C4.1 Populations and Communities Flashcards
population
interacting groups of organisms of the same species living in an area
sample
A subset of a whole population of habitat used to estimate the values that might have been obtained if every individual or response was measured
random sampling
A method of choosing a sample from a population without bias
sampling error
Statistical errors when a sample doesn’t represent the whole population
random errors
Unknown unpredictable differences
imprecision and uncertainty
systematic errors
Inaccuracy
- due to faults in experiment design
how are random errors eliminated
by taking average
how are systematic errors eliminated
with better designs
stratified sampling
two or more different habitat types
proportional area of different habitat types and samples each one accordingly
systematic sampling
when area includes an environment gradient
transect used to sample systematically along the environmental gradient
random quadrat sampling
used to study populations and communities
population size formula
(mean density per quadrat x total area)/ area of each quadrat
standard deviation variation
quantitative measure of the distribution of the values in a data set
standard deviation range
difference between largest and smallest data values
standard deviation
spread of a set of normally distributed data from the mean of sample
small standard deviation
data more reliable
normal distribution
data set distribution that is symmetrical about the mean
bell shaped curve
large standard deviation
unlikely to be significant too small - certainly significant
df
n - 1
one method to estimate population size for motile organisms
capture - mark - release - recapture - method
capture - mark - release - recapture - method
sample taken
animals taken, marked, recaptured, resampled
calculation made - number marked animals compared to size of resampled population compared to total population
Lincoln Index
population size = (M x N / R)
M Lincoln Index
number of animals captured
N Lincoln Index
number of animals recaptured
R Lincoln Index
number of marked animals recaptured
what assumptions have to be made for a Lincoln Index
- mixing is complete - marked individuals have spread out
- marks are not removed
- marks are not harmful
- equally easy to catch each individual
- no immigration/emigration/deaths/births
carrying capacity
maximum number of individuals of a species that can be supported by a given environment
resources can run low, competition, limiting factors
prevent population from increasing further
negative feedback
feedback that tends to counteract any deviation from equilibrium and promotes stability
density dependant factors
factors that lower the birth rate or raise death rate as a population grows
biotic factors that limit population growth
internal density dependant factors
external density dependant factors
internal density dependant factors
fertility/size of breeding territory
external density dependant factors
increased predation and pathogen or pests in dense populations
Density independant
will affect the populations of all species in an ecosystem
weather, climate, natural disasters
Density dependant
varying effects on the population of different species
- define carrying capacity
- tends to push population back towards carrying capacity
exponential growth
increasing rate of growth
occurs in air ideal and unlimited environment
limiting factors dont restrict
plentiful resources
favourable abiotic components
sigmoid growth curve
s shape population curve shows an initial rapid growth and then slows down as carrying capacity is reached
exponential growth
limiting factors dont restrict growth of a population
transition phase
increase in number is slow
limiting factors begin to affect the population
plateau phase
limiting factors restrict population to carrying capacity
NIEM phases
natality
mortality
immigration
emigration
natality
birth rate
mortality
death rate
immigration
movement into population
emigration
departure from population
duckweed features
aquatic plants
staple diet for ducks and other aquatic birds
rapidly growing
used as a model system for studies in population ecology
communities in ecosystems
a group of different species living in an area
biotic parts of the ecosystem
intraspecific competition
competition between individuals of the same species
interspecific competition
competition between individuals of different species
cooperation
action or process of working together
to minimise direct competition
wildebeast in competition
territory fight - intraspecific
hyenas in terms of cooperation
hunt together - clans
cooperation
insects in terms of group work
group work (social insect)
bees, wasp, ants
super organism - all are genetically identical
altruistic behavior
leaf cutter ants
mutualism
symbiosis
interaction in which both species derive benefit
can increase carrying capacity
parasitism
parasite organisms benefits at expense of host
lower carrying capacity of host
pathogenicity
capacity of a microbe to cause damage to a host resulting in disease
can reduce carrying capacity of infected population
alturism
behaviour of an animal that benefits another at its own expense
increases the number of offspring produced by recipient and decreases that of the alturist
root nodules in fabaceae legume
small swelling on the root of plants that contain symbiotic nitrogen fixing bacteria
rhizobium
bacterium living in root nodules
fixes nitrogen gas to form ammonium ions
enables them to live in nitrate deficiet areas
need glucose for respiration
aerobic
needs lots of energy
large amounts of ATP
what does rhizobium contain
nitrogenase (enzyme) which catalyses nitrogen fixation
oxygen exclusion necessary - same size and shape so causes blockage)
mycorrhizae in orchidaceae
fungus that grows in association with roots of a plant in a symbiotic relationship
key role in orchid germination
seed is small so it gets nutrients from fungi
in turn fungi gets glucose
corals and zooxanthellae
mutually beneficial
polyps connect - sharing of nutrients
algae live in endodermis
coral provides algae with protected environment and Co2 for photosynthesis
grey squirell and red squirell
alien invasive species where the grey squirell removed the red completely
who investigated competitve exclusion
joseph connell
what did joseph connell investigat
2 species of banacle
2 species couldnt grow in the same area because of difference in niches
led to competitive exclusion
hypothesis
states that there is a statistially significant difference between 2 variables
null hypothesis
no statistically significant difference between 2 variables
independant variable
experiment changes one variable
measures effect on dependant
control variable
variables kept constant
chi squared test
tests significance of deviations between numbers observed (O) and numbers expected (E)
predator-prey relationships
interrelationships of population size due to predation of one species on another
controlled by negative feedback mechanisms that control population densities
top down control
changes to the food chain occur at the top trophic level and then impact on the trophic levels lower in the food chain
predator controlled food web
bottom up control
changes to food chain occur at the lowest trophic level and then impact on the trophic levels higher in the food chain
imitation due to resources that allow growth etc
allelopathy
chemical inhibition of one plant by another, due to the release of chemicals that act as germination or growth inhibitors
how can allelopathy be carried out in plants
- releasing chemical compounds from roots to soil
- gas from stomata in leaves
- leaves dropping with toxic chemicals
examples of allopathic plants
cabbage
mustard
kale
radish
secretion of antibiotics
penicilin by alexander flemming in 1929
fungi naturally produces antibiotics to kill or stop bacteria growth
how is penicillin allopathic
kill and inhibit bacteria
medicine and antibiotics
