6C Midterm 2

What are the two main ecosystem processes?

Energy flow and Chemical cycling

1st law of thermodynamics

Energy is not created nor destroyed, but transformed

Explain one-way energy flow in ecosystems

--> Energy enters the ecosystem through photosynthesis or chemosynthesis

--> Some energy is used by producers, some is passed through the food chain

--> All energy eventually dissipates as heat

How much energy is transferred to the next trophic level?

5% - 20% of energy is transferred to the next trophic level

How is chemical matter recycled

Atoms are reused and constantly rearranged into new molecules (ex: carbon cycle and nitrogen cycle)

Why are most food chains limited to 4-5 steps?

Small amount of energy is transferred between trophic levels, making it difficult to support additional levels. Variations in primary production can also cause instability in higher levels.

Explain the biogeochemical cycle

Materials enter producers from the atmosphere or solid matter and eventually return to the abiotic world through respiration and decomposition

List reservoirs of material

abiotic: atmosphere, soil, water, geological

biotic: living or dead organic matter

List sources of water used in the global water cycle

- humidity (water in the atmosphere)

- precipitation (rain, snow)

- surface transport (groundwater, rivers, oceans)

- groundwater transport (aquifers)

- evaporation (bodies of water, plants, organisms)

What is evapotranspiration?

The combined amount of evaporation and transpiration

Relationship between the evapotranspiration vs NPP

the more evapotranspiration in a biome the higher the net primary production is in that area

List watersheds

- snow melt

- surface runoff

- tributaries

- groundwater

In what ways does an impacted ecosystem affect watersheds?

- less permeability = less groundwater = more surface runoff

- more erosion, flooding, and sedimentation

- less interflow, evapotranspiration, and primary production

What are two human made diversions of surface water?

Irrigation and dams

List disruptions of soil water retention

- deforestation

- overgrazing

- compaction (less permeability)

- loss of materials through runoff

What is desertification?

Degradation of land primarily because of human actions like excessive crop planting, animal grazing, and deforestation

Explain carbon fixation

Producers use energy (sunlight) to convert CO2 (abiotic pool) into organic biomass (biotic pool)

What is GPP?

gross primary production: the total primary production in an ecosystem

What is NPP?

net primary production

Explain the carbon cycle

--> Consumers eat carbon compounds (sugars, proteins, fats, nucleic acids) made by producers

--> Respiration produces CO2 as waste that is released back into the abiotic pool

Explain the bottom-up regulation model

↑ nutrients = ↑ vegetation = ↑ herbivores = ↑ predators (and vice versa)

Explain the top-down regulation model

↑ predators = ↓ herbivores = ↑ vegetation = ↓ nutrients (and vice versa)

What is a detritus-based food chain?

An area where primary production is indigestible (grasslands, marshlands, kelp forests), requiring detritivores and decomposers to move production from producers to consumers

What is combustion?

Dead organisms return CO2 to the atmosphere when burned (ex: wood or fossil fuel)

What is the greenhouse effect?

CO2 in the atmosphere lets sunlight through but retains the heat it generates, trapping the sun's warmth in a planet's lower atmosphere

Explain temperature-dependent decomposition rates

Colder ecosystems slow down decomposition and retain more organic matter in the soil. In warmer ecosystems, decomposition happens faster, thus releasing more CO2 into the environment

Explain the nitrogen cycle

The transfer of nitrogen from the atmosphere to the soil, to living organisms, and back to the atmosphere

What is nitrogen fixation?

N2 gas converted to another nitrogen component

List the bacteria required for the nitrogen cycle

Nitrogen-fixing bacteria:

- N2 gas --> ammonia (NH4+)

Nitrifying bacteria:

- NH4+ --> nitrite (NO2-) --> nitrate (NO3-)

Denitrifying bacteria:

- nitrate (NO3-) --> N2 gas

What do plants use nitrate for?

produce organic amines (-NH2)

List human influence on the nitrogen cycle

-Deforestation (causes loss through runoff)

-Production of fertilizers (burning of fossil fuels)

-Acid rain production

How is acid rain produced?

Nitrogen and sulfur compounds (from factory and auto emissions), plus water, create nitric acid and sulfuric acid in the atmosphere

Explain how mineral nutrients (like phosphorus, calcium, potassium, and iron) are transported

Sources usually depend on erosion from regional rock and transport in surface water

How important are mineral nutrient cycles ?

