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Environmental Science Test #2


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1) Although total fertility rate may remain constant, a shift toward a higher age to first reproduction may produce a marked change in population growth rate. What sort of change would you expect and why?
Total fertility rate refers to the total number of children an average woman in a population would have if she were to live to menopause (cessation of reproduction). It does not take into account the fact that some women will not survive that long. A shift to a higher age will slow population growth rate for two reasons. First, it lengthens the generation time, extending the time over which a woman would have children. More important, it also means that fewer women will survive to realize their full reproductive potential.
Define the realized and the fundamental niche. What is niche overlap and niche displacement?
The fundamental niche of an organism is the range of conditions for all of the factors in its environment over which it can potentially survive (have positive growth), taking into account interactions among these factors. The realized niche is the actual range of conditions where the organism is found. Niche overlap refers to the overlap between organisms in their fundamental niches and niche displacement refers to the effects of competition that produce the realized niche.
4) Explain (illustrate) how environmental factors may interact to limit the tolerance of organisms to environmental conditions.
This question refers to fact that an organism’s range of tolerance for one environmental variable depends on the values of others. The example I used in class was the interaction between temperature and water availability. In general, an organism’s tolerance for high temperatures increases as water becomes more available. Alternatively, an organism’s requirements for water increase as temperature increases. See my lecture for a graph of this interaction.
What is competitive exclusion? Give an example.
Competitive exclusion refers to the notion that complete competitors cannot coexist. If forced to compete, one competitor will eventually exclude the other. The example I used in class involved Gause’s classic studies of Paramecium.
How do predators benefit their prey species populations?
Predators do not generally take individuals from a population at random. Rather, they seek out the weakest animals. In general, this increases the overall health of the population.
8) What is Thompson’s theory of demographic transitions? Describe its stages and give examples of regions of the world that might be representative of them.
Thompson’s theory is that economic development is accompanied by changes in demographic behavior that eventually slow birth rates and result in increased life expectancy with very low growth rates. The stages are:

1. Population has high birth rates and death rates—subject to fluctuation -- typical of parts of Sub-Saharan Africa today
2. Mortality transition--Improved quality of life—death rate decreases but average birth rate remains high – Countries early in economic development; examples might also include some in Africa and places like Haiti
3. Fertility transition—Death rate remains low and average birth rate declines – This is happening throughout most of Latin America
4. Both birth and death rate stabilize at low levels; population growth rate slows – Typical of some parts of western Europe such as Italy or Spain
Name and define three different measures of biodiversity.
• Biomes and Communities—biogeographic diversity: Groups of organisms occur in repeatable configurations across continents.
• Species diversity/richness: number of species in an area.
• Species Evenness: the distribution of abundance among species
• Genetic diversity: variability in genetic composition within a species or population.
• Functional diversity: variety of functional roles played by organisms within an ecosystem.
• Spatial and temporal complexity: The “arrangement” of species, genotypes or functional types in space and time.
What is speciation and what factors might cause it to occur?
Speciation is the process by which mechanisms that prevent reproduction between populations (reproductive isolation) evolves. This may happen because species are geographically isolated from one another, or it may happen when interbreeding produces offspring (hybrids) that are unfit (have no suitable habitat).
Someone asserts that the world is full of species and that the loss of some—even quite a few—is not a problem. Give three counterarguments to this assertion and explain each with an example.
This question refers specifically to the 6 values of biodiversity that I discussed in lecture these are:
1. Existence value
4. Stability
2. Market value
5. Long-term change
3. Functional Value
6. Indicator value
You do a census of amphibian and fish diversity and find that the total number of species varies widely among ponds around the Duke campus. What factors would you expect to be important in explaining this variation in species numbers and why?
Best answer here would focus on the Equilibrium Theory of Island Biogeography, i.e., that the number of species in a location is a consequence of the equilibrium between the rates of new species arrival (immigration) and local extinction. Immigration rates will be highest for ponds that are in close proximity to a species source (e.g., other large ponds) and lowest for ponds that are isolated. Extinction rates will increase as ponds go from large to small. Thus, you would expect the greatest number of species in large, nearby ponds and the lowest number in isolated small ponds.
Describe four major threats to biodiversity on a global scale.
Here I would be looking for a bit of discussion of habitat loss, habitat fragmentation, pollution, climate change, invasive species, or changing patterns of disturbance.
Describe the pattern of change that you would expect in a typical primary succession such as following glaciation or on newly-exposed rock. What is “facilitation” and what role does it play in such patterns?
Initially invasion involves widely dispersed and hardy pioneer species which modify their environment making it more hospitable for other possible invaders. Successive invaders modify their environments facilitating the invasion of other species. Eventually a suite of species arrives that modifies the environment in such a way as to favor its own long-term persistence. This is the climax stage of succession.
Ecologists are convinced that so-called “successional legacies” are important in the patterns of change following natural and human-caused disturbance. What do they mean by this phrase? Give an example and explain its importance.
Successional legacies refers to such things as soil organic matter, nutrients, woody debris, etc. that influence patterns of establishment following disturbance. An example might be the important role of woody debris and soil organic matter following a forest cutting.
What is the formula for population growth?
Birth Rate - Death Rate +immigration -emmigration
What is the total fertility rate (TFR)?
# of offspring born per female, assuming females survive for full reproductive cycle
What is generation time?
Average age of first reproduction
What are some factors than affect birth rates?
Mode of reproduction (asexual vs. sexual), life history complexity, and quality of life.
What are the three types of mortality rates?
I) Mortality is a largely an old age thing.
II) Mortality is age-independent --% dying is the same regardless of age
III) High infant mortality --"many are called, few are chosen"
What is a carrying capacity?
# of organisms at which birth rate=death rate and population growth is zero
What is maximum sustained yield?
It is the carrying capacity/2. Point of population growth curve where derivative =0.
What's wrong with the concept of carrying capacity?
1) Presumes very tight coupling between resource change and birth rates and death rates.
2) Resource availability and the "law of the minimum"
3) Presumes that resource needs per individual are constant - that carrying capacity can be equated to some particular number of individuals
What are some other factors besides carrying capacity that can regulate population sizes?
Retarding factors - eg. toxins
Other organisms
Predators and parasites.
What are the three theoretical patterns of population growth and which two are the most like the real world?
A. Finely turned feedback -- Population "knows it is nearing carrying capacity.

