Studied by 11 people
Chapters 1,2,3
Ecology
the scientific study of how organisms affect, and are affected by, other organisms and their environment
scientific endeavor not environmental activism
species connections
even species that do not interact directly can be connected by shared environmental features
Ecologists ask questions about
the natural world in order to understand these connections
controlled experiment
experimental groups are compared with a control group that lacks the factor being tested
environmental science
incorporates concepts from the natural sciences (including ecology) and the social sciences and focuses on how people affect the environment and how to address environmental problems
balance of nature
early ecological view in which natural systems are stable and tend to return to an original state after disturbance
each species plays a distinct role in that balance
ecologists now recognize
natural systems do not necessarily return to their original state after disturbance
random perturbations can play an important role
different communities can form in the same area under similar environmental conditions
ecological interactions are much more complex than previously thought
Events in nature are always
interconnected,
a change in one part of an ecological system can alter other parts of that system
scale
the spatial or temporal dimension at which ecological observations are collected
spatial scales: small scale- soil microorganisms/large scale- atmospheric pollutants
temporal scales: short scale- leaf response to sunlight/ long scale- species change over geologic time
population
a group of individuals of a single species that live in a particular area and interact with one another
community
an association of populations of different species living in the same area at the same time
biotic
of or referring to the living components of an environment
abiotic
of or referring to the physical or nonliving environment
earth’s many communities
biosphere, ecosystem, community, population, organism
ecosystem
a community of organisms plus their physical environment
landscapes
areas with substantial differences, typically including multiple ecosystems
biosphere
all the world’s ecosystems comprise the biosphere
all living organisms on Earth plus the environments in which they live
evolution
all living systems change over time
change in genetic characteristics of a population over time
descent with modification- organisms gradually accumulate differences from their ancestors
adaptation
a characteristic that improves survival or reproduction
natural selection
an evolutionary process in which individuals that possess particular characteristics survive or reproduce at a higher rate than other individuals because of those characteristics
individuals with particular characteristics tend to survive and reproduce at a higher rate than other individuals because of those characteristics
then the offspring of individuals favored by natural selection will tend to have the same characteristics that gave their parents an advantage
if adaptation is heritable the frequency of the characteristic may increase in a population over time, the population will have evolved
producers
(autotrophs) use energy from an external source (the sun) to produce their own food. Also called primary producers
net primary production (NPP)
the amount of energy (per unit of time) that producers fix by photosynthesis or olost as heat in cellular respiration
consumers
(heterotrophs) get energy by eating other organisms or their remains
metabolic heat
energy captured by producers is eventually lost from the ecosystem as
how does energy move through ecosystems
energy moved through ecosystems in one direction only- it can’t be recycled
Nutrient Cycle
nutrients are continuously recycled from the physical environment to organisms and back again (food chains)
adaptation
a feature of an organism that improves its ability to survive or reproduce in its environment
How do ecologists answer ecological questions?
no single approach works in all situations, so ecologists use a variety of methods.
observational studies in the field
controlled experiments in the laboratory
experiments in the field
quantitative models
observational field study
research and surveying in the ecosystems like ponds
controlled experiment
in the laboratory
Field experiment
entire ecosystems, such as lakes or forests are manipulated
replication
performing each treatment more than once; reduces the possibility that results are due to a variable that was not measured or controlled in the study
experimental design
replication
assign treatments at random- also limits the effects of unmeasured variables
analyze results using statistical methods: standardized ways to determine whether observed differences are significant (great enough to be of biological importance)
scientific method
make observations and ask questions
use previous knowledge or intuition to develop hypotheses
evaluate by experimentation, observational studies, or quantitative models
use the results to modify the hypotheses, pose new questions, or draw conclusions about the natural world
the process is iterative and self-correcting
why is understanding the physical environment key to understanding all ecological phenomena?
physical environment is the ultimate determinant of where organisms can live, the resources available, and the rate at which populations can grow
weather
current conditions - temperature, precipitation, humidity, cloud cover
climate
long term description of weather, based on averages and variation measured over decades
includes daily and seasonal cycles, as well as yearly and decadal cycles.
greenhouse effect
increased CO2 and other gases in the atmosphere due to human activities, these gases absorb energy and radiate it back to the surface, like a blanket trapping hot air and raising temperature
what does climate determine?
