C)
The difference between allele A and allele S is due to changes in the environment.
The following five limiting factors would control the
population density of weeds;
<span>1.
</span>Supply and nutrients in the soil
<span>2.
</span>Presence/Absence of growth-restricting
substances such as pesticides
<span>3.
</span>The soil aeration and soil structure
<span>4.
</span>Moisture content in the soil.
<span>5.
</span>Biotic factors such as disease and pests
<span>6.
</span>Quality, intensity and duration of light
Organisms that live in water are not totally independent of soil as a resource. These organisms depend on aquatic plants for food and other substances. These aquatic plants in turn require minerals for their sustenance. These minerals are carried to waterbodies from soil by rivers, rainwater etc.
Organic compounds and inorganic compounds differ from each other. Three differences are :
1. Organic compound has carbon and hydrogen atoms while the inorganic compound has other atoms.
2. Organic compounds make the important biomolecules such as amino acids, proteins, DNA, RNA, etc whereas the inorganic compounds make the salts, acids, bases, etc.
3. Organic compounds have carbon hydrogen bonds or carbon carbon bonds. These types are not formed in inorganic compounds.
Answer:
Replacing skin defects has witnessed several developments over the centuries. It started with the introduction of skin grafting by Reverdin in 1871. Since then, varieties of skin grafting techniques have been used successfully. Despite being clinically useful, skin grafts have many limitations including the availability of the donor site especially in circumstances of extensive skin loss, immune rejection in allogenic skin grafts, pain, scarring, slow healing and infection.1,2 For these reasons, scientist have worked hard to find skin substitutes to replace skin defects without the need for a "natural" skin graft. These materials which are used to cover skin defects are called "Skin substitutes". This article briefly discusses the common types of skin substitutes and their clinical uses.