B. Inefficient feeback -- population overshoots, resources rebound, damped oscillation.

C. Population really overshoots -- resource base cannot recover.
What is a metapopulation? Give an example.
A population comprised of dispersed sub-populations. ex. Northern Spotted Owl.
What is the law of the minimum?
A population is limited by that resource in its environment that is present in most limiting supply - too little of something.
What is a "fundamental ecological niche"?
Combined range of tolerance for all factors in the environment, taking interactions into account.
What is competition?
Interaction between two organisms for the same resource(s)generally the growth rate of both competitors is depressed
What is competitive exclusion?
Two organisms vying for the same resource cannot coexist indefinitely - one will eventually exclude the other.
What is a realized ecological niche?
Within its range of tolerance, the actual range over which an organism occurs taking into account the effects of other organisms.
What is exploitation competition? What is an environment where this is extremely important?
When organisms compete by more effectively using a limiting resource. Desert.
What is interference competition?
Competing by preventing would be competitor from exploiting resources?
Exploitation comp. vs. Interference comp.
Eating faster vs. stabbing with a fork
What is the usual limiting factor for population growth of herbivores?
Their predators.
How do predators affect their preys' diversity?
Increase by not letting one prey type become too dominant.
What factors affect parasites population growth?
Life history complexity
Host demography
Density Dependence
What is symbiosis? Give an example.
A mutually beneficial relationship between organisms. Lichens - a symbiosis between fungus and algae.
What were the two factors that Malthus linked to population growth?
Misery - effects of starvation and disease on survival and reproduction.

Vice - referring to the avoidance or delay of marriage and child bearing.
What were the three important insights of Malthusian population growth theory?
1) Exponential growth.
2) Resource limitation.
3) Connection of population change to the quality of human life.
What has been the most important factor in human population growth (in comparison to other animals')?
Inter-generational learning
Explain the four stages of demographic transitions that accompany economic development?
1. Population has high birth rates and death rates - subject to fluctuation.
2. Mortality transition -- improved quality of life- death rate decreases, but average birth rate remains high.
3. Fertility transition - death rate remains low and average birth rate declines
4. Both birth and death rate stabilize at low levels; population growth rate slows
Why is the death rate climbing in the future?
Population is older.
What is an environmental refugee?
Someone who can't attain resources from environment.
What are the 6 S's of strategies to reduce the ecological footprint?
Search for more resource efficient technologies.

