Chapter 53 Flashcards
Population Ecology
Explores how biotic and abiotic factors influence density, distribution, size, and age structure of populations
The number of loggerhead turtle hatchlings that survive their first journey to the ocean is affected by both _ and _ factors.
Biotic; abiotic
Population
A group of individuals of a single species living in the same general area
Populations are described by their _ and _.
Boundaries; size
Density
The number of individuals per unit area or volume
Dispersion
The pattern of spacing among individuals within the boundaries of the population
In most cases, it is _ to count all individuals in a population.
Impractical (or impossible)
_ can be used to estimate densities and total population sizes.
Sampling techniques
Population size can be estimated by either extrapolation from small samples, and index of population size (e.g., number of nests), or the _ method.
Mark-recapture
Determining population size using 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 capture a second sample of individuals (n), and note how many of them are marked (x)
- Population size (N) is estimated by N = (sn)/x
_ is the result of an interplay between processes that add individuals to a population and those that remove individuals.
Density
Immigration
The influx of new individuals from other areas (in)
Emigration
The movement of individuals out of a population (out)
Three patterns of dispersion:
- In a clumped dispersion, individuals aggregate in patches
- A uniform dispersion is one in which individuals are evenly distributed
- In a random dispersion, the position of each individual is independent of other individuals
Demography
The study of the vital statistics of a population and how they change over time (birth and death rates)
_ and _ are of particular interest to demographers.
Death rates; birth rates
Life Table
An age-specific summary of the survival pattern of a population
A life table best made by following the fate of a _, a group of individuals of the same age.
Cohort
Survivorship Curve
A graphic way of representing the data in a life table
Survivorship curves can be classified into three general types:
- Type I: Low death rates during early and middle life and an increase in death rates among older age groups (ex: humans and other high-level eukaryotes)
- Type II: A constant death rate over the organism’s life span (under constant threat of predation)
- Type III: High death rates for the young and a lower death rate for survivors (ex: sea turtles)
Many species are _ to the three types of survivorship curves.
Intermediate
The exponential model describes population growth in an idealized, _ environment.
Unlimited
The exponential model is useful to study population growth in an _ situation.
Idealized
Idealized situations help us understand the _ of species to increase and the conditions that may facilitate this growth.
Capacity
Change in population size =
Births + immigrants entering population - deaths - emigrants leaving population
If immigration and emigration are ignored, a population’s growth rate (r) equals _ minus _.
Birth rate; death rate
_ growth occurs when the birth rate equals the death rate.
Zero population
_ population growth is population increase under idealized conditions. Under these conditions, the rate of increase is at its maximum, denoted as _.
Exponential; rmax
The J-shaped curve of exponential growth characterizes some _ populations.
Rebounding
The elephant population in Kruger National Park, South Africa, grew _ after hunting was banned.
Exponentially
Exponential growth cannot be _ for long in any population.
Sustained
A more realistic population model limits growth by incorporating _.
Carrying capacity
Carrying Capacity (K)
The maximum population size the environment can support
The Logistic Model
Describes how a population grows more slowly as it nears its carrying capacity (“logical”)
In the logistic population growth model, the per capita rate of increase _ as carrying capacity is reached.
Declines
When population size equals the carrying capacity (K), the population _ growing.
Stops
The population growth rate _ as population size approaches K.
Decreases
The growth of laboratory populations of paramecia fits an _ (logistic model) curve. These organisms are grown in a constant environment lacking predators and competitors.
S-shaped
An organism’s _ comprises the traits that affect its schedule of reproduction and survival.
Life history
Life history traits are evolutionary outcomes reflected in the _ of an organism.
Development, physiology, and behavior
A life history entails three main variables:
- The age at which reproduction begins
- How often the organism reproduces
- How many offspring are produced per reproductive episode
Organisms have finite resources, which may lead to trade-offs between _ and reproduction.
Survival
There is a trade-off between survival and _ in European kestrels.
Paternal care
Some plants produce a _ number of small seeds, ensuring that at least some of them will grow and eventually reproduce.
Large
_, or density-dependent selection, selects for life history traits that are sensitive to population density (ex: predation, resources).
K-selection
_, or density-independent selection, selects for life history traits that maximize reproduction (ex: water availability, climate).
r-selection
In _ populations, birth rate and death rate do not change with population density.
Density-independent
In _ populations, birth rates fall and death rates rise with population density.
Density-dependent
Density-dependent birth and death rates are an example of _ that regulates population growth.
Negative feedback
Density-dependent birth and death rates are affected by many factors, such as:
-Competition for resources
-Territoriality
-Disease
-Predation
-Toxic wastes
(not not affect density-independent populations)
Population Dynamics
Study that focuses on the complex interactions between biotic and abiotic factors that cause variation in population size
Long-term population studies have challenged the hypothesis that populations of _ are relatively stable over time.
Large mammals
Both weather and predator population can affect _ size over time.
Population
The moose population on Isle Royale _ during a harsh winter, and then wolf numbers _.
Collapsed; peaked
When a population becomes crowded and resource competition increases, _ often increases.
Emigration
Metapopulations
Groups of populations linked by immigration and emigration
Local populations in a metapopulation occupy patches of _ habitat surrounded by _ habitat.
Suitable; unsuitable
Local populations lost through extinctions can be recolonized by _ from other patches.
Immigration
The human population is no longer growing exponentially but is still _ rapidly.
Increasing
No population can grow _, and humans are no exception.
Indefinitely
The human population increased relatively slowly until about _ and then began to grow exponentially.
1650
The global (human) population is now more than _ billion people.
7
One important demographic factor in present and future growth trends is a country’s _.
Age structure
Age Structure
The relative number of individuals at each age
How many humans can the biosphere support? Population ecologists predict a global population of _ billion people in 2050.
8.1-10.6
The carrying capacity of Earth for humans is _.
Uncertain
Scientists have based estimates on _ growth models, area of habitable land, and food availability.
Logistic
The _ concept summarizes the aggregate land and water area needed to sustain the people of a nation.
Ecological footprint
The ecological footprint is one measure of how close we are to the _ of Earth.
Carrying capacity
Countries vary greatly in _ size and available ecological capacity.
Footprint
