Unit 4: Ecosystems

Question 1

Niche

Answer 1

the ecological role a species plays in an ecosystem

Question 2

Competitive Exclusion Principle

Answer 2

1. no two species can occupy the same niche without competing
2. if two species compete for the same limited resources, one will outcompete the other

Question 3

Resource Partitioning

Answer 3

When two or more species divide resources/avoid competition based on differences in behavior or morphology (body physiology)

Question 4

Amensalism

Answer 4

In this interaction, one species suffers while the other is unaffected.

Ex: allopathy where one species releases a chemical substance to inhibit the growth of another species. Penicillium secretes penicillin, which kills various bacteria.

Question 5

Competition (two types)

Answer 5

This interaction is based upon a competition for resources.

There are two types:
In intraspecific competition, organisms from the same species compete for the same resource.
In interspecific competition, organisms of different species compete for the same resource, usually aggressively.

Question 6

Commensalism

Answer 6

In this interaction, one species benefits from the interaction while the other is neither helped nor harmed

Ex:
small birds and large grazing herbivores. The small birds perch on the backs of large herbivores while they graze in grassy fields. The movement of the large herbivores stirs up insects out of the grass which the small birds then feed on.

Question 7

Mutualism

Answer 7

In this interaction, both species benefit
Ex: bees and flowers

Question 8

Neutralism

Answer 8

While this interaction is almost always implied rather than stated in most superficial interactions, it is crossing paths where neither organism is affected by the other

Question 9

Parasitism

Answer 9

In this interaction, one species benefits while the other is harmed. Parasites generally attach to a host as a consistent source of nutrition. Parasites may be exoparasites, existing outside the host, or endoparasites, existing inside the host. The parasite does not want to kill its host, as this would remove the source of food

Question 10

Predation

Answer 10

In this interaction, one species benefits while the other is harmed. Predators obtain food at the expense of their prey

Question 11

Saprophytism

Answer 11

In this interaction, a dead or decaying organism is fed upon by another organism. Most of these detritivores replenish essential environmental nutrients as part of the biogeochemical cycles

Question 12

What makes a species invasive by nature?

Answer 12

• All invasive species were once introduced species (they are non-native by nature)
• Can be introduced purposefully (as with the cane toad) or accidentally (as with the zebra mussel)
• They outcompete native species for resources & lack a natural predator in their introduced environment
• Invasives are often generalists and r-selected species meaning: 1. they have lots of offsprings in short amounts of time 2. they reach reproductive maturation early in their life spans

Question 13

Ecosystem

Answer 13

All the organisms in a community (biotic) interacting with abiotic factors (water, air, nutrients)

Question 14

What is needed in an ecosystem for it to function?

Answer 14

• the capture of energy (photosynthesis -> primary productivity)
• the transfer of energy
• the cycling of matter (biogeochemical cycles)

Question 15

Net primary productivity (NPP)

Answer 15

Gross primary productivity (GPP) – Respiration

Units : kcal / m^2 / yr

GPP = rate of photosynthesis in a given area
Respiration = rate of energy used by primary producers (plants)
NPP = “surplus” or what’s left over after photosynthesizers (plants) have carried out respiration. Passed on to higher trophic levels

Question 16

Ecological pyramid

Answer 16

primary producers -> primary consumers -> secondary consumers -> tertiary consumers

10% of energy is transferred between trophic levels of the food chain

Question 17

Inefficiency of Energy Transfer

Answer 17

• Based on the 2nd Law of Thermodynamics
• Loss of energy between levels of food chain
• energy is lost largely due to heat but also because of waste and cellular respiration

Question 18

Bioaccumulation

Answer 18

Absorption of a substance by a living organism

Question 19

Biomagnification

Answer 19

Increase in concentration of a substance per unit of body tissue that occurs in successively higher trophic levels/increase in concentration of chemicals in each organism up the food chain.

