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Chapter 50
1. Explain why the field of ecology is a multidisciplinary science.
The field of ecology is a multidisciplinary science because the ecological questions form a
continuum with those from other areas of biology, including thoe of gentics, evolution,
physiciology and behavior, as well as other sciences such as chemistry, physics, geology and
meteorology. It also poses many challenges because of the complexity of the research required,
the complexity of the questions, the diversity of the subjects, and the time span involved in
conducting these studies.
3. Describe the relationship between ecology and evolution.
Ecology is the scientific study of the interactions between organisms and their environment.
Events that occur in the frame of what is sometimes called ecological time transaltes into effects
over the longer scale of evolutionary time. The relationship between evolution and ecology is
also seen in Darwin's experiments where the geographical distribution of organisms and their
exquisite adaptations to specific environments that provided him evidence for evolution.
4. Explain the importance of temperature, water, light, soil, and wind to living organisms.
Abiotic factors such as water, light, etc are important determinants of the biospheres
distribution of organisms. Temperature, for example, is an important factor in the distribution of
organisms because of its effect on biological processes and the inability of most organisms to
regulate body temperature precisely. Water is essential to life but its availability varies
dramatically among habitat. Thus, the evolution of most animals has been shaped by
thenrequirements for obtaining and conserving adequate supplies of water. Sunlight provides the
energy that drives nearly all ecosystems. Light is also important to the development and behavior
of the plants and animals that are sensistive to the relative lengths of daytime and nighttime. The
chemical composition of soil limits the distribution of plants and the animals that feed upon them,
in turn contributing to the patchiness observed in terrstrial biomes. In freshwater biomes, soil also
influences the resident plant and animals. In marine environments, the seafloor determines the
types of organisms that can attach or burrow in those habitats. Lastly, wind amplifies the effects
of environmental temperature on organisms by increasing heat loss due to evaportation and
convection. It also contributes to water loss in organisms.
6. Describe how environmental changes may produce behavioral, physiological, morphological,
or adaptive responses in organisms.
Environmental changes may produce behavioral responses in a variety of ways. Most often,
relocation is the quickest response of many animals, others may burrow due to extreme
temperatures but sometimes animals are able to modify their immediate environment by
cooperative social behavior. Physiological responses are slower than behavioral changes and are
usually expressed with regulation and homeostasis. Morphological responses within animals are
caused by a change in the environment producing a response that alter the form or interan
anatomy of the body. Often, these responses are examples of acclimation since they are
reversible. Adaptation s occur over time and adaptations to an organisms environment represent
a set of evolutionary compromises.
8. Describe the characteristics of the major biomes: tropical forest, savanna, desert, chaparral,
temperate grassland, temperate forest, taiga, tundra.
-Tropical Forest: Found within 23.5 degrees latitutude of the equator. The average
temperature is about 23 degrees Celsius and the length of daylight is about 12 hours and both
vary little throughout the year.
-Savanna: These are grasslands with scattered individual trees. The dominant vegetation is
fire afdapted. They have 3 distinct seasons: cool and dry, hot and dry, and warm and wet.
-Desert: the driest of all the terrestrial biomes; experience low and unpredictable precipitation.
There exists hot and cold deserts.
-Chaparral: stands of dense, spiny shrubs with tough evergreen leaves; the chaparral
experiences aridity, short growing seson, low nutrient soil, and freqient fires
-Temperate grassland: they experience seasonal drought, occasional fires, and grazing by
large mammals, all of which prevent woody shrub from invading and becoming established.
-Temperate Forest: temperatures range from very cold in the winter to extreme heat in the
summer. Precipitation is high and fairly evenly distributed throughout the year .
-Taiga: Largest terrestrial biome on earth . It experiences heavy snowfall and considerable
precipitation .
Tundra: Plant forms are limited here. In the arctic tundra the climate is very cold.
10. Using a diagram, identify the various zones found in the marine environment.
I can identify the various zones found in the marine environment.
Chapter 52
1. Define the scope of population ecology.
I already know this concept.
2. Distinguish between density and dispersion.
Density is the number of individuals per unit area or volume. Dispersion is the pattern of
spacing among individuals within the geographical boundries of the population.
3. Explain how ecologists measure density of a species.
In most cases, ecologists often use a variety of sampling techniques to estimate densities and
total population size. In other cases, population sizes are estimated by indirect indicators like the
numbers of nests or burrows found.
5. Explain how age structure, generation time, and sex structure of populations can affect
population growth.
Age structure affects its sub categories such as birth rate and death rate. These are highest
in a given age group, forexample birth rate is highest among 20- year old women, thus affecting
population growth. Generation time affects population growth where the shorter the generation
span, the larger the population increase. Sex structure directly affects population growth were
the number of females is usually linked to the number of births.
