Homework 3 - Ecology
Which term do ecologists use to describe the community interaction where one organism makes the environment more suitable for another organism?
Facilitation
Which of the following statements are true of logistic growth? Select all that apply. 1 - When the population reaches its carrying capacity, it stops growing 2 - As the population approaches carrying capacity, it grows more slowly 3 - The population grows at a steady rate 4 - As the population approaches carrying capacity, it grows more rapidly
1 and 2
Which of the following statements are true of carrying capacity? Select all that apply. 1 - The rate at which resources are used is equal to the rate at which they are supplied 2 - The birth rate equals the death rate 3 - The population growth rate equals zero 4 - The population continues to grow at a constant rate
1, 2, and 3
A population of ground squirrels has an annual per capita birth rate of 0.06 and an annual per capita death rate of 0.02. Calculate an estimate of the total number of individuals added to (or lost from) a population of 1000 individuals in one year.
40 individuals added
What is the combination of resources used and conditions tolerated in the absence of competitors called?
A fundamental niche See section 52.1
Ignoring migration, the age structure diagram of a human population likely to maintain a relatively stable size will have what shape?
A rectangle tapering toward the top.
It is estimated that a flock of wood buffalo crane should be able to sustain an r of 0.085 for the foreseeable future. If the flock currently contains 350 individuals, how long will it take for that population to double?
Between 7.0 and 9.0 years
Which of the following factors does not contribute to environmental resistance? - environmental toxins - birth rate - competition for space - weather conditions - competition for food
Birth rate
Why does it take 10 times more energy to grow a kilogram of beef than a kilogram of wheat?
Cattle only integrate 10% of their food into biomass. See section 53.1
Is this population of fish represented by the following set growing, stable, or declining? x lx mx 1 0.650 0.00 2 0.520 0.15 3 0.225 1.65 4 0.005 3.50
Declining. R0<1
A study conducted at Hubbard Brook Experimental Forest watershed areas provided experimental evidence that _____.
Deforestation increases the rate of nutrient loss from ecosystems. See section 53.2
Which of the following statements about density-independent growth is true? - A population that is experiencing density-independent growth levels off at the environment's carrying capacity. - Density-independent growth is also known as exponential growth. - Density-independent growth can continue indefinitely in nature. - The per-capita rate of increase may exceed r(max) during density-independent growth.
Density-independent growth is also known as exponential growth.
Which factor does not affect a habitat's carrying capacity? - genetic variation in the population - availability of food - number of nesting sites - Intensity of predation
Genetic variation in the population
Which of the following statements about a population experiencing logistic growth is true? - If N is greater than K, the population will shrink. - If N is less than K, the population will not grow. - If the K and N values are similar, the amount of available resources is high. - If the K and N values are far apart, the population will grow very slowly.
If N is greater than K the population will shrink. This statement is true, since K is the maximum number of individuals that can be supported in a particular habitat over a sustained period of time.
Ignoring migration, the age structure of a human population likely to decrease in size will have what shape?
Inverted pyramid In such a population the majority of individuals are in their post-reproductive years. Such a population is expected to decrease.
There are more species in tropical areas than in places more distant from the equator. This is probably a result of _____. - fewer agents of disease - fewer predators - more intense annual solar radiation - more frequent ecological disturbances
More intense annual solar radiation
What is net primary productivity (NPP)?
Primary producer biomass or organic material that can be consumed NPP measures the amount of primary producer material that is available for consumption after the primary producers have used some portion of GPP for cellular respiration or lost it as heat. See section 53.1
Ignoring migration, the age structure of a human population likely to increase in size will have what shape?
Pyramid This would mean that most individuals are in the pre-reproductive years. Such a population is expected to increase.
As you study two closely related predatory insect species, the two-spot and the three-spot avenger beetles, you notice that each species seeks prey at dawn in areas without the other species. However, where their ranges overlap, the two-spot avenger beetle hunts at night and the three-spot hunts in the morning. When you bring them into the laboratory and isolate the two different species, you discover that the offspring of both species are found to be nocturnal. You have discovered an example of _____. - facilitative commenalism - Batesian mimicry - mutualism - character displacement - resource partitioning
Resource partitioning
What percentage of total nitrogen fixation is caused by human activity?
Roughly 75% See section 53.2
Which of the following is a prediction of the high-productivity hypothesis that is proposed to explain the latitudinal gradient in species diversity? - smaller and younger regions should have higher species diversity - speciation rates increase as niche differentiation occurs - speciation rates should decline as niche differentiation occurs - larger and olderr regions should have more species diversity
Speciation rates increase as niche differentiation occurs.
As N approaches K for a certain population, which of the following is predicted by the logistic equation? - the population will increase exponentially - the growth rate will approach zero - the carrying capacity of the environment will increase - the population with show an Allee effect - the growth rate will not change
The growth rate will approach zero
What is the largest reservoir in the carbon cycle?
The ocean A very large amount of carbon is stored in the ocean as living organisms and other material. See section 53.2
Why does net productivity diminish with increasing trophic levels?
There is poor trophic transfer efficiency at higher trophic levels. See section 53.1
What makes pioneering plant species successful?
They rapidly colonize soil that is exposed and have few or no competitors already present. See section 52.3
True or false? Factors that determine the per capita rate of increase of a population include the age of breeding and the number of offspring produced each year?
True. The per capita rate of increase of a population is the difference between the per capita birth rate and the per capita death rate, and is determined by factors that include the age of breeding and the number of offspring produced each year.
Why might one get mercury poisoning from eating tuna every day, but not from eating sardines from the same water?
Tuna biomagnify the mercury See section 53.1
Under which of the following conditions would a population most likely experience exponential growth? - Environment with a low carrying capacity. - Large number of individuals in the starting population. - Habitat with limited resources. - Young populations with few individuals.
Young populations with few individuals. Young populations with few individuals are more likely to experience exponential growth because they have not used up the supply of resources.
Which processes increase a population's size?
births and immigration
Which human activity has the most direct impact on the global water cycle? - use of fertilizers - burning of coal - building of impervious city streets and sidewalks - use of automobiles
building of impervious city streets and sidewalks The rest are all somewhat indirect. This is also exacerbated by the creation of high capacity wells that pump up groundwater to the surface. See section 53.2
If two species are close competitors, and one species is experimentally removed from the community, the remaining species would be expected to _____. - expand its realized niche - decline in abundance - eventually become competitively superior to the other species - become the target of specialized parasites - change its fundamental niche
expand its realized niche
As a population approaches carrying capacity, environmental resistance __________.
increases.
The competitive exclusion principle states that _____.
it is not possible for two species with the same niche to coexist in the same region.
Carrying capacity is _____.
the maximum population size that a particular environment can support
What equation represents the logistic growth of a population?
ΔN/Δt=rmaxN[(K−N)/K] N = Population size t = time K = carrying capacity
