Lecture Exam 4 Flashcards
What is an ecosystem?
The species present in a region, along with abiotic components such as sol, climate, water and atmosphere
What is the biosphere?
The thin zone of life surrounding the earth
What is the proposed new gelogical timescale epoch called?
The anthropocene – the new human epoch
How does energy enter ecosystems?
Through primary producers
What are primary producers?
Autotrophs – organisms that can synthesize their own food from inorganic sources.
In most ecosystems, primary producers use solar energy + photosynthesis to manufacture food. In deep-sea hydrothermal vents, primary producers use methane and hydrogen sulfide.
Do primary producers create energy?
No. They transform the energy from sunlight or inorganic compounds into the chemical energy stored in sugars.
What is gross primary productivity (GPP?)
The total amount of chemical energy produced in a given area and time period
How do primary producers use chemical energy?
1) Cellular respiration (or in anaerobic microbes, fermentation) produces ATP. ATP fuels metabolic processes.
2) Growth and reproduction. Energy invested in building new tissue or offspring is called Net Primary Productivity
Describe the relationshi pbetween primary producer productivity and respiration/lost energy
NPP = GPP - R
What is net primary productivity?
The total amount of chemical potential energy stored in organic material, or biomass.
How much of the available sunlight energy is harnessed in photosynthesis? Why so little?
0.8%; Why so inefficient
- The pigments in photosynthesis absorb only a fraction of the light wavelengths.
- Plants absorb way less in winter
- If it gets dry in the summer, plants close their stomata to conserve water, stalling photosynthesis due to lack of CO2
- Enzymes are temperature-dependent
How much of GPP goes to production of new biomass?
45% of GPP goes to NPP. The rest goes to respiration or is lost.
Describe the energy flow model for ecosystems.
Energy flows from autotrophs to other organisms in the form of biomass.
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Consumers eat living organisms.
- Primary consumers eat primary producers
- Secondary consumers eat primary consumers
- Tertiary consumers eat secondary consumers
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Decomposers (detritivores) get energy by feeding on the remains of other organisms or waste products
- Detritus - dead animals and dead plant tissues. Many fungi are decomposers.
- Energy flows when one organism eats another
What is a trophic level?
A “feeding” level. Organisms that get energy from the same type of source occupy the same trophic level.
What is a food chain?
A food chain is one possible pathway of energy flow among trophic levels.
What are food webs?
Food chains overlap and consumers often feed at multiple trophic levels, so food webs are a way to summarize energy flows.
Is more biomass eaten dead or alive?
On earth, 95% is eaten dead. In marine environments, only 65% is eaten dead. Important:
- Makes decomposers very important to the study of forest energy flow
- Decomposer food chain is “leaky” – that is, forest detrius easily washes into streams, releasing energy.
Describe the pattern of biomass production according to trophic levels?
Each year, the total biomass produced declines from lower trophic levels to higher trophic levels.
Ex: there is less hawk biomass than chipmunk biomass, and so on up the food chain.
What is the 10 percent rule?
On average, only 10% of energy in one trophic level makes it to the next one.
Describe variation in the 10 percent rule
large mammals are more efficient at producing biomass because they lose less heat and have a smaller surface area to volume ratio.
Ectotherms are more efficient than endotherms because they rely on environmental heat and do not oxidize sugars to keep warm.
What is biomagification and why does it happen?
Pollutants like Mercury and POPs undergo a process called biomagniciation where they increase in concentration at higher levels in a food chain.
What happens in biomagnification?
Persistent atoms or molecules are taken from air/water by primary producers.
Consumers eat the producers and ingest lots of the pollutant but don’t filter it out. (Consumers at 10 times their body mass)
Pollutant gets more concentrated as it moves up food chain.
What is a famous example of a POP?
DDT. Birds were dying in areas sprayed with the mosquito pesticide; egg shells became thin and got crushed.
- How do top predators affect the food web? Give an example.
Top-down control and trophic cascades.
- Top-down control
- When a consumer limits a prey population, like the sea star vs. mussels in the Pacific Coast
- Greater Yellowstone Wolves in the 20th century
- Trophic cascade
- When top-down control changes cause conspicious effects two or three links away in food web
- Greater Yellowstone Wolves
Describe the effects of Greater Yellowstone Wolf dwindling. What is this an example of?
Trophic cascade
- Wolves fed on elk;
- when wolves were reintroduced, elk numbers declined and so more elk food (aspen, cottonwood, willow) is around;
- Changes in plant species triggered increase in beavers, which comete with elk for plants
- beavers dam streams, forming ponds that are a habitat for frogs, etc.
