Population Ecology

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Ecology

study of interactions of living organisms with each other and with their environment

individual

autecology

population

all members of the same species inhabiting a specific area

community

all of the various populations inhabiting a specific area

ecosystem

a community plus its dynamic (often self-sustaining) interactions with its physical environment, including the biotic and abiotic components.

biosphere

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.

demography

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

fish

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]

Births

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.

N_t+1

=rN_t
r=net reproductive rate (per year)
N_t=pop size the following year
____number of females already present

Mayflies

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

N/t=(r*N)x(K-N)/K
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.

Fireweed

Epilobium Angustifolium

Fireweed

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.

3

# 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

Sussex

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".

r-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.

K-selection

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

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