Unit 4-Biochemical Cycles

Question 1

Nutrient Cycles/Biogeochemical Cycles:

Answer 1

• Movement of nutrients through ecosystems
• Processes involved are biological, geological, chemical, and physical
• Materials travel through the atmosphere, hydrosphere, and geosphere from one organism to another in dynamic equilibrium
After death, nutrients in the body spread widely through the physical environment, being incorporated by an untold number of organisms far into the future

Question 2

Reservoir:

Answer 2

Nutrients and other materials (including toxins) move from one pool or reservoir to another

Question 3

Residence Time:

Answer 3

• Amount of tie nutrients remain in each reservoir
• Vary depending on the substance
i.e. average residence time for an atom of carbon in the human body is longer than the residence time in a blade of grass

Question 4

Flux:

Answer 4

• Movement of materials among reservoirs
• Fluxes are rates, stated in terms of mass or volume of material moving among reservoirs per unit of time
• Flux of a material between reservoirs can change over time
• Humans have influenced fluxes
○ Increased flux of nitrogen from atmosphere to terrestrial reservoirs
Shifted flux of carbon from terrestrial reservoirs to atmosphere

Question 5

Sources:

Answer 5

Reservoirs that release more nutrients than they accept

Question 6

Sinks:

Answer 6

• Reservoirs that accept more nutrients than they release

* Carbon sinks are important today- want to lower rate at which carbon is released into the atmosphere

Question 7

Turnover Time:

Answer 7

○ Time it would take for all atoms of a particular material to be flushed through a particular reservoir
○ Function of the balance between fluxes into the reservoir from a source and fluxes out of a reservoir to a sink
○ If input of material was stopped, turnover time would be the amount of time it would take for material to be completely flushed out of the system
Depends on processes that influence residence time of the material (might hold or bind to material or cause it to be flushed out more rapidly)

Question 8

Synergism

Answer 8

○ Combination of 2 or more chemicals is likely to lead to a great effect than each chemical alone
Chemicals leaching from older landfills may become new and different chemicals, making them hard to identify

Question 9

Carrying Capacity:

Answer 9

• Environmental resistance from limiting factors determines the maximum population size of a species that a given environment can sustain
Can change (forest fires decrease carrying capacities for most species, but increase carrying capacities for species that benefit from fire)

Question 10

Cultural Carrying Capacity:

Answer 10

• Number of people an area can support given the prevailing technology
Implies ecological, technological social, and political components

Question 11

Logistic Growth Curve:

Answer 11

• Rises sharply and levels off as the effects of limiting factors becomes stronger (reaches asymptote)

Question 12

Density Dependent Factors:

Answer 12

• Limiting factors whose influence changes according to population density
i.e. high density makes it easier for organisms to find mates, but also increase competition and risk of disease

Question 13

Density Independent Factors:

Answer 13

• Limiting factors whose influence is not affected by population density
i.e. temperature extremes and catastrophic events

Question 14

Biotic Potential:

Answer 14

• Maximum capacity to produce offspring under ideal environmental conditions
• Fish with short gestation period that lays thousands of eggs at a time has high biotic potential
• Whale with a long gestation period that gives birth to a single calf has a low biotic potential
Interaction between an organism’s biotic potential and environmental resistance to population growth determines the fate of its population

Question 15

K-Selected/K-Strategists:

Answer 15

• Organisms that have long gestation periods and have small number of offspring, but compensate by dedicating large amounts of time and energy to care for and protect their young
i.e. giraffes, humans, whales..etc

Question 16

R-Selected Organisms:

Answer 16

• High biotic potential, devote energy and resources to producing as many offspring as possible in a short amount of time
• Offspring do not require parental care after birth, parents often leave survival of offspring to chance
• R- rate at which a population increases in the absence of limiting factors
• Population sizes fluctuate greatly, and are often below carrying capacity
• Natural selection favours traits that leads to rapid population growth
i.e. fish, plants, insects

Question 17

Community:

Answer 17

• Group of population of organisms that live in the same place at the same time
Members interact with one another, direct interactions among species often have indirect effects as they ripple out and affect other members

Question 18

Detritivores

Answer 18

○ Consume nonliving organic matter
○ Consume waste products or dead bodies of other community members
i.e. millipedes and soil insects

Question 19

Decomposers

Answer 19

○ Consume nonliving organic matter
○ Break down leaf litter and nonliving matter into simpler constituents that can be taken up and used by plants
Create nutrients from organic matter available for reuse by living members of the community

Question 20

Resistance

Answer 20

Community that resists change and remains stable despite disturbance

Question 21

Resilience

Answer 21

Community changes in response to disturbance but later returns to its original state

Question 22

Biomes:

Answer 22

• Major regional complex of similar communities

Recognized primarily by its dominant plant type and vegetation structure

Question 23

Ecoregion:

Answer 23

• Large area of land or water that contains a geographically distinct assembly of natural communities that share a large majority of their species and ecological dynamics, share similar environmental conditions, and interact ecologically in ways that are critical for their survival
• Often confused with biome
i.e. Desert biome has several representatives, such as the Sahara Desert, which is part of an ecoregion, with its own particular characteristics and flora, but is still consistent with characteristics of the desert biome