6. Describe the characteristics of populations which exhibit Type I, Type II, and Type III
survivorship curves.
Type I curve reflects low death rates during early and middle life, dropping steeply as death
rates increase among older age groups. Type II curves are intermediate, with mortality more
constant over life span. Type III curve drops sharply at the left of the graph, reflecting very high
death rates for the young, but then flattens out as death rates decline for those few individuals
that have survived to a certain critical age.
8. Explain how density-dependent factors affect population growth.
Density dependant factors regulate population grwoth by varying with the density. Dependant
factors intensify as population density increases and can eventually stabilize a popluation near its
carrying capacity.
9. Describe how weather and climate can function as density-independent factors in controlling
population growth.
Density-independant factors are unrelated to population size; they affect the same percentage
of individuals regardless of population size. Weather and climate reduce population size by a
given fraction, regardles of its density.
10. Explain how density-dependent and density-independent factors may work together to control
a population's growth.
The combination of density independant and dependant factors regulates poplation. For
example, in very cold, snowy areas, many deer may starve to death during the winter. The
severity of this factor is proportional to the season's harshness; colder air increase energy
requirements while deeper snow make it harder to find food.
11. List the three major characteristics of a life history and explain how each affects the:
a. Number of offspring produced by an individual
b. Population's growth
The three major characterisits of a life history
I learned this concept in Honors Biology.
12. Explain how predation can affect life history through natural selection.
I learned this concept in Honors Biology.
13. Distinguish between r-selected populations and K-selected populations.
K-selected populations are those that are likely to be living at a density near the limit imposed
by their resources (K, or carrying capacity).
R-selected populations are likely to be found in variable environments in which population
densities fluctuate, or in open habitats where individuals are likely to face little competition.
Chapter 53
2. Explain the relationship between species richness, relative abundance, and diversity.
Species richness is the number of species a community contains. Ecologists, however, also
recognize that some communities consist of a few common species and many rare ones,
whereas others contain an equivalent number of species that are all about equally common. The
relative abundance of species within a community has an enormous impact on its general
character. A different community that had the same species richness, but in which the numbers
were more evenly divided among the ten species, would seem more diverse. Species diversity
considers both components of diversity, species richness and relative abundance.
3. List four properties of a community, and explain the importance of each.
I already know this concept.
4. Explain how interspecific competition may affect community structure.
Interspecific interactions are those that occur between populations of different species living
together within a community. Four interspecific interactions are predation, competition,
commensalism, and mutualism. Predation is beneficial to one species and detrimental to the
other. Competition is detrimental to both species. Commensalism benefits from the interaction
but the other is unaffected. Mutualism is beneficial to both species.
5. Describe the competitive exclusion principle, and explain how competitive exclusion may affect
community structure.
The competition exclusive principle stats that two species competing for the same limiting
resources cannot coexist in the same place. The ecological niche is the sum of the total of the
organism’s use of the biotic and abiotic resources of its environment. Closely related species
may be able to coexist if there are one or more significant differences in the niches. Resource
partitioning and character displacement provide indirect evidence for the importance of past
competitions.
6. Distinguish between an organism's fundamental niche and realized niche.
An organisms fundamental niche is the niche that an organism ocupies in the absence of
competing species. A realized niche is that which an organism occupies in the presence of
competing species.
10. Distinguish between Batesian mimicry and Mullerian mimicry.
Mimicry allows a predator of species of prey to gain a significant advantage. In Batesian
mimicry, a palatable or harmless species mimics an unpalatable or harmful model. In Mullerian
mimicry, two or more unpalatable, aposemitcalle colored species resemble each other. Here,
each species gains an additional advantage.
12. Explain the role of predators in community structure.
Predation involves a predator eating its prey. These serve as interactions in a community. It
may involve an animal eating a plant, known as herbivory. However, over evolutionary time,
various defensive adaptation have evolved in prey species. These include plant defenses against
herbivores such as the production of chemicals making the vegetation distateful. Also, animal
have evolved defenses against predators like adaptive coloration.
13. Distinguish among parasitism, mutualism, and commensalism.
Commensalism refers to symbiotic interactions in which one species benefits and the other is
not affected. Mutualism refers to symbiotic interactions in which both species benefit. Parasitism
is a symbiotic interaction in which a parasite derives nourishment from its host, but does not kill it
outright.
15. Distinguish between primary succession and secondary succession.
Primary succession is is a type of ecological succession that occurs in an area where there
were originally no organisms. Secondary succession is a type of succession that occurs where an
existing community has been severly cleeared by some disturbance.
Chapter 54
1. Explain the importance of autotrophic organisms with respect to energy flow and nutrient
cycling in ecosystems.
Trophic structure determines an ecosystem’s routes of energy flow and chemical cycling.