climate determines the geographic distribution of organisms
climate is characterized by average conditions but extreme conditions are also important to organisms because they can contribute to mortality
climate change effects on weather and environmental
frequency and severity of extreme temperature climate events have increased in association with global climate change
in a Mediterranean-type climate most precipitation is in winter, and summers are dry which promotes fire
the rate at which climate is fluctuating is concerning, not happening in a common ecological order
How does climate affect abiotic processes and periodic disturbances
affects rate of weathering, which releases nutrients that are released back into the system
also influences rate of periodic disturbances such as fires rockslides and avalanches which kill organisms and disrupt communities but also create opportunities for growth of new organisms and communities
climate is changing so fast that organisms can’t recover quick enough
Sun and climate
the sun must lose the same amount of energy that it is gaining, if not the Earth will over heat
Solar Radiation must be offset by energy losses if earth’s temperature is to remain the same
much of the radiation absorbed by Earth’s Surface is emitted to the atmosphere as infrared (longwave) radiation
Earth’s Surface is also cooled when water at the surface evaporates and absorbs energy
latent heat flux
heat loss by evaporation
our oceans have high latent heat flux
conduction
kinetic energy is transferred by molecules in direct contact with one another (friction)
convection
energy transfer by movements of air or water currents
energy is produced with conduction then transferred with convection
sensible heat influx
energy transfer from warm air immediately above the surface to the cooler atmosphere by convection and conduction
heat transferred back to cooler parts of the atmosphere
greenhouse gases effects on the atmosphere
the atmosphere absorbs and reradiates the infrared radiation emitted by Earth
H2O CO2 CH4 and N2O
some gases are produced through biological activity, linking the biosphere to the climate system
earth without greenhouse gases
climate would be 33 degrees Celsius cooler
climate fluctuations
increased concentrations of greenhouse gases due to human activities altering Earth’s energy balance, changing the climate system and causing global warming
the disturbance of convection winter may be cooler than usual
sun rays on earth
sun strikes the equator directly
north and south poles are more shadowed and take the longer path through the atmosphere
establishes latitudinal gradients in temperature and is the driving force for climate dynamics
subsidence
air descends when it cools and forms a high-pressure zone at about 30 degrees N and 30 degrees S
Major deserts of the world are at these latitudes
uplift
heating leads to uplift and low pressure in a large band
hadley cells
large scale circulation patterns resulting from uplift in the tropics
polar cells
at the north and south poles- cold air descends, creating high-pressure zones with little precipitation (polar deserts)
ferrell cells
exist at mid-latitudes
Circulation cells result in
major climatic zones in each hemisphere - tropical, temperate, and polar zones
create surface wind patterns
prevailing winds
air flows from areas of high pressure to areas of low pressure, resulting in consistent patterns of air movements
Coriolis Effect
winds are deflected due to the rotation of the Earth
water
higher heat capacity than land - it absorbs and stores more energy with less temperature change
vertical ocean circulation
surface waters are warmer and less saline (less dense) than deep waters, so the two layers generally do not mix
top layer of ocean has less salt and is warmer, more evaporation, the deeper they get less sun and denser and cooler water
downwelling
warm currents cool and turn into ice in the polar regions, water becomes more saline, and dense and sinks
this water then moves back toward the equator carrying cold polar water
upwelling
prevailing winds blow parallel to a coastline
upwellings influence coastal climates
surface water flows away and deeper colder water rises to replace it
nutrients that are deep down are brought up to the top otherwise they would never receive those nutrients
phytoplankton and upwelling
brought to the photic zone light penetrates the nutrients and helps phytoplankton grow, gives food to zooplankton and their consumers, and are the most productive in open oceans
Ocean Currents
influence regional climate
“heat pumps” or “thermal conveyers”
great ocean conveyer belt is an interconnected system of ocean currents that link all the oceans and transfers heat from the tropics to the poles
maritime climate
little daily and seasonal variation in temperature, and high humidity
coastal areas
continental climates
much greater variation in daily and seasonal temperatures, especially in temperate zones
center of large continents
how do mountains influence regional climate?
temperature decreases and precipitation and wind speed increase with elevation, vegetation types change as you move upslope. When air masses meet mountain ranges, they are forced upward, cooling and releasing precipitation.
rain shadow effect
the windward mountain slope facing the prevailing winds has high precipitation and lush vegetation; the leeward slope gets little precipitation
albedo
amount of solar radiation a surface reflects; light-colored the surfaces have highest albedo
ex: a dark coniferous forest has a lower albedo than bare dormant grassland and absorbs more solar energy
how can vegetation cool the atmosphere?
