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31 Cards in this Set

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The study of the size, distribution, density, and growth rate of populations

Intrinsic Demographic Factors


Birth + immigration = death + émigration

Additional factions: sex ratio and age structure

Growth Rate

dN/dT = rm

Rm= intrinsic growth rate

K = carrying capacity, when function approaches this density dépendant favors slow pop growth

Density-Dependent Factors

Increase mortality from predation/paratsitism/disease

Decreased birth rates bc territory restrictions

Decreased fitness due to strong competition

Density Independent Factors

Extreme weather events

Catastrophic events

More likely to cause big fluctuations in small populations

Population density graph

Back (Definition)

Deterministic Extinctions

Inexorable changes that provide no hope for escape. Occurs when something essential is removed or something lethal is introduced.

Stochastic Extinctions

Result from normal random changes or environmental perturbations. Don't usually cause extinction in large populations.

Allee Effect

Positive correlation between population density and individual fitness

At very small N

-Increased likelihood of uneven sex ratios

- collapse of social structure (ex flocks)

- plants also suffer, decreased likelihood of pollen transfer

- reproduction may require minimum number of individual (ex lekking for birds)

Demographic Calculations

Back (Definition)

Phylogenetic Species Concept

Monophyletic groups defined by synaptomorphies define species

Predicted number of alleles remaining after one generation of genetic drift is a function of

Original number of alleles present, effective population size, frequencies of each allele

Which invasive species was intentionally introduced to the wild?


Two components of habitat fragmentation

1. Decrease in total amount of a habitat type in a landscape

2. Restriction of remaining habitat to small, isolated patches


Increase of patchiness of landscapes due to human presence

Characteristics of Naturally Patchy Landscapes

Complex internal patch structure

Less contrast b/w adjacent patch types (weak edges)

Not a strong barrier to movement b/w patches

Proportion of landscape in a patch type is relatively stable in ecological time

Mean disturbance is relatively constant

Characteristics of Human Fragmented Landscapes

Very simple patches (concrete/grazed fields)

Strong edge effects

Few suitable unoccupied patches available for recolonization

Increasing isolation and reduction of remaining patches

Why are fragments so species-poor?

Decrease in habitat heterogeneity

Low local effective population size

Fragmented area may be smaller than territory of home range of an individual

Species likely to persist in fragmented landscapes

Species adapted to anthropogenic matrix (ex: weeds, deer, raccoon)

Species with small area requirements

Highly mobile species

Demographic Sinks

Many species continued presence reliant on dispersal from higher quality source habitats

Species vulnerable to fragmentation

1. naturally rare species

2. wide-ranging species that must move through highly fragmented landscapes

3. poor dispersers

4. species with low fecundity

5. interior species (small fragments have no interior)

6. species vulnerable to human exploitation

Increased light and wind in forests due to fragmentation can lead to

Drier habitats and increased fire frequency

Increase in understory vegetation

Biological changes in forests due to fragmentation can lead to

1. Increased nest predation of birds

2. Increased parasitism of insects

3. Increased understory vegetation

4. Increased tree mortality (water stress, blowdowns etc)

What factors determine the impacts of invasive species

Competitive ability, growth rate/fecundity, freedom from population regulation (pathogens, predators, competition etc), prey nativity

Characteristics of successful invaders

High fecundity, long-lived, high variability, broad native range, habitat generalist, broad diet, human commensal

Characteristics of invadable communities

Early successional, low diversity of native species, absence of predators, absence of history of fires, low connectance food web

Impacts of an introduced species on local community structure depend on

It's uniqueness locally, the intimacy of its interactions, is trophic position

Impacts of an introduced species on local community structure depend on

It's uniqueness locally, the intimacy of its interactions, is trophic position

Important markers of genetic diversity

1. Heterozygosity

2. Allelic diversity

Why are genetics important for conservation

1. Evolution depends on genetic diversity R=h*h*s

2. Heterozygosity - high levels indicate increased fitness

3. Global pool of genetic diversity command information for all biological features on the planet, an irreversible loss equals a loss of potentially valuable information