Biological demand is low however, some organisms that need to consume these minerals will often risk their life to get small amounts because they are necessary for life

What is Liebig's law of minimum?

If one growth factor is deficient, plant growth is limited, even if all other vital factors are adequate.

What is a limiting nutrient?

A single essential nutrient that limits productivity in an ecosystem

What are the two most typical limiting nutrients?

Nitrogen and phosphorus

What is cultural (anthropogenic) eutrophication?

When sewage or fertilizer runoff adds limiting nutrients to an aquatic ecosystem, thus stimulating the overgrowth of algae and causing loss of diversity and structure

List the topography in California that makes it so biodiverse in comparison to the rest of the United States

- long coastlines

- a series of mountains and valleys

- rapid transitions in elevation, temp, soil types, rain harvest, and solar exposure

- Isolated populations

List California's "seasons of the sea" and the effect they have on the coastal environment

- Upwelling Season: Causes cooler temperatures, fog, and high ocean productivity in coastal areas

- Oceanic Season: Causes mild temperatures and low ocean productivity in coastal areas

- Davidson Season: Causes storms, warm, wet winters, and low ocean productivity

Explain California's upwelling season and how it results in cooler temperatures and high ocean productivity

Mid-spring --> summer

- High atmospheric pressure offshore pushes wind in a clockwise direction

- Surface water deflected to the right by the Coriolis effect

- Wind moves from north to south

- Cold, nutrient-rich, bottom water "wells up" to replace surface water

Explain California's oceanic season and how it results in mild temperatures and low ocean productivity

Late summer --> autumn

- Low atmospheric pressure offshore pushes wind in a counter-clockwise direction

- Wind moves from south to north

- Nearshore water "wells down" and is replaced by warm oligotrophic surface water

Explain California's Davidson season and how it results in warm, wet weather and low ocean productivity

Winter --> early spring

- Low atmospheric pressure offshore intensifies

- Strong winds move from south to north

- Nearshore water "wells down" and is replaced by a very strong, warm, oligotrophic countercurrent

- Subartic cold generates storms that are pulled counterclockwise by atmospheric pressure

- Storms travel south, absorbing warmth and moisture

North Pacific Gyre

Clockwise current

- Oligotrophic water in the west cools and picks up nutrients as it flows north

- Eastern waters from California flow south towards the equator

- The south current warms and loses nutrients as it flows westward across the tropics

What is an eddy current?

a swirling circular current of water that breaks off from a larger ocean current, causing microenvironments

List the major climate types in California

- mediterranean

- steppe

- cool interior

- highland

- desert

Explain what a Geographic Information System (GIS) does

combines layers of geographical information in various ways to produce maps or conduct analyses

What constitutes a rare or special species in the context of RWRI?

endemic species with very limited distribution, low population levels, and/or are under immediate threat (esp. due to habitat loss)

What is pollution?

Contamination of the air, water, and soil

What is one way we measure air pollution, and why?

Carbon Monoxide levels - produced when fossil fuels burn incompletely (hence a good indicator of pollution)

What different types of pollution?

- addition of Toxic chemicals and synthetic compounds

- Redistribution of natural compounds (excessive eutrophication)

- infectious agents

- physical factors (thermal, light, noise, plastic)

What is eutrophication?

Nutrients that exceed the critical load of a body of wate due to runoff, which causes a dense growth of plant life and death of animal life from lack of oxygen.

What is critical load?

The maximum amount of added nutrient that can be absorbed by plants without damaging the ecosystem

How does over-irrigation affect animals?

Over-irrigation can cause toxic natural elements to leach into the environment, contaminating water and food sources. This leads to poisoning, reproductive issues, deformities, and even death in wildlife.

What is mine tailing?

Mine tailings are the toxic, leftover materials from mineral processing.

What is a xenobiotic?

Chemicals that are not produced by natural biological or abiotic sources, that are foreign to the body or biological system

BTEX compounds

Benzene, Toluene, Ethylbenzene, Xylene

List the types of toxins and their effects

- persistent toxins: bioaccumulate

- neurotoxins: disrupt neural function

- endocrine disruptors: interfere with hormone action and perturb reproduction

- mutagens: carcinogenic, damage DNA

- teratogenic: birth defects

List types of persistent environmental toxins

- PCB

- pesticides

- phthalates

- VOCs

- Dioxins

- Heavy metals (mercury, lead, etc...)

