Environmental Science Exam 2

Salas Class

Asian Carp Example

Asian carp are invasive fish that were brought to the U.S. in the 1960s to clean fish farms, but they escaped into rivers, spread quickly, and now threaten to disrupt ecosystems like the Great Lakes.

Species Interactions

Mutualism , Predation/Parasitism / Herbivory , Competition

Competition

organisms that seek the same resources have a relationships

Intra vs inter species

Intra - takes place between members of the same species

Inter - takes between members of different species

Competitive exclusion

if one species is a stronger competition , it may excluded other species from than resources

Species coexistence

if no single competitor excludes others, species live side by side.

Resource partitioning

over many generations natural selection may favor , where individuals use shared resources in different ways.

Character Displacement

where competing species diverge and develop different characteristics

Predation

is the process by which individuals of one species (predators) capture , kill and consume individuals of another (prey). 

Parasitism

is a relationship where one organism depends on the other for nourishment.

Herbivory

animals feed on the tissues of plants

Mutualism

is a relationship where two or more species benefit each other

Ecological Communities

community 

trophic levels

Community

is an assemblage of populations of organisms living in the same area at the same time

Trophic level

Species in a community
are given a rank within
the feeding hierarchy

producers, primary , secondary , tertiary , detritivores , decomposers

Producers

use photosynthesis or chemosynthesis to make their own sugars.

Primary Consumers

consume producers

Secondary Consumers

prey on primary consumers

Tertiary Consumers

prey on secondary consumers

Detritivores

scavenger waste and dead bodies

Decomposers

break down non-living matter into smaller molecules that cycle back into soil

Food chain vs Food web

food chain - The flow of energy and feeding relationships from lower to
higher trophic levels is depicted 

Food webs -  incorporate all of the interlinking food chains
within an entire community, showing the map of energy
flow.

Keystone species

A species that has an impact far greater than its
abundance . 

‘‘ Ecosystem Engineers’’

Keystone species - examples

beavers , otters and wolves 

Keystone species - Trophic cascade

If top predators are
lost, primary
consumers will
overconsume
producers and alter
the entire ecosystem

Ecological Disturbance

is any event that has rapid and drastic effects on the community and ecosystem

Resistance

A community that resists change and remains stable

Resilience

A community that is changed by a disturbance but returns
to its original state

Succession

Severe disturbances may eliminate all or most of the species in a community, initiating a series of changes

Pioneer Species

Succession begins with the colonization

such as grasses and forbs, spread
over long distances easily and are adapted for growing
quickly

Climax Community

pioneers are overtaken by longer-living

such as hardwood trees 

Primary Succession

occurs when a disturbance removes all plants or soil life

• lichens secrete acids that break down rock , beginning the process of soil formation

Secondary Succession

begins with a disturbance that alters the community
but leaves the soil life intact.
– Farming, fires, storms, and landslides are examples.

Introduced species

are non-native arrivals in a community brought by people

Invasive Species

Most fail to establish populations, but the ones that thrive

Eradication vs Control vs Prevention

Eradication - the total elimination of a population, is very difficult and expensive

Ecological restoration

devise ways to restore altered areas to their condition before industrialized
civilization.

Ecological restoration may have two aims:
– Restore the functionality of an ecosystem.
– Return a community to its “pre-settlement” condition 

Earth’s Biomes

Despite communities being in very different locations, they often have similar structure and function.

Biome

biomes are classified primarily by dominant plant type and vegetation structures , which is turn is the results of climate

Climate determines biomes

Temperature -

Precipitation -

Climate diagrams / Climatographs -depict
seasonal changes in temperature and precipitation and
help to tell the story of a biome.

Temperature deciduous forest

are found at midlatitudes and have relatively even precipitation throughout
the year. 

Temperate grassland

Temperature differences between winter and summer are more extreme and
rainfall diminishes

Temperature rainforest

are rich in rainfall, but still found in midlatitudes

tropical rainforest

have dark, damp interiors, lush vegetation, and highly diverse
communities.

tropical dry forest

have wet and dry seasons that each occupy about half of the year.

savanna

tropical grasslands interspersed with acacias or other
trees.

desert

driest biome, receiving less than 25 cm of rain per year

tundra

also very dry but are consistently cold all year

boreal forest

taiga, are also cold, but receive more precipitation
than tundras

chaparral

is found in only
a few small patches
throughout the world

Chesapeake Bay watershed example 

The Chesapeake Bay watershed is the land area where rivers and streams drain into the Chesapeake Bay.

Because of too many nutrients (pollution) and the loss of oysters (a keystone species), the bay became polluted, leading to low oxygen (hypoxia). Efforts are now being made to restore it.

👉 In short: Too much pollution + fewer oysters = unhealthy bay.

Environmental Systems

systems - is a network of relationships among parts that influence each other through the exchange of energy, matter, or information

Positive and Negative feedback loop 

Positive Feedback

occur when increased output in a system leads to increased input, which
further stimulates output.

