AP Enviro 🏔

Ecosystem

community of living organisms in conjunction with non-living components interacting within an ecosystem

interactions in ecosystems

predator prey +-

parasitism +-

herbivory +-

mutualism ++

commensalism +o

competition --

symbiotic relationship

close and long-term biological interaction between two biological organisms of different species

competition

competitive exclusion principal: no tie - winner and loser

between different species: resource partitioning

same species (intra): increased overall species fitness

resource partitioning

when two species compete over a limited resource, they will eventually limit use of the resource and share to avoid competition

ex: warbler bird species use different parts of preferred habitat

terrestrial biomes

characteristics vary with temperature, precipitation, and latitude

H20 + temp = flora and fauna

sun

ultimate source of energy

photosynthesis: sun to chemical energy

Primary productivity

determines biodiversity

Gross primary productivity (GPP): amount of sunlight photosynthesized by producers)

R : cellular respiration of producers

net primary productivity (NPP): total amount of energy captured by consumers

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GPP - R = NPP

Aquatic biomes

fresh or saltwater

most important factors: **nutrients** (nitrates, phosphates) and **sunlight** (depth dependent)

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* photic zone = light reaches
* aphotic zone = no light
* profundal zone (only freshwater, no sunlight)
* littoral zone: shallow, where most photosynthesis occurs

Oligotrophic lakes

* clear water
* cold
* high 02
* low nutrients
* rocky bottom

Eutrophic lakes

* murky
* warm
* low 02
* high nutrients
* soft bottom

Intertidal zone

above water 50%, below water 50%

Eutrophication

1. runoff of nutrients (phosphorous and nitrogen) from fertilizers, agriculture, mining, etc. into bodies of water
2. algae bloom from nutrients
3. algae pond scum blocks sunlight, killing organisms below
4. decomposers pull 02 from water to break apart dead organisms

results in dead zones - ex: Gulf of Mexico

Trophic levels

1. primary producers
2. primary consumers
3. secondary consumers
4. tertiary consumers

10 % energy transfer up each level

generalist

animal that can withstand more variety

* eats wider variety of food
* handle variation in climate
* reproduce anywhere

specialist

species that requires more specific conditions

* eats specific foods
* reproduces in specific conditions

Keystone species

So interrelated with other species that if anything happens it will have a big effect on the entire ecosystem

ex: otters, wolf in Yellowstone

Indicator species

serve as early warning alarm

presence/absence indicates quality of environment

ex: trout, frogs

Pioneer species

first to establish themselves in an environment and rapidly grow

* broad ecological tolerance


* alter conditions to be more favorable for new species

ex: moss, lichen

energy

the capacity to do work

Biomagnification

the increase in concentration of a substance in organisms at successively higher levels in a food chain

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as organisms eat other plants and animals in which toxins are more widely dispersed, the concentration in that organism increases

Bioaccumulation

the accumulation over time of a substance within an organism; usually a substance that cannot be expelled easily or whose removal is slower than the rate of ingestion

Biogeochemical cycles

regulate flow of matter through ecosystems

disrupted by human activity

places for elements to hide (sinks, reservoirs) and processes to move element

carbon cycle

fast

sinks: living organisms, atmosphere

processes: photosynthesis, cellular respiration

other processes: decomposition, sedimentation and burial (very slow)

water cycle

driven by sun

infiltration: water seeps into soil and reaches groundwater

**percolation**: movement of water through soil

evaporation

**evapotranspiration**: plants lose H20 as they pull it upwards

precipitation

phosphorus cycle

**step 1: phosphorus seeps into ground through water, runoff, decomposition, weathering**

weathering: rocks

decomposition: animals, plants

**Step 2: geological uplift and assimilation bring phosphorus above ground**

assimilation: plant absorbs phosphorus from ground/soil

geological uplift: formation of new rocks

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\*no gaseous component

Nitrogen cycle

cycle carried out by bacteria in soil/ocean

step 1: fixation: N2 to NH3 (ammonia) - lightning

step 2: ammonification: decomposed organic material (humus) and NH3 converted to to NH4

step 3: nitrification 2 stages: NH4 converted to N02, then N03

step 4: assimilation: N03 absorbed by plants then into animals

step 5: denitrification: N03 converted back to N02 gas (released into atmosphere)

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78% of atmosphere in nitrogen

Genetic diversity

genetic variations within and between populations

* less genetic variation reduces ability of species to adapt
* diversity caused by genetic mutations (random)

Species diversity

index of **richness** (number of different species)

and **relative abundance** (proportion of each species compared to all individuals in the community)

