Chapter 53 (Final Exam)

explores how biotic and abiotic factors influence density, distribution, size, and age structure of populations For example, the number of loggerhead turtle hatchlings that survive their first journey to the ocean is affected by both biotic and abiotic factors

DDD population density, dispersion, and demographics

a group of individuals of a single species living in the same general area

their boundaries and size

the number of individuals per unit area or volume

the pattern of spacing among individuals within the boundaries of the population

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 = (M1 x C) / M2

the spacing of individuals in a population

individuals aggregate in patches

one in which individuals are evenly distributed

the defense of a bounded space against other individuals influences dispersion

the position of each individual is independent of other individuals occurs in the absence of strong attractions or repulsions

the study of the vital statistics of a population and how they change over time

an age-specific summary of the survival pattern of a population best made by following the fate of a cohort

group of individuals of the same age

it provides data on the proportions of males and females alive at each age The survivorship curve for Belding's ground squirrels shows a relatively constant death rate

a graphic way of representing the data in a life table

type 1, 2, and 3 many species are intermediate to these curves

Low death rates during early and middle life and an increase in death rates among older age groups

A constant death rate over the organism's life span

High death rates for the young and a lower death rate for survivors

For species with sexual reproduction, demographers often concentrate on females in a population Ecologists use many approaches to estimate the number of breeding females For example, DNA profiling was used to determine the number of female loggerhead turtles laying eggs in a season

or fertility schedule, is an age-specific summary of the reproductive rates in a population describes the reproductive patterns of a population

population growth in an idealized, unlimited environment

exponential model It is useful to study population growth in an idealized situation Idealized situations help us understand the capacity of species to increase and the conditions that may facilitate this growth

Births and deaths can be expressed as the average number of births and deaths per individual during the specified time interval B= bN D=mN b is the annual per capita birth rate, m (for mortality) is the per capita death rate, and N is population size

If immigration and emigration are ignored, a population's growth rate (per capita increase) equals birth rate minus death rate

occurs when the birth rate equals the death rate (r = 0) Change in population size can now be written as _________ Instantaneous growth rate can be expressed as ________ where r_inst is the instantaneous per capita rate of increase

population increase under idealized conditions Under these conditions, the rate of increase is at its maximum, denoted as r_max

equation is ___________

a J-shaped curve The rate of increase is constant, but the population accumulates more new individuals per unit time when it is large than when it is small

how a population grows more slowly as it nears its carrying capacity Exponential growth cannot be sustained for long in any population a more realistic population model limits growth by incorporating carrying capacity

the maximum population size the environment can support Carrying capacity varies with the abundance of limiting resources

the per capita rate of increase declines as carrying capacity is reached The logistic model starts with the exponential model and adds an expression that reduces per capita rate of increase as N approaches K The logistic model of population growth produces a sigmoid (S-shaped) curve New individuals are added to the population most rapidly at intermediate population sizes The population growth rate decreases as N approaches K ΔNΔt=rMmaxN(K−N)K

K before settling down to a relatively stable density

make it difficult to define K

individuals have a more difficult time surviving or reproducing if the population size is too small

products of natural selection evolutionary outcomes reflected in the development, physiology, and behavior of an organism

comprises the traits that affect its schedule of reproduction and survival

1. The age at which reproduction begins 2. How often the organism reproduces 3. How many offspring are produced per reproductive episode

or big-bang reproduction, species that reproduce once and die

or repeated reproduction, species that produce offspring repeatedly

semelparity

iteroparity

at least some of them will grow and eventually reproduce

or density-dependent selection, selects for life history traits that are sensitive to population density

or density-independent selection, selects for life history traits that maximize reproduction

oversimplifications but have stimulated alternative hypotheses of life history evolution

density dependent

What environmental factors stop a population from growing indefinitely? Why do some populations show radical fluctuations in size over time, while others remain stable?

birth rate and death rate do not change with population density

birth rates fall and death rates rise with population density

negative feedback that regulates population growth

many factors, such as competition for resources, territoriality, disease, predation, toxic wastes, and intrinsic factors

know this!

focuses on the complex interactions between biotic and abiotic factors that cause variation in population size

challenged the hypothesis that populations of large mammals are relatively stable over time

population size over time For example, the moose population on Isle Royale collapsed during a harsh winter, and when wolf numbers peaked

regular boom-and-bust cycles

Lynx populations follow the 10-year boom-and-bust cycle of hare populations Two main hypotheses have been proposed to explain the hare's 10-year interval Figure 53.20 Hypothesis: The hare's population cycle follows a cycle of winter food supply If this hypothesis is correct, then the cycles should stop if the food supply is increased Additional food was provided experimentally to a hare population, and the whole population increased in size but continued to cycle These data do not support the first hypothesis Hypothesis: The hare's population cycle is driven by pressure from other predators In a study conducted by field ecologists, 90% of the hares were killed by predators, including lynx, coyotes, hawks, and owls These data support the second hypothesis The availability of prey is a major factor influencing predator population dynamics When prey become scarce, predator species begin to prey on one another, accelerating the collapse of predator populations

Zero population growth = High birth rate - High death rate Zero population growth = Low birth rate - Low death rate

the move from the first state to the second state of zero population growth The demographic transition is associated with an increase in the quality of health care and improved access to education, especially for women Most of the current global population growth is concentrated in developing countries

population's growth trends they can illuminate social conditions and help us plan for the future

vary greatly among developed and developing countries but do not capture the wide range of the human condition

how many humans can the biosphere support? the carrying capacity of Earth for humans is uncertain population ecologists predict a global population of 8.1-10.6 billion people in 2050

summarizes the aggregate land and water area needed to sustain the people of a nation one measure of how close we are to the carrying capacity of Earth Countries vary greatly in footprint size and available ecological capacity Ecological footprints can also be calculated using energy use

food, space, nonrenewable resources, or buildup of wastes

our population growth through social changes

population size over time

comprises the traits that affect its schedule of reproduction and survival

1. The age at which reproduction begins 2. How often the organism reproduces 3. How many offspring are produced per reproductive episode

or big-bang reproduction, species that reproduce once and die

comprises the traits that affect its schedule of reproduction and survival

1. The age at which reproduction begins 2. How often the organism reproduces 3. How many offspring are produced per reproductive episode

comprises the traits that affect its schedule of reproduction and survival

pyramid

inverted pyramid

a rectangle tapering toward the top

Logistic

by a logistic equation

survivorship curve

affected percentage increases as the population density increases

affected percentage remains the same, regardless of increase/decrease in population density

population dynamics

uniform

ecological footprint

r-selection density independent

clumped

influx of new individuals (NOT POPULATIONS) from other areas

the movement of individuals (NOT POPULATIONS) out of an area

The energy cost of reproduction is high, so there are not enough resources to reproduce often, produce many offspring, and take care of them.

the size of a brood

competition for resources disease predation territoriality

a relatively flat line that drops steeply at the end

grows fastest at an intermediate population density

lower the survival rates of the parents

density is the number of individuals of a population in a unit area whereas dispersion is the pattern of spacing of individuals of the population

K-selection

a population remains constant

if there are no limiting factors

the population's age structure

contains many more prereproductive than reproductive individuals

ecological footprint