<span>
Evidence of the existence of life. </span>
Answer:
oxygen
Explanation:
oxygen isn't necessarily a characteristic of life. it's more like an aspect of life
To be reasonably sure that your observation will apply to the group you are studying, you should select a sample from the population and ensure that the selection is unbiased. The participants are selected at random to ensure that all the individuals in the group get equal chance of being represented in the sample. This removes the sampling bias in the sample.
Answer: The greenhouse gas emissions from the extraction of bitumen and the use of large quantities of water.
Explanation:
Bitumen is a natural flammable organic matter formed from kerogen in the process of petroleum generation, which is soluble in carbon disulfide. Asphalt and mineral wax are examples of hydrocarbons which are part of bitumen. Conventional oil is extracted by wells while <u>oil sands deposits are extracted using surface mining sectioning techniques, or are flowed to wells by in situ techniques that reduce bitumen viscosity by steam and/or solvents.</u> So, unlike crude oil extracted in oil wells, bitumen requires an open-pit mining operation, in which large tracts are washed with a mixture of water and chemicals to separate the bitumen from a mixture of sand and clay.
Two consequences of this practice are:
- The greenhouse gas emissions from the extraction of bitumen are larger than the extraction of conventional oil. The emissions produced contribute to enhance the greenhouse effect and cause global warming. The greenhouse effect occurs when certain gases retain part of the energy emitted by the earth's soil when heated by the sun's radiation. This phenomenon occurs naturally, and thanks to it, the average temperature of the Earth is about 14º C (57.2 °F). The problem occurs when these greenhouse gases increase in the atmosphere and the amount of energy that is not released into space also increases and, with it, the Earth's temperature.
- The extraction of bitumen from oil sands requires the use of large quantities of water, and even though water used here can be recycled, only a small amounts is returned to the natural cycle. Also, spills from the transportation of the oil could damage soils and waterways, increasing water pollution. This toxic water could get into surface.
