Chapter 24

Question 1

Ecosystem

Answer 1

Organisms + physical and chemical environment

Question 2

Ecology

Answer 2

The study of ecosystems and how humans interact with the world

Question 3

Food web

Answer 3

The various interconnecting paths of energy flow

Question 4

Biomass

Answer 4

Biomass is the mass of living organisms and is measured by grams per meter squared

Question 5

Biomes

Answer 5

Biomes are distinctive major types of earthly ecosystems

Two types of biomes:

1. Aquatic
2. Terrestrial

Question 6

Biotic and abiotic factors

Answer 6

Biotic: All the living organisms that survive within an ecosystem
Example: All living things

Abiotic: Doesn’t include living organisms
Example: Soil, Water, Weather

Question 7

Trophic levels

Answer 7

Autotrophs: Use inorganic molecules as well as solar energy to derive organic molecules. Known as producers
Example: Diatoms, Trees

Heterotrophs: Cannot create their own organic molecules, and instead need to obtain organic nutrients from other sources. Known as consumers.
Types of heterotrophs:
Herbivores: Caterpillar, Rabbit
Carnivores: Snake, Hawk
Omnivores: Humans

Detritivores: Derive their organic material from feeding off of decomposing organic matter
Example: Bacteria, Mushrooms

Question 8

Energy & Nutrient flow in an ecosystem

Answer 8

Energy flow: Can be represented by the food web or food chain. Energy can be transmitted through the consumption of another organism

Nutrient flow:

Question 9

Water cycle

Answer 9

Evaporation: The sun causes water to evaporate from seawater

Transpiration: Evaporation from plants

Condensation: Evaporated water gases become liquid again

Precipitation: The condensed water falls over the ocean and land

Human impact: Runoff and pollution. Runoff is caused by humans removing plants. This causes the ground to be incapable of absorbing the water, so that area is unfarmable and depleted of nutrients.

Question 10

Carbon cycle

Answer 10

1. Respiration: Plants and animals exhale CO2 into the atmosphere
2. Decay: Dead organisms decay and that CO2 goes into the atmosphere
3. Bicarbonate is converted into CO2
4. Photosynthesis: Plants photosynthesize CO2 into carbon molecules
5. Diffusion: Some of the CO2 diffuses into the ocean and is converted into bicarbonate

Human impact: Humans burn fossil fuels which creates too much CO2.

Question 11

Nitrogen cycle

Answer 11

Nitrogen makes up approximately 78% of the atmosphere in a form that is unusable by plants. As a result of this, nitrogen can be a nutrient that limits the amount of growth in an ecosystem.

1. Nitrogen fixation: Nitrogen gas is converted to ammonium, a form that plants can use
2. Nitrification: Nitrogen gas is converted to nitrate in the atmosphere, where high energy is available for nitrogen to react with oxygen. This energy may be supplied by cosmic radiation, meteor trails, or lightning. Ammonium in the soil from various sources, including decomposition of organisms and animal wastes, is converted to nitrate by soil bacteria. Nitrate-producing bacteria convert ammonium to nitrate. Nitrate-producing bacteria convert nitrite to nitrate
3. Denitrification: The conversion of nitrate back to nitrogen gas, which then enters the atmosphere

Human Impact: Humans alter the transfer rates in the nitrogen cycle by producing fertilizers from N2. This nearly doubles the fixation rate.

Question 12

Phosphorus cycle

Answer 12

1. The phosphorus trapped in oceanic sediments moves onto land after a geological upheaval
2. Once on land, the slow weathering of rocks moves the phosphate ions into the soil.
3. Some of this soil becomes available to plants which cerates many different molecules
4. Some phosphate runs off into aquatic ecosystems enabling the algae to acquire it before it becomes trapped in sediments.
5. The Phosphate in marine sediments will not become available to producers on land until another geological upheaval exposes the sedimentary rocks on land, allowing the cycle to begin again.

Human impact: Humans mining phosphate ores can lead to excessive levels of phosphates in the environment.

Question 13

The relationship between CO2 and climate change

Answer 13

CO2 creates a barrier in the atmosphere. This becomes problematic because light and heat can come in the greenhouse gases, but can’t go back out as easily, meaning more is coming than leaving, so the earth is slowly heating up.