Conditions for life on earth

Question 1

State one role of living organisms other than humans in soil formation (1)

Answer 1

soil formed from the remains of organisms;
decomposers/detritivores;
break down dead organisms/forms humus;
organic sorting/mixing/aeration/improve structure;
release nutrients/ nutrient recycling;
weather/erode/break up bedrock/parent material

Question 2

State one role of living organisms other than humans in soil conservation (1)

Answer 2

vegetation/soil biota reduces the rate of runoff;
vegetation reduces wind erosion;
vegetation reduces impact/damage due to rain;
root binding/slope stabilisation;
humus binds soil together;

Question 3

Describe the main conditions that allow life to survive on earth. (8)

Answer 3

Water:
role of water;;
solvent for chemical reactions
transport within organisms
mineral uptake
required for photosynthesis
aquatic habitats
anomalous expansion
specific heat capacity/temperature regulation
albedo
acts as a carbon sink

Temperature:
importance of temperature range;;
suitable for stable biological molecules/enzymes
warm enough for chemical/metabolic reactions
liquid water

Geology:
importance of geology;;
mass controls gravity/gravitational pull
retention of atmosphere
source of minerals
magnetic field protects from solar wind

Question 4

Give two ways in which atmospheric carbon dioxide is important for life on earth. (2)

Answer 4

needed for photosynthesis;
climate/temperature control/heat absorption/acts as greenhouse gas;
raw material for carbonaceous structure;
eg coral reefs, exoskeletons, shells

Question 5

Describe how sunlight is important for the survival of life on earth. (2)

Answer 5

energy for photosynthesis; energy for hydrological cycle/winds/ocean currents;

Question 6

State one way in which plants increase atmospheric humidity. (1)

Answer 6

(evapo)transpiration/ evaporation;

Question 6

Describe how early photosynthetic organisms changed the composition of the atmosphere. (2)

Answer 6

reduced concentration of/absorbed carbon dioxide/CO2;
increased concentration/released oxygen/O2;
(oxygen enables) formation of ozone/03 layer;

Question 7

Features of earth that created suitable conditions for life

Answer 7

Mass
Distance from sun
Axis of rotation
Speed of rotation
Magnetic field

Question 8

Early conditions on earth that allowed life to develop

Answer 8

Presence of liquid
Temperature range
Atmospheric gases
Solar insulation

Question 9

Presence of atmosphere

Answer 9

1.Large mass and gravitational pull which keeps the atmosphere close
2. Contains important gases: CO2, N2 AND CH4
3. Temperature and pressure means water is in liquid form

Question 10

Solar Insulation

Answer 10

Suitable temperature range for enzyme action and water in liquid state
Provides energy for photosynthesis
Amount absorbed depends upon the albedo of the surface

Question 11

Earth orbital behaviour

Answer 11

1.Rotation and tilt of the earth on its axis and its orbit around the sun
2.Controls daily and seasonal variations in isolation and temperatures
3. Enough day length to stop temperature extremes and light for photosynthesis

Question 12

Presence of liquid water

Answer 12

Solvent water
Transport within organisms
Temperature controls
Anomalous expansion on freezing (most dense at 4°C)
High specific heat capacity
Aquatic habitats
Absorption of UV radiation

Question 13

Atmospheric gases

Answer 13

Carbon dioxide for photosynthesis and the synthesis of carbohydrates, proteins and lipids
Nitrogen for protein synthesis

Question 14

How life on earth caused environmental change

Answer 14

Atmospheric oxygen
Carbon sequestration by photosynthetic organisms
Biogeochemical
Transpiration

Question 15

Limitations of early methods

Answer 15

Lack of ancient historical data.
* Limited coordination between researchers.
* Lack of sophisticated equipment for accurate measurements.
* Lack of data collection in many areas.
* Reliance on proxy data, eg dendrochronology, pollen analysis.

Question 16

Improved methods of proxy data

Answer 16

• Collection of long-term data sets.
• The use of electronic monitoring equipment.
• Gas analysis of ice cores.
• Isotope analysis of ice cores.
• Improved carriers for monitoring equipment, eg helium balloons, aircraft, satellites.

Question 17

How did distance from the Sun allow life to develop on Earth?

Answer 17

Provides a suitable temperature range on Earth which maintains liquid water and allows for photosynthesis

Question 18

How did insolation allow life to develop on Earth?

Answer 18

Provides a suitable temperature range on Earth due to its atmospheric behaviour

Question 19

How did orbital behaviour allow life to develop on Earth?

Answer 19

Earth’s orbit and its rotation and tilt on its axis controls daily and seasonal variations in insolation and therefore temperature

Question 20

How did the magnetosphere allow life to develop on Earth?

Answer 20

Deflects harmful solar radiation which could be biologically damaging

Question 21

How did the atmosphere allow life to develop on Earth?

Answer 21

Earth’s mass and gravitational force retains an atmosphere which provides gaseous resources and maintains liquid water (due to pressure and temperature)

Question 22

In which 4 ways did early life on Earth cause environmental change?

Answer 22

Biogeochemical cycles
Oxygen production
Ozone layer
Carbon sequestration

Question 23

How did oxygen production cause environmental change?

Answer 23

Early photosynthesisers such as cyanobacteria produced oxygen which allowed for organisms to develop using aerobic respiration

Question 24

How did the ozone layer cause environmental change?

Answer 24

Reactions between oxygen and UV in the stratosphere created the ozone layer which protects Earth from harmful UVC and UVB radiation

Question 25

How did carbon sequestration cause environmental change?

Answer 25

Photosynthetic organisms reduced atmospheric CO2 levels which reduced the greenhouse effect

Question 26

What are the 5 examples of proxy data to determine past conditions on Earth?

Answer 26

Historical data
Coral reef analysis
Pollen analysis
Dendrochronology
Ocean and lake sediment analysis

Question 27

How does historical data help determine past conditions on Earth?

Answer 27

Sources such as ships logs, diaries and news articles provide information about the weather and climate at the time

Question 28

How does coral analysis help determine past conditions on Earth?

Answer 28

The density of a coral reef changes due to temperature and the presence of carbon for the CaCO3 structure

Question 29

How does pollen analysis help determine past conditions on Earth?

Answer 29

Pollen grains can be used to determine which types of plants were present in the past

Question 30

What are the limitations of proxy methods?

Answer 30

Historical data may be subjective
Trees do not grow in all climates
Coral is only present in specific climates
Many areas lack data collection

Question 31

What are the 3 examples of improved methods to determine conditions on Earth?

Answer 31

Ice-core analysis
Satellite imagery
Weather balloons

Question 32

Describe how early life caused environmental changes that reduced the amount of ultraviolet radiation reaching the Earth’s surfaces (3 marks)

Answer 32

Photosynthetic organisms released oxygen. The oxygen then reacted with Ultraviolet to create Ozone (03). Ozone then either absorbs UV radiation, reducing the amount reaching the Earth’s surface

Question 33

Explain two ways that atmospheric carbon dioxide has been important for the survival of living organisms on Earth (4 marks)

Answer 33

1) Use in photosynthesis, produces oxygen for aerobic respiration
2) Greenhouse gas, maintains warmer temperatures