1. What two pieces of data are needed to mathematically determine density?
number of individuals per unit area or volume
2. What is the difference between density and dispersion?
dispersion: pattern of spacing among individuals within boundaries of pop
Note and understand what the letters of the formula mean. Next, try the following problem.
N=mn/x N=estimated pop size m= number of individuals parked and released in first sampling n=total number of individuals captured 2nd time x= number of marked animals recaptured in the second sampling
4. Explain the impact of immigration and emigration on population density. (To avoid confusion between these two terms, it might help to use this memory trick: immigration is the movement into a population, while emigration is the exiting of individuals from a population.)
immigration: increase density (like births) emigration: decreases density (like deaths)
5. Label the dispersion pattern shown by each population in the figure below. Second, and most important, what do the dispersion patterns tell us about the population and its interactions?
clumped: group where food is uniform: maintained by aggressive interactions btw neighbors random: mostly plants. random spreading of seeds
6. In what population statistic do demographers have a particular interest? How is this data often presented?
birth and death rates. summarize population size growth. presented in life table
7. Is your biology class a cohort? Explain.
cohort: group of individuals of the same age, from birth until al are dead.
8. Survivorship curves show patterns of survival. In general terms, survivorship curves can be classified into three types. Using the figure below, label and explain the three idealized survivorship patterns.
Type 1: most live to average lifespan. few offspring, well cared for. K-selected Type 2: constant death rate. K-selected Type 3: a lot die initially. release lots of eggs, no parenting, few survive. R-selected
10. What does a reproductive table show?
age-specific summary of reproductive rates in a population. Number of female offspring produced by each age group (in sexual species)
11. On what is the life history of an organism based?
The traits that affect an organisms schedule of reproduction and survival from birth to death.
12. What three variables form the life history of a species?
-when reproduction begins -how often organism reproduces - how many offspring are produced.
13. Explain the difference between semelparity (big-bang reproduction) and iteroparity (repeated reproduction) as life history strategies.
semelparity : single reproductive episode before death (release eggs). can wait for right conditions, release a lot. survival rate of offspring is low. iteroparity: multiple reproductive cycles over the course of its lifetime. more dependable environments.
14. Explain how two critical factors influence whether a species will evolve toward semelparity or iteroparity.
survival rate of offspring, likelihood that the adult will survive to reproduce again
15. Explain the effect of offspring care on parental survival in kestrels.
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Do not let the math in this section be a problem. Instead of trying to understand the calculus involved, concentrate on the idea of exponential growth, how it is graphed, and what this type of growth indicates about a population.
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16. What is the advantage to using per capita birth and death rates rather than just the raw numbers of births and deaths?
per capita birth rate: number of offspring produced per unit time by an average number of the population
17. What will the per capita birth and death rates be if a population is demonstrating zero population growth?
equal
18. What does it mean for a population to be in exponential population growth?
ideal conditions: access to abundant food, free to reproduce at capacity. per capita rate of increase=max
19. In the graph below, explain why the line with the value of 1.0 shows a steeper slope that reaches exponential growth more quickly than does the line with the value of 0.5. On this graph, add a third line that approximates a population with an exponential value of 1.25.
different maximum per capita rates==different slopes
20. What are two examples of conditions that might lead to exponential population growth in natural populations?
no predators. protected species, humans
21. What is carrying capacity?
maximum population size that a particular environment can sustain. K
22. What are six examples of limiting resources that can influence carrying capacity?
energy shelter refuge from predators nutrient availability water suitable nesting sites
23. In the logistic population growth model, the per capita rate of increase approaches zero as the __________________________ is reached.
carrying capacity
24. If the carrying capacity (or K) is 1,000 and N is 10, the term (K - N)/K is large. Explain why a large value for (K - N)/K predicts growth close to the maximum rate of increase for this population.
environment can sustain more, rate will be high
25. In the graph below, explain why the logistic model predicts a sigmoid (S-shaped) growth curve when the population density is plotted over time. Hint: The critical part of this answer concerns why growth slows as N approaches K.
new individuals are added to the population most rapidly at intermediate population sizes. pop growth slows as N approaches K
26. The end of this concept attempts to bring together the ideas of life histories and growth models This is done with the introduction of two new terms: K-selection and r-selection. Explain the ideas behind the creation of these two terms.
k-selection: density-dependent selection. selection for life history traits that are sensitive to population. operates on populations near density limit imposed by resources and competition is strong. r-selection: selection for life history traits that maximize reproductive success in uncrowded environments. ex. disruption of habitats.
27. Compare and contrast these two terms: density-independent regulation density-dependent regulation
density-independent regulation: a birth rate or death rate that does not change with population density density-dependent regulation: death rate that rises with pop density
28. Explain how negative feedback plays an essential role in the unifying theme of regulation of populations. Does negative feedback play a role in both density-independent and density-dependent regulation?
density decreases pop growth. or else pops wouldnt stop growing
Negative Feedback Mechanisms
Competion for resources Territoriality-limits density. compete for territory Disease- spread with crowding. Predation-if predator captures more food as density of prey increases Toxic wastes-metabolic waste can poison. Intrinsic factors- (physiological/internal) aggressive interactions/stress with crowding can decrease reproduce rate
30. Give both biotic and abiotic reasons for population fluctuations over the last 50 years in the moose population on Isle Royale, based on population dynamics.
weather/seasons predation
31. Explain the importance of immigration and emigration in metapopulations.
link populations
32. Summarize human population growth since 1650.
exponential growth
33. What is demographic transition? Use the figure below to explain the process in Sweden and Mexico.
when birth rates approach death rates. associated with increased health care, sanitation, access to education (esp women)
34. You should be able to look at age-structure graphs and make predictions about the future growth of the population. Using Figure 53.25, describe the key features for the three age-structure graphs and predict how the population of each country will grow. Country Key Features Predicted Future Growth
age structure: relative number of individuals of each age in a population
35. Why do infant mortality and life expectancy vary so greatly between certain countries?
reflect quality of life.
36. Can the world's population sustain an ecological footprint that is currently the average American footprint? Explain.
NO