learning objectives 14

Question 1

What does ecosystem ecology include that community ecology does not?

Answer 1

Ecosystem ecology includes communities plus the abiotic environment (nutrients and energy). It focuses on the movement of energy, nutrients, and matter among the various community members and the environment.

Question 2

Why do nutrients cycle within ecosystems but energy flows through them?

Answer 2

Nutrients are reused and cycled continuously, whereas energy flows in one direction and is lost as heat. Energy must be replenished by the sun.

Question 3

Describe the process by which nutrients are made available to primary producers.

Answer 3

Decomposers break down detritus, releasing inorganic carbon (CO₂) and nutrients into the soil, making them available to plants. Sunlight and CO₂ are used by plants to create glucose.

Question 4

Define net primary production (NPP) and its importance.

Answer 4

NPP is the biomass/energy that primary producers generate minus what they use for cellular respiration. It measures the energy available for consumers in an ecosystem.

Question 5

Which areas have higher net primary production, and why?

Answer 5

Terrestrial ecosystems with warm, wet conditions have higher NPP because these conditions promote plant growth.

Question 6

Why is energy transfer inefficient within communities (trophic efficiency)?

Answer 6

Only about 10% of energy at one trophic level is transferred to the next, while 90% is lost as heat. This limits the length of food chains (usually fewer than 6 links).

Question 7

How does trophic inefficiency affect biomass at each trophic level?

Answer 7

Biomass decreases at higher trophic levels due to energy loss. This is why there are fewer predators compared to plants and herbivores.

Question 8

How is trophic inefficiency relevant to human diet choices?

Answer 8

Eating lower on the food chain (e.g., plants) is more energy-efficient than consuming animals, as more plant biomass is needed to support animal growth.

Question 9

Describe the major processes in the water cycle.

Answer 9

Evaporation (water moves to the atmosphere), condensation (cloud formation), and precipitation (rain). The water cycle is solar-powered.

Question 9

What is the major reservoir of nitrogen, and how does it enter biological pathways?

Answer 9

The major reservoir is atmospheric N₂. Nitrogen enters biological pathways through nitrogen fixation by bacteria, often in association with legumes.

Question 10

How have human activities influenced the nitrogen cycle?

Answer 10

Human activities, such as nitrogenous runoff, have created dead zones in coastal areas by increasing algae populations, leading to oxygen depletion and ecosystem collapse.

Question 12

Describe the carbon cycle and how carbon gets into the atmosphere.

Answer 12

Carbon enters the atmosphere as CO₂ through respiration, combustion, volcanic eruptions, and decomposition. It moves to primary producers through photosynthesis and then to consumers and decomposers.

Question 13

How do humans affect the balance of the carbon cycle?

Answer 13

Burning fossil fuels adds CO₂ to the atmosphere, and deforestation increases atmospheric carbon by reducing trees that absorb CO₂ and by releasing stored carbon.

Question 14

What causes ocean acidification, and how does it affect marine life?

Answer 14

Increased CO₂ in the atmosphere dissolves into oceans, making them 30% more acidic. This harms corals, seashells, and marine ecosystems, leading to declines in fish populations

Question 15

How do greenhouse gases like CO₂ increase Earth’s temperature?

Answer 15

Greenhouse gases absorb infrared radiation emitted by Earth’s surface, trapping heat and warming the planet. This is the greenhouse effect.

Question 16

How does climate change affect sea levels, glaciers, diseases, wildfires, and extreme weather?

Answer 16

Climate change causes sea level rise, glacier melting, disease spread (e.g., mosquito-borne illnesses), more wildfires, and increased extreme weather events like hurricanes and droughts.

Question 17

Give two examples of harmful effects from the 1.1°C warming already observed.

Answer 17

1. Spread of diseases like dengue fever and Lyme disease.
2. More extreme weather events like hurricanes and droughts.

Question 18

What is one way people are reducing carbon emissions?

Answer 18

Actions include driving electric cars, eating vegetarian or vegan diets, reducing air travel, and recycling. The Paris Climate Agreement and initiatives like the UCSD Green New Deal aim to reduce fossil fuel use.