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Ecology Exam 2
| Question | Answer |
|---|---|
| Keystone Species | A species on which other species largely depend on, if it were removed the ecosystem would change drastically. |
| Population | Group of individuals that are the same species living in the same place at the same time Community is different species. |
| Population size | number of individuals in a population |
| Population Density | number of individuals per unit area or volume |
| Clones | genetically identical copy of an individual Form by budding, apomixis or horizontal spread |
| Genet | genetic individual, resulting from a signal fertilization event |
| Ramet | actually or potentially physiologically independent member of a genet that may compete with other member for resources |
| Absolute pop size | actual number of individuals in a population |
| Relative pop size | estimate of pop size based on data that are related in a unknown way to the absolute size, but can be compared from one time period or place to another |
| Area- Based Count | Immobile organism. Counted in series of quadrants. Quadrants have to represent area well and organisms have to be counted accurately |
| Distance Method | Immobile or mobile organisms. Line transect or point sampling. Larger number=lower density |
| Detection Function | How the change of seeing an individual decreased with its distance from the transect or point |
| Mark Recapture | Mobile organisms only. N=(M1 x M2)/ R N= pop size M1= total # of animals marked in 1st sample M2= total # of animals captured in 2nd sample R= # of marked animals captured in 2nd sample |
| Best describes the measurement of population density | the number of individual genets or ramets on a per area basis |
| How is the absolute population size related to the relative population size | the relative population size is based on data that are correlated with the absolute population size but is not an actual measure of all the individuals in a population |
| What is the relationship between populations, metapopulations, and geographic ranges for species? | A species geographic range is the entire area in which the species occurs and could consist of metapopulations or groups of isolated populations linked by dispersal |
| Which best describes the use of species distribution models? | Species distribution models are used to predict the current and future geographic ranges of known species, and to find unknown species. |
| Which of the following factors are important to the habitat suitability of a species? | Climate, food resources, and disturbance |
| A non-native species is introduced to a habitat outside of its native geographic range. If the species becomes invasive, what factors could be responsible for its original absence in the new habitat? | Dispersal limitation and its evolutionary origins |
| Under what conditions will a metapopulation eventually become extinct? | The rate of population extinction is greater than the rate of population colonization |
| How can a metapopulation become extinct even when some suitable habitat is present within the metapopulation range? | Because the suitable habitat is not large enough to sustain individual populations and/or it is isolated by distance so it is unable to receive immigrants |
| Place a species distribution in order from smallest to largest. | Population < Metapopulation < Geographic range |
| Which type of mammals would you most likely find on a small oceanic island that is 2,000 kilometers away from any other land mass and has not been colonized by humans? | Bats |
| Which negative effect can habitat fragmentation have on a metapopulation? | It can make patches smaller, thus increasing the patch extinction rate. |
| Which statement about the influence of evolutionary and geologic history on species distribution and abundance is true? | Geological history influences distribution of suitable habitat and thus influences where an organism exists today. |
| What is the most likely reason that polar bears are found in the Arctic but not in Antarctica? | Polar bears, which were derived from brown bears that lived in the Northern Hemisphere, can migrate long distances, but they are either unable or unwilling to travel across tropical areas that lie between the Arctic and Antarctica. |
| What are the four main patterns of population growth observed in nature? | Exponential, logistic, fluctuating, and cycling |
| How is exponential growth related to logistic growth? | Both exponential growth and logistic growth show a rapid increase in the number of individuals in the population at first, but then logistic growth slows down and stabilizes at the maximum population size. |
| Which of the following is true about population size fluctuations seen in nature? | Fluctuations occur in all populations. |
| Why is there often a time lag in a population's response to changes in its population size? | Because of delayed growth, reproduction, and/or survival |
| What mechanism(s) explain the population cycles seen in some predator-prey interactions? | Delayed predator population growth to prey population growth |
| How could you cause a population to cycle? | Provide unlimited food for the adults but limit the food for juveniles in the population |
| Which of the following best describes why fluctuations in population growth rate can increase a population's risk of extinction? | Compared to populations that do not fluctuate, populations that fluctuate in size show slower growth rates, resulting in smaller population sizes with greater risk of extinction. |
| Why do small populations that experience genetic drift and inbreeding have an increased chance of extinction? | Genetic drift and inbreeding reduce genetic variation, limiting the ability of small populations to respond to environmental change and harmful alleles. |
| Assuming that their average population growth rates and all other factors are equal, which population would most likely be at risk for extinction? | A small population with high variation in its growth rate |
| Due to their low density, females of a species of turtles have difficulty finding mates. As a result, the population’s growth rate has been low, despite ample resources. This is an example of | an Allee effect. |
| How does geometric population growth differ from exponential population growth? | Geometric growth occurs when individuals reproduce over discrete time periods while exponential growth occurs when individuals reproduce continuously. |
| What is λ in the geometric growth rate equation? | λ is a constant whose value is determined by the per capita birth rate minus the per capita death rate over discrete time periods. |
| What is r in the exponential growth rate equation? | r is a constant whose value is determined by the per capita birth rate minus the per capita death rate over continuous time |
| You plot the relationship between population growth and population density and find no relationship between the two variables. What does this relationship indicate about the population? | The population growth rate is independent of the number of individuals in the population. |
| Which of the following are examples of density-independent factors? | Forest fires, hunting, and trampling by elephants |
| How do density-dependent factors regulate population size? | Density-dependent factors increase λ or r when the population size is small and decrease λ or r when the population size is large |
| How does logistic growth compare to exponential growth? | Logistic growth is similar to, but slightly slower than, exponential growth when densities are low. When densities are high, logistic growth slows down as it approaches the carrying capacity |
| With logistic growth, when the term (1 — N/K) is close to 1, what happens to population growth | Population growth is similar to that of exponential growth (dN/dt = rN) |
| Which best describes the pattern of U.S. population size over time? | U.S. population size followed a logistic growth curve until the 1950s but then continued to increase past its projected carrying capacity. |
| What is the advantage of using life table data to determine population growth rate? | Life table analysis incorporates how reproduction and survival vary with the age, size, or life stage of individuals within a population |
| If R0 = 2 and G = 1, what is r and λ? | r = 0.69; λ = 2 |
| A population of turtles contained 342 individuals at the end of the year 2013. Since then, 44 have died, 37 were born, 17 immigrated, and 6 emigrated. What is the population size now? | 346 |
| Which population would be expected to remain stable in size | A population with a λ of 1 or an r of 0 |
Created by:
emsnyder2003