Answers to STUDY BREAK Questions
Essentials 5th
Chapter 12
LIFE IN THE OCEAN
1. What do I mean when I write “all life in Earth is fundamentally the same?” A shark and a seaweed don’t seem similar.
A shark and a seaweed are certainly superficially dissimilar, but the physical and biochemical organization of the cells that comprise both is startling in its similarity. On the molecular level, there are few differences.
2. How does an atom of iron in steel differ from an atom of iron in your blood?
An atom of iron is an atom of iron wherever it is found. There are no differences in the structure of an iron atom incorporated into a hemoglobin molecule and an atom or iron holding up a bridge. The definition of life depends on the manipulation of energy, not the physical composition of the objects themselves.
3. What are the starting products for photosynthesis? The end products?
Photosynthesis requires carbon dioxide, water, and light energy. The carbohydrate glucose and oxygen are end products.
4. How is chemosynthesis different from photosynthesis?
Chemosyntheis does not require light, but instead releases the energy held in chemical bonds in molecules of simple hydrogen- and sulfur-containing compounds to construct glucose from carbon dioxide.
5. What do primary producers produce? How is productivity expressed?
The immediate organic material produced is the carbohydrate glucose. Primary productivity is expressed in grams of carbon bound into organic material per square meter of ocean surface area per year (gC/m2/yr).
6. What is a trophic pyramid? What is the relationship of organisms in a trophic pyramid?
A trophic pyramid is a representation of mass flow through a system of producers and consumers . A food web a more accurate representation of what actually happens: a group of organisms interlinked by complex feeding relationships in which the flow of energy can be followed from primary producers through consumers.
7. Does this have anything to do with food webs? How?
A trophic pyramid implies an oversimplistic view of a marine community. Real communities are more accurately described as food webs, an example of which is provided as Figure 12.9. A food web is a group of organisms linked by complex feeding relationships in which the flow of energy can be followed from primary producers through consumers. Organisms in a food web almost always have some choices of food species.
8. What is an extremophile?
Extremophiles are capable of life under extreme conditions of temperature, salinity, pressure, or chemical stress.
9. What is an autotroph? A heterotroph? How are they similar? How are they different?
Autotrophs make their own food. The bodies of autotrophs are rich sources of chemical energy for any organisms capable of consuming them. Heterotrophs are organisms (such as animals) that must consume food from other organisms because they are unable to synthesize their own food molecules.
10. What’s a limiting factor? Can you provide an example?
Often too much or too little of a single physical factor can adversely affect the function of an organism. Lack of light would be limiting to a photosynthetic organism.
11. How characterizes the photic, euphotic, and disphotic zones?
Light illuminates the entire photic zone (during the day). The euphotic zone is the upper segment of the photic zone in which illumination is sufficient for photosynthesis to occur. The disphotic zone, while still lit, is too dark to support photosynthesis.
12. How does metabolic rate vary with temperature?
An organism's metabolic rate increases with temperature. Clearly there is an upper limit – too much heat and the organism cooks.
13. How do dissolved gas concentrations vary with temperature? Now look at your answer to the last question. Do you see a problem for marine organisms?
Colder water contains more gas at saturation. Metabolic rates rise with rising temperature. As temperature rises, metabolic demand for oxygen will exceed supply which may lead to the death of the plants and animals in the area.
14. Does the great hydrostatic pressure of the seabed crush organisms?
Land animals live in air pressurized by the weight of the atmosphere above them. Pressures inside and outside an organism are virtually the same, both in the ocean and at the bottom of the atmosphere. Nobody gets mashed.
15. How is diffusion different from osmosis?
Liquids and gases diffuse through water from zones of high concentration to zones of low concentration. Osmosis is more specialized -- it is diffusion of water through a membrane.
16. Distinguish between the pelagic and neritic zones.
The pelagic zone consists of ocean water. If the water is over the continental shelf, it is considered neritic. (Water over the deep seabed is in the oceanic zone.)
17. Where would you look for a benthic organism?
Benthic organisms are found on or in the seabed.
18. Is evolution by natural selection a random process?
Although mutations occur randomly, evolution by natural selection is anything but random. The natural environment winnows favorable mutations from unfavorable ones—hence the origin of the term natural selection.