through transpiration (evaporation of water from inside a plant via its leaves)
Evapotranspiration
water loss by transpiration, plus evaporation from the soil
transfer water and energy (as latent heat) into the atmosphere, thereby affecting air temperature and moisture
deforestation effects on climate
increases albedo = less absorption of solar radiation and less heating; offset by less cooling by evapotranspiration, this results in less moisture in the atmosphere and less precipitation
in the tropics this can lead to a warmer, dryer regional climate
seasonality
earth is tilted at 23 degrees
angle and intensity of the sun’s rays change as Earth orbits the sun, resulting in seasonal changes, especially in temperate and polar zones
influences biological activity and distributions of organisms, especially in temperate and polar zones
intertropical convergence zone (ITCZ)
zone of maximum solar radiation and atmospheric uplift
seasonal changes in precipitation result from movement of the ITCZ
stratified
warm surface water on top of colder, denser water results in layers that do not mix
influences the movement of nutrients and oxygen which are important to organisms
in temperate zone lakes stratification changes with seasons
thermocline
zone of transition between the upper epilimnion and hypolimnion
turnover happens in spring and fall when temperature and density in the water become uniform with depth
El Nino Southern Oscillation ENSO
a switch in the positions of high and low pressure cells over the equatorial Pacific leads to a weakening of the trade winds that normally push warm water toward Southeast Asia
La Nina
stronger phases of the normal pattern; usually follow el nino but are less frequent
comes back with forces and resets the currents in the right direction usually associated with unusual climate change and extreme storms
salinisalty
concentration of dissolved salts in water
salts are highest near equator and come from gases emitted by volcanic eruptions early in earth’s history and the gradual break down of earth’s crust
salinization
soils in arid regions become saline when water is brought to the surface by plant roots or irrigation and high rates of evapotranspiration result in salt build up
acidity
ability of a solution to act as an acid - a compound that gives up protons to a solution
alkalinity
ability of a solution to act as a base - a compound that takes up H+ or gives hydroxide ions
measured as ph
biosphere
lies between the lithosphere (earth’s surface crust and upper mantle) and the troposphere (lowest layer of the atmosphere)
biomes
large scale terrestrial communities shaped by the physical environment, categorized by dominant plant growth forms and characteristics such as leaf deciduousness or succulence
convergence
evolution of similar growth forms in response to similar selection pressures
What influences biome distribution?
determined by Earth’s climate zones
topography, ocean currents, and other factors
human impact
land use change
conversion of land for agriculture, logging, resource extraction, urban development
potential and actual distributions of biomes are very different
climate diagram
a graph of average monthly temperature and precipitation at a location, showing the characteristic seasonal climate pattern
Tropical Rainforests
very rare, found in sparce parts of Africa, Southeast Asia and South America
20% of landmass
abundant rainfall, high biomass and diversity about 50% of earth’s species
Layers of vegetation, each different and dependent on light exposure
Issues with Tropical Rainforests today
about half has been deforested due to logging and conversion to pastures and croplands
recovery is slim, soils are nutrient-poor and recovery takes a very long time
Loss of forest means less biosphere to take up carbon that is being released from soils and decaying vegetation
Tropical Seasonal forests and savannas
north and south of the wet tropics
shorter trees, deciduous in dry seasons, more grasses and shrubs, includes tropical dry forests, thorn woodlands, and tropical savannas
fires promote establishment of savannas- grasses mixed with intermixed trees and shrubs
deserts
at high-pressure zones
high temperatures, low moisture, sparse vegetation, and animal populations
low water availability constrains plant abundance, but diversity can be high, many plants have succulent stems that store water
desertification
long-term droughts and unsustainable grazing
loss of plant cover and soil erosion
temperate grasslands
between 30 and 50 latitude
warm, moist summers and cold dry winters
grasses dominate, maintained by frequent fires and large herbivores such as bison
high soil fertility
North American and Eurasian grasslands
much has been converted to agriculture
grazing can exceed capacity for regrowth leading to grassland degradation and desertification
temperate shrublands and woodlands
between 30 and 40 latitude
evergreen shrubs and trees
mediterranean type climate- cool wet winters and hot dry climates
plants can keep leaves during cool wet winters and not make new ones every year
without the 30 to 40 year intervals of fires shrublands would turn into forests
temperate deciduous forests
30 to 50 latitude
continental edges for tree growth, leaves are deciduous in winter
oaks, maples, and beeches occur everywhere, species diversity is lower than tropical rainforests
4 seasons, becoming less common due to climate change, southern animals are beginning to move north
fertile soils and climate make this biome good for agriculture
temperate evergreen forests
30 to 50 N or S latitude
coastal, continental and maritime zones
high rainfall and mild winters, located on west coasts
lower diversity, leaves tend to be acidic and soils nutrient poor
used for paper pulp, logged extensively
issues impacting evergreen forests today
density of forests has increased which results in more intense fires and increases the spread of pathogens and insect pests
air pollution has damaged some temperate evergreen forests
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