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Biology CIE IGCSE > Organisms and enviroment > Flashcards

Organisms and enviroment Flashcards

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1
Q

What is the main source of energy in biological systems?

A

The sun

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2
Q

Decribe the flow of energy in biological systems.

A
  • Light energy from the sun is trapped by photosynthetic organisms
  • Energy is then stored as chemical energy.
  • Energy is eventually lost to the enviroment
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3
Q

What is a food chain?

A

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

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4
Q

How is energy transferred between organisms in the food chain?

A

By ingestion ( organisms eating other organisms ).

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5
Q

What is a trophic level?

A

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

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6
Q

Why are biomass transfers not 100% efficient?

A

Energy is lost through:

  • Egestion (removal of faeces)
  • Excretion (removal of waste products e.g urine)
  • Respiration
  • The production of inedible bones and shells
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7
Q

Why do food chains have fewer than 5 trophic levels?

A

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

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8
Q

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

A
  • 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.
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9
Q

What is a food web?

A

Multiple interconnected food chains.

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10
Q

What is a producer?

A

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

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11
Q

What is a consumer?

A

An organism that gets energy by eating other organisms.

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12
Q

What is a primary consumer?

A

An organism that feeds on producers.

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13
Q

What is a secondary consumer?

A

An organism that feeds on primary consumers.

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14
Q

What is a tertiary consumer?

A

An organism that feeds on secondary consumers.

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15
Q

What are herbivores?

A

Animals that only eat plants.

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16
Q

What are carnivores?

A

Organisms that mainly eat animals.

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17
Q

What are decomposers?

A

Organisms that break down dead matter.

18
Q

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

A

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

19
Q

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

A

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

19
Q

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

A

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

20
Q

What is the pyramid of numbers?

A

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

21
Q

What is a biomass pyramid?

A

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

22
Q

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

A

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

23
Q

Describe the carbon cycle.

A
  • 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.
24
Q

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

A

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

25
Q

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

A
  • 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.
26
Q

Describe the water cycle

A
  • 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
26
Q

Describe the water cycle

A
  • 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
27
Q

Why is the water cycle important?

A

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

28
Q

How is nitrogen cycled through the ecosystem? (brief)

A
  • 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
29
Q

What is deamination?

A

The removal of amine group in a amino acid.

29
Q

What is deamination?

A

The removal of amine group in a amino acid.

30
Q

State 4 roles of bacteria in the nitrogen cycle.

A
  • Decomposition
  • Nitrification
  • Denitrification
  • Nitrogen fixation
31
Q

Define population?

A

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

32
Q

Define community.

A

All the different populations in the ecosystem.

33
Q

Define ecosystem.

A

Both the community and their physical enviroment.

34
Q

State 3 factors that affect population growth rates.

A
  • Disease
  • Predation
  • Availability of food
35
Q

Describe the lag phase in population growth.

A

The organisms are adjusting to the enviroment.

Key: Lag can also mean the lag on computer, the computer is adjusting to the internet

36
Q

Describe the log phase in population growth.

A

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

37
Q

Describe the stationary phase of population growth.

A

The amount of births and deaths are equal.

38
Q

Describe the death phase of population growth with limited resources.

A

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

39
Q

State 4 implications of a rapidly increasing population size.

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

Biology CIE IGCSE (21 decks)

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