Chapter 53 - Population Ecology Flashcards
What is a population?
A group of the same species living in a defined area at a defined time.
What is population dynamics?
(Population ecology) the study of how a population changes over time
Population density
Number of individuals per unit area (terrestrial) or volume (aquatic)
Define immigration.
Individuals coming into a population (includes birth)
Define emigration.
Individuals moving away from a population (includes death)
How is population density measured?
Measure the number and density of individuals
Rates of demographic events (immigration/births, emigration/deaths)
Locations of individuals
Large populations vs small populations; mobile ones vs sedentary ones
Describe the Mark-recapture method.
Scientists capture, tag, and release a random sample of individuals (s) in a population Marked individuals are given time to mix back into the population Scientists recapture a second sample of individuals (n) and note how many of them are marked (x) Population size (N) = sn/x
Described clumped patterns of dispersion.
Most common in nature and often related to the environment
Can be a social thing (mating)
Describe uniform patterns of dispersion.
Species usually very territorial and in competition for resources.
Describe random patterns of dispersion.
Absence of any influences
Mostly wind pollinated plants
What is demography?
The study of population statistics/sizes and how they change over time
Describe the type I survivorship curve.
Starts off horizontal because of good parental care then drops off rapidly because of disease or lack of care; species usually have few offspring
Describe the type III survivorship curve.
Rapid drop off at the beginning because of no parental care with good survival after adulthood; common in species that produce tons of offspring
Describe type II survivorship curve.
Relatively constant/continuous death rate throughout; parental care depends on the species.
Define the per capital rate of increase.
Change in population size (per capita increase) = Births + immigrants entering population - Deaths - emigrants leaving population
Zero growth (ZPG): births = deaths or immigration = emigration
Describe exponential population growth.
Occurs when there is population increase under idealized conditions and results in a J-shaped curve.
When can natural populations grow exponentially?
Release from predators Increase in food availability Increase in shelter (which can increase release from predators) Immunity to disease Resistance to medicine
Why is the elephant population in Kruger National Park a J shaped curve? What are the axes to the graph?
It is a J-shaped curve because hunting was banned (release from predators)
Y-axis = elephant population X-axis = year
Why do the Northern elephant seals show a J-shaped curve? What are axes labeled as?
Banned hunting because they were endangered. Had increased food availability because squid isn’t overfished. Their predators (sharks) were hunted.
Y-axis = number of pups born X-axis = year
Describe carrying capacity (K).
Varies with the abundance of limiting resources (environment always changing)
Describe logistic growth.
When some populations overshoot the carrying capacity before settling down to a relatively stable density resulting in an S shaped curve
Define the Allen effect.
When individuals have a more difficult time surviving or reproducing because the population is too small. This is common for social species
How do some species over come the Allee effect?
White rhinos: cooperative defense
Wind pollinated plants, corals: mate limitation
African wild dogs: group foraging
Pacific Salmon: habitat alteration
Define life history.
The traits that affect its schedule of reproduction and survival. Can vary dramatically.
