Harnessing Biology: Human Impacts

Question 1

define biodiversity.

Answer 1

the measure of how many different species live in an ecosystem

Question 2

which areas are more biodiverse compared to others?

Answer 2

• areas like tropical rainforest have millions of different species and are very biodiverse
• other areas like the polar regions have far fewer species and are less biodiverse

Question 3

how do we estimate the biodiversity?

Answer 3

• to estimate the biodiversity of an area use quadrats and random sampling (random number generator to find coordinates to place multiple quadrats in the sample area)
• for each individual quadrat, use an identification key and record the number of each different species

Question 4

how do we find out the effect of an abiotic (non-living, e.g. temperature or light intensity) or biotic (living, e.g. trampling or predation) variable on biodiversity ?

Answer 4

• select at least two areas where the variable is different
• measure/describe the variable in each area
• estimate the biodiversity in each area using the method above

Question 5

what has meant an increase in deforestation?

Answer 5

• the increase in the human population and development of industrial machinery has meant that much larger areas have been cleared
• this is often by large companies who deforest to provide land to cattle, rice field and growing crops for biofuels

Question 6

what does deforestation do?

Answer 6

• destroys the habitats of the organisms that live there
• scientists estimate that several hundred species of plant, animal and insect are lost each day partly as a result of deforestation
• this means that deforestation is causing extinctions and dramatically reducing biodiversity

Question 7

what happens to carbon if deforestation occurs?

Answer 7

• during photosynthesis carbon dioxide is taken into plants and becomes part of the carbohydrates and other biological molecules
• the plant effectively becomes a ‘carbon sink’
• if deforestation occurs, there are less plants to store carbon and carbon dioxide levels in the atmosphere will increase
• oxygen levels will decrease as there is less photosynthesis.

Question 8

what happens when felled trees are burned as a source of energy?

Answer 8

• this released carbon dioxide back into the atmosphere causing a further increase in atmospheric carbon dioxide

Question 9

name the effects of deforestation.

Answer 9

• leaching
• soil erosion
• evapotranspiration

Question 10

describe leaching.

Answer 10

• normally water is absorbed by soil and then taken up by the roots of plants
• if deforestation occurs then the water is no longer taken by plants and can begin to ‘run off’ from the soil into rivers and lakes
• mineral ions that occur in the soil are dissolved in the soil’s water
• if this water is then absorbed plants, the minerals are transferred to the plant for growth
• if deforestation has occurred the dissolved mineral ions are removed from the soil in the water which runs off into the nearby rivers/lakes which means that the mineral ions are removed from the soil and some of these nutrients, espec. nitrates, can lead to further problems such as eutrophication
• the process of the loss of nutrients from the soil due to this run off/washing out of the soil is known as leaching

Question 11

describe soil erosion.

Answer 11

• the water running off from deforested areas may carry away some of the topsoil, causing erosion
• because of deforestation there are no plants present in the soil and therefore there are no roots holding the soil in place
• the topsoil contains the most fertile, mineral ion rich materials: when it is lost due to erosion the minerals are also lost, making the land very difficult to use for crop growth and reducing the chance of plants re-growing

Question 12

describe evapotranspiration.

Answer 12

• this is the process by which water is transferred from the land to the atmosphere by evaporation from the soil and other surfaces and by transpiration from plants
• transpiration is the evaporation and diffusion of water through the stomata of leaves
• this evaporated water moves into the atmosphere and eventually (through the water cycle) makes rain in rain clouds
• when deforestation occurs, this cycle is broken
• transpiration stops, as no plants are present, thus meaning that water is not put into the atmosphere and rain doesn’t occur which can lead to droughts

Question 13

describe air pollution by sulphur dioxide.

Answer 13

• sulphur dioxide, nitrogen monoxide and nitrogen dioxide are released into the atmosphere from cars and factories
• these gases then react with the atmospheric water vapour to form dilute acids (sulphuric and nitric acids)
• this dilute acid can dissolve limestone buildings and statues, though this is often not counted as the environment
• the rain when it falls can decrease the PH of rivers and lakes, resulting in the death of fish and other animals
• the acid rain can also kill trees and other plants
• can increase dissolution of some metal ions in the soil, including aluminium, these run off into rivers and lakes where they poison fish

Question 14

why has increasing population led to an increase in pollution?

Answer 14

some of this is due to:
- more fossil fuels being burnt for heat and power
- more movement and use of transport
- higher levels of industry for houses and goods

Question 15

when is carbon monoxide formed?

Answer 15

• when substances containing carbon are burned in a limited supply of oxygen, carbon monoxide is formed
• vehicle exhaust gases contain significant amounts of carbon monoxide

Question 16

why is carbon monoxide a bad pollutant?

Answer 16

• carbon monoxide is a dangerous pollutant as it binds more strongly with haemoglobin than oxygen
• if a person inhales carbon monoxide for a period of time, more and more haemoglobin becomes bound to CO and not O2, and the person will lose consciousness and eventually die, due to reduced aerobic respiration

Question 17

what is leaching?

Answer 17

• farmers add fertilisers to the soil to increase the yield of their crops
• fertilisers usually contain nitrates and phosphates which are v soluble
• when a lot of fertiliser is present on farmland surrounding a river it is washed out of the soil when it rains into the rivers
• this is called leaching

Question 18

what are the effects of leached nitrates?

Answer 18

1. the nitrates are absorbed by the green algae in the water
2. these multiply rapidly and may completely cover the water. the great growth of algae is called algal bloom
3. this blocks out the sunlight for other plants in the river/lake
4. this means that they are unable to photosynthesise and die
5. even the algae on the top eventually die
6. the dead remains provide a good source of food for bacteria
7. the bacteria multiply rapidly
8. the large population of bacteria respire, increased the biological oxygen demand, using up oxygen in the water
9. this decreases the level of oxygen and results in the death of other organisms in the water like fish as they cannot respire aerobically

Question 19

what is the name for the effects of leached nitrates?

Answer 19

• eutrophication

Question 20

how does water get polluted by sewage?

Answer 20

• the sewage provide a good source of food for bacteria
• the bacteria therefore multiply rapidly
• the large population of bacteria respire, increasing the biological oxygen demand, using up oxygen in the water
• this decreases the level of oxygen and results in the death of other organisms in the water like fish as they cannot respire aerobically

Question 21

what is sewage and how does it enter water supplies?

Answer 21

• undigested food material - it contains lots of biological molecules, including carbohydrates, proteins, nucleic acids and fats

Question 22

is water pollution the same as eutophication?

Answer 22

no - it does not involve an algal bloom!