Organisms and enviroment

Question 1

What is the main source of energy in biological systems?

Answer 1

The sun

Question 2

Decribe the flow of energy in biological systems.

Answer 2

• Light energy from the sun is trapped by photosynthetic organisms
• Energy is then stored as chemical energy.
• Energy is eventually lost to the enviroment

Question 3

What is a food chain?

Answer 3

A way of showing the flow of energy between organisms starting with the producer.

Question 4

How is energy transferred between organisms in the food chain?

Answer 4

By ingestion ( organisms eating other organisms ).

Question 5

What is a trophic level?

Answer 5

The position that an organism hold in the food chain, food web, pyramid of number or pyramid of biomass.

Question 6

Why are biomass transfers not 100% efficient?

Answer 6

Energy is lost through:

• Egestion (removal of faeces)
• Excretion (removal of waste products e.g urine)
• Respiration
• The production of inedible bones and shells

Question 7

Why do food chains have fewer than 5 trophic levels?

Answer 7

Biomass transfers are not 100% efficient and so there is not enough energy to support 5 trophic levels.

Question 8

Why is it most efficient to supply plants as food for humans?

Answer 8

• Using plants as food for livestock waste energy as the biomass transfers are not 100% efficient
• Eating plant transfers can maximise the amount of energy gained as there is only one transfer.

Question 9

What is a food web?

Answer 9

Multiple interconnected food chains.

Question 10

What is a producer?

Answer 10

An organism that makes its own food (usually through photosynthesis)

Question 11

What is a consumer?

Answer 11

An organism that gets energy by eating other organisms.

Question 12

What is a primary consumer?

Answer 12

An organism that feeds on producers.

Question 13

What is a secondary consumer?

Answer 13

An organism that feeds on primary consumers.

Question 14

What is a tertiary consumer?

Answer 14

An organism that feeds on secondary consumers.

Question 15

What are herbivores?

Answer 15

Animals that only eat plants.

Question 16

What are carnivores?

Answer 16

Organisms that mainly eat animals.

Question 17

What are decomposers?

Answer 17

Organisms that break down dead matter.

Question 18

Explain the impact humans have on food chains and webs by overharvesting certain species?

Answer 18

Many organisms rely on other organisms for food, overharvesting can reduce the amount of food available for other animals.

Question 19

Explain the impact humans have on food chains and webs by introducing other species into a habitat.

Answer 19

Introducing new organisms increases competition and can interfere with the food chain, causing organism who cannot compete to die.

Question 19

Explain the impact humans have on food chains and webs by introducing other species into a habitat.

Answer 19

Introducing new organisms increases competition and can interfere with the food chain, causing organism who cannot compete to die.

Question 20

What is the pyramid of numbers?

Answer 20

A pyramid of numbers shows the number of organisms at each trophic level.

Question 21

What is a biomass pyramid?

Answer 21

A pyramid that shows a total dry mass of organisms at each trophic level

Question 22

Why is the pyramid of biomass a better way of representing a food chain than a pyramid of numbers?

Answer 22

Pyramids of biomass take into account the size of the organisms and are less easily misinterpreted.

Question 23

Describe the carbon cycle.

Answer 23

• Plants fix carbon dioxide into carbon molecules during photosynthesis
• The organic carbon-containing molecules are passed down onto organisms that eat plants
• Carbon dioxide is released back into the atmosphere by respiration from animals and plants
• Burning fossil fuels also release carbon dioxide into the atmosphere.

Question 24

State the effect of burning fossil fuels on carbon dioxide concentration inthe enviroment.

Answer 24

It releases more CO2 into the atmosphere and therefore increases the concentration of carbon dioxide.

Question 25

State the effects of deforestation on carbon dioxide concentration in the enviroment.

Answer 25

- Trees take in CO2 during photosynthesis(decreasing the atmospheric carbon dioxide concentration) - Cutting down trees will prevent this and so the atmospheric carbon dioxide concentration does not decrease.

Question 26

Describe the water cycle

Answer 26

- Water from lakes and oceans evaporate - The evaporated water condenses into clouds and returns to earth as precipitation - The water from precipitation is useful for life on land - The water then returns to the rivers and oceans through surface runoff

Question 26

Describe the water cycle

Answer 26

- Water from lakes and oceans evaporate - The evaporated water condenses into clouds and returns to earth as precipitation - The water from precipitation is useful for life on land - The water then returns to the rivers and oceans through surface runoff

Question 27

Why is the water cycle important?

Answer 27

Living organisms needs water. The water cycle provides organisms on land a continous supply of water.

Question 28

How is nitrogen cycled through the ecosystem? (brief)

Answer 28

- Nitrogen is fixed by lightning and bacteria - Decomposers break down dead matter into ammonium ions - Nitrifying bacteria ammonia turns into nitrites turns into nitrates - Plants absorb nitrate ions - Denitrifying bacteria releases nitrogen back into the atmosphere

Question 29

What is deamination?

Answer 29

The removal of amine group in a amino acid.

Question 29

What is deamination?

Answer 29

The removal of amine group in a amino acid.

Question 30

State 4 roles of bacteria in the nitrogen cycle.

Answer 30

- Decomposition - Nitrification - Denitrification - Nitrogen fixation

Question 31

Define population?

Answer 31

A species that occupy the same habitat at the same time.

Question 32

Define community.

Answer 32

All the different populations in the ecosystem.

Question 33

Define ecosystem.

Answer 33

Both the community and their physical enviroment.

Question 34

State 3 factors that affect population growth rates.

Answer 34

- Disease - Predation - Availability of food

Question 35

Describe the lag phase in population growth.

Answer 35

The organisms are adjusting to the enviroment. | Key: Lag can also mean the lag on computer, the computer is adjusting to the internet

Question 36

Describe the log phase in population growth.

Answer 36

The growth of the population is increasing at a fast exponential rate.

Question 37

Describe the stationary phase of population growth.

Answer 37

The amount of births and deaths are equal.

Question 38

Describe the death phase of population growth with limited resources.

Answer 38

Once the resources have been used up. The population begins to compete for resources and organisms will die as soon as resources become scarce.

Question 39

State 4 implications of a rapidly increasing population size.

Answer 39

- More land needed for living - Greater demands for health care - Greater demands for education - More resources needed which puts pressure on the enviroment