Separate the more damaging activities from the more benign.

Substitute the more benign for the more damaging.

Shrink energy and material thoroughputs.

Satiate some consumption needs.

Sublimate consumption desires.
What are some confounding factors for human population predictions?
Belief systems
What are the six measures of biodiversity/biocomplexity?
Biogeographic diversity
Species diversity/richness
Species evenness
Genetic diversity
Functional diversity
Spatial and temporal complexity
What is biogeographic diversity?
Groups of organisms occur in repeatable configurations across continents.
What is species diversity/richness?
Number of species in an area.
What is species evenness?
The distribution of abundance among species.
What is genetic diversity?
Variability in genetic composition within a species or population.
What is functional diversity?
Variety of functional roles played by organisms within an ecosystem.
What is spatial and temporal complexity?
The "arrangement" of species, genotypes, or functional types in space and time.
What is Deoxyribonucleic acid?
An information molecule comprised of a squence of nucleotides.
What is a genome?
The genetic identity of an organism as determined by the sequence of nucleotides in its DNA.
What is a gene?
A specific segment of genome coding for a specific trait (enzyme). e.g. eye color
What is an allele?
A specific form of a particular gene. e.g. brown eye color
What is a genotype?
The specific combination of alleles possessed by an individual. (Bb, bb or BB)
What is a phenotype?
The actual expression of the trait (Apperance)
What are the nitrogenous bases of DNA?
Thymine, Adenine, Cytosine, and Guanine
Compare the terms genome, gene, allele, geontype, and phenotype.
Genome is genetic identity (think species). A gene is for a specific trait (such as eye color). An allele is a specific form of a particular gene (but can have two, like b of Bb, etc). The genotype is the specific combination of alleles possesed by an individual (such as BB, bb or Bb). The phenotype is the actual expression of the gene (a person has blue eyes).
What is the term for when alleles are identical? How about when alleles are different?
Homozygous vs. heterozygous.
What is a mutation?
a change in the sequence of nucleotides creates new alleles.
What is recombination?
Sexual reproduction "sorts the cards" at each generation.
What is the result of the processes of mutation and recombination?
Extent of variation within a species may be enormous.
What is random genetic drift?
The generation to generation genetic recombination produces random change.
What is natural selection?
Certain genotypes-phenotypes produce more/fewer offspring at each generation and are, therefore represented to a greater or lesser extent in subsequent generations.
What are the three types of natural selection. Explain how they are different.
Stabilizing selection - extreme forms are at a disadvantage (think tails of a normal curve)

Directional Selection - One end of curve at a disadvantage - diminishes variation unless mutation adds new phenotypes.

Disruptive selection - extremes are at an advantage.
Give an example of natural selection.
Peppered moth in Great Britain.
What is a species?
A population of genetically similar (though not identical) organisms isolated from other such populations.
What is reproductive isolation? What are three factors that create reproductive isolation?
Species possess genetically based mechanisms that prevent them from interbreeding with other species. Happens due to genetic incompatabilities, behavioral requirements, or polination mechanisms.
What is speciation and how does it occur?
The process by which new species are generated. It occurs due to geographic separation and/or disruptive selection.
What is disruptive selection?
Selection for breeding barriers to prevent production of unfit hybrids.
What is niche specialization?
The selection for specialization within populations. (Many species depend on unique habitats and food sources)
What are endemic species?
Species that have restricted geographic ranges or habitat requirements.
What are the 6 methods used to attempt to quantify complexity and diversity?
1. Existence Value
2. Market Value - have economic value created through business ventures leveraging biological diversity.
3. Functional importance - species play key roles in ecosystem processes.
4. Stability - resistance to and resilience from disturbance.
5. Long-term adaptability (genetic diversity) - provides a resevoir of oppurtunity in the face of likely future change.
6. Environmental indicators - species diversity is a powerful indicator of environmental change.
What is the "defense in depth" concept? How do the points relate to environmental management?
Engineering concept central to preventing system failure
- Robustness
- Redundancy
- Complexity
- Multiple Independent Pathways
Explain why islands have lots of variation and complexity in their biological makeup?
- Partly due to variation in habitat - e.g. mountainous islands more diverse than coral atolls.
- Geographic barriers (water) and isolation
What is the diversity of any island decided by?
The equilibrium between processes that bring species to the island (immigration from mainland) and species lost on extinction rates.
What factor affects the rate of immigration on an island?
Distance to the mainland (will vary among species)
What factors affects the rate of extinction?
Primary factor is island size, because its direct link to population size. Smaller populations have to worry that natural population variation will lead to extinction.
What type of islands have the most species?
Big islands that are close to mainland.
What is causing the rate of extinction to begin to match those of geologic extinction events?
1. Habitat loss.
2. Habitat fragmentation.
3. Pollution.
4. Invasive species
5. Climate Change
6. Changes in patterns of disturbance.
What is an example of habitat fragmentation?
Yellowstone National Park.
What is an example of an invasive species?
American chetnut blight fungus.
What are the 6 general rules for conservation management?
1. Big "environments" are better than small.
2. Connected environments are better than unconnected.
3. Close environments are better than distanat.
4. High population growth is better than low population growth.
5. Low population variance is better than high population variance.
6. Complex environments are better than simple.
What are the 5 major conservation policies in the US?
1. In 1872, Yellowstone is the world's first national park
2. National Environomental Policy Act (1970) - mandated protection on Federal lands.
3. Marine Mammals Protection Act (MMPA) - a focus on "flipper"
4. Endangered Species Act (ESA 1973) - listing as threatened or endangered
5. National Forest Management Act (NFMA) - national forests must be manged for diversity.
What is an endangered species? vs. threatened
An endangered species is in danger of extinction throughout all or a significant portion of its range.

