Population Dynamics Flashcards
survivorship curves
- describe the life history of a species
- has a characteristic shape for each species depending on typical life expectancy at each age
type III survivorship
most individuals do not survive very long past birth
R-selected: their life history prioritizes reproduction which produces many small offspring to maximize the chance that some will survive
better adapted to unstable environments
type II survivorship
mortality doesn’t change with age
type I survivorship
- reflects a higher mortality rate in old age vs. young
- K-selected: larger bodied and take longer to grow to maturity and a reproductive age so there are fewer, larger offspring
- parental care and parental investment
- populations tend to be influenced by carrying capacity and do better in stable environments
type I conservation
- avoid killing adult individuals
- species that take a long time to reach sexual maturity are slow to bounce back from the loss of a breeding population
ex: sharks, whales, tortoises, elephants, mountain goats
ex: atlantic bluefin tuna spawn once a year and do not reach reproductive maturity until 8-12
type III conservation
- avoid killing young individuals
- species that reproduce in their first year need to survive infancy
ex: marine invertebrates with planktonic larvae, amphibian eggs and tadpoles, insects - conservation can be more difficult as their survival depends on climate
life table
summarizes demographic date
cohort: group of individuals born at the same time period or year
cohort life table: tracks what happens to a cohort over time given constant conditions
survivorship
fraction of individuals that survive to a given age
Lx
Nx/N0
fecundity
average number of offspring the average individual produces at each age
mx
net reproductive rate of a population
- sum[lx * mx]
- R0
- in its whole life, how many offspring on average an individual will add to the population
- brings together likelihood of surviving to a certain age and the average number of offspring at that age
reproductive rate
in any year of life, this is how many offspring each individual that was originally born will add to the population
generation time
- average number of parents in the population
- G
- [sum(lx * mx * x)]/R0
intrinsic rate of increase
- how many individuals are being added to the whole population at any given moment
- how fast the population is growing
- r>0 = growing r<0 = shrinking
- r = [ln(R0)]/G
exponential growth using instantaneous growth rate
Nx = N0 * e^rt
- instantaneous, continuous, or per captita growth rate is the amount by which the population is increasing at any given moment per individual
- only occurs when the number of organisms is well below K
carrying capacity
number of individuals that can be supported by a particular environment
K
depends on density dependent factors
logistic model
forms at N -> K
density dependent factors
most decrease r as N grows
- intraspecific competition: more individuals competing for limited resources
- predation: large groups attract more predators
- disease and parasites: large group increases likelihood of transmission
- always why r increases when N is low, so why exponential growth occurs
predation
density dependent
- predators may target a more densely populated area of prey
- when prey population is high, predator population is also high, so prey population will become lower, which leads predator population to become low, which leads prey population to be high
allee effect
describes how r may decrease when N is low
- larger groups increase your chance of finding a mate
- large group social behavior increases your chance of obtaining food or being eaten
- therefore, some density dependent factors increase r as N grows
density independent factors
effect does not change with N
have a consistent effect on populations at any N
do not contribute to carrying capacity
population density
affects how rapidly a population can grow
