otherwise cells shrink causing dehydration
over come by
salt glands

Question 20

how has the aquatic problem of sense disruption been overcome when in water

Answer 20

eyes
= water causes light to bend less, travel slower and filters cooler colours
- larger eyes, more rod cells (more photoreceptors allowing sight at low light levels) , Taputum lucidium

hearing
= sound travels faster and over longer distances
- on lnad vibration passed through air and outer ear canal, in water no external ear (reduce drag) and robust middle ear bones attached to skull OR ecolocation

Question 20

how has the movement of species from land back to sea provided a good example of convergent evolution

Answer 20

analouge structures - similar structures such as fins evloved not due to relatedness but due to similar environmental conditions

secondary adaptations of spp provide perfect example of evolutionary concept of convergent evolution

Question 20

how has the aquatic problem of heat conductivity been overcome

Answer 20

water moves heat 24 x faster than air so spp get cold faster
homeotherms have adpated to this by
- thick blubber
- water repellent oils
- fur
- no dorsal fin = reduced surface area

ectotherms
= tropical distribution