Population ecology Flashcards
What is population size?
the number of individuals
larger populations = larger variety = more potential for adaptation
What is population density?
the number of individuals per unit geographic area
What are population density limiting factors?
limitations to population growth
What are the 2 types of population density limiting factors?
density-dependent
density-independent
What are density-dependent population density limiting factor?
disease OR Predators
competition Availability of resources
predation Nutrient supply
food Disease
nesting sites Accumulation of wastes
mates
What are density-independent population density limiting factors?
often abiotic OR Phenomena
sunlight Abiotic factors
temperature Weather conditions
reainfall
What are terms to describe population distribution?
Random
Clumped
Uniform
What is the difference btw natality and mortality?
natality -
increase population size as offspring are added to the population
mortality -
decreases the population size as some individuals get eaten, die of age, get sick
What is the difference btw immigration and emigration?
immigration -
increases population size as individuals have moved into the area from somewhere else
emigration -
decreases the population size as individuals have moved out of the area
What is the population size formula (general)?
Pop. size = (Immigration + Natality) - (Mortality + Emigration)
Mnemonic:
Pee IN ME
What are the phases of the sigmoid population growth curve?
- Exponential
- Traditional
- Plateau
What occurs during the exponential phase of the sigmoid curve?
rapid increase of population
natality > mortality
Resources = ABUNDANT
Diseases + predators = RARE
What occurs during the traditional phase of the sigmoid curve?
natality = DECREASE mortality = INCREASE
Resources = DECREASE
Pop. = increase but at SLOWER RATE
What occurs at the plateau phase of the sigmoid curve?
No more population growth = constant population size
natality = mortality
pop. reached CARRYING CAPACITY of environment
resources = limited
Predators + disease = common
What is carrying capacity?
is the MAXIMUM a population size that can be supported by the environment
e.g. if pop. is limited by resource shortage = carrying capacity
What are r reproductive strategies?
small resource investment
= low effort babes
nop protection
= increase mortality %
egg fertilised THEN dispersed
More common for animals wt shorter lifespan
What are k reproductive methods?
relates to carrying capacity (competitive world)
heavy investment (i.e protection + parenting) = increase survival %
common in larger animals + animals that are long lived wt longer period of maturation + adulthood
How can you measure a population size?
Immigration + Natality + Emigration + Mortality + limiting factors
= IMPRACTICAL TO COUNT POP. OVER LARGER AREA
therefore: SAMPLING e.g.
sampling -
identifying individual #s in small areas (RANDOM + UNBIAS) then estimating totals
quadrats -
for non-mobile / sessile species
How does the capture-mark-release-recapture sampling method used?
area defined & marked off
selection of individuals captured, counted, marked, released (n1)
after time (n1 reintegrated) second capture made (n2) all animals (marked & not marked) counted (n3)
related to Lincoln Index
What is the Lincoln Index?
pop. size = (n1 x n2) / n3
n1 = # in 1st capture n2 = # collected in 2nd capture n3 = # marked in 2nd capture
What are the assumptions associated wt the Lincoln Index?
- ALL INDIVIDUALS EQUAL CAPTURE %
- MARKED individuals RANDOMLY DISTRIBUTED after release (n1 CANNOT AFFECT n3)
- MARKING will NOT AFFECT natality + mortality
How can Lincoln Index accuracy be improved?
Increase capture sample size
take REPEATED samples
What are quadrats?
a square wt a known frame
placed randomly then count # of species/ coverage %
REPEAT
observe presence / absence of species
therefore, # quadrats wt both species compared to total # quadrats
What are the quadrat formulas?
pop. size = (mean # per quadrat x total area) / area of each quadrat
estimated average density = total # individuals counted / (# quadrats x area of quadrat)
What is the purpose of the chi square test?
tp determine if there is a statistically significant association btw distribution of 2 species
applied to quadrat sampling
CAN ONLY USE IF > (or equal to) 5 frequency & random sample
What are the steps to the chi square test?
- hypothesis (null / alternative)
- table of frequencies (observed & expected)
- formula
- degree of freedom (fd)
- ‘p’ value
What does the hypothesis step of the chi square test consist of?
null (H0)
2 species INDEPENDENTLY distributed
alternative (H1)
2 species associated POSITIVELY or NEGATIVELY
What does the table of frequencies step of the chi square test consist of?
make a table of observed frequencies
make a table of expected frequencies using formula:
(row total x column total) / grand total
What does the chi squared formula step of the chi square test consist of?
apply formula and insert calls into the TOTAL areas
formula:
x^2 = (sum of (O - E) ^2) / E
O = observed frequency E = expected frequency
What does the degree of freedom step of the chi square test consist of?
mathematical restriction the designates what range of values fall within each significant level
df = (m - 1) (n - 1)
m = # rows n = # columns
when distribution patters for 2 species compared : D SHOULD ALWAYS = 1
What does the ‘p’ value step of the chi square test consist of?
determines if result is statistically significant (< 5% probability = p < 0.05)
