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IGCSE Biology > 19. Organisms and their environment > Flashcards

19. Organisms and their environment Flashcards

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1
Q

What is photosynthesis (carbon cycle)?

A

converts carbon dioxide into carbohydrates, removes carbon dioxide from the atmosphere

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2
Q

What is respiration (carbon cycle)?

A

chemical process inside cells that releases energy

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3
Q

What is feeding (carbon cycle)?

A

ingesting organic matter from other organisms

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4
Q

What is decomposition (carbon cycle)?

A

breakdown of dead organic matter into simple nutrients/molecules that can be recycled back into the ecosystem

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5
Q

What is fossilisation (carbon cycle)?

A

dad organic matter compressed under optimum conditions into fossil fuels after millions of years

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6
Q

What is combustion (carbon cycle)?

A

complete oxidation of organic matter such as fossil fuels and biomass

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7
Q

What is decomposition (nitrogen cycle)?

A

proteins to ammonium ions

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8
Q

What is nitrification?

A

ammonium ions to nitrate ions

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9
Q

What is denitrification?

A

nitrate ions to nitrogen gas

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10
Q

Which organisms carry out nitrification?

A

nitrifying bacteria

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11
Q

What is a necessary condition for denitrification?

A

no presence of oxygen

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12
Q

For _______ to occur, no oxygen must be present.

A

denitrification

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13
Q

What is nitrogen fixation?

A

nitrogen gas to nitrates

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14
Q

Which organisms carry out decomposition?

A

by bacteria and fungi (decomposers)

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15
Q

Which organisms carry out nitrogen fixing? Where are they located?

A

nitrogen fixing bacteria
found in root nodules of legume plants

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16
Q

Which organism absorbs nitrate ions?

A

plants

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17
Q

What substance do plants absorb?

A

nitrate ions

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18
Q

What process can also carry out nitrogen fixation?

A

lightning

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19
Q

How do nitrates from lightning reach the soil?

A

rainwater

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20
Q

Where are amino acids/proteins made?

A

plants

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21
Q

Plants are responsible for producing which substance which is part of the nitrogen cycle?

A

amino acids/proteins

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22
Q

How are proteins transferred from producers to herbivores?

A

feeding

23
Q

What is feeding?

A

process in which proteins transfer from producer to herbivore by ingestion

24
Q

What happens once a herbivore feeds on a plant?

A

it will gain protein from the plant, digest it into amino acids, then used to make proteins.
carnivores eat herbivores and process restarts.

25
Q

Which organisms carry out denitrification?

A

denitrifying bacteria

26
Q

Define ‘population’.

A

a group of organisms of the same species, living in the same area at the same time

27
Q

Define ‘community’.

A

all of the populations of different species in an ecosystem

28
Q

Define ‘ecosystem’.

A

community interacting with abiotic factors in the environment

29
Q

What are 4 factors that affect the rate of population growth for a population of an organism?

A

food supply
competition
predation
disease

30
Q

State, in order, the phases of population growth (sigmoid curve).

A

lag phase
log phase
stationary phase
death phase

31
Q

What happens in the lag phase? Why is population growth very slow in this phase?

A
  • although abiotic factors are optimum, there are too few individuals, making it hard to find compatible mates
32
Q

What are some examples of abiotic factors being optimum?

A

low competition for resources
high food + water availability
low spreading of diseases

33
Q

What happens in the log phase? Why is population growth exponential in this phase?

A
  • there are enough individuals to mate
  • optimum conditions for reproduction
  • no limiting factors
34
Q

What happens in the stationary phase? Why is population growth stationary in this phase?

A

the high number of individuals increases competition for resources and mates
diseases spread more quickly
this keeps population stable

35
Q

In terms of birth, death, emigration and immigration, what is a declining population?

A

death and emigration > brith and immigration

36
Q

In terms of birth, death, emigration and immigration, what is an increasing population?

A

birth and immigration > death and emigration

37
Q

What 4 factors can be used to calculate population growth?

A

birth,
immigration,
death,
emigration

38
Q

What is the ‘formula’ for population growth?

A

births - deaths + immigration - emigration

39
Q

What happens in the death phase? Why is population growth declining in this phase?

A
  • struggle for survival as resources become limiting (used up)
    individuals die
40
Q

What are some limiting factors in population growth? (not in syllabus, ignora Anna <3)

A

resources
food
water
mates/partners
space
shelter

41
Q

what is the principal source of
energy input to biological systems

A

Sun

42
Q

what does a food chain show

A

the transfer of
energy from one organism to the next, beginning
with a producer

43
Q

what is a food web

A

a network of
interconnected food chains and interpret food
webs

44
Q

what is a producer

A

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

45
Q

what is a consumer

A

organism that gets its
energy by feeding on other organisms

46
Q

how can consumers me classified

A

as primary,
secondary, tertiary and quaternary according to
their position in a food chain

47
Q

what is a herbivore

A

animal that gets its
energy by eating plants

48
Q

what is a carniovre

A

animal that gets its
energy by eating other animals

49
Q

what is a decomposer

A

organism that gets
its energy from dead or waste organic material

50
Q

Organic forms of nitrogen

A

protein, amino acids, DNA, urea

51
Q

Inorganic forms of nitrogen

A

chemical fertilisers (NH4NO3), Nitrate (NO3), Ammonium gas (NH4), gas (N2)

52
Q

What are the stages of the nitrogen cycle?

A
  1. ingestion
  2. digestion
  3. assimilation
  4. deamination
  5. decomposition
  6. nitrification
  7. absorption
  8. denitrification
  9. nitrogen fixing
53
Q

inorganic forms of carbon

A

carbon dioxide, methane, ethanol

54
Q

organic forms of carbon

A

carbohydrates, hydrocarbons, proteins, fats

IGCSE Biology (28 decks)

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