Ecology Exam #2

M/N=R/C

Mark-recapture studies: Used for mobile organisms

M=marked at time 1

N= population size

R=recaptured

C=Captured at time 2

Nt = Noλ

Growth from one season to the next

Nt= individuals at time t

λ=rate of geometric growth (ratio of population size from one year to the next)

Nt = N_o^ert

Equation for exponential growth to find N for future

r=intrinsic growth rate/rate of change

t= time step of interest

N₀ = starting population

Nt= population at time t

dN/dt = rN

Exponential growth

r= intrinsic growth rate (birth-death)

N=population size

dN/dt = rN(1-N/K)

Logistic growth rate equation

K= carrying capacity

𝑑𝑁1/𝑑𝑁 = r1N1((𝐾1―𝑁1―𝛼𝑁2)/K1 )

Lotka-Volterra (L-V) competition equation for interspecies competition

𝑑𝑁/𝑑𝑡 = rN-aNP

L-V equation for change in pray over time

a= predator attack rate

P=number of predators

𝑑𝑃/𝑑𝑡 = baNP-mP

Change in predator population over time

b=efficiency of converting consumed prey into new predator offspring.

aNP=The rate of predation

mP= Represents the decline of the predator population due to natural causes (starvation, disease) in the absence of prey.

Geometric growth

A change in N by a constant proportion over discrete time intervals (ideal for species with non-overlapping generations like plants or insects)

Demographic stochasticity

random fluctuations in population size caused by chance variations in birth and death rates among individuals

Environmental stochasticity

random, unpredictable fluctuations in environmental conditions—such as climate, food supply, or habitat—that affect the birth and death rates of an entire population simultaneously

Allee effects

a biological phenomenon where small or sparse populations exhibit reduced per capita growth rates, or lower individual fitness

Source populations

a group of organisms living in a high-quality habitat where reproduction exceeds mortality (birth>death)

Sink population

a group of organisms living in a low-quality habitat where local death rates and emigration exceed birth rates and immigration

Exploitative competition

Use of resources by one or more individuals, thereby reducing the availability of resources for other individuals

Interference competition

Direct aggressive interaction between individuals

Competitive exclusion principle

Two species using a limited resource in the same way can’t exist

indefinitely

Fundamental Niche

niche space determined by physical factors and resource requirements. Manifest in the absence of other organisms

Realized niche

niche space determined by combined physical and biological factors (comp. and predation)

Character displacement

Occurs when the phenotypes of competing species evolve to become different over time

Parasitoidism

predator (a parasite) lives symbiotically on or in the prey (its host) and consumes certain tissues; may not kill the host. Some parasites (pathogens) cause disease

Commensalism

Individuals of one species benefit; individuals of the other species do not benefit but are not harmed (+/0 relationship).

Facultative mutualist

A facultative mutualist can live without its mutualistic partner, though it performs better with the partner.

Obligate mutualist

An obligate mutualist depends on its partner, in that survival and/or reproduction are not possible in the absence of the partner.

Trophic mutualist

Receives energy or nutrients from its partner

Habitat mutualist

provides a place to live for the other partner.