**species:** a group of organisms with similar characteristics able to produce viable offspring

Speciation

with enough time, a species in different locations will accumulate mutations and become different species that are unable to reproduce

* reproductive isolation key
* geographical isolation

**adaptive radiation:** organisms diversify from ancestor to fit different niches ( ex: finches in Galapagos)

Ecosystem diversity

variety of habitats, living communities, and ecological processes

* nearly 24 terrestrial biomes and 12 aquatic biomes

Benefits of diversity

diversity = stability

* productivity: more productive
* resilient: better comeback after stress
* stable: consistency in productivity
* resistant: resistance to invasive species

biogeographic factors affecting community diversity

**latitude:** biodiversity increases near the equator

**climate:** tropical = more solar energy and water = more diverse

**area:** more space = more biodiversity

**evapotranspiration**

Island biogeography and diversity

diversity increases with closer distance to mainland and greater size

island species usually specialist species

habitat islands

**habitat fragmentation:** humans split habitat islands and decrease biodiversity (buildings, roads, deforestation)

**habitat corridors:** reconnect fragmented habitats

Evolution

driven by natural selection

* change in allele frequency in gene pool over time

Natural selection

1. high reproductive capacity
2. heritable variation
3. limitations on population growth
4. differential reproductive success

Population bottlenecks

sharp reduction in size of population or sudden vanishing

**caused by** **environmental** (famine, earthquake, flood, drought) or **human** (violence, human population planning) factors

Ecological succession

disturbed area colonized by new groups of species that replace each other

primary succession

begins in lifeless area (volcanic rock, rock)


1. prokaryotes
2. lichen/moss
3. grasses
4. shrubs
5. trees

takes thousands of years to become climax community

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secondary succession

after an existing community has been cleared by disturbance


1. dirt
2. pioneer species alter soil properties
3. grasses
4. shrubs
5. trees

only takes months/decades (starting with soil vs rock)

disturbances

human caused (anthropogenic) or natural

periodic: same time, predictable (spring rains)

episodic: slightly more frequent (earthquakes)

random: rare (tornadoes)

* change community by removing organisms or altering resource availability
* high level exceeds tolerance
* low level allows more competitive species to dominate

intermediate disturbance hypothesis

moderate disturbance counteracts competitor

* results in greater biodiversity than high or low level disturbances

Climate variation

caused by changing solar radiation and atmospheric composition

pathogens

disease causing organisms

* includes bacteria, fungi, viruses, protists, prions


* impact swift and extensive
* greater impact when introduced into new habitats, as there has not been time for natural selection to select resistant individuals

ecological tolerance

range of conditions an organism can endure before dying

* goldilocks curve

ecosystem services

**provisional:** nature provides food, timber, oil

**regulating:** regulates climate, flood prevention, erosion control, clean air

**supporting:** photosynthesis, nutrient cycling; sustaining basic life forms

**cultural:** recreation, ecotourism, spirituality

niche

position in a community; includes job, food, environment

no 2 species can have the same niche

population change

world: birth and death

national: birth, death, immigration, emigration

\*factors calculated per 1000

R = (b-d) + (i-e)

growth rate = (birth - death) + (immigration - emigration)

fecundity

potential reproductive capacity of an individual or population

natality

birthrates, number of live births per 1000 per year

mortality

death rate, number of deaths per 1000 per year

biotic potential

potential growth under ideal conditions (intrinsic rate of growth)

maximum population growth

growth under ideal conditions

**exponential/J curve**: unlimited resources = unlimited growth until

**environmental resistance**: limited resources prevent infinite reproduction

K = carrying capacity - overshoots & diebacks

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environmental resistance factors

slow population growth

biotic: competition, predation, disease; effect dependent on population size

abiotic: natural disasters, drought; affect all

k-selected species

quality

hover around carrying capacity

* low broods
* long life span
* high parental care

r-selected species

quantity

never reach carrying capacity

* lots of babies
* short life span
* early maturity
* low parental care

survivorship types

type I: high survivorship, long life span; humans

type II: chance of death consistent; mice

type III: most die young; pine cones

Total fertility rate (TFR)

average number of children a woman has during her childbearing years (15-49)

**influenced by cultural traditions** (religion, arranged marriage, child labor) **and societal factors** (education, family planning, governmental policies)

Doubling time

time for population to double at constant growth rate

doubling time = 70/r

\* r must be a percentage

ONLY way to calculate future size!