Question 20

A substance will biomagnify if

Answer 20

1. It’s oil/fat soluble (can be built up/stored in body tissues)
2. It’s persistent (stays in the body for a long time)
3. It’s biologically active

Ex:
pesticides (like DDT), heavy metals (lead, cadmium, mercury), environmental toxins (like PCBs)

Question 21

Removal of a keystone species results in

Answer 21

“trophic cascades” (a.k.a. “downgrades” → ecosystem collapses & biodiversity declines)

trophic cascades = an ecological phenomenon triggered by the addition or removal of top predators and involving reciprocal changes in the relative populations of predator and prey through a food chain, which often results in dramatic changes in ecosystem structure and nutrient cycling.

Question 22

Biomes

Answer 22

The land surface of the Earth is divided into a number of geographic areas distinguished by particular types of dominant flora and fauna.

flora and fauna = collection of all plants and animals living in a particular region

Question 23

Factors that can affect the location of biomes include

Answer 23

• Latitude: how far north and south from equator
• Temperature: represented as a line graph on a climate graph
• Rainfall: represented as a bar graph on a climate graph

(Climatic conditions are depicted in climatographs (a.k.a. climate graphs or climate diagrams))

Question 24

Each biome is characterized by

Answer 24

amount of precipitation and the average annual temperatures recorded

Question 25

The big 6

Answer 25

CHNOPS

Carbon
Hydrogen
Nitrogen
Oxygen
Phosphorus
Sulfur

Question 26

Biogeochemical Cycles

Answer 26

Movements of matter within & between ecosystems involving biological, geological, and chemical processes.

Question 27

What roles do matter and energy play?

Answer 27

• ENERGY comes from the Sun, FLOWS through biotic & abiotic components, then emits back into space. It is never lost, just transformed!
• MATTER never leaves but CYCLES in a variety of forms.
  Remember: Earth is an open system w/ respect to energy but closed w/ respect to matter

Question 28

How do the 1st and 2nd Laws of Thermodynamics apply to cycles of energy and matter?

Answer 28

1st Law states that matter and energy are never created nor destroyed, but transformed.

2nd Law states that when these transformations happen, they are never 100% efficient or useful; some energy is lost as “waste heat”

Question 29

Reservoirs

Answer 29

A pool or holding place for a nutrients

Question 30

Sinks

Answer 30

Reservoirs that accept more nutrients than they release

Question 31

The 6 processes of the carbon cycle

Answer 31

6 processes drive this cycle:
- Photosynthesis
- Respiration
- Exchange
- Sedimentation & Burial
- Extraction
- Combustion

1: Photosynthesis
- Plants hold carbon for a short amount of time.
- They take in CO2 in this process and make glucose (C6H12O6)
- Plants are carbon sinks

2: Respiration
- Consumers & decomposers (via metabolic processes) release CO2 into the atmosphere and soil.
- does not contribute to carbon emissions in the air
- the soil is a carbon sink

3: Exchange
- CO2 moves back and forth from the ocean & atmosphere (a.k.a. “diffusion”).
- The ocean is the largest sink of carbon

4: Sedimentation & Burial
- Organisms die, decompose, get buried, and become fossil fuels.
- In both cases, carbon is held or “sequestered” in these reservoirs for a long time (millions of years!)
- Sedimentary rock (ex: limestone) is the largest reservoir of inorganic carbon.

5: Extraction
- Fossil fuels are removed from underground via mining, drilling/fracking.
- This quickly releases CO, CH4 and CO2
- Fossil fuels are sources of “new” carbon

6: Combustion
- Combustion of fossil fuels releases CH4 and CO2 in the atmosphere
- This quickly adds “new” carbon to the atmosphere

Question 32

Explain how carbon cycles through ecosystems

Answer 32

Plants and other photosynthetic organisms capture atmospheric carbon dioxide (CO₂) during photosynthesis, using it to produce glucose and other organic compounds, which serve as energy sources for themselves and the consumers that eat them. When organisms respire, they release CO₂ back into the atmosphere. Additionally, when plants and animals die, decomposers break down their remains, returning carbon to the soil or releasing it as CO₂. Some carbon is stored long-term in fossil fuels and sediments, which can re-enter the cycle through combustion or erosion. This dynamic movement of carbon helps sustain life, regulate global temperatures, and maintain the balance of ecosystems. Further, the ocean and atmosphere constantly exchange carbon (but not always equal amounts).

Question 33

anthropogenic impacts on the carbon cycle?

Answer 33

1. Increased extraction & combustion of fossil fuels via human activities (such as driving gasoline-powered cars) releases more CO2 & CH4
2. Deforestation increases the amount of CO2 in atmosphere b/c of the removal of carbon “sinks”
   Both contribute to accelerating climate change b/c greenhouse gases are released/there’s more greenhouse gasses in the atmosphere

Question 34

Why do living things need nitrogen?

Answer 34

Nitrogen atoms are needed to build nucleic acids (for DNA and RNA synthesis) and amino acids (for protein synthesis)

Question 35

What is the significance behind how molecular nitrogen is chemically found?

Answer 35

N2 is not biologically “useful” so it needs to be chemically “fixed” to make it useful

Question 36

Steps of the Nitrogen Cycle

Answer 36

First way:
Step 1: Nitrogen fixation
- Abiotic form: Lightning converts N2 to nitrate (NO3-)
- Nitrate = most “useable form” of nitrogen
- nitrogen gets fixed in one step because of lightning
- Equation: N2 –(by lightning)—> NO3-

Second way:
Step 1: Nitrogen fixation
- Biotic form: Nitrogen-fixing bacteria (often found in the roots of legume/bean plants) convert nitrogen gas (N2) from the atmosphere into ammonia (NH3) and/or ammonium (NH4+) in the soil
- Equation: N2 —(by bacteria on roots of legumes)—>NH3 and NH4+

Step 2: Nitrification
- Nitrifying bacteria in the soil convert ammonium (NH4+) and/or ammonia (NH3) to nitrites (NO2-) and then nitrates (NO3-)
- Nitrate = most “useable form” of nitrogen
- Equation: NH3 and/or NH4+ —(by nitrifying soil bacteria)—-> NO2- & NO3-

Step 3: Assimilation
- Plants and animals incorporate the nitrates into their tissues when they eat or make their food

Step 4: Ammonification/Mineralization
- When animals and plants die, decomposers break down the amino acids into NH4+ and return it to the soil
- Nitrifying bacteria again convert the NH4+ to NO3- or NO2-
- Equation: NH3 and/or NH4+ —(by nitrifying soil bacteria)—-> NO2- & NO3-

Step 5: Denitrification
- Denitrifying bacteria in the soil convert NO3- into N2O, which then converts to N2 in the atmosphere
- Equation: NO3- —(by denitrifying bacteria)—-> N2O —-> N2

Question 37

Explain the nitrogen cycle

Answer 37

Nitrogen gas (N₂), which makes up about 78% of the atmosphere, is not directly usable by most organisms. The atmosphere is the largest reservoir of nitrogen. Nitrogen-fixing bacteria in the soil or in the roots of legumes convert N₂ into ammonia (NH₃) or ammonium (NH₄⁺) in a process called nitrogen fixation. Other bacteria convert ammonia into nitrites (NO₂⁻) and then nitrates (NO₃⁻) through nitrification, forms that plants can absorb and use to build proteins and DNA. The absorption of nitrites and nitrates by plants and animals is called assimilation. Animals obtain nitrogen by consuming plants or other animals. When organisms die or excrete waste, decomposers return nitrogen to the soil as ammonia through ammonification. Some bacteria convert nitrates back into nitrogen gas in a process called denitrification, completing the cycle. This intricate process ensures nitrogen is continuously available for living organisms and maintains ecosystem balance.

Question 38

What are the anthropogenic impacts on the nitrogen cycle?

Answer 38

1. Using synthetic fertilizers adds nitrates (NO3-) to an ecosystem when they runoff into bodies of water
   → lead to algal blooms
   Fertilizers are NOT the same as pesticides!
2. Discharging animal waste/untreated sewage into bodies of water adds nitrates (NO3-) → lead to algal blooms
3. Cars & power plants emit NO2 into the air → leads to the formation of ozone (O3) that accumulates in the troposphere (“bad” ozone). This contributes to global warming and is a harmful gas.