Negative Feedback 

results when the system moving in one direction acts as an input that cause
the system to move in the opposite direction 

Describe the process of eutrophication

1. Nutrient input 🌱 

Extra nutrients (nitrogen and phosphorus) enter water from fertilizers, manure, or sewage. 

2. Algal bloom 🌊 

The nutrients act like “food” → algae and phytoplankton grow rapidly on the water’s surface. 

3. Light blocked ☀ 

Thick algae prevent sunlight from reaching underwater plants (like grasses). These plants die off. 

4. Decomposition 🦠 

When algae die, decomposer bacteria break them down. This process uses up oxygen in the water. 

5. Oxygen depletion (hypoxia) 💨 

Oxygen levels drop so low that fish, crabs, and other aquatic life can’t survive. 

6. Dead zones ⚠ 

The area becomes nearly lifeless, with very few species able to live there. 

impacts of run- off

runoff - precipitation that flows over land and into
waterways, might define the Chesapeake Bay watershed as a system

significance of high concentration of nutrients (N&P)

High N & P → algal blooms → oxygen loss → harm to aquatic ecosystems.

Resulting hypoxia 

Hypoxia = low oxygen in water caused by too many nutrients and algal decay, which leads to the death of aquatic organisms.

describe how energy and matter flow through an ecosystem

Energy Flow ⚡

• Starts with the sun → plants (producers) capture sunlight through photosynthesis.

• Moves through food chains → plants → herbivores → carnivores → decomposers.

• Lost as heat at each step (cannot be recycled).
  👉 Energy flows one way only, from the sun to producers to consumers, then out as heat.

Matter Flow 🌍

• Matter is recycled in cycles (carbon, nitrogen, water, phosphorus).

• Example: Plants take in carbon dioxide → animals eat plants → decomposers return carbon to soil/air.

• Unlike energy, matter circulates continuously within the ecosystem.

---

💡 Easy way to remember:

• Energy = one-way street (sun → food chain → heat).

• Matter = recycling loop (used again and again).

Production

The rate at which energy is converted to biomass

primary production

The conversion of solar energy into chemical bonds in sugars

gross

The total energy captured by producers.

net production 

The energy left after plants use some for their own respiration.

why do difference ecosystems have different levels of productivity 

Ecosystem productivity depends on sunlight, temperature, water, and nutrients. That’s why tropical rainforests and coral reefs are highly productive, while deserts and tundras are low.

What does it mean that nitrogen and phosphorus are limiting nutrients

Nitrogen and phosphorus are called limiting nutrients because they are usually scarce, and their availability sets the limit for plant and algae growth in an ecosystem.

relating to dead zones

Too much N & P → algae boom → oxygen gone → dead zone forms.

biogeochemical cycling

Biogeochemical cycles are the natural pathways by which elements and compounds (matter) move through living organisms (bio), the earth (geo), and the atmosphere (chemical).

biogeochemical cycling - sources

When a reservoir releases more materials than it accepts

biogeochemical cycling - sinks

When a reservoir accepts more materials than it releases

the water cycle

summarizes how water flows as a solid, liquid, and gas, through our environment

Evaporation

Converts water from a liquid to gaseous form , taking it to the atmosphere.

Increased by warmth , wind, and  a high degree of exposure. 

Transpiration

is the release of water vapor by plants through their leaves.

transpiration and evaporation both leave any substances dissolved in water behind 

precipitations

when it condenses into rain or snow.
▪ May be taken up into plants or used by animals, but
most of it flows as runoff into surface waters

the carbon cycle

describes the routes that carbon takes through the environment

the carbon cycle - explain how carbon cycle through the environment

Carbon moves between the air, living things, water, and Earth through processes like photosynthesis, respiration, decomposition, combustion, and geological activity.

the carbon cycle - why is this cycle significant for climate change 

The carbon cycle matters for climate change because humans are adding too much carbon to the air, upsetting the natural balance, and making the planet warmer.

nitrogen cycle

Under the right conditions, nitrogen can become
biologically active and enter the biosphere and
lithosphere

nitrogen cycle - explain how nitrogen cycle through the environment

Nitrogen goes from the air → soil → plants → animals → back to the soil → and finally back to the air.

nitrogen cycle - the significance of nitrogen fixation

• Nitrogen fixation is important because plants and animals can’t use nitrogen gas from the air.

nitrogen cycle - significance nitrogen fixing bacteria

• Nitrogen-fixing bacteria change nitrogen gas into a form plants can use to gro

haber - bosch process 

enabled people to artificially fix nitrogen, greatly enhancing agriculture.

haber - bosch process  - implications of this process on population 

In simple terms: these cycles directly affect population growth, decline, survival, or extinction, because they control how much food, oxygen, and livable habitat are available.