Topic 4 Ecology: Human Impact on Biosphere

Question 1

• The burning of fossil fuels, deforestation, factory emissions, cars, etc., increases CO2 in the atmosphere. This causes more heat to be trapped and increases the greenhouse effect. Normally, the greenhouse effect is a good thing for maintaining heat on Earth, but the large increase of CO2 emissions is overkill for the greenhouse effect. Thus, global temperature rises, which raises the sea level by melting ice. Agriculture output is also decreased by affected weather patterns. Greenhouse gases include methane, CO2, ozone, and CFC’s, which all cause heat to build up in the lower atmospheres.

Answer 1

Global Climate Change

Question 2

• O3 is ozone, which absorbs UV radiation. This prevents excess UV from reaching the surface of the earth. CFCs (chlorofluorocarbons) enter the upper atmosphere and break down O3. Normally, ozone quickly reforms as it is split by sunlight. Formation of the ozone layer allowed land colonization since organisms no longer needed water to shield them from damaging UV rays.

Answer 2

Ozone Depletion

Question 3

• The burning of fossil fuels (e.g., coal) releases SO2 and NO2 into the air. When these compounds react with water vapor, sulfuric acid and nitric acid (H2SO4 and HNO3) is created. This acid then rains back down on earth and can kill plants and animals.

Answer 3

Acid Rain

Question 4

• Overgrazing of grasslands that border deserts transforms the grasslands into deserts. Agricultural output decreases, or habitats available to native species are lost.

Answer 4

Desertification

Question 5

• The clear-cutting of forests causes erosion, flooding, and changes in weather patterns. Additionally, the slash and burn method of clearing tropical rain forests increases CO2, which increases the greenhouse effect. Nutrients in the soil are destroyed as well.

Answer 5

Deforestation

Question 6

• Air, water, and land pollution contaminate materials essential to life. Many pollutants remain in the environment for decades. Eutrophication is the process of nutrient enrichment in lakes, which causes subsequent increases in biomass. Lakes polluted with fertilizer runoff have abundant nutrients, especially phosphates. This stimulates algal blooms, which are massive algae/ phytoplankton patches of growth. These blooms respire and deplete oxygen. When the blooms breakdown, detritivorous bacteria deplete even more oxygen. Thus, many animals die of oxygen starvation, and the lakes fill with carcasses of dead animals and plants. Note that phytoplankton does photosynthesis, but at night they reduce oxygen when they respire, and the detritivores continue to multiply as organisms die. This further decreases O2. Phytoplankton are autotrophic organisms that float near the surface of oceans, lakes, and ponds. Eutrophication occurs naturally but human influence accelerates it, leading to an imbalance. Critical load is the amount of added nutrient, usually nitrogen or phosphorous, that can be absorbed by plants without damaging the ecosystem integrity. When the critical load is exceeded, the runoff overwhelms and leaches into other ecosystems, creating the above problem.

Answer 6

Pollution

Question 7

• This is a result of human activities, especially with regards to the destruction of their habitats.

Answer 7

Reduction in Species Diversity

Question 8

• New species can be moved intentionally or accidentally by humans. This can disrupt a new community because the invasive species preys on native organisms. The invasive species can outcompete native organisms for resources as well. For example, when killer honeybees were introduced, they stung and killed people. Another invasive species, zebra mussels, outcompeted original residents.

Answer 8

Introduction of New Species

Question 9

• Pesticides are effective but are dangerous to humans. Biological control alternatives are safer. These alternatives include crop rotation, natural enemies, or insect birth control.

Answer 9

Pesticides vs. Biological Control

Question 10

• As one organism eats another, toxins (e.g., pesticide) become more concentrated at each higher trophic level. This is biological magnification. Toxins include antibiotics, hormones, carcinogens, teratogens (causes birth defects), which can all get into the food chain and cause biomagnification.

Answer 10

Biological Magnification

Question 11

• Using organisms to detoxify a polluted ecosystem.

Answer 11

Bioremediation

Question 12

• Using organisms to add essential materials to a degraded ecosystem.

Answer 12

Biological Augmentation

Question 13

• Biodiversity has three levels. Endangered species are in danger of extinction, and threatened species are considered likely to become endangered soon. A biological hotspot is a small area with numerous endemic species and a large number of endangered and threatened species.

Answer 13

Note

Question 14

• A small population size leads to inbreeding, and genetic drift has a significant effect. The loss of genetic variability leads to reduced fitness and lower survivability. To avoid this situation, a population must sustain itself at the minimum viable population. If the populations drops too low, it can cause an extinction vortex.

Answer 14

Extinction Vortex

Question 15

• Are events (e.g., storm, flood, drought, human activity) that change communities by removing organisms or altering resource availability.

Answer 15

Disturbances

Question 16

• Human activities lead to increases of acidity in the ocean. Edges are boundaries between ecosystems. Human alterations can increase edges, which have reduced biodiversity overall, and create imbalances that favor edge-adapted species. This leads to fragmentation. In fragmented habitats, movement corridors (small habitat clumps/strips connecting otherwise isolated patches) are important for conserving biodiversity. Movement corridors can be created artificially, such as bridge tunnels that let animals cross without getting hit by cars.

Answer 16

Ocean Acidification

Question 17

• Suggests that low to moderate levels of disturbances actually increase species diversity, while high levels of disturbances reduce diversity.

Answer 17

Intermediate Disturbance Hypothesis

Question 18

• Translocation of a species to a favorable habitat beyond its native range to protect it from human-caused threats.

Answer 18

Assisted Migration

Question 19

• These are areas of dry land that form on the leeward side (downwind) of a high mountain. Rain clouds approach a mountain range and thus rise in elevation. The surrounding air becomes cooler, and the dew point is eventually reached. The dew point is the temperature that air must be cooled at to become saturated with water vapor. When the air is further cooled, water vapor will condense to form dew (liquid water). After the dew point is reached, precipitation occurs as the clouds gain precipitation and continue to rain towards the peak of the mountain. As the clouds begin to descend down the leeward side of the mountain, there is a decrease in elevation and an increase in air temperature. Precipitation decreases and causes a dry rain shadow (desert biome). Rain shadows can occur in the high mountains of Europe and even the Andes of South America.

Answer 19

Rain Shadows