19. How is evolution by natural selection thought to operate?
Write a summary of the steps, and then check the list in the chapter.
20. How are new species thought to originate?
Species can arise by physical isolation. Because the number of breeding animals within an isolated species may be small, evolutionary change may be rapid. Generation after generation, the species will change relatively rapidly to suit its new habitat.
21. What’s convergent evolution?
Since physical conditions in the open ocean are relatively uniform, large marine animals with similar life-styles but different evolutionary heritages eventually tend to look much the same. That is, similar conditions may result in coincidentally similar organisms.
22. How is a natural system of classification different from an artificial system?
A natural system of classification for living organisms relies on organism's evolutionary history and developmental characteristics. Any system dependent on other schemes is artificial – that is, it does not reflect the underlying biological relationships between categorized organisms.
23. What are the three domains of living things?
Bacteria, Archaea, and Eukarya
24. How are organisms named?
Linnaeus's system of classification was decidedly natural. Though Darwin's insights into evolutionary relationships were nearly a century in the future, Linnaeus's understanding of the relationships between organisms, and his ability to arrange organisms into like categories, was remarkable. His was a system of classification based on hierarchy, a grouping of objects by degrees of complexity, grade, or class. In this boxes-within-boxes approach, sets of small categories are nested within larger categories. Linnaeus devised names for the categories, starting with kingdom (the largest category) and passing down through phylum, class, order, family, and genus, to species (the smallest category).
25. How is a community different than a population?
A community is comprised of the many populations of organisms that interact with one another at a particular location. A population is a group of organisms of the same species occupying a specific area. The location of a community, and the populations that comprise it, depend on the physical and biological characteristics of that living space.
26. How are benthic communities different from pelagic communities?
Benthic organisms live on or in the bottom; pelagic organisms live suspended in the water column.
27. How is a niche different from a habitat?
There are many different places to live and many different "jobs" for organisms within even a simple community. Those “jobs” are called niches. A habitat is an organism's "address" within its community, its physical location. Each habitat has a degree of environmental uniformity. An organism's niche is its "occupation" within that habitat, its relationship to food and enemies, an expression of what the organism is doing. For example, the small fishes living among the coral heads in a coral reef community share the same habitat, but each species has a slightly different niche. Each population in the community has a different "job" for which its shape, size, color, behavior, feeding habits, and other characteristics particularly suit it.
28. How would you describe the species diversity of an “easy” habitat – perhaps an estuary?
Generally, the “easier” the habitat (that is, the milder the environmental extremes and the larger the quantity of food and energy available), the more organisms will attend the party. Species diversity in these places is relatively high.
29. What’s a climax community? What process terminates in a climax community?
A stable, long-established community is known as a climax community. This self-perpetuating aggregation of species tends not to change unless disrupted by severe external forces such as violent storms, significant changes in current patterns, epidemic diseases, or influx of great amounts of fresh water or pollutants.
30. Can you think of any way to prevent a cataclysmic asteroid or comet impact once the object’s path has been shown to be on a certain collision course?
The near-space environment is being scanned for Earth-crossing comets and asteroids (bodies whose orbits intersect that of the Earth). The resources dedicated to this task are meager, however, and it will be decades before most of the potential threats are catalogued. Congress has not supported a significant increase in funds for this purpose, and the attention of the public waxes and wanes with Hollywood’s interest in the topic.
Some indication of public response can be gleaned from the same Hollywood movies. Among the earliest and best of these is a 1950s George Pal production titled “When Worlds Collide” that greatly influenced me to study science when I was a small and impressionable boy. In that memorable film, a select few folks left Earth in large transport ships moments before the collision to settle on another world. A better solution (or so it seems to me) would be to identify and then deflect any incoming asteroids. How might that deflection be accomplished? Hmmmm.
31. Do you think all life on Earth would be wiped out by a huge impactor?
Life is tenacious. Unless surface temperatures rose everywhere to high temperatures, some extremophiles might survive. Given another billion years or so, evolutionary processes would again produce some interesting organisms.
32. Why do we see relatively few impact craters on Earth?
Because, unlike the Moon or Mars, our active atmosphere supplies erosive water to scour the surface, erasing the images of impacts more than a few million years old.
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