- Wolves hate coyotes, and fewer coyotes means more mice, which means more hawks that prey on mice.
is productivity higher on land or sea? why?
land, probably because light is more available to drive photosynthesis
Which terrestrial ecosystems are most productive?
wet tropics.
productvitiy declines going from equator to poles (except for Sahara) due to less sunlight and colder temperature
What factors determine global productivity of terrestrial ecosystems?
sunlight, location, water, nutrient availability, temperature
Which marine ecosystems are most productive?
Along the coastlines. Shallow water receives more nutrients from rivers, etc.
Which biomes are most produtive?
- Tropical wet forests and tropical seasonal forests cover <5% of earth’s surface but account for over 30% of total NPP
- Aquatic: Algal beds and coral reefs, wetlands, estuaries
- NPP per square meter is low in open ocean, but biome is so extensive that total NPP is still high.
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Of total NPP on earth, how much are humans using?
About a quarter of the planet’s biomass
What is the biogeochemical cycle?
the path an element takes as it moves from abiotic systems through producers, consumers, and decomposers.
What happens to detritus as it decomposes?
Microscopic decomposers form soil organic matter until the detritus is totally decayed and becomes humus.
Eventually, decomposition converts nutrients in soil organic matter to an inorganic form, and then the nutrients can be taken up by plants again.
What factors control the rate of nutrient cycling?
- Biggest limiting factor is often decomposition of detritus
- decomp is influenced by
- abiotic conditions like oxygen availability, temperature, precipitation
- quality of detritus as nutrient source for fungi/bacteria/archaea
- abundance and diversity of detritivores present
Describe how abiotic conditions could affect detritus decomposition rate
tropical areas have consistently warm temperature,optimal for detritivores; boreal forests get cold, which is bad for them
How can detritus quality influence growth of decomposers and the decomp rate?
decomposition is inhibited if detritus is low in nitogen or high in lingin. Additionally, oxygen must be present.
How can nutrients exit an ecosystem?
- eaten by organism which then leaves
- wind or water carries particles or inorganic ions and deposits them somewhere else
- man-made acccelerated nutrient export: farming/logging; soil erosion; runoff
How can nutrients be replaced in an ecosystem for normal functioning?
- ions that act as nutrients are released as rocks weather
- nutrients can blow in on soil particles or arrive dissolved in streams
- nitrogen is added when nitrogen-fixing bacteria convert N2 into ammonium or nitrate ions
Scientists did an experiment where they devegtated one of two similar stream areas in the same watershed; what was the lesson?
Once soil is lost, it is difficult to regain. Soil takes a very long time to form.
What are the three main questions in the study of the global biogeochemical cycle?
- **What are the reservoirs? **What are the size and nature of the reservoirs – areas or “compartments” where elements are stored for a period of time?
- ex: Carbon can be in biomass, coal, soil etc.
- **How and how fast are reservoir switches? **How fast How fast does the element move between reservoirs, and what processes move elements from one reservoir to another?
- ex: Photosynthetic rate tells us how fast carbon moves from CO2 to biomass carbon
- **How do cycles interact? **How does one biogeochemical cycle interact with another biogeochemical cycle?
- ex: How do changes in nitrogen cycle affect the carbon cycle?
Summarize the water cycle
- Water evaporates out of ocean
- water precipitates back into ocean, but slightly less
- water vapor moves over continents and is joined by evap from lakes and is transpired by plants; rain falls
- water moves from land back to oceans via streams and groundwater
Where is most groundwater stored?
aquifiers, layers of porous rock, sand, or gravel that are saturated with water
What effects do humans have on the water cycle?
- asphalt/concrete stop water from percolating down to deep soil
- grassland –> agricultural fields destroy root systems that hold water
- irrigated agriculture removes massive amounts of groundwater and brings it to the top
What is the water table?
The level where soil is saturated with stored water. It’s dropping on every continent.
Summarize the global nitrogen cycle
- N2 gas comes mainly from atmosphere. must be “fixed” into ammonium or nitrate.
- Reduced/fixed nitrogen builds up slowly in soils and water
- Reduced/fixed nitrogen cycles among animals, soil, fungi, plants, etc.
- bacteria digest nitrogen-containing molecules and return N2 to atmosphere
How does nitrogen fixation happen?
lightning-driven reactions
bacterial reactions
How have humans modified the nitrogen fixation cycle?
human sources of N2 fixation almost equal natural sources.