Question 39

Explain the water (hydrologic) cycle

Answer 39

It begins with evaporation, where solar energy causes water from oceans, lakes, and rivers to change from liquid to vapor. Plants also contribute through transpiration, releasing water vapor from their leaves. This water vapor rises, cools, and condenses into droplets, forming clouds in a process called condensation. When these droplets grow large enough, they fall to Earth as precipitation—rain, snow, sleet, or hail. Precipitated water can infiltrate the soil through infiltration, recharging underground aquifers in a process known as percolation. Some water flows over the land as surface runoff, returning to rivers, lakes, and oceans. Meanwhile, water stored as ice or snow can enter the cycle through sublimation (direct change from solid to vapor) or melting into liquid water. This cycle, driven by solar energy and gravity, ensures the distribution and renewal of Earth’s water supply.

Question 40

What are the anthropogenic impacts on the hydrologic (water) cycle?

Answer 40

1. Deforestation
   Reduce transpiration from plants → More runoff → erosion
2. Paving over land surfaces
   Water is less likely to permeate through the soil in that particular area → increases runoff & erosion

Question 41

Why do livings things need phosphorus?

Answer 41

Phosphorus is needed to form:
- DNA
- Cell membranes (phospholipid bilayer!)
- Bones and teeth

Question 42

Why is phosphorus a limiting factor in plant growth?

Answer 42

Phosphorus doesn’t cycle in the air so it takes longer for plants and animals to access it via the water and soil.
Found in nature as PO4-3 (phosphate) in a mineral called apatite

Question 43

How does phosphorus cycle in the lithosphere & biosphere?

Answer 43

1. Weathering of rocks leaches out PO4-3 (phosphate)
2. Plants and animals assimilate PO4-3 They die & decomposers release the PO4-3 back into the soil
3. Animal excretions (ex: guano from birds and bats) contain phosphate that returns to the soil

lithosphere = earth’s crust and biosphere = where life exists

Question 44

How does phosphorus cycle in the hydrosphere?

Answer 44

1. Weathering/erosion causes leaching of phosphate into streams/rivers.
2. Aquatic plants and phytoplankton assimilate the phosphate and the cycle continues.

hydrosphere = water bodies

Question 45

Explain the Phosphorus Cycle

Answer 45

1: Weathering of Rocks
Phosphorus begins in rocks and minerals as phosphate ions (PO₄³⁻). Through weathering caused by rain, wind, and other natural forces, phosphate is released into soil and water.
2: Absorption by Plants
Plants absorb phosphate ions from the soil through their roots. Phosphorus is an essential nutrient for plants, forming part of DNA, RNA, and ATP (energy molecules). Plants take up available phosphate (not phosphorus) dissolved in soil water. Phosphorus is stable and insoluble (cannot be taken up by plants).
3. Movement Through the Food Chain
Phosphorus moves through the food chain as herbivores eat plants and carnivores eat herbivores. It becomes part of their body structures, such as bones and teeth, and their metabolic processes.
4. Return to Soil and Water
When plants, animals, and other organisms die, decomposers (bacteria and fungi) break down their organic material, returning phosphorus to the soil.
5. Leaching and Runoff
Excess phosphorus in the soil can dissolvfe in water and be carried away to nearby water bodies through runoff.
6. Sedimentation in Water Bodies
Phosphorus settles at the bottom of water bodies, becoming part of sediment.
7. Geological Uplift
Over millions of years, geological processes lift phosphate-rich sedimentary rocks back to the Earth’s surface. Tectonic activity exposes these rocks to weathering, restarting the phosphorus cycle.

Question 46

What are the anthropogenic impacts on the phosphorus cycle?

Answer 46

1. Using synthetic fertilizers adds phosphates (PO4-3) to an ecosystem when they runoff into bodies of water
   → lead to algal blooms
   Fertilizers are NOT the same as pesticides!
2. Discharging animal waste/untreated sewage into bodies of water adds phosphates (PO4-3)

