population ecology: the study of intraspecific interactions

intraspecific interactions: organisms interacting with members of the same species in relation to environment

biotic and abiotic factors affect density, size and age structure of populations

density: the number of individuals per unit area/volume

dispersion: pattern of spacing among individuals in the population

How do scientists measure density?

• counting individuals, nests, burrows, tracks, etc

• quadrant sampling

  • ex: counting the number of oak trees in 100mx100m plots in Troy, then calculate average in the city

• Mark-recapture: mark individuals from a sample of the population, release back into the population. once mixed, take new sample and record ratio or marked to unmarked

3 types of dispersion: clumped, uniform, random

Demography: study of statistics of populations and changes over time

Life tables: age-specific summaries of the survival pattern of a population from birth to death

cohorts: individuals of the same age

data from life table is put into a survivorship curve

reproductive table: based on female cohorts producing offspring from birth to death

What cycles do many mammals have that reabsorbs endometrial lining when not pregnant? estrous cycle

What bone in the penis aids in copulation(mating) in most mammals(not humans)? baculum

Generation time: amount of time between birth of individual vs it’s offspring

small organisms - shorter generation times

• ex: bacteria dividing asexually by binary fission every 20 minutes

large organisms - longer generation times

What factors limit colony size of bacteria? limited resources, toxic waste accumulation, predation, viruses(bacteriophages)

Viruses at minimum have : nucleic acid(DNA + RNA) and protein coat(capsid)

exponential population growth(r-selected) - populations that have access to abundant resources and reproduce without limits

logistic population growth(k-selected) - populations with limited resources that cause populations to reach a plateau

the plateau in logistic population growth is also called: carrying capacity(K)

semelparity - a single, large reproductive effort

iteroparity - repeated reproduction

life history - traits that affect an organism’s schedule of reproduction and survival

1. start of reproduction

2. how often reproduction occurs

3. how many offspring per reproductive episode

r-selected - reproductive success in uncrowded environments

k-selected - life history traits sensitive to population density

Fewer offspring = longer lifespan of parents

more offspring = more energy invested in offspring

“principle of allocation” : more energy for on function = less energy for other function

reproductive diapause: allocation of energy from breeding to migration for survival

density-dependent factors: factors that affect populations as it becomes denser

density-independent factors: factors that affect population size regardless of the number of individuals

populations can fluctuate in density with regular boom-and-bust(periodic) cycles

• cicadas emerge from the ground every 13-17 years depending on the species

age structure - number of individuals of each age in the population

ecological footprint - land and water required by each person, city, or nation to produce all resources consumed and absorb the waste

limiting factors that could lead to Earth reaching carrying capacity

1. Food(Malnutrition/famine)

2. sustainable space

3. lack of resources(decline of non/renewable resources)

4. inability to absorb waste