2.2 Communities and Ecosystems

Question 1

Define ecosystem

Question 2

What is the difference between ecosystem and community

Answer 2

Ecosystems include the abiotic components whereas community is only living components that interact within the habitat.

IMPORTANT: The habitat is not a part of the community just the stage which populations act out their interactions 🍿

Question 3

What are producers?

Answer 3

Producers are the ones who convert inorganic compounds into food (photosynthesis). All ecosystems depend on producers

Known as autotrophs or self-feeders

Question 4

What are consumers?

Answer 4

referred to as heterotrophs, cannot manufacture their own food

Question 5

What is the role of producers in an ecosystem

Answer 5

• Provide food for all other life on earth
• Regulate the hydrological cycle by taking water in and releasing it in to the atmosphere through transpiration.
• Maintain the balance of gases in the atmosphere by absorbing COand releasing oxygen. This may also help redress global warming
• Provide habitats
• The roots of plants help bind the soil and reduce erosion

Question 6

What are decomposers

Answer 6

Decomposers absorb and metabolise waste and dead matter on a molecular level then release it as inorganic chemicals that can be recycled through the ecosystem via plants.

Question 7

What are detritivores

Answer 7

Detritivores are the first stage of the decomposition cycle and gain their nutrients by consuming detritus (plant and animal parts, faeces)

Question 8

Why are decomposers and detrivors vital for an ecosystem

Answer 8

• Clear ecosystems of dead bodies.
• Prevent the spread of disease by disposing of dead bodies.
• Facilitatethe continued functioning of ecosystems by releasing the nutrients that were locked up in the organic matter and making them available again

Question 9

Photosynthesis what is it + equation

Answer 9

Plants are able to take light energy from the sun and use it to make chemical energy

Equation:
Light energy + Carbon dioxide + water → oxygen + glucose

Question 10

Respiration what is it + equation

Answer 10

Respiration is the oxidation of glucose to release energy that is then used in all activities in the organism

Equation:
Glucose + Oxygen = Energy + Carbon dioxide + water

Question 11

How does respiration show the second law of thermodynamics?

Answer 11

• During respiration energy is transformed from chemical energy to kinetic energy and eventually dissipated into the environment as heat energy.
• thus: showcasing that the entropy (disorder) increases in an ecosystem over time

Question 12

Define trophic level

Answer 12

Trophiclevelis the position an organism (or group of organisms in a community) occupies in the food chain.

Question 13

How much (%) of energy gets transferred from one trophic level to the next

Answer 13

Amount of energy that reached the primary consumer / amount of energy that reached the primary producer ✖️ 100 to make it a percentage

Question 14

What do ecological pyramids show? And which are the three types

Answer 14

Ecological pyramids show feeding relationships between a group of organisms

They are quantitative models to show information about the organisms at each trophic level

The three types:
Pyramid of numbers, pyramid of biomass, pyramid of productivity

Question 15

Pyramid of numbers- what does it show?

Answer 15

shows the number of organisms at each trophic level in the food chain and the unit is whole numbers

Question 16

what does the pyramid of biomass show

Answer 16

A graphical representation of the amont of biomass at each trophic level

Question 17

What unit is biomass measured in?

Answer 17

Biomass is measured in mass per unit of area or g m–2(grams per meter squared)

Question 18

How is biomass measured (process)

Answer 18

• Biomass is measured as dry weight— to eliminate the variation in water content between organisms
• to find the biomass of a specie you must dry and weigh the specie— very destructive and imoral if you are dealing with animals

Question 19

Pros and cons of pyramids of biomass (hint: 2 cons and 1 pro)

Answer 19

Pros:
Pyramids of biomass overcome the problems of counting seen in pyramids of numbers

Cons:
The method is very destructive
Biomass may vary seasonally

Question 20

What does the pyramid of productivity show?

Answer 20

it shows the turnover of biomass at each trophic level. It is not a snapshot in time as it shows the flow of energy over a period of time.

Question 21

In what unit is the pyramid of productiviyu measured?

Answer 21

Joules per metre squared

Question 22

Pros and cons of the pyramid of productivity （hint 2 pros and 2 cons)

Answer 22

Pros:

These are the most accurate pyramids as they show actual energy available and the rate of production over a period of time

Ecosystems can be compared

Cons：

Data collection is not easy as you need to know the rate of biomass production over a period of time

Species can be difficult to assign to a particular tropic level

Question 23

How does energy transfer between trophic levels impacts terrestrial food chains vs aquatic food chains

Answer 23

in terrestrial food chains the number of trophic levels is around four and in aquatic around seven. this is because: aquatic food chains start with microscopic phytoplankton as primary producers— this means that there are more and can pass more energy aquatic species use less energy in making skeletons so there is potential for longer food chains

Question 24

Define bioacummulation

Answer 24

Bioaccumulationis the increase in the concentration of a pollutant in an organism as it absorbs or it ingests it from its environment

Question 25

Define biomagnification

Answer 25

Biomagnificationis the increase in the concentration of the pollutant as it moves up through the food chain.

Question 26

Bioaccumulation in DDT

Answer 26

When an animal consumes DDT it accumulate in the tissue

Question 27

Biomagnification in DDT

Answer 27

The higher an animal is on a food chain, the greater the DDT concentration