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 that warms the Earth’s surface. Here's a breakdown:
1. Solar Radiation: The Sun emits energy in the form of solar radiation, which reaches
Earth. Some of this energy is absorbed by the Earth's surface, warming it, while the rest is
reflected back into space.
2. Infrared Radiation: As the Earth’s surface warms, it radiates heat in the form of infrared
radiation. This heat energy is emitted from the Earth and rises into the atmosphere.
3. Greenhouse Gases: The atmosphere contains gases like carbon dioxide (CO₂), methane
(CH₄), water vapor (H₂O), nitrous oxide (N₂O), and ozone (O₃), known as greenhouse
, gases. These gases absorb and trap the infrared radiation, preventing it from escaping
back into space.
4. Heat Retention: After absorbing infrared radiation, greenhouse gases re-radiate the heat
in all directions, including back towards the Earth’s surface. This keeps the planet
warmer than it would otherwise be.
5. Importance for Life: Without the greenhouse effect, Earth would be too cold to support
life as we know it, with average temperatures being around -18°C instead of the current
average of approximately 15°C.
6. Enhanced Greenhouse Effect: Human activities, such as burning fossil fuels and
deforestation, increase the concentration of greenhouse gases in the atmosphere, leading
to more heat being trapped and contributing to global warming and climate change.
In summary, the greenhouse effect is essential for maintaining Earth’s temperature, but its
intensification due to human activities is a major driver of climate change.
The Greenhouse Effect (7 marks)
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 this energy in the form of infrared radiation (heat).
Greenhouse gases (GHGs) in the atmosphere, such as carbon dioxide (CO₂), methane (CH₄),
nitrous oxide (N₂O), and water vapor (H₂O), trap some of this outgoing heat, preventing it from
escaping into space. This trapped heat warms the Earth’s surface and atmosphere — similar to
how a greenhouse retains heat, hence the name.
Without the greenhouse effect, the Earth would be too cold to support most life forms. However,
human activities such as burning fossil fuels, deforestation, and industrial processes have
increased the concentration of GHGs, enhancing the greenhouse effect and leading to global
warming and climate change.
1.2 Distinguish between hypertonic, hypotonic, and isotonic solutions. (6)
1.2 Distinguish between hypertonic, hypotonic, and isotonic solutions (6)
Hypertonic solution:
A hypertonic solution has a higher concentration of solutes compared to the inside of a
cell. Water moves out of the cell into the solution, causing the cell to shrink or shrivel
(a process called crenation in animal cells).
Hypotonic solution:
A hypotonic solution has a lower concentration of solutes compared to the inside of a
, cell. Water moves into the cell, causing the cell to swell and potentially burst (this
bursting is called lysis in animal cells).
Isotonic solution:
An isotonic solution has the same concentration of solutes as the inside of a cell. There
is no net movement of water into or out of the cell, so the cell retains its normal shape
and size.
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.
Water moves into the cell by osmosis.
The cell swells and may burst (lysis in animal cells; becomes turgid in plant cells).
3. Isotonic Solution
A solution that has the same solute concentration as the cell's cytoplasm.
Water moves in and out of the cell at equal rates.
The cell stays the same size (no net movement of water).
1. Hypertonic Solution:
o A solution that has a higher concentration of solutes (e.g., salts or sugars)
compared to the concentration inside the cell.
o Effect on Cells: Water will move out of the cell to balance the concentration,
causing the cell to shrink or undergo plasmolysis (in plant cells).
2. Hypotonic Solution:
o A solution that has a lower concentration of solutes compared to the
concentration inside the cell.
o Effect on Cells: Water will move into the cell to balance the concentration,
causing the cell to swell or even burst (lysis in animal cells, turgidity in plant
cells).
3. Isotonic Solution:
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 that warms the Earth’s surface. Here's a breakdown:
1. Solar Radiation: The Sun emits energy in the form of solar radiation, which reaches
Earth. Some of this energy is absorbed by the Earth's surface, warming it, while the rest is
reflected back into space.
2. Infrared Radiation: As the Earth’s surface warms, it radiates heat in the form of infrared
radiation. This heat energy is emitted from the Earth and rises into the atmosphere.
3. Greenhouse Gases: The atmosphere contains gases like carbon dioxide (CO₂), methane
(CH₄), water vapor (H₂O), nitrous oxide (N₂O), and ozone (O₃), known as greenhouse
, gases. These gases absorb and trap the infrared radiation, preventing it from escaping
back into space.
4. Heat Retention: After absorbing infrared radiation, greenhouse gases re-radiate the heat
in all directions, including back towards the Earth’s surface. This keeps the planet
warmer than it would otherwise be.
5. Importance for Life: Without the greenhouse effect, Earth would be too cold to support
life as we know it, with average temperatures being around -18°C instead of the current
average of approximately 15°C.
6. Enhanced Greenhouse Effect: Human activities, such as burning fossil fuels and
deforestation, increase the concentration of greenhouse gases in the atmosphere, leading
to more heat being trapped and contributing to global warming and climate change.
In summary, the greenhouse effect is essential for maintaining Earth’s temperature, but its
intensification due to human activities is a major driver of climate change.
The Greenhouse Effect (7 marks)
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 this energy in the form of infrared radiation (heat).
Greenhouse gases (GHGs) in the atmosphere, such as carbon dioxide (CO₂), methane (CH₄),
nitrous oxide (N₂O), and water vapor (H₂O), trap some of this outgoing heat, preventing it from
escaping into space. This trapped heat warms the Earth’s surface and atmosphere — similar to
how a greenhouse retains heat, hence the name.
Without the greenhouse effect, the Earth would be too cold to support most life forms. However,
human activities such as burning fossil fuels, deforestation, and industrial processes have
increased the concentration of GHGs, enhancing the greenhouse effect and leading to global
warming and climate change.
1.2 Distinguish between hypertonic, hypotonic, and isotonic solutions. (6)
1.2 Distinguish between hypertonic, hypotonic, and isotonic solutions (6)
Hypertonic solution:
A hypertonic solution has a higher concentration of solutes compared to the inside of a
cell. Water moves out of the cell into the solution, causing the cell to shrink or shrivel
(a process called crenation in animal cells).
Hypotonic solution:
A hypotonic solution has a lower concentration of solutes compared to the inside of a
, cell. Water moves into the cell, causing the cell to swell and potentially burst (this
bursting is called lysis in animal cells).
Isotonic solution:
An isotonic solution has the same concentration of solutes as the inside of a cell. There
is no net movement of water into or out of the cell, so the cell retains its normal shape
and size.
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.
Water moves into the cell by osmosis.
The cell swells and may burst (lysis in animal cells; becomes turgid in plant cells).
3. Isotonic Solution
A solution that has the same solute concentration as the cell's cytoplasm.
Water moves in and out of the cell at equal rates.
The cell stays the same size (no net movement of water).
1. Hypertonic Solution:
o A solution that has a higher concentration of solutes (e.g., salts or sugars)
compared to the concentration inside the cell.
o Effect on Cells: Water will move out of the cell to balance the concentration,
causing the cell to shrink or undergo plasmolysis (in plant cells).
2. Hypotonic Solution:
o A solution that has a lower concentration of solutes compared to the
concentration inside the cell.
o Effect on Cells: Water will move into the cell to balance the concentration,
causing the cell to swell or even burst (lysis in animal cells, turgidity in plant
cells).
3. Isotonic Solution:
