Populations Flashcards
population definition
group of individuals of the same species living in the same location with the individuals
- same resources
- similar environmental conditions
- interacting with each other
with geography being at different scales
boundaries of populations
geographic areas, including natural features such as lakes, or arbitrary features like national parks or countries
matched to the purpose of studying the organism
size in population property
how many individuals are in the population and how does this change over time
births, death, immigration and emigration (leaving)
distribution population properties
clumped (helping one another)
uniform (competition between individuals of the same species, not enough resources to be close to one another)s
random (just kind of becasue lol)
population structure properties
male or female, age etc.
what is population ecology?
the scientific study of population in relation to the environment and resources
how to reduce population size
increase in deaths (introduce a disease)
decrease births (contraceptives)
reduce immigration into the population (barriers such as fences)
increase in emigration (introduce a potential predators or competitor)
accuracy vs precision
accuracy is close to the expected
precision is close together in trials
Imperfect detection
abundance = number seen/probability of detection
pr detection is 75%
individuals remain undetected and there is a risk of underestimating species you use this
Mark recapture
catch some, mark, release, catch more, calculate with imperfect detection
assumptions:
- marks dont decrease survival
- marks are durable
- probability of recapture remains constant
- closed populations
can also use natural marks
R species
small, short lived species wiht large reproductive output
k species
large, long lived, species with small reproductive output
demography
quantifying the patterns of births and deaths to help determine population size changes
exponential population growth
population grows exponentially (births greater than deaths)
population at time = initial population x e ^ per capita growth rate x time interval between 0 and t
logarithmic population growth model
when population growth is limited by resources
exponential growth x ( carrying capacity - initial population)/ carrying capacity
density dependent factors
competiton for resources
predators
disease
these factors are negative density factors
they have more impact the more dense a population is
density independent factors
severe heat waves
storm events
pollution
mostly abiotic factors
regardless of population size, these events will have large effects on the population size
what is environmental stochasticity
unpredictable fluctuations in environmental conditions that effect population sizes
demographic stochasticity
change in birth and death of individuals caused by chance
metapopulations
group of geographically isolated populations linked together by dispersals, together many metapopulations make up a geographic range
source vs sink populations
source
- source of individuals for a population
- support local growth and can be net exporters of indivduals to other patches
sink
- get more immigration than they produce
- mortality rates exceed births and populations are reliant on source population immigration
colonisation rate
the proportion of unoccupied sites that become occupied per unit time
extinction rate
the proportion of occupied sites that go extinct per unit of time
3 types of dispersal
regular/uniform
random
clumped
natal vs breeding dispersal
natal dispersal
from place of birth to place of first breeding
breeding dispersal
change of place of breeding
dispersal vs migration
dispersal refers to the spreding of individuals from others
migration is the large-scale movement of members of a species to a different environment (periodically and generally unpredictable)
how does dispersal effect population dynamics?
invasive species
dynamics of metapopulations
- contribute to local extinction
- colonisation
what is an ecological community?
a community is a group of potentially interacting species that occur together in space and time
how are ecological communities defined?
subset of species
proportion of species
the bioregions (plain, hill, coastal biomes etc)
why are not all species present in a particular community?
dispersal
environment isnt suitable
species interactions are unfavourable or more favourable elsewhere
the species present can be viewed as the result of a set of filters where these are the sieves
how does regional species pool effect ecological communties?
evolution and diversification
extinction
dynamic interactions between teh two
dispersal effects species and ecological communities
species introduced by poeple are clear examples of changing dispersal
can also occur naturally
environmental/abiotic features that affect ecological communities
disturbances that change resource availability or the physical environment
bushfire, flood etc.
species interactions effect on EC
invasive species can have large impact on species populatiosn
succession
natural changes in the composition and structure of an ecological community over time
the replacement of one community by another
ecological succession
a gradual change in community structure over time due to environmental disturbance
can be primary or secondary
primary succession
organisms colonise bare rock either by volcanoes or retreting glaciers
often pioneer (hardy) species like fungus, algae, lichen and cyanobacteria
climax community
a community wiht a relatively stable species composition
secondary succession
organisms re-colonise a habitat that was cleared by a disturbance that left the soil in place
colonisation with succession process
pioneer plants, soil, shrubs, trees
hwo do communities differ?
species and relative abundance
the sizes and layers of vegetation
species richness
number of species
shannon-wiener index
species richness with species evenness
how many species, and how evenly are they proportioned to each other?
does not measure abundance!
what is an ecosystem?
community of living and non-living things that interact in an area
biodiversity
measure of teh variety of biological species in an ecoststem
How to measure species richness and evenness
quadrat (region) is selected and the used to represent the ecosystem diversity estimates.
Usually use more than one randomly placed, but make sure you analyse the composition of the area (meadow, forest, edge area etc), so you get an accurate representation
Functional diversity
ecological communities that have greater species diversity can also have greater functional diversity
making them more productive and more stable
this can be because
- wider range of resources
- wider range of responses
