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
Three types of dispersion?
- uniform
- random
- clumped
Dispersion
- Uniform?
- not very common (usually things that are territorial have this dispersal ..like penguins in nesting grounds …plants can do tis too by releasing toxins form roots stopping other plants from growing in the area around them
Dispersion
- Random?
- each individuals position is independent of other individuals (not very common but can happen)
Dispersion
-Clumped?
-very common…..colonial individuals tend to all want to nest together …organisms want to be around other initials…social organism ex fish…or can happen due to patchy resources …individual clumps where they are available
Dispersion patterns can have important effect on ?
density
BBC Life of Mammals video:
-explain the reindeer situation
-18 million reindeer
low resources
need to keep moving for foraging
defence start against biting flies…push into an area where there are fewer flies…(they clump)
flies can’t go on higher ground
how would you measure their population??
samples….pick an area within a group of populations and count them…then scale them
L> observer bias!
- use quadrate
How do we determine density?(2)
- quadrats
- mark recapture technique
How do we determine density
- quadrats?
- often used to estimate density of plants and sessile animals. Aerial surveys of larger, mobile animals
How do we determine density
- mark recaptured technique
- used with many mobile populations
#marked/totalN=#recaptured / #collected - TotalN= (#collected x #marked)/#recaptureed
How do we determine density
- mark recaptured technique
- Assumptions?
- during counting period no individuals are arriving or leaving
- none of the arks have fallen off
- marking them does not change how they are behaving or physically harm.
How do we determine density?
- measures of relative density????
- counts of vocalization , scat or tracks (indexes of abundance)
- *indirect observations= lots of biases…not a true count but an INDEX
Age Structure:
- Populations have age structure unless?
generations do not overlap
age structure?
- proportion of individuals within the age classes
* *different demographics within age classes …= important in understanding trends with population
Age Structure:
-how does it affect population growth?
- some age classes are more likely to reproduce or to die
How do we determine the age of Animals and plants?
- ring width in plants
- rings in the teeth of carnivores for age estimation
How do we determine the age of Animals and plants?
= mark individuals and follow them through time.
- approximate age of seasonal trees by counting growth rings
**other structures have annual rings
***longitudinal studies are very difficult to do depending on the species like birds
(very movie…young do not always come back to the same area whereas adults usually do )
Morphological differences
a way of determining age class (relative age in that case)
Age Pyramids show Age structure…explain the examples
- snap shots of a population age structure at some point for 3 human populations
- age structure relates to age specific patterns of mortality and reproduction
A) Uneven distribution: lots of you not many old = growing population
B) fairly even…still have a few more young but far more sub reproduce individuals…..therefore not much reproduction: overall trend is fairly trending but it is growing or very slowly…maybe tapering off
C) no growth in the population…number of individuals being born and dying =same
What do the two examples graphs to do with trees tell us in terms of age structure? What could the cause be?
A) high—>decrease…..the population is likely increasing..lots of young individuals and not many old
B) lots of individuals mid age range…you had lots of reproduction that happened but it is starting to taper off..dropping in seedling pop…more of a mature population!
-Causes:
-removing older trees = decreasing reproductive population
- when a tree falls it allows seeds to grow and germinate since it is no longer shading an area inhibiting growth..
Dispersal?
movement of individuals through space (the location where they are )
Dispersal?
- most organisms do not have a mobile phase??True? False?
FALSE
- most organisms have a mobile at some stage
- *even plants tend to have a mobile phase at some point in their life cycle…
Why does dispersal occur?
dispersal= movement of individuals through space (the location where they are )
L> movement of individuals away from each other… OR movement away from very closely related individuals to reduce inbreeding
often individuals move from their place of birth to mating areas to reduce inbreeding
some individuals return to their place of birth to reproduce there.
sub pops in a meta have to be linked therefore dispersal must be occurring to connect them
Dispersal is important in linking…?
metapopulations and maintaining gene flow
Plants and (some animals) rely on what kind of dispersal?
- rely on passive means of dispersal…wind…gravity…animals carrying seeds
Dispersal:
- Mobile animals??
active dispersal but can depend on a passive mechanism
*ex: tides and circulation patterns to disperse (ie crabs)
Dispersal may occur mostly among __ and __.
- young and subadults…
Two types of dispersal?
- Stimulate dispersal in an individual
2. Migration
Two types of dispersal
Stimulate dispersal in an individual
crowding , temperature change, food quality and abundance and photoperiod can stimulate dispersal
Two types of dispersal
- Migration?
round trip ..dispersal (daily or seasonal) over short (m) or long (up to 1000 of km) distances
- *semipalmated Sandpipers
- *varies in length
Why does migration keeping happening.
-once you are a breeding adult if you found a suitable breeding area etc to increase your fitness you will probably stay there BUT as a young individual you have to FIND that place therefore they are the ones doing the most dispersal
Dispersal and Daily migration of zooplankton?
- vertical migration
- move closer to oceans depth during day and come up to the surface at night via relation of light levels.
Dispersal!
- migratory pathway of ring-neckelace ducks and gray whales..
- **A) cold arctic water is where foraging is prime
- other area = breeding ground bc young whales can survive on their own **birds do not get used up much
Births are used a lot for dispersal studies
breeding ground = bc young whales can survive the temps
Distribution and Density Change in Time and Space.
L>changes in species range?
- dispersal can gift spatial distribution of individuals and patters of population density
- *may be changes ins species range s due to changes in environmental conditions or species introductions
Distribution and Density Change in Time and Space.
- Ex with climate change explain it!
Ex: climate change….is it happening so fast that individuals cannot adapt fast enough therefore not being able to move to where they need to be
dispersal can also result in the expansion of a population ….ie ideal geographical range is increasing so they are becoming more mobile
Distribution and Density Change in Time and Space.
- what happens when you introduce a new species to the area
Gypsy moth:
species introduction
can cause species displacement via introducing invasive species etc
