Ecosystems

Question 1

What causes the largest loss of energy in food chains/webs ?

Answer 1

The process of cellular respiration

Question 2

Consumer

Answer 2

Any organism they can’t make it’s own food, has to eat producers or other consumers to survive

Question 3

Saprotroph

Answer 3

Organisms that live on non-living organic matter and release enzymes to absorb nutrients, ex: mushrooms and mold

Question 4

Autotroph

Answer 4

An organism that is able to form nutritional organic substances from simple inorganic substances like CO2, ex: algae

Question 5

Detritivore

Answer 5

An animal that feeds on detritus or humus via internal digestion, ex: crabs and snails

Question 6

Explain how energy enters, flows through and is lost from food chains/ food webs (and how this limits the number of trophic levels/ biomass at each trophic level).

Answer 6

Most ecosystems rely on a supply of energy from sunlight
Light energy is converted to chemical energy in carbon compounds by photosynthesis
Chemical energy in carbon compounds flows through food chains by means of feeding
Energy released from carbon compounds by respiration is used in living organisms and converted to heat
Living organisms cannot convert heat to other forms of energy
Heat is lost from ecosystems
Energy losses between trophic levels restrict the length of food chains and the biomass of higher trophic levels

Question 7

Outline the role of methanogenic archaens in the carbon cycle

Answer 7

Methanogenic archaeans are microorganisms that produce methane as a metabolic byproduct in anaerobic conditions

Methane produced will either accumulate underground (forming natural gas) or diffuse into the atmosphere

Question 8

Environmental conditions for peat formation

Answer 8

Acidic, waterlogged, aerobic/little oxygen

Question 9

Outline the formation of peat

Answer 9

In many soils, saprotrophic bacteria and fungi will decompose dead organisms and return nutrients to the soil for cycling
This decomposition process requires oxygen (cell respiration is required to fuel digestive reactions)
Waterlogged regions may lack oxygenated air spaces within the soil and thus possess anaerobic conditions
Anaerobic respiration by organisms in these regions produces organic acids (e.g. acetate), resulting in acidic conditions
Saprotrophic bacteria and fungi cannot function effectively in anaerobic / acidic conditions, preventing decomposition
Since the organic matter is not fully decomposed in waterlogged soils, carbon-rich molecules remain in the soil and form peat

Question 10

What are the most significant greenhouse gasses?

Answer 10

Water vapor and carbon dioxide

Question 11

Population

Answer 11

Group of organisms of the same species, living in the same area at the same time

Question 12

Community

Answer 12

A group of different populations living together and interacting in a given area

Question 13

Ecosystem

Answer 13

A community and also its environment (all biotic and abiotic factors)

Question 14

Outline the features of ecosystems that make them sustainable

Answer 14

Energy availability – light from the sun provides the initial energy source for almost all communities
Nutrient availability – saprotrophic decomposers ensure the constant recycling of inorganic nutrients within an environment
Recycling of wastes – certain bacteria can detoxify harmful waste byproducts (e.g. denitrifying bacteria such as Nitrosomonas)

Question 15

Outline general characteristics of all ecosystems

Answer 15

• Organisms and community plus the environment and abiotic components
• Environments show sustainability
• Nutrients are recycled in ecosystems
• Energy flows through ecosystems
• Producers, decomposers are part of all ecosystems

Question 16

Explain how increasing carbon dioxide levels in the atmosphere can lead to ocean acidification and coral death

Answer 16

• oceans are a carbon sink meaning they store carbon
• Some of the CO2 remains dissolved, but most of it is chemically converted
• CO2 is converted into carbonic acid, which dissociates to release H+ ions
• this increases ocean acidity and stresses coral
• lowers carbonate levels which is needed for shells and exoskeletons
• can cause coral to expel mutualistic algae

Question 17

Explain the movement of inorganic nutrients in ecosystems

Answer 17

Autotrophs obtain inorganic nutrients from the air, water and soil and convert them into organic compounds
Heterotrophs ingest these organic compounds and use them for growth and respiration, releasing inorganic byproducts
When organisms die, saprotrophs decompose the remains and free inorganic materials into the soil
The return of inorganic nutrients to the soil ensures the continual supply of raw materials for the autotrophs