Population Dynamics Flashcards
Explain Density vs Dispersion.
Density: volume of individuals per area.
Dispersion: how the individuals are spread out
Name the two methods of measuring population density. Define both.
Census: a complete count of all individuals
Population sampling: small subsets are counted, data is extrapolated to entire population
What are the two population sampling methods for organisms that stay in ONE PLACE?
Quadrant method (series of stationary fixed frames) and transect method (frames moving along a line or path).
What is the equation for determining population density?
Total # organisms / total area.
Explain how to give the popular estimate of a population of MOBILE organisms.
Take two random samples (making the organisms from the first capture), use formula.
(Total # marked)(total # from 2nd capture) DIVIDED BY (total # recaptured with mark)
Name the two types of factors that regulate population numbers, and give an example of each.
Density dependent limits: eg. Food.
Density independent limits: eg. Weather
Define competition as a population limiting factor.
Individuals compete for a limiting resource.
Define predation as a population limiting factor.
An interaction between species where one species uses another for food. Prey population usually much higher than predator population.
Name three defenses against predation.
Cryptic colouring: camouflage
Warning colouration: brightly coloured = poison
Batesian mimicry: harmless species looks like a poisonous one
Describe symbiosis
Individuals of two or more species live in direct contact
Define mutualism
A relationship between two species where BOTH benefits (symbiotic relationship)
Describe commensalism
One organism benefits, other is neutral.
Describe amensalism
One partner negatively affected, other is not affected. Eg. Black walnut trees release chemicals that harm plants around it.
Describe parasitism
One organism (host) is the source of food or shelter for another organism (parasite). Host harmed, parasite benefits.
How do we calculate growth rate?
Growth rate = (births - deaths)/total population
Describe exponential growth vs logistic growth. Give equations for each.
Exponential: as population increases, birth increases. (Growth rate x population size)
Logistic : population growth is limited by carrying capacity. As it approaches capacity, growth slows. (Carrying capacity - population size, divided by CC)
Define survivorship. Give the three types.
Survivorship is the number of offspring that survive into old age
Type I: most organisms live to old age
Type II: percentage of deaths are consistent across age groups
Type III: most deaths occur shortly after birth
Define fecundity
Average number of offspring produced by a female over her lifetime.
Describe r vs k selected species. Give another name for both. Which type is prime to extinction?
r-Selected (opportunitists): maximize birth rate. Many offspring, little parental care.
k-Selected (competitors): maximize survivorship of offspring. Prone to extinction, parental care to adulthood.
Describe the four theoretical stages of demographic transition.
1 - birth and death rate high. Least developed countries.
2 - birth rate high, death rate falls. Improved healthcare/food production.
3 - birth rates falls. Death rate falls. Low infant mortality. Increase standard of living.
4 - birth/death rates low. Steady population, higher than in stage 1.
Give the formula to calculate frequency of a species
(Number of quadrats in which the species occurs)/(total number of quadrats). Exists as a percentage.
Explain how relative frequency is calculated. What do these percentages mean about dispersion patterns?
Frequency of a species/total frequency of all species. 0-30% means clumped, 31-80% means random, 81-100% means uniform.
Explain how abundance is calculated.
Number of a certain species/total number of plants.
Define frequency vs relative frequency.
Frequency: % of quadrats occupied by a species.
Relative frequency: frequency of a species / total frequency of all species
Define abundance vs frequency vs density.
Abundance: compares # of a species with total.
Frequency: % of quadrats occupied by a species.
Density: # of plants of a species per unit area.
Why do invasive plants demonstrate random dispersion?
Outcompete native species: no predators
Name the formula for exponential growth of a population
(Growth rate)(population)
Give the formula for LOGISTIC growth of a population
(Growth rate x population)(carrying capacity - population, divided by carrying capacity)
Describe a predator/prey population graph
predator population always lower, usually relatively stable. prey population much higher, but has extreme highs and lows depending on season.
