Agriculture

Question 1

Explain how basic principles of energy flow and chemical cycling apply to agricultural ecosystems?

Answer 1

Harvesting removes chemical nutrients from the system.

Nutrient regeneration is critical for long-term productivity.

Question 2

Agricultural ecosystems have complex food webs, what interactions increase and decrease crop yield?

Answer 2

Some interactions increase crop yield (pollination, predation, parasitism).

Some interactions reduce crop yield (herbivory, competition, disease).

Question 3

Complex interaction networks can give rise to indirect effects. Give two examples:

Answer 3

Weeds may provide food for pollinators.

Pest insects may help maintain populations of predators.

Question 4

When and where was agriculture invented?

Answer 4

In several places during the early to mid Holocene.

Question 5

What was probably the earliest farming?

Answer 5

Shifting cultivation

Question 6

The amount of food produced by farming can be increased in two ways?

Answer 6

• Extension = increasing the area
under cultivation.

• Intensification = increasing the
yield per cultivated hectare.

Question 7

Benefit of traditional farming is its ability to support up to 10,000 more people in an area than hunting and gathering. But!

Answer 7

Traditional farming is very labour-intensive. 80-90% of the population is directly involved in farming, and the standard of living is at a basic subsistence level.

Question 8

How is modern farming different from traditional farming?

Answer 8

More productive and less labour-intensive, by substituting fossil fuels and machinery for human and animal power,

Question 9

High-yield crop varieties produce more food per plant, what qualities do they have and what are the most important food for increasing global food supply?

Answer 9

• Shorter, less vegetative growth
• More grain (seeds) produced per plant
• Require high levels of water and fertilizer for maximum yield

High-yield grains such as corn, wheat, and rice.

Question 10

The Green Revolution?

Answer 10

A deliberate effort to introduce modern agricultural practices to other parts of the world after 1950. Modern agriculture developed initially in Europe, North America, and Australia.

Question 11

As a result of the Green Revolution, how much did the food increase in 1960?

Answer 11

Production of most food crops increased faster than population after 1960 and undernutrition has declined.

Question 12

Where does crop yield still remain low?

Answer 12

Saharan Africa remained low through the end of the 20th century.

Question 13

The spread of modern industrial agriculture led to an increased use of?

Answer 13

rapid increases in water, fertilizer, and pesticide use.

Question 14

Where are the largest environmental impacts of modern agriculture from?

Answer 14

Irrigation, fertilizers, and deforestation.

Question 15

Mechanical plowing, seeding, and harvesting has what consequence on the soil?

Answer 15

Disrupt soil structure and lead to soil erosion.

But there are many ways to reduce soil erosion.

(The world loses almost 2.5 tons of soil per hectare of cultivated land each year.)

Question 16

Why are most industrial irrigation systems are inefficient? And what is a better alternative?

Answer 16

They are designed to maximize the amount of water available to crops, but much of the water is lost to evaporation.
More efficient systems such as drip irrigation deliver water precisely to where it is needed, avoiding unnecessary evaporation.

Question 17

What does inefficient irrigation in dry areas lead to?

Answer 17

Salinization.
Water dissolves mineral salts in the soil. When the water evaporates, salts are drawn to the surface.
Salinized soil can be toxic to plants

Question 18

What is the most important mineral nutrient for plant growth?

Answer 18

Nitrogen (N)
Phosphorus (P)
Potassium (K)

Nitrogen is needed in the largest amounts and is the slowest to replenish.
Nitrogen is a critical element for all living things because it is needed to make protein and DNA.

Question 19

Plants require fixed nitrogen in the from of?

Answer 19

ammonium NH4 or nitrate NO3

Question 20

Who perform most natural nitrogen fixation and where can they be found?

Answer 20

N-fixing bacteria. 
Found in three places:
Free-living in water 
Free-living in soil
As endosymbionts in root nodules of some plants, mostly in the pea family (legumes).

Question 21

Ahat is the Haber- Bosch process (Detonator of the population explosion)? And how much do we use it?

Answer 21

An industrial process for producing fixed nitrogen.

We now produce more fixed N through this process than all natural sources combined.

Question 22

What does applying more fixed N to crops then they can utilize result in?

Answer 22

Excess N is washed off the fields and into rivers as runoff.
N eventually accumulates in lakes and coastal oceans, leading to the formation of dead zones.
Excess fertilization also contributes to air and groundwater pollution.

Question 23

Some species are considered pests if they reduce yields, what des pests include?

Answer 23

Weeds (other plants that compete with crops for light, water, and nutrients), herbivores, and pathogens (mostly fungi and viruses).

Question 24

What happens without crop protection? + solution

Answer 24

Most of a crop is often lost to pests.

Synthetic chemical pesticides came into use after World War II and have become an integral part of modern agriculture.

Question 25

How are never synthetic chemical pesticides better than the old ones?

Answer 25

Less toxic and persistent, and are applied at lower rates.

Question 26

What does the repeated application of pesticides lead to?

Answer 26

The evolution of resistance.

A good example of natural selection – most populations already contain resistant genetic variants, but they only become common after selection is imposed, in this case by the application of a pesticide.

Question 27

Why are we constantly developing new pesticides?

Answer 27

To keep up with the evolution of resistant pest populations.

Question 28

Pesticides also kill non-target organisms, like?

Answer 28

Beneficial species such as predators and pollinators.

Question 29

Integrated pest management (IPM)?

Answer 29

Uses a variety of techniques to control pests and increase the diversity of beneficial organisms.

Question 30

Genetic engineering or the production of genetically modified organisms (GMOs)?

Answer 30

Has become a common and controversial part of modern agriculture.
Genetic engineering most commonly involves moving genetic material from one species to another.

Question 31

Roundup Ready?

Answer 31

Trademark for its patented crops genetically modified to be resistant to the herbicide Roundup

Question 32

What happends when affluence increases?

Answer 32

People shift to a diet higher in meat and seafood.

Question 33

What are many of the impacts of meat-eating are related to?

Answer 33

Low trophic efficiency of most ecosystems.

A.K.A The same area of cropland can support many more vegetarians than meat-eaters.

Question 34

What does lower trophic efficiency lead to?

Answer 34

Higher requirements for land and water, and higher greenhouse gas emissions.