Chapters 45 and 47 work

Derek Lee

Ap Biology

22 January 2010

Chapters 45 and 47 Work

II. Connections

a.       Carrying Capacity and Biotic Potential – In situations that are ideal where there is no predation, lack of vital resources, shelter, food, etc, a biotic potential which is the maximum rate of increase per individual for any population that is growing under ideal conditions occurs. However, in reality, these things to not normally exist in nature and thus the sustainable supply of resources a habitat has will determine the population size. This sustainability of resources determines the carrying capacity, which is the maximum number of individuals of a population that a given environment can sustain indefinitely.  

b.      Organisms of an ecosystem are classified by their functional roles in a hierarchy of feeding relationships called trophic levels. It is basically who its whom and the transfer of energy from one level to the next. Biological magnification shows the concentration of a slowly non/degradable substance in body tissues as it passed along food chains i.e. DDT as it is passed from one trophic level to the next thus also passing down the toxin from one level of animals to the next.

c.       Like consumers, detritivores rely on autotrophs in order to decompose organic matter. Autotrophs capture energy from the sun whom themselves become energy for herbivores, and then consumers. Once plants and consumers die, they begin to decay and their remains become an energy and food source for detritivores.

d.      The mitochondria of living organisms such as plant and humans produces metabolic waste which is released as CO2. Atmospheric molecules of carbon dioxide, water, nitrous oxide, etc are among the main players in interactions that affect global temperature. Collectively these “greenhouse gases” act as pane glasses in a green house which impede the escape of heat energy from Earth into space thus causing the temperature to rise.

III. a. Outline 45.4 Limits on the Growth of Populations

A.    Density-Dependent Limiting Factors

1.      Large and growing populations require a substantial amount of nutrients among other factors to continue to prosper; otherwise risk death

2.      Limiting Factor – Any essential resource that is in short supply.

3.      i.e. food, mineral ions, refuge from predators, living space, absence of pollutants, etc.

4.      One factor alone is often enough to put brakes on population growth.

B.     Carrying Capacity and Logistic Growth

1.      The resources available to a small population of individuals dispersed through a habitat decreases as the population increases in size – growth rate declines

2.      Carrying capacity – the maximum number of individuals of a population that a given environment can sustain indefinitely.

3.      Logistic Growth – shows how carrying capacity may affect population size by changes in growth vs.  number of individuals and unused resources.

4.      When either exponential or logistic growth leads to overcrowding, abiotic and biotic factors function as density-dependent controls – reduce odds for individual survival.

C.     Density-Independent Limiting Factors

1.      Density-independent factors- Any factors that cause more deaths or fewer births regardless of population density.

2.      i.e. availability of a vital resource, exert control after populations become too dense as a result of exponential/logistic growth.

3.      Other factors exert control independently of population density.

b. Summarization of 3 curves & example

1. Type I curves reflect high survivorship until fairly late in life, then a large increase in deaths. For example elephants which give birth to 4-5 calves in her lifetime and devotes several years to parenting each one. Type one curves are similar to human populations where populations have access to good health care services.

2. Type II curves reflect a fairly constant death rate at all ages. They are typical of organisms just as likely to be killed or die of disease at any age, such as lizards, small mammals, and large birds.

3. Type III curves signify a death rate that is highest early in life. They characterize species that produce many small offsprings and do little, if any, parenting. Examples include sea stars and marine invertebrates, insects, fishes, plants, and fungi.

c. 1. The age structure diagram for a population undergoing negative growth would look much skinnier than other graphs, much like the outline of a small fish. Populations experiencing negative growth have nearly equal male-female rations at youth but begin to shift towards females as the population matures.

2. Populations undergoing almost no growth have the shape of the empire state building. The graph is proportional to that of a sky riser that becomes skinnier at the top. The female to male ration remains nearly constant from birth to death.

3. A population undergoing rapid growth has a very large birth growth which consistently becomes smaller at a rapid rate at each level of maturity. By the end of the age graph, the post-reproductive graph is extremely small in proportion to the pre-reproductive years.

4. A graph that grows slowly is very similar to a graph of rapid growth. The main difference is the rate and size at which the graph changes from the pre-reproductive years to post-reproductive years. The graph of slow growth remains more uniform though the changes in age are more subtle. Also, graphs of slow grow have populations which live longer than those of rapid growth which, while growing more rapidly, have populations which also die more quickly.