Senescence . Question 5 options: a) begins at the moment of conception and accelerates after age 40 b) occurs across all parts of the body at the same time and speed c) begins once body structures reach maximum capacity and efficiency d) occurs because the physical body wears out from use

c. Senescence begins once body structures reach maximum capacity and efficiency

Explanation: Senescence is simply ‘growing old’. Aging sets in at the time when physical development is complete - when a person reaches their ‘prime’. After that a person is ‘past their prime’ which is the subjective recognition of the on set of gradual deterioration. The biological rationale is that the purpose of life is to survive to reproductive age and to reproduce, and in some species to assist progeny to survive to reproductive age. Beyond that, survival has limited value.

An analogy is the length of an elephant’s trunk. It is as long as it needs to be, determined by natural selection, but no longer than it needs to be for optimum efficiency, again determined by natural selection.

sodium i think the chemical element of atomic number 11, a soft silver-white reactive metal of the alkali metal group.

question#1

ans:

cell is the basic unit of organization of all living things. cells are often called the building block of life and it is the smallest unit of life. the study of cell is called cell biology. cell consists of cytoplasm enclosed within membrane, which contain bio-molecules such as proteins and nucleic acid.

two third of cell is water, which means that two-third of your whole body is water. the rest is the mixture of molecules, mainly proteins, lipids and carbohydrates.

question#2

ans:

organ:

an organ is a group of tissues specialized to form a functional unit. an example is the heart in animals.

organ system:

an organ system is a group of several organs whose functions are synchronized to release an effective action in a living organism. an example is digestive system.

question#3

different systems perform different function at tissue level. for example, the respiratory system facilitates breathing. in the alveoli tissue of the lungs, the exchange of oxygen and carbon dioxide molecules between the air and the bloodstream occurs by passive transport, so that oxygen is taken in and carbon dioxide and water are removed. different systems of the body carry out different functions. for example, your digestive system is responsible for taking in and processing food, while your respiratory system working with your circulatory system is responsible for taking up oxygen and getting rid of carbon dioxide.

question#4

different systems perform different function at tissue level. for example, the respiratory system facilitates breathing. in the alveoli tissue of the lungs, the exchange of oxygen and carbon dioxide molecules between the air and the bloodstream occurs by passive transport, so that oxygen is taken in and carbon dioxide and water are removed. different systems of the body carry out different functions. for example, your digestive system is responsible for taking in and processing food, while your respiratory system—working with your circulatory system is responsible for taking up oxygen and getting rid of carbon dioxide.

question#5

our body works because of the interactions that happen between organs and organ systems.  

for example:  

the heart to regulate blood flow throughout the body. the blood carries oxygen and nutrients to the cells and carries carbon dioxide and waste away from the cells. body systems work together in maintaining a constant internal environment. when this balance is disrupted, the body systems may not function properly, and human health can suffer.   you start to feel bad.