97 terms

Population Ecology

study of interactions of living organisms with each other and with their environment
all members of the same species inhabiting a specific area
all of the various populations inhabiting a specific area
a community plus its dynamic (often self-sustaining) interactions with its physical environment, including the biotic and abiotic components.
all of the various communities and ecosystems of the Earth whose members exist in the air, water, and on land.
difference b/w ecosystem and biosphere
bisophere includes all the water (lakes, streams, and all air in the atmosphere for global wise); smaller biosphere has everything on the land, in the soil (microbes, etc), pollution, birds flying in air, etc.
the statistical study and analysis of a population in terms of defining or distinguishing features or characteristics.
population size
number of indivs at a given time that contribute to the gene pool
population density
number of individuals per unit of habit
age structure/distribution
numbers of individuals in various age classes of the population
population distribution
the 2 or 3 dimensional (spatial) arrangement or location of individuals in their habitat
pop dynamics
directional changes in any defining aspects of pop structure (e.g. growth)
pop genetics
includes breeding behavior, gene pools and gene flow, micro-evolutionary trends.
Population Distribution Patterns
Random, Clumped, & Uniform
factors affecting distribution patterns
availability of resources, presence of limiting factors (temp, pH gradients, pollution), behavioral patterns (breeding, migration, territoriality, etc), best exhibited in plants pops
availability of resources
examples include light, water, space, food mates
presence of limiting factors
temperatures, pH gradients, pollution
behavioral patterns
examples include breeding, migration, territoriality behavior, dispersal mechanisms
clumped distribution
indivs in pop are dependent on a componenet of the environment that is not randomly distributed
example of clumped distribution
roots suckers--grow together in this plant and they need to be close together to grow from root suckers-
alpine plant
in tops of mountains, clumped together because of protection/benefit to the plant--keeps it warm by growing in tight cushion (keeps away from wind)--stores heat in foliage below--clumped distribution
aspen herd
animals lives in herds for clumped distribution for protection
clumped distribution (always a school of ....)
Nearly Uniform Distributions
desert plants --evenly distributed because competing for water
Uniform distribution
strong competition for limited resources forces maximum dispersion.
Random Distribution
in habitats that are nearly uniform, abundance of resources readily available, no attraction or repulsion between members of same pop or different species
Tropical Rain Forest
place of random distribution
Random Distribution
true ___ ____ are rare; because somewhere in nature something has affected how a plant has came to a specific site (wind, fire, etc). Deciduous and tropical forest come pretty close though.
where minerals are
difference between tropical and deciduous forest and oceans
living biomass
where minerals are kept in tropical and ocean ecosystems
in soil
where minerals/nutrients are held for deciduous forest.
Patterns of population growth
births, deaths, immigration, emigration
Pop growth
= [Births + immigrants]-[deaths+emigrants]
how to optimize this condition: number of offspring per reproductive event, how often each individual reproduces, age at which reproduction occurs, changes of survival until reproductive age.
biotic potential
the highest possible rate of natural population growth under conditions of unlimited resources; rare.
r=net reproductive rate (per year)
N_t=pop size the following year
____number of females already present
females produce once per year, each reproductive event produces 2.4 eggs per adult individual, entire adult pop dies right after reproduction occurs. Majority of year under water; sink to the bottom and eventually other organisms eat/kill them.
exponential growth
curve for pop growth
logistic growth
takes on exponential growth stage and then tapering off until pop stabilizes
logistic growth
lag phase, period of exp growth, max growth period, decelerated growth period (because something becomes limiting), then finally stable equilibrium
carrying capacity
maximum number of individuals of a given species that the environment of a given area or habitat can support.
habitat carrying capacity
population size gradually levels off at a "stable equilibrium"
maximum growth
stage in logistic growth where you reach biotic potential
logistic growth expression of yeast cells
When N is smal, sigmaN/sigmat=rN
when N reaches K sigmaN/sigmat=0
N small
this is when DeltaN/Deltat=rN
N reaches K
when deltaN/deltat=0 due to reaching carrying capacity
Quadrat Sampling
how to determine pop size of plants
mark and recapture sampling
how to determine pop size in animals
Quadrat Sampling
area/population to be sampled is mapped with a regular distribution of grids. Multiples "squares" are chosen at random. All desired observations made only for pop w/in the square. Data/observations are extrapolated to entire study area.
Mark and recapture sampling
animals to be monitored are captured. Permanently marked and then released back into the pop at "time 1". After some time (time 2), animal pop is sampled a second time (or more). Proportion of marked individuals in subsequent captures represents their proportion in entire pop.
