Exam (elaborations)
BLG1501 Assignment 2 Semester 1 Memo |
Due 11 April 2025 Course
Basic Biology (BLG1501)
Institution
University Of South Africa (Unisa)
Book
Campbell Biology
BLG1501 Assignment 2 Semester 1 Memo | Due 11 April 2025. All questions
answered.
Question 1 [20] 1.1 Write explanatory notes on the greenhouse effect. (7)
1.1 Explanatory notes on the greenhouse effect (7)
The greenhouse effect is a natural process that warms the Earth's surface. When the Sun’s
energy reaches the Earth, some of it is reflected back to space and the rest is absorbed, warming
the planet. The Earth then emits energy in the form of infrared radiation. Greenhouse gases in the
atmosphere, such as carbon dioxide (CO₂), methane (CH₄), water vapor (H₂O), and nitrous
oxide (N₂O), absorb this infrared radiation and trap heat in the atmosphere.
This trapped heat helps to keep the Earth's temperature at a level necessary to sustain life.
Without the greenhouse effect, the average temperature of the Earth would be around -18°C,
making it too cold for most life forms.
However, human activities like burning fossil fuels, deforestation, and industrial processes are
increasing the concentration of greenhouse gases. This leads to an enhanced greenhouse effect,
which causes global warming and climate change.
In summary, the greenhouse effect is crucial for maintaining life-supporting temperatures on
Earth, but human activities are intensifying the effect, leading to environmental problems.
The greenhouse effect is a natural process in which certain gases in Earth's atmosphere trap heat,
preventing it from escaping into space and thus maintaining the planet's temperature at a level
suitable for life. Here’s a breakdown of how it works:
1. Solar Radiation: The Sun emits energy in the form of radiation, some of which reaches
the Earth's surface. This energy heats the Earth's surface and is reflected back into the
atmosphere in the form of infrared radiation (heat).
, 2. Greenhouse Gases: Some gases in the atmosphere, such as carbon dioxide (CO2),
methane (CH4), water vapor (H2O), nitrous oxide (N2O), and ozone (O3), are capable of
absorbing and re-emitting infrared radiation. These are called greenhouse gases.
3. Heat Trapping: After the Earth's surface absorbs solar radiation, it releases this energy
as heat (infrared radiation). Greenhouse gases absorb some of this heat and then re-
radiate it in all directions, including back toward Earth's surface, which keeps the planet
warmer than it would be without them.
4. Natural vs. Enhanced Greenhouse Effect: The natural greenhouse effect is essential for
life, as it keeps the Earth's average temperature around 15°C, allowing ecosystems to
thrive. However, human activities, such as burning fossil fuels and deforestation, have
increased the concentration of greenhouse gases in the atmosphere, leading to an
enhanced greenhouse effect, which contributes to global warming and climate change.
5. Impact of the Greenhouse Effect: The enhanced greenhouse effect is causing
temperatures to rise, which results in melting polar ice caps, rising sea levels, and more
extreme weather patterns. This effect is one of the key drivers of climate change.
6. Carbon Cycle: The carbon cycle involves the movement of carbon between the
atmosphere, oceans, and land. Human activities are disrupting this cycle by adding more
CO2 to the atmosphere, which intensifies the greenhouse effect.
7. Global Warming: The enhanced greenhouse effect leads to global warming, which
refers to the long-term increase in Earth's average temperature. This has wide-ranging
environmental, social, and economic consequences, including shifting weather patterns,
ecosystem disruption, and increased occurrence of extreme weather events.
In summary, while the greenhouse effect is a natural and necessary phenomenon for maintaining
life on Earth, human-induced factors are amplifying it, leading to global warming and climate-
related challenges.
1.2 Distinguish between hypertonic, hypotonic, and isotonic solutions. (6)
Distinction Between Hypertonic, Hypotonic, and Isotonic Solutions (6 marks)
1. Hypertonic Solution
A solution that has a higher solute concentration than the cell's cytoplasm.
Water moves out of the cell by osmosis.
The cell shrinks (crenates in animal cells or undergoes plasmolysis in plant cells).
2. Hypotonic Solution
A solution that has a lower solute concentration than the cell's cytoplasm.
