Intro to Ecology (BIO 262) Unit 2 - Population Ecology

Monogamy

One male and one female mate

Polygamy

more than one female and more than one male; any difference in the number of males and females

Polygyny

One male, several females

Polyandry

One female, several males

Simultaneous polygyny

1 male ♂ with 2 or more ♀ at same time

Simultaneous polyandry

1♀ with 2 or more ♂ at same time

Harem

a social and mating system where one dominant male (or occasionally a small number of males) defends, lives with, and maintains exclusive reproductive access to a group of multiple females and their offspring

Extra-pair copulations (EPCs)

a mating behavior in socially monogamous animal species where an individual mates with someone other than their established social partner

Sessile

lacking self-locomotion and remaining permanently attached to a solid surface or substrate

Minimum convex polygon method

• Smallest area that encloses all points or has points on boundary

• No inner angle greater than 180 degrees

Territory

• Behavioral: a defended area

• Ecologically: an exclusive area (no other animal or group occurs there)

In both cases, they are characterized by the fact that individuals are spaced out over the environment

Center of gravity method

take home range and compute average X and Y coordinates in space; if home ranges are on average spaced out, they are overdispersed and likely territorial

Sex Ratio

# males per female

Age structure

% of individuals in different age classes

Cohort

those individuals in the population born during a specific time interval (e.g., 1/1/1987 through 12/31/1987)

L_x

% of individuals in a cohort surviving to age X (i.e., probability of surviving from birth to age

Net reproductive rate

the expected number of offspring produced by an average individual over its lifetime

M_x

‘fecundity,’ the number of offspring produced by an individual of age X while at that age (a number, not a probability)

Reproductive value

the number of offspring expected to be produced by an organism of age A over the rest of its life

Population

individuals of a given species in a given place.

R₀

number of female offspring per female per lifetime or generation, averaged across all ages. (net reproductive rate)

T

average generation time per population

r

Intrinsic rate of increase for a population (per capita births – per capita deaths) ( = lnR0/T)

Geometric population growth

Used to model population growth for organisms that experience pulsed reproduction (i.e., insects that produce a single generation per year, annual plants) (note: in order for this to be the appropriate model, generations cannot overlap)

N_t = N₀ λ^t

Exponential population growth

N_t = N₀e^rt

Used to model continuous population growth in an unlimited environment

Logistic growth

• dN/dt = rN[1-(N/K)]

• Population starts low relative to K

Iteroparity

• Organisms reproduce many times

  • Humans and most mammals

  • Most perennial plants

Semelparity

organisms produce only once

• Many insects, most annual plants

• Some long-lived organisms

  • Agave

  • Bamboo

  • Salmon

r-selected populations

species that maximize their intrinsic growth rate. They produce many small offspring quickly, provide little to no parental care, and thrive in unstable or disturbed environments

K-selected populations

organisms adapted to stable environments where population size stays near the environment's carrying capacity. These species invest heavily in fewer, larger offspring, feature slow development, long lifespans, and extensive parental care.

Maximum sustained yield (MSY)

the largest average harvest or catch that can be continuously taken from a species' population over an indefinite period without causing the population to shrink