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 (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).
1.3 Explain how edges and corridors can strongly influence landscape
biodiversity. (7)
1.3 How edges and corridors influence landscape biodiversity (7)
Edges and corridors are important features in a landscape that can significantly affect
biodiversity:
Edges are the boundaries where two different ecosystems meet (for example, a forest and
a grassland). These areas often have greater biodiversity because they contain species
from both ecosystems, plus species that specialize in living at the boundary (called edge
species). However, edges can also expose species to threats like predators, invasive
species, and human disturbance.
Corridors are strips of natural habitat that connect isolated patches of ecosystems, such
as strips of forest linking two woodlands. Corridors allow animals to move safely
between habitats, which helps maintain genetic diversity, supports species migration, and
prevents populations from becoming isolated and vulnerable to extinction.
In summary, edges can increase species richness but may also introduce risks, while corridors
promote movement, reproduction, and survival of species across fragmented landscapes,
supporting overall biodiversity.
Influence of Edges and Corridors on Landscape Biodiversity (7 marks)
1. Edges
Edges are the boundaries between different ecosystems (e.g., forest and grassland).
These areas often support a greater diversity of species due to the presence of species
from both adjoining habitats, plus species that specialize in edge environments — known
as edge species.
This increased variety of habitats and resources at the edge is known as the edge effect.
However, excessive edge habitats can also lead to habitat fragmentation, which may
negatively impact some interior-dwelling species.
2. Corridors
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 (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).
1.3 Explain how edges and corridors can strongly influence landscape
biodiversity. (7)
1.3 How edges and corridors influence landscape biodiversity (7)
Edges and corridors are important features in a landscape that can significantly affect
biodiversity:
Edges are the boundaries where two different ecosystems meet (for example, a forest and
a grassland). These areas often have greater biodiversity because they contain species
from both ecosystems, plus species that specialize in living at the boundary (called edge
species). However, edges can also expose species to threats like predators, invasive
species, and human disturbance.
Corridors are strips of natural habitat that connect isolated patches of ecosystems, such
as strips of forest linking two woodlands. Corridors allow animals to move safely
between habitats, which helps maintain genetic diversity, supports species migration, and
prevents populations from becoming isolated and vulnerable to extinction.
In summary, edges can increase species richness but may also introduce risks, while corridors
promote movement, reproduction, and survival of species across fragmented landscapes,
supporting overall biodiversity.
Influence of Edges and Corridors on Landscape Biodiversity (7 marks)
1. Edges
Edges are the boundaries between different ecosystems (e.g., forest and grassland).
These areas often support a greater diversity of species due to the presence of species
from both adjoining habitats, plus species that specialize in edge environments — known
as edge species.
This increased variety of habitats and resources at the edge is known as the edge effect.
However, excessive edge habitats can also lead to habitat fragmentation, which may
negatively impact some interior-dwelling species.
2. Corridors
