When conducting an investigation, we often observe or make measurements of things that change. These are variables. Keeping track of variables in an experiment is important because it helps you analyze and understand your results. Remember from the experiment your class conducted in Lesson 2, there are two major types of variables . An independent variable is not affected by the other variables in an experiment . It is often something that a scientist changes in order to do an experiment . Experiments should have only one independent variable . A dependent variable depends on other factors in the experiment . It is often the thing we are trying to learn more about and is the experimental results . A third type of variable is a controlled variable . This is what a scientist keeps similar in all parts of the experiment . There are often multiple controlled variables . Scientists try to make sure that controlled variables do not affect the outcome or results of an experiment . In the explore section of your text, you conducted several experiments on the phase changes of water.

1.What was the independent variable in these experiments?

2.What was the dependent variable?

3.What were the controlled variables, or the things you tried to keep the same in each part of the experiments.

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.

what are the options

explanation: