chapter 40. scientific study of the interactions between organisms and the environment ecology
TRANSCRIPT
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Population Ecology & the Distribution of Organisms
Chapter 40
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scientific study of the interactions between
organisms and the environment
ecology
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a group of individuals of the same species
living in an area
population
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a group of populations of different species
living in an area
community
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the community of organisms in an area and
the physical factors with which they interact
ecosystem
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a mosaic of connected ecosystems (includes
seascapes)
landscape
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the sum of all of Earth’s ecosystems and
landscapes
biosphere
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organismal ecology population ecology community ecology ecosystem ecology landscape ecology global ecology
framework of ecology
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how the organism meets the challenges
posed by its environment
organismal ecology
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factors that affect population size and how
and why it changes through time
population ecology
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how interactions between species affects
community structure and organization
community ecology
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energy flow and chemical cycling
between organisms and the environment
ecosystem ecology
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factors controlling exchanges of energy,
materials, and organisms across multiple ecosystems
landscape ecology
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how regional exchange of energy and
materials influences the functioning and distribution of organisms across the biosphere
global ecology
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long-term prevailing weather conditions in a
given area components include:
temperature precipitation sunlight wind
climate
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nonliving parts of the environment that affect
the distribution and abundance of organisms
abiotic factors
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living factors (other organisms) in an
individual’s environment that affect the distribution and abundance of organisms
biotic factors
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major life zones
terrestrial biomes characterized by vegetation type
aquatic biomes characterized by physical environment
biomes
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area where one biome grades into another may be wide or narrow
ecotone
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tropical forest Savanna desert chapparal temperate grassland coniferous forest temperate broadleaf forest tundra
terrestrial biomes:
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wetland estuaries lakes streams and rivers intertidal zones coral reefs oceanic pelagic zone marine benthic zone
aquatic biomes
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constant rain high temperatures great biodiversity includes:
tropical rain forest (200-400 cm of rain/year) tropical dry forest ( 150-200 cm of rain/year)
tropical forest
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seasonal rain (30-50 cm/year) dry season (up to 9 months) high temperatures fires common grasses, nonwoody plants large herbivores and predators
savanna
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low precipitation (less than 30 cm/year) temperatures vary seasonally and daily low, scattered vegetation (many C4 and CAM
plants) many nocturnal animals
desert
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seasonal precipitation (30-50 cm/year) hot, dry summers; cool, rainy winters shrubs and small trees
chapparal
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seasonal precipitation (30-100 cm/year) cold, dry winters; hot, wet summers grasses and nonwoody plants large, grazing mammals; borrowing mammals
temperate grassland
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30-70 cm of precipitation/year cone-bearing trees (conifers) migratory birds, brown bears, moose, Siberian
tigers, etc.
coniferous forest (taiga)
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70-200 cm of precipitation/ year deciduous trees (drop leaves before winter) migratory birds, hibernating mammals
temperate broadleaf forest
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20-60 cm of precipitation/ year cold winters, cool summers mosses, grasses, nonwoody plants and lichens permafrost (permanently frozen soil layer) migratory birds, musk ox, caribou, reindeer,
bears, wolves, etc.
tundra
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saturated by water at least sometimes high nutrient levels cattails, sedges frogs, alligators, herons, crustaceans, etc.
wetlands
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transition zone between a river and the sea high nutrient levels saltmarsh grasses oysters, crabs, fish, etc.
