Chapter 14 - Ecology of Human Populations

Question 1

What are the pros/cons of 2/3 of the global pop living in urban areas by 2050?

Answer 1

pros: could ease GHG emissions per capita (less car driving)
cons: cities require land and so they must take away from natural areas to get this land

Question 2

What is the root of most environmental problems?

Answer 2

The large, growing global population because more people means an increased requirement for energy and resources

Question 3

What is a demographic transition?

Answer 3

It is the switch form high birth and death rates to low birth and death rates.

ex. after baby boomers

Question 4

Why has a demographic transition from high to low occurred?

Answer 4

B/c medical advances reduce death rates while personal choices reduce birth rate (voluntary). Important with the assumption of a global carrying capacity

Question 5

What are emerging infectious diseases?

Answer 5

They are diseases appearing in the human population for the first time or expanding rapidly in incidence or geographic range (must faster than environmental change).

ex. HIV, ebola, SARS, lyme disease

Question 6

What are most emerging infectious diseases classified as?

Answer 6

Most are zoonoses, meaning they are infections that circulate naturally in non-human vertebrate hosts, but they can be transmitted to humans

Question 7

What is a pest species?

Answer 7

It is a species that humans consider undesirable, usually because it harms us directly or damages/competes with crops. Essentially, it is any species causing economic damage

Question 8

What is economic injury level (EIL)?

Answer 8

It is the point in pest control in which further reduction would cost more than would be gained in improved yield. Therefore, total eradication is never profitable

Question 9

What is monoculture?

Answer 9

It is when a single species is farmed in dense pops, which often increases the pest problem

Question 10

What is the main approach to pest control?

Answer 10

Mainly different kinds of pesticides

Question 11

What is a pesticide? What are the types?

Answer 11

It is a chemical used to control pests and was developed with increased use in synthetic N fertilizers

1. herbicides - targets weeds
2. insecticides - targets insects
3. fungicides - targets fungi

Question 12

What is bioaccumulation?

Answer 12

It is an environmental issue often caused by pesticides because it occurs when a pesticide is present in an organism that becomes the prey of another and the predator fails to excrete/metabolize the pesticide, causing it to accumulate in the predators body.

ex. tuna is at the top of the food chain because it is a longer living species, meaning it has longer to accumulate more mercury

Question 13

What is biomagnification?

Answer 13

It is an environmental issue often caused by pesticides because when a pesticide is present in prey, there will be more present in predators and is magnified the most at the top of the food chain, which can be lethal.

ex. tuna is at the top of the food chain (K-selected species) so it will have the most mercury

Question 14

What is target pest resurgence?

Answer 14

It occurs when treatment kills a large number of pests and its natural enemy, which causes surviving pests to find themselves with fewer enemies and plentiful food, so the pop could explode

Question 15

What is resistance?

Answer 15

It is when pests become resistant to a pesticide, causing the pesticide to lose all value

Question 16

What is biological control?

Answer 16

It manipulates natural enemies of a pest to control it (is biologist decision-based). One form is importation biological control, which imports a known natural enemy from another location to help maintain low pest pops.

Question 17

What is integrated pest management (IPM)?

Answer 17

It is a practical philosophy of pest management combining physical control (keeping pests away), cultural control (rotating crops to avoid pest buildup), biological/chemical control, and using resistant crop varieties. This method uses pesticides sparingly.

Question 18

What is desertification?

Answer 18

It is when arid/semiarid land that has supported natural ecosystems gives way to desert (which can be slowed by irrigation, but that lowers the water table and accumulates salt in the soil - salinization). This often occurs on agricultural land

Question 19

What is salinization?

Answer 19

Agricultural land is also susceptible to this, which makes continued agriculture use as it spreads and leads to the expansion of sterile, white salt deserts

Question 20

What are biofuels?

Answer 20

They are sources of energy developed from biomass derived from agriculture/natural ecosystems. Liquid biofuels can substitute for gas/diesel, but currently does not supply much ethanol. Also, making ethanol is inefficient as it requires lots of land and energy, and causes air pollution while aggravating GHG emissions

Question 21

What is maximum sustainable yield (MSY)?

Answer 21

It is the highest number of new fish we could regularly remove from the population each year so that the pop can still replenish itself indefinitely. It can regularly be obtained through fixed quota and/or fixed effort - but is very theoretical, so its often not practical.

Look at graph in notes

Question 22

What are some problems with MSY?

Answer 22

1. Ignores all aspects of pop structure (size, age, growth, survival/reproductive rates)
2. Based on single recruitment curve, so it treats the environment as unvarying
3. It may be impossible to obtain a reliable MSY estimate
4. Achieving MSY isn’t the only, or even the best, criterion for successful harvesting management

Question 23

What is fixed quota?

Answer 23

It removes the same amount (MSY) from a pop each year. If a pop stayed at peak net recruitment, this could work, but it is not practical because if numbers fall below MSY, the species could go extinct

Question 24

What is fixed effort?

Answer 24

It is where the amount harvested increases with the size of the pop being harvested. If density drops below peak, the new recruitment exceeds the amount harvested and the pop can recover (reduces risk of extinction). However, yield varies with pop size (good & bad years), so no one can make a greater effort than they’re supposed to

Question 25

What is aquaculture?

Answer 25

It is the farming of domesticated fish, shellfish, and algae that occurs in coastal marine and freshwater ecosystems