Mark and recapture sampling
marked indiv in sample 2/(total-marked + unmarked in sample 2) = (marked in sample 1)/total pop size
Factors that regulate pop growth
density dependent factors, density independent factors
density dependent factors
food and nutrient supply (e.g. Reindeer in Alaska), competition for space, predation, parasitism, disease (e.g Canadian Lynx and hare cycle), accumulation of metabolic by-products and wastes.
density independent factors
extreme weather conditions or sudden changes in weather (drought, snowstorms, heat, cold), lightning, fires, floods, environmental pollution (oil spills, mining wastes, pesticides,etc)
environmental disturbance
cause for an adjustment period
Reindeer in Alaska
geographically isolated in Bering Sea, 40 sq mi, undisturbed vegetation, 4 male, 21 female reindeer released in 1911. No hunting, no predators. Had max growth until food ran out; way exceeded carrying capacity.
Malthusian (irruptive) growth
when pop maxes out; growth exhibited by pop offers an opportunity to reach biotic potential, but suddenly crashes due to something that causes it to stop (food supply, disease, etc).
Canada Lynx ad Showshoe Hare
Hudson's Bay Company kept detailed sales records of lynx and hare furs. Lynx is a specialist predator that feeds primarily on snowshoe hares. Hare pop cycles every 10 years; lynx pop followers 3-5 years after; cause of are cycling is not well understood.
Epilobium Angustifolium
has a tightly linked ecology to occurence of forest fires in coniferous regions--oppurtunistic weed is adaptive to invade area--produces seeds dispersed by the wind. Produces copious amounts of windborn seeds (dont have any dormancy associated). Seeds germinate immediately on bare soil.
poa annua
a winter annual; germinates in late summer/early fall; seedling mature in late fall, overwinter in the vegetative state,and produce seed the following spring and early summer.
Survivorship curves
logarithmic plots of surviving population vs percent of life span; where most pop survives majority of life span, then something triggers death.
# of main curves for survivorship
Death occurs after midpoint
survivorship curve where pop lives longer than expected, then suddenly dies off.
Death comes early on
survivorship curve where pop lives shorter than expected, and dies off early.
death unrelated to age
perfect neg linear line for survivorship curve
3 types
survivorship #'s
Type I
humans, bears, elephants have this type of survivorship
Type II
most birds, squirrels, hydras type of survivorship
Type III
plants, fish, jellyfish, insects type of survivorship.
Age structure diagram
a graphical representation of the age and sex group distribution in a population; often used to predict (or observe) the natural increase, birth, and death rate w/in a pop
Three ideal age distributions
increasing populations, stable populations, and decreasing populations.
stable population
reproductive ages produce enough offspring to replace itself.
decreasing population
reproductive ages do not produce enough offspring to replace itself.
increasing population
reproductive ages produce enough offspring to replace itself plus more; so the pop goes up.
Rocky Mountains
stable climax condition, self replacement
unstable, no self replacement
oak seedlings
cannot tolerate shade--need to be growing in full sunlight until they reach surface of canopy.
Logistic growth curve
suggests that natural selection promotes two extremes of populatoin behavior: ''r-selection" vs. "K-selection".
some species spend most of apparent resources on growing/reproducing--making as many offspring as they can but somehow their population declines; something else is happening.
slow-growing species that focus on care and survival of themselves and their offspring; they hang onto the habitat.
r-selected species
opportunistic pattern; small individuals, weak competitors, short life span, fast to mature, many offspring, little to no care of offspring, early reproductive age, few reproductions, high mortality before reproduction, adapted to unstable environments, population below carrying capacity.
r-selected species
bacteria diatoms, weeds, and small rodents are an example of
K-selected species
large indiv., strong competitors, long life span, slow to mature, few and large offpspring, much care of offspring, later reproductive age, many reproductions, most survive to reproduce, adapted to stable environments, pop @ carrying capacity
K-selected species
bears, humans, whales, elephants, and climax trees are examples of
11000 BC
humans learned how to save food for the winter
9000 BC
plants and animals first domesticated--used for agricultural purposes.
5000 BC
started to move from farmland into urban society; still a lot of agricultural activity, but ppl collected in urban centers.
1000 BC
bubonic plague; known as black death; only thing in history that had measurably neg impact on the size of the population. 50-75% of population wiped out; bacterium that causes lethal infection--carried by fleas--ramped through Europe.
Industrial Revolution
exponential growth took back up again after bubonic plague.
lesser developed
most of pop growth occurs in _____ _____ countries
Green revolution
learned how to get nitrogen from atmosphere and convert into ammonia and fertilizers.
Green revolution
could make hybrids; hybrids make a lot more useful product than the two separate pops
Green revolution
pesticides were created--killed insects and weeds. Allows us to produce a lot more food on the land we have.
Environmental impact of More developed countries
more developed countries have only 20% of pop, 60% of fossil fuel, producing 90% of the trash.
environmental impact of less developed countries
use 10% of the fossil fuels, 80% of the world's pop