estuaries
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light decreases with depth includes:
oligotrophic lakes nutrient-poor, oxygen-rich
eutrophic lakes nutrient-rich, oxygen-poor due to high
decomposition
lakes
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headwater streams
often cold, clear and swift narrow with rocky bottom
downstream rivers generally wide and meandering; silty bottoms
streams and rivers
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periodically submerged and exposed by the
tides great variations in temperature and salinity high oxygen and nutrients levels many animals attach to rocks or bury
themselves when tides go out
intertidal zones
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formed from skeletons of corals much biodiversity
coral reefs
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open, blue waters (70% of Earth’s surface) low nutrient levels clear water; photic zone extends deeper high oxygen content due to surface winds phytoplankton (photosynthetic bacteria) zooplankton (invertebrate larvae, krill,
protists, etc.) fishes, sea turtles, marine mammals
oceanic pelagic zone
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seafloor mostly cold and dark with increased pressures deep-sea hydrothermal vents;
chemoautotrophic prokaryotes fishes, arthropods, echinoderms
marine benthic zone
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pelagic zone benthic zone
Aquatic Biome Zones
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includes:
photic zone upper zone sufficient light for photosynthesis
aphotic zone lower zones little light penetrates
pelagic zone
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bottom of the pelagic zones may be deep or shallow
benthic zone
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narrow layer of abrupt temperature change separates upper, warm layer from deeper,
cold layer
thermocline
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dispersal biotic factors abiotic factors
distribution of organisms is affected
by:
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movement or individuals or gametes away
from their area of origin or from areas of high population density
contributes greatly to global distribution of organisms
dispersal
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negative interaction with predators or
herbivores presence of pollinators (bees, birds), food
resources, parasite and pathogens, competitors
biotic factors
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temperature, water, oxygen, salinity, sunlight,
rocks, soil, etc.
abiotic factors
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number of individuals per unit area or volume examples:
number of oak trees per km2 number of bacteria per mL in a culture
population density
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pattern of spacing among individuals within
the boundaries of the population
dispersion
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immigration
influx of new individuals from other areas emigration
movement of individuals out of a population birth rates death rates
population density is affected by:
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clumped uniform random
dispersion patterns
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individuals aggregate in certain areas most common pattern certain areas more favorable to survival than
others
clumped
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evenly spaced dispersion may be due to territoriality (defense of a
bounded physical space)
uniform
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unpredictable spacing individuals have no strong attractions or
repulsions common with wind-seeds (dandelions)
random
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study of the vital statistics of populations and
how they change over time involves investigation of birth rates and death
rates
demography
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age-specific summary of the survival pattern
of a population best constructed by following the fate of a
cohort* from birth to death life table determines the number of individuals
that die in each age-group and calculate the percentage of the individuals that survives to the next age-group
*cohort a group of individuals of the same age
life table
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a plot of the proportion (or numbers) of a
cohort’s surviving individuals at each age
survivorship curve
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Type I curve Type II curve Type III curve
types of survivorship curves
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flat at the start (low death rates in early and
middle life) followed by a steep drop (as death rate increases in older age groups)
common in large mammals (including humans) that care for young
Type I curve
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drops sharply at the start (due to high death
rate of the young) then levels off common in organisms that produce large
numbers of young but provide little or no care
Type III curve
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Intermediate curve constant death rate over the organism’s life
span
Type II curve
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age-specific summary of the reproductive
rates in a population constructed by measuring the
reproductive output of a cohort from birth until death
for a sexual species, it tallies the number of female offspring produced by each age-group
reproductive tables vary greatly by species
reproductive table
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change in population size = birth + immigrants – deaths – emigrants
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ΔN = B – DΔt
(ΔN = change in population size, Δt = change in time, B = # of births, D = # of deaths)
If N= population size and t = time, then:
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expected # of births per year B = bN
(b = per capita birth rate, N = population size)
expected # of deaths per year D = mN
(m = per capita death rate, N = population size)
Also:
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ΔN = bN - mNΔt
So:
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difference between the per capita birth rate
and death rate r = b - m
per capita rate of increase (r)
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when per capita birth and death rates are
equal (b = m) (r = 0)
ΔN = 0Δt
zero population growth
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population increase under ideal conditions
(abundant resources) ΔN = rmaxN
Δt
(rmax = r under ideal conditions)
exponential population growth
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maximum population size that a particular
environment can sustain limiting factors may include food, shelter,
water, etc.
carrying capacity (K)
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density-dependent selection selection for traits that are sensitive to
population density and are favored at high densities
operates in populations near the carrying capacity (strong competition)
example: mature trees in an old growth forest
K-selection
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density-independent selection selection for traits that maximize reproductive
success at low densities (uncrowded) occurs in populations well below the carrying
capacity (less competition) example:
weeds growing in an abandoned agricultural field
r-selection