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CHAPTER 50
AN INTRODUCTION TO ECOLOGY
AND THE BIOSPHERE
1. Explain why the field of ecology is a multidisciplinary science.
a. Ecology is simply not just the study of how organisms interact with
their environment; in of itself the study of ecology includes areas of
Biology including genetics, evolution, physiology and meteorology.
2. Describe the relationship between ecology and evolution.
a. An important cause of evolution is an organism’s response to biotic
and a biotic change in their environment. Distribution and
abundance of organisms are products of both long-term
evolutionary changes and ongoing interactions with the
environment.
3. Explain the importance of temperature, water, light, soil, and wind to
living organisms.
a. Temperature is an important factor in the distribution of organisms
because of its affect on biological processes and the inability of
most organisms to regulate body temperature precisely. The
availability of, or lack of, water and sunlight are vital to life in that
they are sources of energy. Wind amplifies the effect of
environmental temperature on organisms by increasing heat loss
due to evaporation and convection. The physical structure, pH, and
minerals composition of rock and soil limit the distribution of plants
and the animals that feed on them.
4. Describe how environmental changes may produce behavioral,
physiological, morphological, or adaptive responses in organisms.
a. Environment changes such as temperate changes can trigger a
response in the form of adaptations. Behavioral adaptations are
almost instantaneous and are easily reversed, while physiology
adaptation may be implement and changed over time scales
ranging from seconds to weeks. Morphological adaptations may
develop over the lifetimes of individual organisms or be with
generations. Adaptive genetic changes usually evolve over several
generations.
5. Describe the characteristics of the major biomes: tropical forest, savanna,
desert, chaparral, temperate grassland, temperate forest, taiga, and
tundra.
a. Tropical rainforest have an abundance of life due to its gracious
rainfall and short dry seasons. They are found in areas near the
equator. Savanna is grassland with scattered individual trees. They
have 3 distinct seasons that occur in this order: Cool and dry, hot
and dry, and warm and wet. Deserts are the driest of all terrestrial
biomes, characterized by mild, rainy winters and long, hot, dry
summers cause aridity, short growing seasons, low nutrient soil,
and frequent fires result in shrubby vegetation.
6. Using a diagram, identify the various zones found in the marine
environment.
a. Figure 56.26
CHAPTER 52
POPULATION ECOLOGY
1. Define the scope of population ecology.
a. Population ecology can be thought as individual of one species that
simultaneously occupy the same general area; they rely on the
same resources and are influenced by similar environment.
2. Explain how ecologists measure density of a species.
a. An actual count of the population may be taken, but that is
impractical, and so indirect indicators, such as the number of nests
or burrows, may estimate population sizes or droppings and tracks
left by the organism. Another commonly used technique is the
mark-recapture method.
3. Explain how carrying capacity of the environment affects the intrinsic rate
of
increase of a population.
a. Carrying capacity is the maximum stable population size that a
particular environment can support. Crowding and resource
limitation can have a profound effect on the population growth
rate. If individuals cannot obtain sufficient resources to reproduce,
per capita birth rate will decline. If they cannot consume enough
energy to maintain themselves, per capita death rates may
increase.
4. 10. Explain how density-dependent and density-independent factors may
work together to control a population's growth.
a. Many populations remain fairly stable in size and are presumably
close to the carrying capacity that is determined by densitydependent factors. Superimposed in this general stability are shortterm fluctuations due to density independent factors.
5. 11. List the three major characteristics of a life history and explain how
each affects the:
6. Number of offspring produced by an individual
7. Population's growth
a. The traits that affect tan organisms schedule of reproduction and
death make up its life history. Clutch size (the number of offspring
per reproductive episode), frequency of reproduction, and
investment in parental care are the three parts that makeup an
organisms` life history. How long it takes and organism to reach
maturity and how much time will be invested in parenting is
determined by the organisms` fecundity and mortality.
CHAPTER 53
COMMUNITY ECOLOGY
1. Explain the relationship between species richness, relative abundance, and
diversity.
a. Species diversity with a community: An assemblage of species
living close enough for potential interaction, includes both the
species richness (number of species present) and the relative
abundance of each species.