- industrial fertilizers
- crops that harbor N2 fixing bacteria
- fossil fuel burning
Adding N2 to terrestrial ecosystems usually makes them more productive. But why is overfertilization with nitrogen bad?
N2-laced runoff causes algae blooms, and when all the algae die and are decomposed by microbes, all the oxygen is depleted, creating oxygen-free dead zones.
Productivity increases but species diversity decreases
Describe the global carbon cycle
- movement of carbon among terrestrial, ocean, and atmosphere
- ocean largest; atmosphere fastest
- photosynthesis takes C out of atmosphere and incorporates it into tissue in terrestrial/aquatic ecosystems
- Cell resp releases carbon back as CO2
How have humans changed the carbon cycle?
- deforesting land for agriculture and settlements
- fossil fuel burning
- current CO2 levels are 30% higher than the highest level measured in the last 800,000 years
What are the three main drivers of environmental change?
- changes in land use
- massive loss of species
- global climate change (global warming)
What alarms scientists about climate change?
not that it is happening, but its rate
What is a greenhouse gas?
A gas that traps heat radiated from earth and keeps it from being lost into space
A major study on climate change took place in Mauna Loha, HI. Its findings:
- rate of increase of CO2 is not slowing
- temp fluctuates but there is a clear increase in average
- no net increase in solar energy over time
Why are atmospheric CO2 and temp rising so fast?
- human population explosion
- per-person fossil fuel use increase
How much will the climate change?
average global temperature will increase another 1-7 degrees celsius (2-12 degrees F) by 2100
Describe positive feedback in climate change and cite examples
changes due to GW accelerate GW
- warmer/drier climate increases forest fires, which release CO2
- Tundra sequesters carbon in soil, but warm summers release carbon stores into atmosphere
- polar ice caps melt, leaving open water darker and absorbing more solar heat/energy
What negative feedback happens with regard to GW?
- plants grow faster, which should reduce atmospheric CO2
What climate factors other than temperature are affected by climate change?
- temperature affect the water cycle, increasing precipitation in some areas and drying other areas
- variability in extreme weather conditions/events
- sea level rise due to melting glaciers/ice caps
- ocean currents change due to ice caps
what is phenology?
timing of seasonal events (i.e. arrival of spring)
What are the effects of climate change on organisms?
- Phenology shifts (timing of seasonal events –> changes in hatching, flowering, feeding, etc.)
- Geographic range shifts (species redistribute as climate changes)
- Evolutionary adaptaiton to new environment
- Extinction
- **Acidification **(ocean absorbs CO2 into bicarbonate and then deprotonates to form carbonic acid). Bad for corals, mollusks, etc.
How is net primary productivity changing in the oceans?
Overall, NPP is decreasing in the oceans. Seawater stratifies because its density depends on temperature, and currents are modified.
BIOME ID: Identify the temperature, precipitation, and notes on
Tropical Wet Forest
- also called tropical rainforests
- equatorial regions
- plants with broad leaves and are evergreen with lots of growth, extremely high productivity, and diversity
- temp: no seasonal variation in temp
- precip: very very wet
BIOME ID: Identify the temperature, precipitation, and notes on
Subtropical Deserts
- 30 degrees latitude north and south
- temp: temperature variation; sometimes very cold
- precip: low precipitation
What comprises an organism’s environment
abiotic factors and biotic factors
Describe the types of survivorship rates
Type 1 - lots live til old, then die
Type 2 - steady dying off
Type 3 - lage initial dying off, then strong survivotrs
Describe metapopulations and extinction
Populations within a metapopulation can go extinct and be reestablished by migration. Each population in a metapop is expected to go extinct at some point.
What are some types of constitutive defenses?
- cryptic coloration
- escape behavior
- toxins
- schooling/flocking
- defense and armor weapons
Describe bacteria, archaea, and eukarya in terms of:
- DNA in nuclear envelope
- Plasmid DNA
- Membrane-bound Organelles
- Rotating flagella
- Multicellular species
- Cell walls with peptidoglycan
- RNA polymeras has >10 units
- Translation initiated with methionine
Describe bacteria, archaea, and eukarya in terms of:
- DNA in nuclear envelope (BN, AN, EY)
- Plasmid DNA (BY, AY, EY)
- Membrane-bound Organelles (BN, AN, EY)
- Rotating flagella (BY, AY, EN)
- Multicellular species (BN mostly, AN, EY)
- C
ell walls with peptidoglycan (BY, AN, EN)
- RNA polymerase has >10 units (BN (5), AY, EY)
- Translation initiated with methionine (BN, AY, EY)
