Chapter 8: Populations Flashcards
What is a population in ecology?
- group of individuals of the same species that inhabit a given area
- they have really unique features and interesting dynamics
- they have structure which relates to different characteristics
Populations are the ___ and ___ concept.
- genetic unit (potential for interbreeding) and spatial concept
Modular vs unitary organism
- modular= a species that is hard to distinguish ( organism has many parts and it’s hard to tell if it is two organisms or 1) like some mosses and plants etc
- unitary organism: ingle organisms thay can easily be pointed out…like humans or mammals
Populations are aggregates of?
individuals
What can we observe in populations?
- birthrate, growth rate and mortality rate
- also have collective age and sex structure
- *sex ratio is important in terms of reproduction
- adults vs juveniles
Distribution?
area in which an organism occurs
Geographical range?
- total area occupied by a population
- if you had a map and separated it out into squares and very time you saw an individual you put a dot in a square…once you have many you can circle the cluster and thats the geo range
Geographical range can be restricted by?
- environmental factors
High degree of tolerance may equal a ___ geographical distribution.
wide
*** adaptable to environment …can have large geographical distributions
Just bc you have a large area for a population does that mean they live in every cell?
NO they just surround those portions
Explain the red maple example for species distribution !
- northern limit: minimum winter temps (-40)
- western limit: dry conditions
- wide tolerance
- widespread geographic distribution
- dry conditions stop migration west-direciton
- ** generalist species…found at varying elevations…wooded swamps..dry ridges…variety of pH etc
Distribution can be defined on?
- several scales
* scale can be very important when looking at a population - it needs to be very well defined
Subpopulations?
- patches of landscape may have isolated subpopulations ..aka local populations…..ex: individuals of a species that lives in NB
- *have their own specific characteristics
Metapopulation?
- if patches of subpopulations are close enough to be connected by movement !
ex: subpop= individuals of a species that live in NB BUT individuals of that species also live somewhere in the states….so they are geographically isolated BUT there is mixing of the two….therefore collectively = metapopulation…
Does ecology focus more on meta or subpopulations?
sub
___extent is something we need to really define
spatial
Abundance?
- number of individuals in a population
* * it reflects area over which the pop occurs and the pop density ( number of individuals per unit of space)
Abundance :
- depends on population ___ and __.
- density and area over which it is distributed
Abundance :
- Density?
- the number of individuals per unit of space (crude density)
Abundance :
- Density:
L> how does high or low density affect organisms ?
- low= hard to find a mate
- high: less suitable areas for settling and breeding
How do we get the abundance over a large area?
count entire lot of individuals within certain blocks and scale them up to 25 blocks (total in examined area) …measured five times…take em and multi by 25
**estimation
How do we define the area for density?
- individuals might not live in all available space
- small scale differences in physical conditions
**-to say the density is even across the entire geographical range is not often the case
ecological density= # of individuals per suitable area = solution
map out habitat…area of suitable area is this..density within that is this…
abundance and density can change over an area
Ecological density?
- number of individuals per unit of available space
Dispersion??
- how organisms are distributed relative to each other