Answer:
(a). soft substrates
Explanation:
Mobile organisms can be measured by both direct and indirect methods. Direct methods may involve observing the actual behavior (e.g., scoring via timing). Moreover, indirect methods are those where the technique used depends on the species being examined, collecting information such as through recording of tracks in the soft substrate (e.g., mud, sand, snow), presence of fur/feathers, droppings (mammals), etc. For example, indirect observation of insects may involve the determination of exoskeletons, sounds, etc.
The answer is <span>Time is the independent variable, and the number of birds is the dependent variable. </span>
<span>An independent variable is variable that is not affected in the experiment. It is what experimenter controls. On the other side, a dependent variable is called dependent because it depends on the independent variables. It is what is affected during the experiment.
In Sam investigation, he controls time - he counts birds at 6 a.m. and 6 p.m. So, time is the independent variable. The number of birds is affected during the experiment, so it must be the dependent variable.
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Fluid means being able to move, relating to the membrane as it can freely move allowing molecules in and out. The word mosaic means something of many different components which also relates to the plasma membrane as it consists of phosphates glycoproteins, cholesterol and integral proteins.
Van Leeuwenhoek discovered "protozoa" - the single-celled organisms and he called them "animalcules". He also improved the microscope and laid foundation for microbiology. He is often cited as the first microbiologist to study muscle fibers, bacteria, spermatozoa and blood flow in capillaries.