Question 47

Tundra

Answer 47

• Location: 60° to 75° North (Arctic tundra). Areas below the ice caps in the Arctic; tend to be present in mountainous areas in North America, Europe, and Siberia
• Climate: Tundras have low precipitation which makes them similar to a desert Extremely cold temperatures in the winter, but can warm up in the summer
• Soil Fertility: Low; tundras have short growing seasons and a large amount of frost which makes it difficult for plants to grow; however, certain species such as lichens and mosses are able to withstand the temperatures in a tundra. The permafrost covers the ground under the surface which leaves little space for species to grow.
• General Plant Adaptions: Small, low-growing plants like mosses and lichens conserve heat. Many plants grow in clumps for protection against cold.
• General Animal Adaptions: Thick fur or fat layers (e.g., polar bears, caribou). Migration and hibernation are common strategies.
• Anthropogenic Effects:
  1. Removal of permafrost: rising temperatures is decreasing the amount of permafrost in the ground which releases carbon dioxide and methane that contribute to overall global warming.
  2. Mining/Industrialization: the drilling of oil and gas in tundras leads to the deaths of animals in their habitats as well as the removal of vegetation which is vital for their survival.
  3. Hunting: a surge in the amount of caribou and foxes that are hunted ruins the balance of the ecosystem and leads to disrupted food webs which ultimately impact other animals in the environment.

Question 48

Tropical Rainforests

Answer 48

• Location: found between the latitudes 23.5°N and 23.5°S.
• Climate: The average temperature is approximately 25-30°C (77-86ºF) throughout the year.
• Soil Fertility: Nutrient-poor and non-fertile soil
• General Plant Adaptions: Broad leaves for capturing sunlight, drip tips to shed excess water, and buttress roots for stability in thin soils.
• General Animal Adaptions: High biodiversity with specialized traits like prehensile tails (monkeys), camouflage (tree frogs), or symbiosis (ants and acacia trees).
• Anthropogenic Effects: Deforestation for agriculture, logging, and mining reduces biodiversity and increases carbon emissions.

Question 49

Coral Reefs

Answer 49

• Location: 30° North to 30° South (tropical and subtropical waters).
• Climate: Warm, stable water temperatures (18-29°C) with lots of sunlight. Water is typically clear and nutrient-poor.
• Soil Fertility: N/A; relies on nutrient cycling within the water. Surrounding water is typically nutrient-poor.
• General Plant Adaptations: Symbiotic algae (zooxanthellae) live in coral tissues, providing energy through photosynthesis.
• General Animal Adaptations: Bright coloration for communication and camouflage; mutualism between species (e.g., clownfish and anemones).
• Anthropogenic Effects: Coral bleaching due to warming oceans, overfishing, and pollution (especially plastic and runoff from agriculture).

Question 50

Wetlands

Answer 50

• Location: Found at all latitudes except Antarctica.
• Climate: Varies by location. Tropical wetlands are warm and humid, while temperate wetlands experience seasonal temperature changes. Rainfall varies but is typically abundant to maintain waterlogged conditions.
• Soil Fertility: Generally rich in nutrients; supports diverse plant life. Anaerobic conditions in waterlogged soils can slow decomposition.
• General Plant Adaptations: Aerenchyma tissue in roots and stems helps transport oxygen in waterlogged conditions. Floating leaves (e.g., water lilies) aid photosynthesis.
• General Animal Adaptations: Amphibians (e.g., frogs) thrive in wet environments. Wading birds have long legs and beaks for foraging.
• Anthropogenic Effects: Drained for agriculture and urban development, pollution, and invasive species reduce their extent and biodiversity.

Question 51

Temperate Deciduous Forests

Answer 51

• Location: 30° to 50° North and South.
• Climate: Four distinct seasons with moderate temperatures. Warm summers (20-25°C) and cold winters (-1°C to 10°C). Precipitation is evenly distributed (75-150 cm/year).
• Soil Fertility: Moderate to high; decaying leaf litter enriches the soil with nutrients.
• General Plant Adaptations: Deciduous trees shed leaves in fall to conserve water during winter and regrow in spring for photosynthesis.
• General Animal Adaptations: Animals hibernate or migrate in winter. Many are generalists, capable of eating a variety of foods (e.g., bears, deer). Thick coat in winter that helps animals like deer stay warm, and a lighter coat in summer to keep cool.
• Anthropogenic Effects: Urbanization, deforestation, and pollution threaten habitats. Acid rain alters soil chemistry.