Population/Community Ecology Exam 2

population

group of individuals of same species that live in same area and interact with each other

Abundance

pop size (number individuals) or density (individuals per area)

Population Concepts

1. We estimate population abundance and density with sampling, & we use models to predict

2. Populations of a species are dynamic: they vary over time and space

3. Patchy populations are limited by habitat suitability, historical factors, and dispersal

4. The dispersion of individuals depends on essential resources, competition, dispersal, and behavioral interactions

Population Dispersal

1) Emigration: male (mates) vs female (nutrition) distribution

2) wind transport - dandelion

3) H2O transport - salmon fry

4) passive navigation - portoguese man o’war genetic polymorphism

5) animal vector

6) coordinated gamete release - coral

density independent vs dependent dispersal

density independent: passive dispersal depend on natural kinetic energy (eg wind, gravity)

density dependent: active dispersal depend on population size, resource competition, habitat quality, and habitat size

natal dipersal

permanent movement from where organism give birth to new place to reproduce - eg male lions leave pride

breeding dispersal

adults move between breeding attempts

Metapopulation

a population of subpopulations/groups connected when individuals move between patches

limits to population distribution

Patchy distribution: limited by habitat (large scale - climate, small scale - soil)

dispersal limitation - seeds/species cannot expand to take up all possible habitat eg devils hole pupfish

What determines dispersal distancce

1) Proximate Causes

A. Environmental dispersal

-absent or highly variable resources

-parental aggression

B. "Innate" dispersal

-genetic predisposition to disperse (e.g., migration cues via body condition, etc.)

2) Ultimate Causes - evolutionary underpinnings

1. inbreeding avoidance - avoiding extinction vortex

2. competition for mates

3. competition for resource

Life History

record of major events related to growth & development, reproduction, and survival

Measuring growth & development: size at maturity, metamorphosis, speed of juvenile growth

Measuring reproduction: age at first reproduction, frequency/number of reproductive events, sexual vs asexual reproduction, size vs number of offspring

measuring survival: juvenile vs adult survival probability, cost of reproduction, senescence, lifespan

Life History Generation Time Equation

Life HIstory Vital Rates Chart

Tradeoffs between survival and reproduction - when reproduce and size vs quantity

Amount variation

fish > amphibians/reptiles > birds > mammals

Logistic Population Growth

r vs k selected species

r selected species: maximize population growth; early maturity, lots of babies, less survive, small parental investment; unstable habitats so below carrying capacity

k selested species: maximize competitive success in crowded environment; delayed maturity, few offspring, high parental inestment, long generation time; stable habitats so near/at carrying capacity

survivorship curves

Factors in population change

Growth: births and immigration

Decline: deaths and emigration

Population Growth Phases

Lag phase → exponential phase → stationary phase → death phase

carrying capacity over time

Carrying capacity, K, not constant over time, it changes and represent range of values

Delayed Density Dependence

Delayed Density Dependence rτ

when rτ < 0.368, no fluctuation at K

when 0.368 < rτ < 1.57 damped oscillation at K

when rτ > 1.57 indefinite fluctuations at K - stable limit cycle/stable equilibrium state

based on intraspecific competition

Allee affect

balance between context small population density limiting growth and positive density dependence for the minimum viable population

about how much individuals can find each other in space

When population is large, positive relationship between population density and the reproduction and survival of individuals

When the population is small, increased difficulty of finding mates or reproducing at low population size (negative relationship).

community interactions (+, 0, -)

Exploitation: +, -

Amensalism:

intraspecific vs interspecific competition

Intraspecific: Competition between individuals of the same species

Interspecific: Competition between different species

Competition and Distribution

competition → uniform distribution

Territoriality (inter or intra) occur when benefits of controlling the

territory > costs of defending

Interspecific Competition Equation

Conditions under Lotka-Volterra for stable coexistence

intraspecific competition has a greater effect than interspecific competition

Lotka-Volterra two species competition outcomes

Lotka-Volterra two species competition outcomes (K2/K1)