Topic 9 Flashcards
Population
group of individuals of the same species living together
Population ecology
How the processes of birth, death, migration influence the abundance & distribution patterns of groups of organisms
Population structure is characterized by..
- spatial structure
- agre/size structure
- genetic structure
Spacial structure
how individuals organize themselves in space. geographic distribution/ranger. patterns of dispersal/dispersion and population size
Age/size structure
number of individuals in each age/size class
Genetic structure
genetic composition of all individuals combined within the population
Demographic rates of an individuals..
change their lifetime
Geographical distribution/range =
geographical area in which a species occurs. determines by presence of suitable environmental conditions/resources
Habitat patch=
area of homogenous environmental conditions
Habitat patches can be ..
heterogeneously distributed over the range, separates by unsuitable habitat
Habitat patches result in..
many local populations of a species within a range (subpopulations)
Red maple
northern limit (-40C) western limits dry conditions. grows in variety of soils, moisture conditions, elevations, acidity levels. high degree of tolerance
Devils hole pupfish
exists in single deserve pool in Nevada, very small area.
Coyotes
over most north america
Rats and ecoli
spread w human movements
Whales
very large migratory species w lots of ground to cover
Range limitations are a..
malleable contraint as environmental conditions shift
Just because ideal conditions exist doesn’t mean..
you will find a species there. must account for colonization abilities of ancestral species
Environmental heterogeneity causes..
most population to be divided into subpopulations
Each subpopulation exists in a ..
suitable habitat and is separated from other subpopulations by unsuitable habitat
Metapopulations
collective of all subpopulations
Ecology typical occurs at the level of
subpopulation rathe than the entire population over its geographic range
At some stage in their life/lifecycle most organisms are ..
mobile
Movements of individuals directly..
influences their local density
Dispersal
movements of individuals in space
Movements of individuals around the subpopulations is key to..
the dynamics of meta population
Winds and water (passive) dispersal
wind carries young of spiders and mothers. larval forms of many invertebrates are carries downstream by currents
Dispersal of seed involves
gravity, wind, water and animals
Release of fluid pressure allows
some plants to physically eject seeds a considerable distance
What do other plants sue to attract herbivores
sugar rewards. intensive to consume fruit and transport seeds to other locations. seeds unharmed through digestive tract
Fruits and seeds armed with ..
hooks and spines to catch on the fur on animals
Dispersal is movement of individuals away from..
place of birth or area of high population density
Emigration
movement of individuals out of a population
Immigration
movement of individuals into a population
The degree of interaction among local populations depends on
- ability of individuals to disperse between habitat patches
- habitat patch size and quality
Ability of individuals to disperse between habitat patches
- distance between habitat patches
- suitable of environmental conditions/resource abundance between patches
- barriers
Habitat patch size and quality
- larger/higher quality patches tend to support more individuals
- a higher number of individuals immigrate to smaller/lower quality local populations with fewer individuals
Metapopulation concept
Metapopulation dynamics differ from our discussions of subpopulations in that they include both the local (small) and regional scales (large)
At the local level meta population dynamics relate to..
subpopulations in which individuals interact with each other (feedings, growing etc)
At the regional level meta population dynamics relate to..
- Dispersal of individuals between subpopulations
- Dispersal of individuals leading to the colonization of new previously unoccupied patches
- Extinction of all individuals from existing patches
Dispersion
Where geographical distribution refers to the extent of a population, patterns of dispersion can also be used to describe the spatial position of one individual to another
Random dispersion
individuals have no influence on each other, recourses are randomly scattered across the range
Uniform dispersion
individuals engage in negative interactions such as intense competition for space. they space themselves evenly to minimize interactions
Clumped dispersion
most common type, where individuals form groups. patch resource distribution or environmental conditions. social tendencies. cloning
Northern gannet
in newfoundland clumped for breeding habitat. moderate scale is clumped for predator avoidance. smaller scale is even for competition.
Population represent the
ecological unit within which individuals mate and offspring are produced
2 types of individuals can make up a population
- unitary individuals
- modular individuals
Unitary individuals
physically and genetically distinct individuals each arising from a genetically distinct zygote (humans, dogs)
Modular individuals
consist of man interconnected units derived from the same zygote (plants, corals, sponges). can exist separately and be physiologically dependent
Genets
genetically distinct individuals, each derived from single zygote (sexual reproduction)
Modules with the potential to exist separately are
ramets= genetically identical, asexual reproduction
Aspen tree
develops from a seed (zygote) reproduces asexually from horizontal roots. gives rise to what appears to be another individual tree. but each tree produced is a ramet, while all trees together are a genet
Important to distinguish between ..
unitary (genetically distinct) and modular (genetically identical) individuals
Must be a genetic variation for..
natural selection to occur
Conservation
if a population of ramets → no genetic variation→ less likely to adapt to environmental changes → high risk of extinction
Population size
abundance of population refers to the population size or number of individuals
Population density
number of individuals per unit square. can be estimated in crude form by grid. problem is individuals tend to not be equally numerous everywhere and density is often not uniform
Generally cannot count all individuals in a population instead need to..
estimate
Accurate estimates combine..
- geographical range
- patterns of dispersion
- patterns of dispersion of local population density can mislead measures of total population size
Local density =
of individuals per unit area
Methods of estimation
- quadrant sampling
- line transects
- mark recapture
Quadrent sampling
best on sessile/immobile organisms
Line transects
measure distance to observes specimens while talking a straight line. use formulas to estimate pop size
Mark recapture
create identifiable mark on all specimens captures in first sample. sample again and estimate pop size based on proportion recaptured