BLG1501 Assignment 2 Semester 1 Memo |
Due 11 April 2025 Course
Basic Biology (BLG1501)
Institution
University Of South Africa (Unisa)
Book
Campbell Biology
BLG1501 Assignment 2 Semester 1 Memo | Due 11 April 2025. All questions
answered.
Question 1 [20] 1.1 Write explanatory notes on the greenhouse effect. (7)
1.1 Explanatory notes on the greenhouse effect (7)
The greenhouse effect is a natural process that warms the Earth's surface. When the Sun’s
energy reaches the Earth, some of it is reflected back to space and the rest is absorbed, warming
the planet. The Earth then emits energy in the form of infrared radiation. Greenhouse gases in the
atmosphere, such as carbon dioxide (CO₂), methane (CH₄), water vapor (H₂O), and nitrous
oxide (N₂O), absorb this infrared radiation and trap heat in the atmosphere.
This trapped heat helps to keep the Earth's temperature at a level necessary to sustain life.
Without the greenhouse effect, the average temperature of the Earth would be around -18°C,
making it too cold for most life forms.
However, human activities like burning fossil fuels, deforestation, and industrial processes are
increasing the concentration of greenhouse gases. This leads to an enhanced greenhouse effect,
which causes global warming and climate change.
In summary, the greenhouse effect is crucial for maintaining life-supporting temperatures on
Earth, but human activities are intensifying the effect, leading to environmental problems.
The greenhouse effect is a natural process in which certain gases in Earth's atmosphere trap heat,
preventing it from escaping into space and thus maintaining the planet's temperature at a level
suitable for life. Here’s a breakdown of how it works:
1. Solar Radiation: The Sun emits energy in the form of radiation, some of which reaches
the Earth's surface. This energy heats the Earth's surface and is reflected back into the
atmosphere in the form of infrared radiation (heat).
, 2. Greenhouse Gases: Some gases in the atmosphere, such as carbon dioxide (CO2),
methane (CH4), water vapor (H2O), nitrous oxide (N2O), and ozone (O3), are capable of
absorbing and re-emitting infrared radiation. These are called greenhouse gases.
3. Heat Trapping: After the Earth's surface absorbs solar radiation, it releases this energy
as heat (infrared radiation). Greenhouse gases absorb some of this heat and then re-
radiate it in all directions, including back toward Earth's surface, which keeps the planet
warmer than it would be without them.
4. Natural vs. Enhanced Greenhouse Effect: The natural greenhouse effect is essential for
life, as it keeps the Earth's average temperature around 15°C, allowing ecosystems to
thrive. However, human activities, such as burning fossil fuels and deforestation, have
increased the concentration of greenhouse gases in the atmosphere, leading to an
enhanced greenhouse effect, which contributes to global warming and climate change.
5. Impact of the Greenhouse Effect: The enhanced greenhouse effect is causing
temperatures to rise, which results in melting polar ice caps, rising sea levels, and more
extreme weather patterns. This effect is one of the key drivers of climate change.
6. Carbon Cycle: The carbon cycle involves the movement of carbon between the
atmosphere, oceans, and land. Human activities are disrupting this cycle by adding more
CO2 to the atmosphere, which intensifies the greenhouse effect.
7. Global Warming: The enhanced greenhouse effect leads to global warming, which
refers to the long-term increase in Earth's average temperature. This has wide-ranging
environmental, social, and economic consequences, including shifting weather patterns,
ecosystem disruption, and increased occurrence of extreme weather events.
In summary, while the greenhouse effect is a natural and necessary phenomenon for maintaining
life on Earth, human-induced factors are amplifying it, leading to global warming and climate-
related challenges.
1.2 Distinguish between hypertonic, hypotonic, and isotonic solutions. (6)
Distinction Between Hypertonic, Hypotonic, and Isotonic Solutions (6 marks)
1. Hypertonic Solution
A solution that has a higher solute concentration than the cell's cytoplasm.
Water moves out of the cell by osmosis.
The cell shrinks (crenates in animal cells or undergoes plasmolysis in plant cells).
2. Hypotonic Solution
A solution that has a lower solute concentration than the cell's cytoplasm.
