Key Concept Review (Answers to in-text “Concept Checks”)
Chapter 13
1. 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. 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 of iron holding up a bridge. The definition of life depends on the
manipulation of energy, not the physical composition of the objects themselves.
3. Living things don’t “get around” the Second Law. They temporarily forestall the
eventual disintegration of any complex system by an organized flow of energy
dedicated to maintaining order. “Death” is the name we give to the cessation of
that organizing flow.
4. Photosynthesis requires carbon dioxide, water, and light energy. Glucose (a
carbohydrate) and oxygen are end products.
5. 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.
6. 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).
7. 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.
8. Extremophiles are capable of life under extreme conditions of temperature,
salinity, pressure, or chemical stress.
9. 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. Four elements—carbon, hydrogen, oxygen, and nitrogen—make up 99% of the
mass of all living things, with nine additional elements comprising nearly all of
the remainder.
11. In the surface mixed layer, the atoms and small molecules that make up the bodies
of organisms may cycle rapidly for a time between predators, prey, scavengers,
and decomposers. When these organisms die, their bodies can sink below the
sunlit upper sea, beneath the pycnocline, where they are isolated from the rapid
biological activity of the surface. Regions of upwelling are critical in returning
these substances to the surface.
12. Carbon dioxide provides carbon for the production of glucose by primary
producers.
1|Page
13. Before it can be incorporated into biological molecules, nitrogen must be bound
with oxygen or hydrogen, or fixed, into usable chemical forms by specialized
organisms, usually bacteria or cyanobacteria.
14. The most rapid recycling occurs in the daily feeding, death, and decay of surface
organisms. A slower loop occurs as the bodies of organisms fall below the
pycnocline, and phosphorus escapes downward into deep ocean circulation. The
longest loop begins with the phosphorus or silicon locked into rocks or shells that
become marine sediments. The sediment is subducted at converging plate
margins, and the phosphorus- and silicon-containing compounds reemerge into
the ocean through volcanoes.
15. 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.
16. 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.
17. An organism's metabolic rate increases with temperature. Clearly there is an
upper limit – too much heat and the organism cooks.
18. Colder water contains more gas at saturation. Metabolic rates rise with rising
temperature. As temperature rises and cell activity increases, metabolic demand
for oxygen will exceed supply which may lead to the death of the plants and
animals in the area.
19. 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 crushed.
20. 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.
21. The smaller the cell, the greater its surface-to-volume ratio, and the more
efficiently materials can cross the outer cell membrane to be distributed through
the interior.
22. 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.)
23. Benthic organisms are found on or in the seabed.
24. 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.
25. Write a summary of the steps, and then check the list on pages 365-6.
26. 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.
27. Since physical conditions in the open ocean are relatively uniform, large marine
animals with similar life-styles but different evolutionary heritages eventually
2|Page
tend to look much the same. That is, similar conditions may result in
coincidentally similar organisms.
28. 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.
29. Living organisms are subdivided into three Domains: Bacteria, Archaea,
Eukarya.
30. Scientific names describe organisms, usually in Latin or ancient Greek (because
words in these languages do not change their meanings over time). Additionally,
organisms are grouped with similar organisms in a category-within-category
hierarchy (as seen in Figure 13.25).
3|Page