Chapter 12 - Ecosystems

Question 1

What is the definition of an ecosystem?

Answer 1

The interactions between a community (biotic) and the abiotic factors of the environment.

Question 2

What are the two things an ecosystem needs?

Answer 2

Energy (solar, chemical, etc.),

Matter (H2O, P, N, C, etc.).

Question 3

How does energy enter and leave the system?

Answer 3

Energy usually enters the food chain as solar energy through photosynthesis, and leaves the system as heat radiation.

Question 4

What is biomass?

Answer 4

The total mass of organisms in a given volume or area.

Question 5

What are the different trophic levels in a food chain?

Answer 5

Producers (do photosynthesis), herbivores (eat producers), 1st degree carnivores (eat herbivores), 2nd degree carnivores (eat 1st degree).

There are also detrivores which eat dead matter.

Question 6

What are decomposers?

What are detrivores?

Answer 6

Decomposers break down non-living organic molecules into smaller molecules, examples are most fungi.

Detrivores feed on dead organic matter.

Question 7

What are trophic cascades?

Answer 7

When there is a disturbance in the ecosystem that affects many organisms. They usually start at the top of the food chain.

Question 8

What is biomagnification?

Answer 8

It is best described by an example.

If toxins are present in small amounts in plants, they will be present in even larger amounts in primary consumers, as they will eat many many plants. Then, those who eat primary consumers don’t just consume one, and so the toxin concentration magnifies as we go up in the food chain.

The definition is as follows:

Substances that are stored in tissues, such as mercury and organic pesticides, get concentrated in the tissues of animals that are higher up the food chain.

Remember that microplastics do not themselves biomagnify, but they absorb toxins that do.

Question 9

What are the two main nitrogen fixing bacteria?

What do they do?

Answer 9

Cyanobacteria and rhyzobium.

They convert N₂ from the atmosphere to NH₃ and NH₄⁺.

Question 10

What is the main denitrifying bacteria seen in class?

What do denitrifying bacteria do?

Answer 10

Pseudomonas.

Denitrifying bacteria remove nitrogen from the soil, as they use it as a source of energy. They eventually release nitrogen in the atmosphere.

Question 11

What are the nitrifying bacteria in the nitrogen cycle (must include these when drawing the N cycle).

What do these do?

Answer 11

Nitrosomonas and nitrobacter.

They take the NH₃ or NH₄⁺ from the nitrogen fixing bacteria and convert it to NO₂^- and NO_{<span>3</span>}^-.

Question 12

What is nitrogen used for in our bodies?

Answer 12

It is used to make proteins (NH₂ bonded to C) and DNA (in the base attached to the sugar).

Question 13

How do plants cope in low Nitrogen soil?

Answer 13

Some plants become carnivorous, others come to have nitrogen fixing bacteria in their roots.

Question 14

What is another source of nitrogen fixation (other than bacteria)

Answer 14

Lightning.

There are also human sources, such as nitrogen fixing crops, nitrogen fertilizer and fossil fuels.

Question 15

What is an oligotrophic lake?

Answer 15

Oligotrophy is the opposite of eutrophy. These lakes would have low N and P concentrations, which results in a high oxygen concentration, which is good for fish and other forms of life.

Question 16

Describe the phosphorous cycle.

Answer 16

First, through weathering, phosphrous is washed away from rocks into the soil. Then, leaching brings phosphates from the soil into the water, where it sediments at the bottom to form rocks.

An alternate path is from the phosphates in the soil, which are absorbed in the plants, assimilated into the herbivores and carnivores, all 3 of which excrete it in the form of feces and death in the form of dead biomass. From this dead biomass the phosphates go back into the soil.

Question 17

What did the Hubbard Brook experiment prove?

Answer 17

It prooved the importance of trees in the prevention of flooding, erosion and eutrophication.

Question 18

Describe the water cycle.

Answer 18

Gaseous water in the atmosphere condensates and precipitates, going into lakes, rivers, the ground, and oceans. From there, it evaporates back into the atmosphere. Water is also made into the gas form by the transpiration of plants and animals.

Question 19

Describe the carbon cycle.

Answer 19

CO₂ from the atmosphere is converted into energy by plants as they do photosynthesis. From the plants, it is assimilated to herbivores and carnivores, which with the plants do cellular respiration, putting CO₂ directly back into the atmosphere. Another method in which CO₂ is brought back into the atmosphere is through death, excretion and feces of plants, herbivores and carnivores, where are taken up by decomposers, who do cellular respiration, and converted into fossil fuels, which are burned up to release their CO₂.

Question 20

How does acid rain occur?

Answer 20

Acid rain is created from the sulfur emissions from industries. They kill many organisms.

Question 21

What are the greenhouse gases?

Answer 21

Carbon dioxide, methane, nitrous oxide and ozone.