Lecture 16 - Megafauna Flashcards

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1
Q

What is the average depth of water at the shelf break?

A

150m

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2
Q

What percentage of the sea surface is the oceanic zone?

A

92%

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3
Q

What percentage of the Earth’s surface area is the oceanic zone?

A

65%

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4
Q

Why is the oceanic zone referred to as a heterogeneous environment?

A

It varies in physiological and biological parameters over large and small geographic scales.

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5
Q

What are megafauna?

A

Large animals (over 40 kg)

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6
Q

Megafauna are what type of selected animal?

A

K-selected

  • Large
  • Long-lived
  • Low fecundity
  • Vulnerable to exploitation
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7
Q

What are top down effects?

A

Predation and grazing by higher trophic levels on lower trophic levels ultimately controls ecosystem function.

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8
Q

What are bottom-up effects?

A

The nutrients supply to the primary producers that ultimately controls how ecosystems function.

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9
Q

Give an example of top down effects.

A

Shift in killer whale behaviour resulted in declining sea otter numbers, resulting in explosion in sea urchin numbers, which overgrazed the kelp.

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10
Q

What is a trophic cascade?

A

When predators limit the density and/or behaviour of their prey and thereby enhance survival of the next lower trophic level.

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11
Q

Other than size, what can we classify organisms according to?

A
  • Taxonomic group
  • Lifestyle (e.g. sessile vs pelagic)
  • Trophic level
  • Habitat
  • Depth
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12
Q

What area do the public tend to associated megafauna with?

A

The tropics, because warmer waters are more accessible.

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13
Q

How many species of marine megafauna are observed?

A

78

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14
Q

Give the six categories of marine megafauna.

A
  • Pelagic seabirds
  • Cetaceans
  • Pinnipeds
  • Sharks
  • Marine turtles
  • Large pelagic teleost fish
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15
Q

How many species of megafauna are there that belong to the group

a) Pelagic seabirds?
b) Cetaceans?
c) Pinnipeds?
d) Sharks?
e) Marine turtles?
f) Teleost fish?

A

a) Seabirds = 43
b) Cetacenas = 20
c) Pinnipeds = 6
d) Sharks = 4
e) Marine turtles = 4
f) Teleosts = 1

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16
Q

Give some UK megafauna.

A
  • Herring gull
  • Atlantic puffin
  • Great shearwater
  • Harbour seal
  • Fin whale
  • Arctic tern
  • Great skua
  • Northern gannet
17
Q

Give some adaptations for buoyancy in marine megafauna.

A
  • Some marine mammals have accessory air sacs.
  • Some marine mammals use air trapped in dense wool undercoats.
  • Swim bladders lost in fast-moving fish as they prevent rapid depth change.
  • Many marine fish (sharks) rich in lipids that help with buoyancy.
18
Q

Give some examples of adaptations for locomotion in marine megafauna.

A
  • Body shapes that create propulsive force, e.g. turtle flippers
  • Body shapes that reduce resistance of body during movement, e.g. teardrop-shaped tuna.
19
Q

Describe the lifecycles of leatherback turtles.

A
  • Pelagic and forage on zooplankton
  • Reach maturity 8-15 years of age, females mate every 2-3 years but can breed annually
  • Extensive movement after egg-laying with little consistency.
20
Q

How do turtles navigate?

A

Using geomagnetic cues

21
Q

Describe the migrations of Atlantic bluefin tuna.

A
  • Western population breed in Gulf of Mexica, forage towards eastern-Atlantic
  • Eastern population breed in Mediterranean, forage towards western Atlantic.
22
Q

Where are there mixed populations of Atlantic bluefin tuna?

A

On the feeding grounds of the Mid-Atlantic bight.

23
Q

What is an optimal strategy when searching complex prey landscapes?

A

Levy flight

24
Q

What is Levy flight?

A

Many small movements, and fewer larger movements.

25
Q

What is the ideal Levy exponent?

A

2

26
Q

What groups of marine megafauna display Levy-like movements?

A

Sharks, teleosts, sea turtles, penguins.