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Demographic transition

stage 1: preindustrial

* poor, lack of infrastructure, birth and death rates high

stage 2: transitional

* death rate drops, population increases

stage 3: industrial

* women’s rights, birth rate decreases, death rate stable, population increases

stage 4: postindustrial

* birth rates plummet, death rate low and stable, population stable

stage 5: birth rate lower than death rate, population decreases

Uniformitarianism

principle that the biological process forming and modifying the Earth are the same now as they were in the past

plate tectonics

solid and floating on magma in asthenosphere; constantly moving

**convergence**: forms mountains, volcanoes erupt, earthquakes

**divergent**: pulled apart, volcanoes erupt

**transform**: strike/slip, earthquakes common

pangea

all plates combine to form one plate

happened a really long time ago

earthquakes

measured using richter scale (logarithmic)

80% of tsunamis started with earthquakes

mechanical weathering

breaks apart rocks into smaller particles physically

Soil horizons

O horizon: organic litter layer

A horizon: top soil, mostly mineral particles mixed with organics; supports crop growth

E horizon: leached materials and organic matter

B horizon: deposited materials and metal salts

C horizon: partly weathered rock

R horizon: beadrock, unweathered

soil texture pyramid

percent of sand, silt, and clay

loam = best soil, equal parts of all three

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tropical rainforests have bad soil, low nutrients

humus: insoluble residue from dead plants and animals

atmospheric levels

troposphere

stratosphere (ozone layer here)

mesosphere

thermosphere

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temperature zig-zags

Absolute humidity

number of grams of water in one kilogram of air

relative humidity

moisture present in air compared to total amount it could hold if fully saturated **at given temperature**

Insolation

solar radiation/area

intensity of sunlight decreases away from equator

angle of incidence

angle at which the sun rays hit the earth’s surface

Tropic of Cancer

23\.5 ˚ North of equator

Tropic of Capricorn

23\.5˚ South of equator

weather

what’s happening now with the atmosphere near the ground

climate

average global weather; always changing

global climate patterns

caused by sun and ocean currents

rainshadow

prevailing winds hit mountains on the windward side, where it precipitates and wind goes over leeward side

mountain blocks precipitation for plants on leeward side

El Nino

winds above the southern ocean between SA and Australia stall and precipitation falls sooner than usual

* areas where the rain usually falls experience drought (Indonesia)
* causes above-average water temperatures in southern ocean
* affects global weather patterns (opposite)

La Nina

enhanced normal weather patterns

Watershed

high point/area of land that channels all water to a common outlet

* most water returns to oceans or reservoirs
* some infiltrates
* some evaporates

affected by people (logging, dams, farming, urban development)

tragedy of the commons

area used by all but regulated by none

* we exploit shared resources

externalities

cost being unpaid

maximum sustainable yield

the maximum amount of a resource that can be used without depletion

methods to fix tragedy of the commons

**regulate:** hunting/fishing licenses, land use permits, selective tree cutting

**replenish:** replant trees, rotate grazing

**ensure compliance**: E.P.A., treaties, fines

**privatize commons:** incentivize care

timber

trees that you cut down

lumber

harvested wood; boards cut from trees for use

economic benefits of forests

* livestock grazing space
* agricultural products
* mining
* ecotourism
* potential medicine
* impact on nearby real estate values

ecological benefits of forests

* soil retention/decreased erosion
* moderate climate
* habitat
* food source
* clean air and water

impacts of clearcutting

* invasive species increase
* emerging disease (zoonotic organisms in forests)
* increased atmospheric C02 levels
* decrease infiltration/deplete aquifers
* increase temperature/evaporation
* increase runoff/leaching

Solutions to deforestation

selective cutting

seed tree cutting: cut all but a few well-distributed trees of desired species

shelterwood cutting: leave areas of mature trees to provide shelter for growing trees

the green revolution

period of technological advances that drastically increased crop yields and agricultural production; began after WWII

mechanization

shifting from human labor to using machinery

pros:

* efficient
* customizable
* no need to hire extra workers

cons:

* use fossil fuels
* machine repair

monoculture

cultivation of single crop

pros:

* easy to plant/maintain/harvest
* only impacted by certain pests

cons:

* loss of biodiversity
* loss of ancestral varieties
* increased risk of catastrophe

irrigation

supply of water to crops or land

fertilization

pros:

* customizable
* easily shipped and produced
* ensures higher yield

cons:

* eutrophication
* can change the acidity of soil over time

weeds and pests

GMOs

artificial selection of advantageous genes

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modifying DNA in plants to achieve some benefit or desired trait

BT corn

GMO corn; bacteria that acts as a natural insecticide inserted into DNA

pros:

* pest and weed resistant
* can grow on previously unusable land
* greater tolerance

cons:

* may kill non target species
* BT crops can lead to insecticide resistant pests
* cross contamination