Deck 17: The Open Sea

Question 1

Life in the open sea is characterized by

A) uniform distribution
B) low trophic efficiency
C) dense populations
D) food chains of 7 to 10 links
E) patchiness

Answer 1

A

Question 2

Although less diverse and abundant than in coastal waters, life in the open sea is remarkably diverse. Viruses, bacteria, and archaeons live there and play important roles in food webs and biogeochemical cycles. Eukaryotic phytoplankton primarily are microbes, but sargassum weeds are notable among the megaphytoplankton. Zooplankton include many kinds of microbes, but larvae of fish and several kinds of adult cnidarians, molluscs, and urochordates occur in the open sea. Nekton specialized for open-ocean life include billfish, sharks, yellow-bellied sea snake, leatherback sea turtle, penguins, and many species of whale.

Answer 2

The open ocean zone is that area seaward of the neritic zone, which is further divided vertically. There are two groups of organisms that inhabit the oceanic zone: plankton and nekton. The plankton group is divided into nine categories according to size; there are also classifications that sort them according to their characteristics. Nekton include invertebrates, many species of fish, rays, reptiles, birds, and mammals. Plankton and nekton, along with their decaying excretions and remains, are practically the only sources of nutrients in the open ocean.

Question 3

Describe some of the ways that animals living in the open sea hide from predators.

Answer 3

Most strategies to avoid predation in all environments involve utilization of the environmental objects; in the open ocean there is only, mostly, water. The organisms in the open ocean use strategies that camouflage their presence with the water. Countershading of dark dorsal surfaces creates an appearance of water when viewed from above; light ventral surfaces give the appearance of sunlight from below. Some organisms are transparent, such as jelly fish. Also among jellyfish, as well as other organisms, is the adaptation of stinging cells.

Question 4

The layer of ocean that receives enough sunlight to power photosynthesis is the

A) photosynthetic zone
B) photic zone
C) aphotic zone
D) abyss
E) benthic zone

Question 5

The rate of sinking can be slowed by anatomical adaptations that increase

A) mass
B) volume
C) friction
D) streamlining
E) density

Question 6

What are some adaptations in open-ocean plankton that allow them to be productive despite the nutrient-poor environment

Question 7

Describe some of the strategies animals use to increase their survival in the open sea.

Question 8

Why does it make good ecological sense for the largest sharks to be plankton feeders rather than predators of other nekton

Question 9

Which one of the following is not true of gelatinous zooplankton

A) Bodies are high in water content.
B) Bodies are high in protein content.
C) They reduce density by ion replacement.
D) They have reduced skeletons.
E) They are consumed by few kinds of predators.

Question 10

Life in the open sea is limited mainly by the low concentrations of nutrients, which keep primary production low. In addition, viral lysis of bacterioplankton slows the recycling of dissolved organic matter and the passage of production up the food web. Despite the high efficiency of trophic transfer, the nearly complete daily conversion of new biomass of primary producers to consumer levels keeps the standing crops of phytoplankton small.

Question 11

Describe how the upside-down lifestyle of the purple sea snail and the nudibranch Glaucus has influenced their coloration.

Question 12

A collective term for animals whose distribution is not governed by waves or currents is

A) zooplankton
B) pelagic
C) nekton
D) akinetic
E) pleuston

Question 13

The type of coloration exhibited by many large animals of the open sea is called

A) countershading
B) disruptive
C) cryptic
D) warning
E) reticulated

Question 14

What is marine snow, and what is its significance

Question 15

Describe how a swordfish feeds.

Question 16

The water of the North Atlantic Ocean is colder than that of the tropical Atlantic Ocean. Do you think this difference might affect the shapes of phytoplankton living in these two areas Explain your answer.

Question 17

The largest members of the zooplankton are

A) copepods
B) diatoms
C) jellyfish
D) sharks
E) whales

Question 18

Life in the open sea is challenging because of low levels of nutrients, lack of hiding places, and the need to remain afloat. Small cell size and reliance on a small number of genes reduce the dependence of primary producers and osmotrophs on mineral and organic resources. Patchiness, large numbers, transparency, and low-nutritive quality are several ways in which organisms in the open sea deal with predation. Many plankton and nekton swim by cilia, flagella, appendages, and undulatory tails, but mechanisms of buoyancy and increasing frictional drag also prevent pelagic organisms from sinking from the surface waters.

Question 19

Describe how tunas are adapted for fast swimming.

Question 20

Productivity in the open ocean is limited in most cases by

A) sunlight
B) temperature
C) space
D) nutrients
E) salinity

Question 21

The greatest diversity of nekton is among the

A) squids
B) fishes
C) reptiles
D) birds
E) mammals

Question 22

What are some adaptations that help organisms in the open ocean remain afloat

Question 23

Why is the photic zone of the open ocean not as productive as the photic zone of coastal seas

Question 24

Why is it difficult to keep large tunas alive in public aquariums

Question 25

Food webs in the open sea are based on

A) phytoplankton
B) seaweeds
C) dissolved organic matter
D) viruses
E) marine snow

Question 26

What aspects of reproduction in pelagic sharks indicate adaptations to life in the open sea

Question 27

What problems in feeding mechanics, digestion, physiology, or nutrition might be encountered by predators that feed on gelatinous zooplankton What additional problems might they face in today's seas with drifting bottles and plastic bags