Waec Expo Runz: 2015/2016 Biology Essay/Theory and OBJ Free Answers
3ai.
Sewage is a water-carried waste, in solution or suspension, that is intended to be removed from a community.
3aii.
-Increased organic matter (from the sewage) breaking down in the river reduces the amount of dissolved oxygen in the water body as the decomposition process uses up the available dissolved oxygen.
-Sewage heightens the levels of nutrients, increasing the bioavailability of nutrients, which can increase productivity of plankton near the sewage outfall
-Release of sewage can degrade vegetation and soil by depositing harmful chemicals in bottom sediment
-If the water was contaminated with disease-causing bacteria, these could be consumed as food by shellfish. When eaten raw or partially cooked, these shellfish can make people sick.
-Detergents can cause liver and kidney damage, while sewage water carries diseases such as Giardiasis, Amoebic dysentery and Cholera.
3b.
Terracing is a soil conservation practice applied
to prevent rainfall runoff on sloping land from
accumulating and causing serious erosion.
Terraces consist of ridges and channels
constructed across-the-slope.
Terracing is also practice of creating nearly
level areas in a hillside area. The terraces
form a series of steps, each at a higher level
than the previous. Terraces are protected
from erosion by soil other barriers.
Terraced farming is more common on small
farms and in underdeveloped countries, since
mechanized equipment is difficult to deploy
in this setting.
3c.
The special characteristics that enable plants and animals to be successful in a particular environment are called adaptations.
3d.
An adaptation is a physical or
behavioral characteristic that has developed to
allow an organism to better survive in its
environment. Adaptations are the result of
evolution, and may occur when a gene mutates,
or changes by accident. That mutation causes
the organism to better survive and reproduce,
and it pa$$es on that trait to its offspring. It
can take many generations to develop an
adaptation.
Examples: One physical adaptation used in the
intertidal zone is a crab’s hard shell, which
protects it from predators, drying out and
being crushed by waves. A behavior@l
adaptation in the oceans is the use of loud,
low-frequency calls by fin whales to
communicate with other whales over great
distances.
3d.
I.
Hydrophytes
1. the moisture inside the plants leaves its
function is to lessen water loss it does this by
not letting the water diffuse out so easily.
The cutile is like a protective film covering the
epidermis of the leaves it works as a
protective waxy covering and tends to be
thicker on the top of the leaf. Without it the
sun would evaporate all the moisture leaving
the leave dry shrivelled and worth less.
2. The roots work by
absorbing water and minerals to be from
the soil and transported by the xylem and
phloem (vascular bundle) to be used for
photosynthesis and respiration
Sewage is a water-carried waste, in solution or suspension, that is intended to be removed from a community.
3aii.
-Increased organic matter (from the sewage) breaking down in the river reduces the amount of dissolved oxygen in the water body as the decomposition process uses up the available dissolved oxygen.
-Sewage heightens the levels of nutrients, increasing the bioavailability of nutrients, which can increase productivity of plankton near the sewage outfall
-Release of sewage can degrade vegetation and soil by depositing harmful chemicals in bottom sediment
-If the water was contaminated with disease-causing bacteria, these could be consumed as food by shellfish. When eaten raw or partially cooked, these shellfish can make people sick.
-Detergents can cause liver and kidney damage, while sewage water carries diseases such as Giardiasis, Amoebic dysentery and Cholera.
3b.
Terracing is a soil conservation practice applied
to prevent rainfall runoff on sloping land from
accumulating and causing serious erosion.
Terraces consist of ridges and channels
constructed across-the-slope.
Terracing is also practice of creating nearly
level areas in a hillside area. The terraces
form a series of steps, each at a higher level
than the previous. Terraces are protected
from erosion by soil other barriers.
Terraced farming is more common on small
farms and in underdeveloped countries, since
mechanized equipment is difficult to deploy
in this setting.
3c.
The special characteristics that enable plants and animals to be successful in a particular environment are called adaptations.
3d.
An adaptation is a physical or
behavioral characteristic that has developed to
allow an organism to better survive in its
environment. Adaptations are the result of
evolution, and may occur when a gene mutates,
or changes by accident. That mutation causes
the organism to better survive and reproduce,
and it pa$$es on that trait to its offspring. It
can take many generations to develop an
adaptation.
Examples: One physical adaptation used in the
intertidal zone is a crab’s hard shell, which
protects it from predators, drying out and
being crushed by waves. A behavior@l
adaptation in the oceans is the use of loud,
low-frequency calls by fin whales to
communicate with other whales over great
distances.
3d.
I.
Hydrophytes
1. the moisture inside the plants leaves its
function is to lessen water loss it does this by
not letting the water diffuse out so easily.
The cutile is like a protective film covering the
epidermis of the leaves it works as a
protective waxy covering and tends to be
thicker on the top of the leaf. Without it the
sun would evaporate all the moisture leaving
the leave dry shrivelled and worth less.
2. The roots work by
absorbing water and minerals to be from
the soil and transported by the xylem and
phloem (vascular bundle) to be used for
photosynthesis and respiration
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