A threatened species is likely to become endangered in the forseeable future.
What does ESA prohibit?
The taking of any endangered or threatened spcies.
What are some challenges with the ESA?
Economic values - owls vs. jobs
Property rights vs. the rights of species.
Compensation to property owners?
Perverse incentives to private land owners? - Safe Harbor agreements.
What are some strategies for global conservation policy?
1. Knowlege and guilt.
2. Ecotourism development.
3. Community based conservation.
4. Debt for nature swaps.
What is succession?
Change in the composition and structure of a community as the available competing organisms respond to and modify the environment.
What are the key lessons of the Alaska glacier succession story?
1. Follows a distinct and directional path.
2. Early pioneers characterized by high dispersal ability and tolerance to limited resources.
3. Succeeding stages modify environment making it more favorable for other invaders.
4. Ultimately leads toa stable community of organisms 9climax) that is able to sustain itself indefinitely (except disturbance).
What is secondary succession?
Starting with a few ecological legacies.
What is secondary succession accelerated by? What is included in this term?
Legacies - soil structure, organic matter, mineral nutrients, woody debris, seeds, etc.
What is a biotic reaction?
An organism's effect on its environment.
What affects the amount of fuel/thatch in a given environment?
# of herbivores
In regards to succession what does higher productivity lead to?
Lower return time.
What is allogenic change?
Change caused by outside factors or forces (e.g. ice storm).
What is autogenic change?
Change caused by intternal factors (e.g. fuel accumulation).
What are the four measures of disturbance?
1. Disturbance magnitude/size - the spatial extent
2. Disturbance severity - impact on ecosystem functions; extent of loss of legacies.
3. Disturbance frequency/return time - at a given location, the likely interval between successive disturbance events.
4. Minimum dyanmic area - the spatial area necessary to contain the full range of disturbance and change dynamics.
Why is fire important?
1. Major agent of decomposition.
2. Generates considerable diversity.
3. Many species are dependent on fire for survival.
What is ecosystem resilience?
The capacity to recover from a disturbance.
Is there a discernable pattern of recovery or change following disturbance?
Multiple patterns –some directional, others cyclic and yet others variable
If so, what are the mechanisms underlying that change?
May be allogenicand/or autogenic
Does the pattern of change relate to disturbance size or severity?
In general, pattern depends on nature of ecosystem legacies leftby disturbance
What determines timing and severity of disturbance?
-Often determined by status of ecosystem (e.g., fuels)

-May be affected by regime change
Are these patterns changing? If so, why?
–“Variable converging on a variable”
–Changing patterns of land use
–Climate change
How are natural and human-caused disturbances different?
Vary in rates and nature of legacies
What are the policy and management implications of ecosystem disturbance and change?
General rule of thumb –imitate nature in scale, frequency and key legacies
What is the paradox of predation?
predators actually increase the diversity of prey communities because they prevent any single prey species from becoming so abundant as to out compete the others. Thus, more prey species can co-exist.

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