Organisms use a diversity of methods to obtain proper nutrit

Organisms use a diversity of methods to obtain proper nutrition.

a.Describe two structural features of the human stomach or small intestine. For each, explain how the structure relates to the function.

b.Plants have a variety of mechanisms for obtaining nutrients. Describe two plant structures and explain how each structure is utilized in nutrient uptake.

Solution

1. Two structural features of human stomach are:

A. Presence of logitudnal and circular smooth muscles: These muscles contract and relax to cause rhythmic movement of stomach to help mixing of food and gastric contents. Stomach releases HCl, gastric juice and enzymes. These all are mixed with the food through churning caused by movement of smooth muscles.

B. Presence of sphincter at opening and ending of stomach : the sphincter present at entry of stomach is called cardiac sphincter and towards end of it is pyloric sphincter.Sphincters are modified muscles that regulate opening and closing of an aperture. When food enters stomach its back flow its prevented by closure of cardiac sphincter. When food leaves stomach its back entry from intestine to stomach is regulated by pyloric sphincter.

2. Structural features of plants:

A. Presence of Root nodules in leguminuous plants: The root nodules in leguminuous plants are structures associated with roots that inhabit rhizobium bacteria. These bacteria live in colonies symbiotically in root nodules and help in fixation of atmospheric nitrogen. They convert atmospheric nitrogen to ammonia and provide it to plants to manufacture amides and proteins.

2. Presence of extensive root hair: root hairs are thread like structures present on roots. They increase surface area for absorption of nutrients.Sometimes roots of higher plants get associated with fungus. These structures are called mycorhizza. They help in increased absorption of phosphorus from the soil and make it available to the plants.