- Chlorine and chloroform

Explain what happens in the body when a xenobiotic is introduced to an organism

- Enzymes try to neutralize toxins

- If enzymes fail toxin reaches the site of action and can interfere with a biological site (DNA, RNA, etc..)

- The body tries to biotransform the xenobiotic (this can make the toxin less harmful or unintentionally make it more toxic)

What is a static model?

short-term modeling of ecosystems

What is a strategic model?

model of a specific aspect of a system

What is a testable model?

model that makes a prediction that can be tested in a feild or laboratory

What is biotransformation?

metabolic process, mainly by environmental bacteria that alter the structure of a toxic compound

What is biodegradation?

breakdown of a xenobiotic to CO2 and water

What happens when a toxic chemical interferes with cell signaling?

It disrupts cell communication by mimicking or blocking natural molecules

What happens when a toxic chemical interferes with proteins in a membrane?

alters the transport or response function of membrane proteins

What happens when a toxic chemical interferes with DNA replication?

affects DNA copying, risking cell malfunction or death

What happens when a toxic chemical interferes with protein synthesis?

interferes with the creation of functional proteins

How does a toxic chemical cause DNA damage?

mutations or strand breaks

What happens when a toxic chemical causes strange breakage?

unusual molecular break patterns suggesting an unknown mechanism

How can a toxic chemical cause chromosome abnormalities?

Changes in structure or number causing dysfunction

How can a toxic chemical cause cancer?

A mutation is triggered, leading to uncontrolled cell growth

What non-genotoxic effects can chemicals cause?

immunosuppression or hormone disruption

How can you asses toxicological effects on population?

- tissue lesions

- tumors

- reproductive success

What is LC50?

Lethal concentration: causes mortality in 50% of the population

What is EC50?

Effective concentration: causes a significant effect or a defined biological response in 50% of the population

What are the routes of toxic chemical exposure?

dermal, inhalation, ingestion

Explain half-life in the context of toxicology

refers to the amount of time it takes for the concentration of a toxic chemical in an organism to be reduced by half through biological, chemical, or physical processes.

What does HIPPO stand for?

habitat destruction, invasive species, pollution, population growth, overexploitation

(human insults to the biosphere)

What are some disrupted biochemical cycles?

- water cycle

- nitrogen cycle

- carbon cycle

- soils

How have humans disrupted the water cycle?

desertification, contamination, saltwater intrusion

How have humans disrupted the nitrogen cycle?

nutrient depletion, eutrophication, nitrite contamination, acid rain

How have humans disrupted the carbon cycle?

excess CO2, depleted fossil pools

How have humans disrupted the soil?

erosion, nutrient depletion, fire suppression

Finish the sentence: Extinction rates of aquatic species...

are five times that of terrestrial

What are some local species at risk?

- bald eagle

- southern sea otter

- ohlone tiger beetle

- long toes slaamander

- harvest mouse

- presidio manzanita

- burrowing owl

What is habitat fragmentation?

breakup of a habitat into smaller pieces, usually as a result of human activities.

source habitat vs sink habitat

source habitats are high-quality habitats where reproduction exceeds deaths, meanwhile sink habitats are low-quality habitats where deaths exceed reproduction

What does low genetic variation lead to?

extinction

What is a zoonotic host?

An animal capable of hosting pathogens that can be harmful to humans (zoonosis or zoonotic disease)

How has the invasive asian clam affected SF bay?

changed the food web in SF Bay estuary by severely restricting phytoplankton blooms

How has pollution affected the California condor?

The birds have ingested high levels of lead (likely due to bullet fragments in scavenged food) and ethylene glycol (due to antifreeze in contaminated puddles)

How has pollution affected the red-legged frog?

Many male frogs are intersex in ponds polluted with atrazine (weed-killer)

What is bycatch?

Organisms unintentionally killed during the harvesting of a different, desirable species

List overharvested species in California

- abalone

- blue oaks

- black bears

Sample vs population

Population: the entire group of people about which information is wanted

Sample: a part of the population that is used to gain information about the whole population

Explain the empirical rule

When nearly all of the data in a distribution falls within 3 standard deviations of the mean.

1 SD: 68%

2 SD: 95%

3 SD: 99.7%

What are the types of variance?

population and sample variance

S^2

Sample variance