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Oceanography > The Nekton Realm > Flashcards

The Nekton Realm Flashcards

1
Q

Nekton

A
  • Pelagic province: neritic and oceanic zones
  • Active swimmers with specialised muscles for locomotion
  • Can migrate long distances
  • Adaptations to environmental conditions
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2
Q

3 clades of nektons

A

Molluscs, crustaceans, vertebrates

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3
Q

Molluscs

A

Second largest phylum of invertebrates. Invertebrate phylum with great morphological diversity

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4
Q

Features of molluscs

A
  • Mantle with a significant cavity for breathing and excretion
  • Radula: feeding apparatus used for cutting or scraping food before entering the oesophagus
  • Structure of the nervous system- paired nerve chords
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5
Q

Molluscs- cephalopods

A

E.g. cuttlefish, squid , octopuses, nautiluses

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6
Q

Cuttlefish

A
  • Internal cuttlebone, gas-filled shell used for buoyancy control
  • Implodes at 200-600m
  • Live in shallow or continental shelf benthic ecosystems
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7
Q

Squid

A
  • Catch > 2 million tonnes/year
    Can swim 10ms-1
  • Water jet propulsion via mantle and siphon- rotates for agility and speed
  • Intelligent
  • Eat 15-20% of body weight/day
  • 5cm-20m
  • Long distance migration: 4000km yr-1
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8
Q

Nautilodia

A
  • Chambered Nautilus
  • Free swimming (slowly) cephalopods w up to 90 tentacles
    Jet propulsion- expel water from the hyponome
    Keeps external shell
  • Large body chamber w subchambers filled with gas similar to air
  • NEUTRALLY BUOYANT
  • Jaws= beak like- feed on crustaceans
  • 5 species exist today
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9
Q

Crustaceans

A

Phylum- Arthropods
Class- Crustacea
e.g. shrimp, krill
- Some swimming ability, restricted capacity to swim against currents
- Many benthic species

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10
Q

Vertebrates

A

Subphylum of Chordata
- Diverse group >100 species
- Depend on ocean for food - primarily ocean dwelling

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11
Q

Cetaceans

A

Whales, dolphins, porpoises

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12
Q

Sirenians

A

Manatees, duongs

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13
Q

Pinnipeds

A

Seals, sea lion, walruses

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14
Q

Otters

A

Sea otters, marine otters

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15
Q

Vertebrates - marine fish

A

Largest and most diverse group
3 classes:
- Agnatha: primitive jawless fish
- Chondrichthytes: cartilaginous fish
- Osteichthytes: bony fish

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16
Q

Agnatha

A

= without a jaw
- Evolved 550 mil years ago
E.g. Sea lamprey- skeletons= cartilage and are parasitic feeders on blood and body fluids
E.g. Hagfish- enter bodies of dead animals and eat from inside

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17
Q

Chondrichthyes

A
  • Cartilaginous skeleton, jaws, paired fins, paired nares, scales, heart with chambers in series
  • Appeared 450 mil years ago
  • 300 species e.g. sharks, skates, rays
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18
Q

Osteichthyes- group 1: Actinopteygii, ray finned fish

A
  • Fins are webs of skin supported by bony spines
  • Highly diverse group- 29,000 marine species
    -Evolved ~ 400mya
19
Q

Osteichthyes- group 2: Sarcopterygii, lobe finned fish

A

Fleshy, lobed paired fins joined to the body by a single bone
- Only 8 living species
- Tetrapodomopha evolved into tetrapods- vertebrates w legs

20
Q

Epipelagic fish

A
  • Most common
  • Commercially harvested
21
Q

Osmosis

A

Movement of water through a semi-permeable membrane that separates 2 solutions of different concentration

22
Q

Hypotonic

A

Internal salinity= lower than external salinity

23
Q

Osmoconformers

A

Marine inverterbrates, maintain internal salinity to equal surrounding seawater

24
Q

Osmoregulators

A

Marine and freshwater fish tightly regulate body osmolarity

25
Q

Internal salinity

A

Stays constant- may be lower or higher than surrounding water

26
Q

Osmoregulation

A

Controls amount of water and mineral salts in blood. Fish must counteract effects of osmosis

27
Q

Hypertonic

A

When internal levels of salt= higher than external levels

28
Q

Marine fish

A

Hypotonic to surroundings- lose water, gain salt.
- Drink lots of water and excrete salt via gills

29
Q

Freshwater fish

A

Hypertonic to surroundings - gain water, lose salt
- Don’t drink freshwater and absorb salt via gills, hypotonic urine to expel excess water

30
Q

Buoyancy

A
  • Fish, marine mammals, molluscs and crustaceans control their deoth habitat by counteracting their tendency to sink
  • Maintain neutral buoyancy
31
Q

Adaptations of sharks - buoyancy

A
  • Reduced specific gravity of bodily fluids
  • Cartilage skeletons
  • No swim bladders
  • Oils and lipids concentrated in tissues and organs (lipids=incompressible)
  • Dynamic lift from forward motion and fins- control depth by swimming
32
Q

Swim bladders

A

Only found in ray-finned fish
- Control buoyancy by adding or removing gases from the blood at different depths
- Lacking in bottom-dwelling fish
- Reduced in continuously swimming fish e.g. tuna

33
Q

Disadvantage of swim bladders

A

-PROHIBIT rapid vertical movements or migrations

34
Q

Sperm Whales

A
  • Dive 300-800m up to 1-2km to feed
  • Spermaceti: Changes in specific density regulate buoyancy and facilitate long deep dives
  • Hold breath for up to 2 hours
35
Q

Locomotion

A
  • Swimming = rapid locomotion
  • 3 types of drag must be overcome for efficient swimming
36
Q

3 types of drag

A
  • Surface Drag
  • Turbulent Drag
  • Form Drag
37
Q

Methods of locomotion to minimise drag

A
  • Manoeuvrability
  • Cruising
  • Acceleration
38
Q

Adaptation strategies

A

Defence and camouflage
- Light colour if viewed from below
- Dark colour if viewed from above

Echolocation

39
Q

Adaptation : mesopelagic fish

A

Scarcity of life=
- large eyes- maximum light
- Bioluminescence- camouflage, predator defence, attract prey, communication

Scarcity of food=
- Large mouth, hinged jaw
- Increased prey choice
- Large ingestions capability, slow growth

40
Q

Influences on migration

A

Temperature variations, water masses, ocean currents (transport system) ; breeding cycle

41
Q

Diadromous fish migration

A

Migrate to select favourable conditions for feeding and reproduction- food and climate

42
Q

Anadromous fish migration

A

fish lay eggs in freshwater and migrate to the sea to grow and mature, then return to spawn e.g. salmon

43
Q

Catadromous fish migration

A

fish breed at sea and spend most of their adult life in freshwater e.g. American eel

Oceanography (23 decks)

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