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IGCSE Biology > Chapter 18:Organisms and their envirnment > Flashcards

Chapter 18:Organisms and their envirnment Flashcards

1
Q

Definition of habitat

A

The place where organisms live

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2
Q

What is a ecosystem

A

A unit containing all the organisms in a community and thier environment,interacting together

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3
Q

What is the principal source of energy into biological systems

A

The sun

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4
Q

Where does Chemical energy come from

A

Organisms

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5
Q

What is the principal source of energy to the biological systems

A

the sun

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6
Q

What is a food chain

A

A diagram showing the flow of energy from one organism to the next,beginning with a producer.

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7
Q

What is a food web

A

A network of interconnected food chains

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8
Q

How do food chains sequence

A

Producer > primary consumer > secondary consumer > tertiary consumer > quaternary consumer

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9
Q

Describe a producer

A

An organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis

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10
Q

Describe a consumer

A

An organism that gets its energy by feeding on other organisms

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11
Q

are primary consumers herbivores or carnivores

A

Herbivores

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12
Q

Describe herbivore

A

An animal that gets its energy by eating plants

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13
Q

Describe carnivores

A

an animal that gets its energy by eating other animals

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14
Q

Describe decomposers

A

An organism that gets its energy from dead or waste organic material

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15
Q

What’s o the arrows show on a food chain or food web

A

The direction of energy flow

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16
Q

Describe the pyramid of numbers

A

The area of the block represents the number of organisms at that level in the food chain

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17
Q

What is tropical level

A

The position of an organism in a food chain,food web or pyramid of biomass or numbers

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18
Q

What is a pyramid of biomass

A

A graph showing the relative quantity of biomass at each tropical level

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19
Q

What’s the advantage of using a pyramid of biomass rather than a pyramid of number to represent a food chain?

A

Pyramids of biomass provide a much better idea of the quantity of the plant or animal material at each level of a food chain and therefore are a better way of representing interdependence within the food chain

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20
Q

What is pyramid of energy

A

A graph showing the relative quantity of energy at each trophic level

21
Q

Name 3 ways energy loss happens

A

1-when an organism uses glucose and other organic compounds for respiration,some of the energy realises from the glucose is lost as heat energy to the environment
2-when an organism eats another,it rarely eats absolutely all of it
3- when an animal eats another organism,enzymes in its digestive system break down most of the large nutrient molecules so they can be absorbed

22
Q

Why is the pyramid of numbers shaped like that

A

Because there is less energy available as you go up the tropical level.so there are fewer organisms at each level

23
Q

Why is the pyramid of biomass in that shape

A

Because one large organisms (tree) can produced food for hundreds of small organisms (caterpillars)

24
Q

What is the unit for the quantity of energy

A

kJ per square meter per year

25
Q

what is the best way to show the energy flow

A

Pyramids of energy are the best way to show the energy flow through an ecosystem,they are very difficult to produce

26
Q

What do3s the carbon cycle show

A

How carbon circulates through an ecosystem

27
Q

what is the process that removes carbon dioxide from the air

A

Photosynthesis

28
Q

What is the process that adds carbon dioxide to the air

A

Respiration and combustion

29
Q

How much percent of carbon dioxide is in the air

A

0.04%

30
Q

How does carbon dioxide in the atmosphere increase

A

When we burn fossil fuels the carbon in them changes to carbon dioxide and goes into the air

31
Q

Living things need nitrogen to make (2)

A

-to make proteins
-make DNA

32
Q

name 1 source of nitrogen

A

78% nitrogen gas

33
Q

What is nitrogen fixation

A

Converting inert nitrogen gas into a more reactive form such are ammonia or nitrate ions

34
Q

Name 5 ways nitrogen fixation happens

A

-lighting
-artificial fertilisers
-nitrification
-denitrification

35
Q

Describe the carbon cycle

A

-plants fix carbon dioxide into organic molecules during photosynthesis
-the organic carbon containing molecules are passed onto organisms that eat the plants
-carbon dioxide is released back into the atmosphere by respiration from animals and plants
-burning fossil fuels also releases carbon dioxide into the atmosphere’s

36
Q

State the effect of deforestation on carbon dioxide concentration in the environment

A

-trees take in carbon dioxide during photosynthesis ; decreasing the atmospheric carbon dioxide concentration
-cutting down trees prevent this and ask the atmospheric carbon dioxide concentration does not decrease

37
Q

Describe how nitrogen is cycled through an ecosystem

A

-nitrogen is fixed by lighting and bacteria
-decomposers break dead matter down into ammonium ions
-nitrifying bacteria convert ammonia into nitrates
-plants absorb nitrate ions
-denitrifying bacteria release nitrogen back to the atmosphere

38
Q

What is deamination

A

Breakdown of amino acids to ammonium ions

39
Q

What is nitrification

A

Ammonium ions to nitrate ions

40
Q

What is denitrification

A

Nitrate ions to nitrogen gas

41
Q

Define population

A

A group of organisms of one species living in the same area at the same time

42
Q

What affects the rate of growth of a population

A

-food supply
-predation
-disease

43
Q

Describe the lag phase in population growth

A

The organisms are adjusting to their environment

44
Q

Describe the log phase in population growth

A

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

45
Q

Describe the stationary phase

A

The pupation remains constant as the birth rate and death rate are equal

46
Q

Describe the death phase

A

The population falls as the death rate exceeds birth rate

47
Q

What is a population graph called

A

A sigmoid growth curve as it is in a ‘S’ shape

48
Q

Limiting factor

A

A factor that is short in supply which stops an activity happening at a fast rate

49
Q

define community

A

All of the populations of different species in an ecosystem

IGCSE Biology (23 decks)

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