Topic 4 - Ecology

Question 1

Define ecosystem

Answer 1

abiotic (non-living) and biotic (living) factors interacting with each other

Question 2

Examples of abiotic factors (3)

Answer 2

rainfall, pH of soil, temperature

Question 3

Examples of biotic factors (3)

Answer 3

plants, animals, bacteria

Question 4

Define habitat

Answer 4

the environment where the organism lives

Question 5

Define population

Answer 5

group of the same species living in the same area at the same time

Question 6

Define community

Answer 6

a group of populations living and interacting with each other in the same area

Question 7

Define species

Answer 7

a group of organisms that can interbreed and produce fertile offspring

Question 8

State the 4 categories that an organism could belong to

Answer 8

1. Autotrophs
2. Heterotrophs
3. Detritovore
4. Saprotroph

Question 9

What is the function of autotrophs ? with e.g

Answer 9

Also known as producers, they are organisms that produce their own food (via photosynthesis). They obtain inorganic molecules from the abiotic environment to synthesise organic molecules.
E.g plants

Question 10

What is the function of heterotrophs ? with e.g

Answer 10

Also known as consumers, they obtain their nutrition by eating other living organisms.
E.g lion

Question 11

What is the function of detritivores ? with e.g

Answer 11

Otherwise known as decomposers, they ingest non-living organic matter.
E.g worms

Question 12

What is the function of saprotrophs ? with e.g

Answer 12

Organisms that live on/in non-living organic matter, secrete digestive enzymes into it and absorb the products of digestion
E.g fungus

Question 13

What is the Law of Thermodynamics ?

Answer 13

Explains that every time energy is transferred from one trophic level to the next, only 10% is transferred while the remaining 90% is lost as heat.
Measured in kj/m^2/y

Question 14

Differentiate between food chain & food web

Answer 14

Food chain: shows the linear flow of nutrients and energy from one organism to another

Food web: shows the connection between all the food chains present in an ecosystem

Question 15

How is the heat lost in the transfer of energy between trophic levels ?

Answer 15

• certain parts of the organism are not consumed (hair, bone)
• indigestible material is egested (cellulose in plant wall)
• cell respiration as the energy needed for active processes is lost as heat

Question 16

state the energy conversion that occurs during photosynthesis

Answer 16

light —> chemical

Question 17

state the energy conversion that occurs when we eat food then break it down

Answer 17

chemical —> kinetic

Question 18

state the energy conversion that occurs when the broken down food initiates the brain to send signals to the nerves

Answer 18

chemical —> electrical

Question 19

state the energy conversion that occurs due to the broken down food acting as an insulator to keep the body warm

Answer 19

chemical —> heat

Question 20

What is a mesocosm ?

Answer 20

A model that replicates earth which is a closed ecosystem. Only light is able to come in not nutrients.

Question 21

What is an advantage and disadvantage of mesocosms ?

Answer 21

Advantage: it’s able to replicate earth on a small scale and variables are controlled so results are accurate
Disadvantage: might not reflect that true state of the earth

Question 22

What are 3 components for sustainability in an ecosystem

Answer 22

1. light source
2. nutrient availability
3. recycling waste products

Question 23

What is the carbon cycle

Answer 23

A main nutrient cycle that occurs naturally.

Question 24

What are fluxes ?

Answer 24

Shows the transfer of of carbon represented by arrows.

Question 25

What are sinks ?

Answer 25

Describes the method of carbon storage at each stage of the cycle.

Question 26

How is methane produced ?

Answer 26

It is produced in anaerobic conditions (lacking O2) i.e swamps by bacteria called methanogenic archaeans. They perform decomposition on dead organisms, which in turn releases methane. Once it’s in the air it becomes oxidised and turns into CO2.

Question 27

What is the chemical notation for methane ?

Answer 27

CH4

Question 28

How does combustion contribute to the carbon cycle?

Answer 28

Burning of fossil fuels and biomass cause carbon dioxide and water to be released as a by-product. Thus, there is an increased concentration of carbon in the air.

Question 29

How does limestone contribute to the carbon cycle ?

Answer 29

Calcium carbonate (CaCO3) is found in marine organisms with a shell. When the organism dies, the shell isn’t broken down meaning there is some carbon still there. When the limestone comes into contact with acidic rainwater, carbon is released.