2. List four properties of a community, and explain the importance of each.
3. Explain how interspecific competition may affect community structure.
a. In interspecific competition the population growth of a species may
be limited by the density of competing species as well as by the
density of its own population. As a result mortality rates mortality
rates increases, birth rates decreases, and population growth is
curtailed.
4. 13. Distinguish among parasitism, mutualism, and commensalisms.
a. Parasitism is a type of predation in which a parasite lives on or in a
host, deriving nourishment from it but usually mutualism is a
relationship. In commensalisms one partner benefits without
significantly affecting the other.
5. 15. Distinguish between primary succession and secondary succession.
a. Succession is a process of change that results from disturbance in a
community. Primary succession occurs no soil previously existed.
Secondary succession occurs begins in an area where soil remains
after a disturbance.
CHAPTER 54
ECOSYSTEMS
1. Explain the importance of autographic organisms with respect to energy
flow and nutrient cycling in ecosystems.
a. Each ecosystem has a strophic structure of feeding relationships
that determines the pathways of energy flow and chemical cycles.
The species in a community or ecosystem into strophic level that
ultimately supports all others consists of autotrophy, or the primary
producers of the ecosystem.
2. List and describe the importance of the four consumer levels found in an
ecosystem.
a. Primary consumers eat plant life such as algae. Secondary
consumers are carnivores that eat herbivores. Higher carnivores
called tertiary consumers then eat these carnivores. Decomposer
then derive their energy from waste, such a feces and carcasses
and organic waste.
3. Explain how gross primary productivity is allocated by the plants in an
ecosystem.
a. All organisms require energy for growth, maintenance and
reproduction. Primary consumer use light energy to synthesize
energy – rich organic molecules, which can subsequently be.
4. Explain why productivity declines at each trophic level.
a. As energy flows through an ecosystem much of it is dissipated
before organisms at the next level can consume it. The amount of
energy available at each trophic level is determined by net primary
productivity and the efficiencies with which food energy is
converted to biomass in each link of the food chain.
5. Distinguish between energy pyramids and biomass pyramids.
a. In an energy pyramid the 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. In a biomass (the total dry weight of all organisms) in a
trophic level.
6. Describe the carbon cycle, and explain why it is said to result from the
reciprocal processes of photosynthesis and cellular respiration.
a. In the carbon cycle, the reciprocal processes of photosynthesis and
cellular respiration provide a link between the atmosphere and
terrestrial environment. Plants acquire carbon in the form of CO2,
form the atmosphere through the stomata of their leaves, and
incorporate it into the organic matter of their own biomass through
the process of photosynthesis. Some of this organic material then
becomes a carbon source for consumers. Respiration by al
organisms returns CO2 to the atmosphere.
7. Describe the nitrogen cycle, and explain the importance of nitrogen
fixation to all living organisms.
a. The plants in the form of nitrate take up most of the nitrogen
cycling through the food web. Most of this, in turn, comes from the
nitrification of ammonium that results from the decomposition of
organic material. Also, in some ecosystems, an atmospheric
deposition of NH4+ and NO30- that is dissolved in rain adds to the
nitrogenous materials to the soil. Via nitrogen fixation certain
prokaryotes convert N2 into minerals that can be used to the
synthesize nitrogenous organic compounds such as amino acids.
8. Explain how phosphorus is recycled locally in most ecosystems.
a. Plants absorb and use phosphate for organic synthesis. The
weathering of rocks gradually adds phosphate to soil. After
producers incorporate phosphorous 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.
9. Describe how increased atmospheric concentrations of carbon dioxide
could affect the Earth.
a. CO2 and water vapor intercept and absorb much of the reflected
and infrared light given to off by the sun, reflecting it back towards
the earth. This maintains the earths` temperature. Since the
Industrial Revolution large amounts of CO2 have been introduced
into the atmosphere through the burning of natural gases. The
increases in CO2 levels allow more heat to be retained and over
time it has raised the earths temperature.