Chapters 12 and 13: population ecology Flashcards
Population
group of individuals from 1 species; live in 1 area at same time
Population ecology
study of how and why # of individuals in a population change over time
- Changes in ages of individuals in a population, male/female proportion, geographic distributon
Demography
study of factors that determine size and structure of population
- Ex: birth rates, immigration/emigration rates
Population characteristics:
natality and mortality
Natality
birth rate; # of individuals added through reproduction
Mortality
death rate; # of individuals removed through death
Fecundity
number of female offspring produced by each female in the population
Immigration
when individuals enter a population by moving from another population
- mvmnt in
Emigration
when individuals leave a population to join another population
- mvmnt out
2 factors that effect population dynamics
- Environmental Stress
- Changes in Environmental Conditions
what factors limit population growth
predation, nutrients, competition, space, resources
- abiotic and biotic factors
population growth equation
(change in population) / (change in time)
what factors directly effect population
size- # of organisms in population
density- # of individuals/area
dispersion- how organisms are arranged in environment
age distribution- proportion of individuals of each age
Biotic Potential:
aka: Inherent reproductive capacity: how many babies a female can have at once
- biotic potential is much above replacement level.
- Natural tendency for increase. No population can increase indefinitely, there are always limits!
Intrinsic Rate of Increase (r)
the rate at which a population would grow if it had unlimited resources
- exhibiting high rates of:
- (1) early reproductive age
- (2) short generation times (periods between successive generations)
- (3) long reproductive lives
- (4) lots of offspring
Sex Ratio
Relative number of males and females in a population
Age Distribution
Number of individuals of each age in the population.
- Greatly influences reproductive rate of a population.
Age Distribution
Number of individuals of each age in the population.
- Greatly influences reproductive rate of a population
Age Distribution
Number of individuals of each age in the population.
- Greatly influences reproductive rate of a population
expanding age structures
- graph with a wide base and narrow top
- pyramid graph
- high pre reproductive ages, less reproductive ages, even less post reproductive ages
stable age structures
- dome/hill shaped graph
- high pre reproductive ages, high reproductive ages, even more post reproductive ages
declining/diminishing age structures
- dome, restricted at bottom shaped graph
- low pre reproductive ages, more reproductive ages, less post reproductive ages
Lag Phase (logistical growth curve)
First portion of the curve; slow population growth.
Exponential Growth Phase (logistical growth curve)
More organisms reproducing causing accelerated growth; continues as long as birth rate exceeds death rate.
Stable Equilibrium Phase (logistical growth curve)
Death rate and birth rate equilibrate; population stops growing; achieved in logistical growth curves
Exponential Growth
Growth at a constant rate of increase per unit time (Geometric)
- distinct breeding period
Arithmetic Growth
Growth at a constant amount per unit time.
Exponential growth occurs when…
r does not change over time
- does not depend on the number of individuals
- when increases in the size of a population do not affect r, growth is density independent.
density dependent growth
When population density—the number of individuals per unit area—gets very high, we would expect the population’s per- capita birth rate to decrease and the per-capita death rate to increase, causing r to decline.
logistical curves have a ___, whereas exponential growth curves do not.
maximum carrying capacity
Carrying capacity (K)
maximum number of individuals in a population that can be supported in a particular habitat over a sustained period of time.
Environmental Resistance
Any factor (limiting factor) in the environment limiting carrying capacity.
four main factors of environmental resistance
- Raw material availability
- Energy availability
- Waste accumulation and disposal
- Organism interaction
density-independent controls
affects the population’s size regardless of the population density (independent of # of individuals in a population)
- almost always abiotic
- ex: floods, fires, hurricanes, bad weather, habitat loss, pesticides
density-dependent controls
limiting factors that are proportional with a populations density (larger population size = worsening effects)
- almost always biotic
- ex: competition for resources, parasitism, predation, disease
positive density dependence
(+) population growth = (+) population density
- as population grows, density grows
- usually small populations
negative density dependence
when population reaches carrying capacity; after that it exhibits negative density dependance
- population grows, density decreases
equation for time to double population (years)
70 / (population growth %) = # years
K-strategists have fewer ___, with more ___.
- fewer babies
- more parental care
K-strategists are limited by…
density-dependent limiting factors
factor(s) that become more severe as the population grow in size?
diseases
R-strategists are limited by…
density independent limiting factors
Populations size is irrelevant to the limiting factor ____.
weather conditions
Zero Population Growth (ZPG)
When stability is reached in a population
- mortality=natality
- birth rate = death rate
most populations exhibit survivorship curves that combine features of ___ and ____.
type I and type III curves
K-strategists = type __ curve
type I
R-strategists = type __ curve
type III
life table
class-specific survival and fecundity data
cohort life table
life table that follows a group of individuals born at the same time form –> death of last individual (exactly how long organisms born at 1 times are able to survive)
- following age group throughout whole life
static life table
life table that quantifies survival and fecundity of all individuals in a population during 1 time interval (“aging” dead animals)
- can collect data of how old they are today
- fossils (skulls, bones, etc.)
- dating back organisms found
population dynamics
changes in populations over time
- patterns of population size fluctuations over time
population fluctuations due to…
factors such as availability of resources, predation, competition, disease, parasites, and climate
- Fluctuations include random and cyclic changes through time
Cyclic populations
occur among related species and across large geographic areas
age structure fluctuations
- if an age group contains a high or low number of individuals, the population likely experienced high birth or death rates in the past
Overshoot
when a population grows beyond its carrying capacity
- often occurs when the carrying capacity of a habitat decreases from one year to next
- ex: because less resources are produced
Die-off
a substantial decline in density that typically goes well below the carrying capacity
Die-offs often occur when….
a population overshoots its carrying capacity
___ populations are more vulnerable to extinction than __ populations.
- small populations >
- larger populations
stochastic model
a model that incorporates random variation in population growth rate; assumes that variation in birth and death rates is due to random chance
deterministic model
a model that is designed to predict a result without accounting for random variation in population growth rate
Demographic stochasticity
variation in birth rates and death rates due to random differences among individuals
Environmental stochasticity
variation in birth rates and death rates due to random changes in the environmental conditions (ex: changes in the weather)
Habitat fragmentation
the process of breaking up large habitats into a number of smaller habitats
sources
high-quality patches that produce a large number of individuals that disperse to other patches
Sinks
low-quality patches that produce few individuals and rely on dispersers to keep the sink population from going extinct
_____ patches that are close to ____ patches are more likely to be colonized.
- unoccupied
- occupied
Rescue effect
when dispersers supplement a declining subpopulation and thereby prevent it from going extinct
uses of meta population theory
- reintroducing species resistant to extinction
population viability analysis (PVA)
- a model that estimates the likelihood that a population will avoid extinction for a given time period
- attempts to combine basic demographic models with data on geographic structure and the rate and severity of habitat disturbance
Basic model of metapopulations (p =)
proportion of occupied patches when colonization and extinction have reached an equilibrium
geometric growth =
exponential growth
logistical growth model
a growth model that describes slowing growth of populations at high densities
