2.1: species & populations Flashcards
species definition:
a group of living organisms, sharing common characteristics that interbred and produce fertile offspring.
habitat definition:
environment in which a species lives
niche:
the particular set of abiotic and biotic conditions and resources to which an organism or population responds
two forms of niches;
fundamental: full range of conditions and resources in which a species survives and reproduces
realised: actual conditions in which a species exists due to biotic interactions
biotic egs. of niches -
- where it lives
- relations
- how it responds to resources available
- how much space there is
- availability of light & water
diff b/w abiotic & biotic -
abiotic - non-living physical factors:
- temperature
- soil salinity
- PH
- sunlight
- precipitation
biotic - interactions b/w the organisms:
- predation
- parasitism
- mutualism
- competition
population definition:
a group of organisms of the same species, living in the same area at the same time, which are capable of inter-breeding.
how a scientific name is composed -
- genus name
- species name
for eg. Homo sapiens
population density:
average number of individuals in a stated area
factors affecting population size -
- birth rate
- death rate
- migration (immigration & emigration)
limiting factors:
factors which slow down the growth of a population as it reaches its carrying capacity
carrying capacity:
the maximum number of a species that can be sustainably supported by an area
egs of limiting factors -
- limited phosphate in aquatic systems
- low temperature in the tundra which freezes the soil and limits water availability to plants
population dynamics:
study of the factors that cause changes to population sizes
population interactions -
- competition
- predation
- herbivory
- parasitism
- mutualism
competition:
when any resource in an ecosystem exists only in a limited supply, competition takes place
two types of competition;
intra-specific competition: between members of the same species
inter-specific competition:
different species competing for the same resource
predation:
when one animal (the predator) eats another animal (the prey)
eg. lions eating zebras
herbivory:
an animal (herbivore) eating a green plant
some plants have defence mechanisms against this. for eg. thorns on a cacti
parasitism:
relationship b/w two species, in which one species (the parasite) lives in or on another (the host) gaining its food from it
eg. vampire bats
mutualism:
relation between two or more species, in which all benefit and none suffer. form of symbiosis.
eg. lichen & green algae - where the fungus benefits from obtaining sugars from the algae and the algae benefits from minerals and water from the fungus.
leguminous plants and nitrogen fixing bacteria. bacteria gets shelter in the plant while the plant gets nitrogen in the form of ammonium compounds.
symbiosis:
living together
- mutualism
- parasitism
- commensalism
commensalism:
when one partner is helped and the other is not significantly harmed.
eg. orchid or fern growing halfway up a tree trunk
what do no limiting factors lead to?
exponential or geometric growth.
S & J population curves:
generalised response of populations to a particular set of conditions; abiotic and biotic factors.
S curves:
starts [lag phase] w. exponential growth - [exponential phase] (due to no limiting factors)
however, above a certain population size, the growth rate slows down gradually.
finally, resulting in a population of constant size. [stationary phase]. this is when the carrying capacity has been reached.
environmental resistance -
area between the exponential growth curve and the S curve is called environmental resistance
J curve:
population grows exponentially at first and then collapses [die-back]. population exceeds carrying capacity before the collapse [overshoot]
typical of microbes, fishes, and small mammal populations.