Energy and nutrients pass through the trophic levels of an ecosystem when organisms feed on
one another. Most autotrophs are organisms that use light energy to synthesize sugars and other
compounds which they use as fuel for cellular respiration and as building material for growth.
2. List and describe the importance of the four consumer levels found in an ecosystem.
The trophic level that ultimately supports all others consists of autotrphs, or the primary
producers are organisms that use light energy to synthesize sugars and other compounds which
they use as fuel for cellular respiration and as building material for growth.
All other organisms in an ecosystem are consumers. Primary consumers, or herbivores,
directly or indirectly depend on the photosynthetic output of producers. The next trophic level
consists of secondary consumers, carnivores that herbivores. These carnivores may in turn be
eaten by other carnivores that are tertiary consumers, and some ecosystems have carnivores of
an even higher level, quaternary.
3. Explain how gross primary productivity is allocated by the plants in an ecosystem.
The amount of light energy converted to chemical energy by autotrophs of an ecosystem
during a given time is called primary productivity. Total primary productivity is known as gross
primary productivity. Gross primary productivity results from photosynthesis; net primary
productivity is the difference between the yeild of photosynthesis and the consumption of organic
fuel in respiration.
5. Explain why productivity declines at each trophic level.
Productivity declines at each trophic level because as energy flows through an ecosystem,
must is lost at each trophic level. The amount of energy available to each trophic level is
determined by the net productivity and the efficiencies with which the food energy is converted
into biomass at each link of the food chain. The percentage of energy transferred from one
trophic level to the next is called ecological efficiency. Eighty to ninety percent of the energy
available at one trophic level never transfers to the next.
6. Distinguish between energy pyramids and biomass pyramids.
Energy pyramids represent the multiplicative loss of energy from a food chain in which trophic
levels are stacked in blocks, with primary producers forming the foundation of the pyramid. The
size of each block is proportional to the productivity of each trophic level.
A biomass pyramid represents the ecological consequence of decreasing energy transfers
through a food web, in which each tier represents the standing crop biomass in a trophic level.
Biomass pyramids generally narrow sharply from producers at the base to top-level carnivores.
8. Describe the carbon cycle, and explain why it is said to result from the reciprocal processes of
photosynthesis and cellular respiration.
The reciprocal procession of photosynthesis and cellular respiration are responsible for the
major transformations and movements of carbon. A seasonal pulse in atmospheric CO2 is
caused by a decreased photosynthetic activity during the Northern Hemisphere's winter. On a
global scale, the return of CO2 to the atmosphere by respiration closely balances its removal by
photosynthesis. However the burning of wood and fossil fuels adds more CO2 to the atmosphere
as a result, the amount of atmospheric CO2 is steadily increasing.
9. Describe the nitrogen cycle, and explain the importance of nitrogen fixation to all living
organisms.
The majority of the nitrogen cycling through food webs is taken up by plants in the form of
nitrate. Most of this, in turn, comes from the nitrification of ammonium that results from the
decomposition of organic material. The addition of nitrogen from the atmosphere and its return
via denitrification involve relatively small amounts compared to the local recycling that occurs in
the soil or water. In some ecosystems, atmospheric deposition of NH+4 and NO-3 that is
dissolved in rain adds nitrogenous minerals to the soil.
A way for nitrogen to enter ecosystems is by way of nitrogen fixation. Only certain
prokaryotes can fix nitrogen into minerals that can be used to synthesize nitrogenous organic
compounds such as amino acids. Nitrogen is fixed in terrestrial ecosystems by free-living soil
bacteria as well as symbiotic bacteria.
10. Explain how phosphorus is recycled locally in most ecosystems.
Phosphorus is recycled locally in most ecosystems by way of the following: The weathering of
rocks gradually adds phosphate to the soil. After producers incorporate phosphorus into
biological molecules, it is transferred to consumers in organic form, and added back to the soil by
the excretion of phosphate by animals and by the action of decomposers on detritus.
17. Describe how increased atmospheric concentrations of carbon dioxide could affect the Earth.
Increased atmospheric concentrations of carbon dioxide on Earth may increase productivity of
vegetation. However, the increase in Carbon dioxide may be the spread of C3 species into
terrestrial habitats previously favoring C4 plants. Thus, for example, in areas where corn was
more favorable may soon be replaced by wheat and or soy beans. The increase in Carbon
Dioxide may also affect Earth's heat budget. By the next centurym global temperatures may be
up by 3-4 degrees Celsius.
18. Describe how human interference might alter the biosphere.
Human interference alters species distribution and reduces biodiversity. The introduction of
exotic species has disrupted many communities and ecosystems, often through predation or
competition with native species. Human intrusion into natural ecosystems has destroyed many
habitats. Species are becoming extinct at a rate fifty times greater that at any time largely
because of loss of habitat.