There are three types of variables in a scientific experiment:
Independent: Changes which you, the experimenter, control.
Dependent: Changes which occur based on the changes you make (Independent)
Control: Anything else which might change or influence the dependent variables outside of the independent changes made by the experimenter.
Control variables must be monitored and controlled during an experiment to make sure that they are kept equal, otherwise they could make your results false or unreliable.
In the Cool Science Projects link, they discuss a plant growing project. You wish to determine the growth difference between plants which have a full eight hours of sunlight versus plants which receive four hours of sunlight. The amount of time the plant is in the full sunlight is the independent variable and one of the dependent variables is the growth rate of each plant. There may be other dependent variables, such as the overall height of each plant.
A good example of a control variable might be the amount or type of water used to hydrate the plants during the experiment. If you were to give one plant more water than another, or different qualities of water, you would be further influencing the experiment beyond the initial independent variable. You could not then say that it was strictly the duration of time in the sun which caused the growth or height differential, as it may have been other variables which caused these changes.
It's important to be aware of exactly what changed within an experiment, and what did not, in order to keep your findings valid.
Historically, you sent someone out into your garden or field with a hoe, and they chopped weeds or pulled them out by the roots. Chemical weeding involves spraying herbicides that target the most common weeds--not including the crop. Today, you might release an insect that feeds on the weeds but leaves the crop alone. These biological methods are not in common use yet. The biological method to get rid of tomato worms (horn worms), for example, is to pluck them off and stomp on them. Of course, that is pest control, not weeding.
I personally feel it is a biological response of human civilization
trichoderma viren
biological control
The promotion of declining populations and of fatal disability and disease is the role of micro-organisms in the biological control of pests. Micro-organisms can include such entities of household recognition as bacteria and fungi. They may introduce disabling and terminal viruses into pest-minded arthropods, birds, mammals and reptiles.
A biological refrigerator and refrigerator have many similarities. A biological refrigerator is created especially for a hospital or pharmacy, and has different variants of temperature control.
A thermobar is used as "a control for random temperature and pressure changes in the room"Dolphin WD. (2008) Biological Investigations: Form, Function, Diversity, and Process. McGraw Hill Higher Education.
Biological control is the beneficial action of predators, parasites, pathogens, and competitors in controlling pests and their damage.
Biological control is the use of a pey species to control pests and parasites i.e. to use Encarsia formosa the Chalcid wasp to control Whitefly. This avoids the use of pesticides.
The gender and age should be the same.
A biological Control Of Insect Pests. ! (; (*:
In biological pest control the pests are killed with a living organism whilst in chemical cultural pest control a chemical is used.
Paul DeBach has written: 'Biological control by natural enemies' -- subject(s): Agricultural pests, Biological control, Insect pests, Pest control, Pests, Weeds
Biological Clock
I think biological Pest control.
Michael J. Samways has written: 'Biological control of pests and weeds' -- subject(s): Biological control, Pests, Weeds
Jaroslav Weiser has written: 'An atlas of insect diseases' -- subject(s): Atlases, Biological control, Diseases, Insect pests, Insects 'Biological control of vectors' -- subject(s): Biological control, Communicable diseases, Prevention, Vector control 'Die Mikrosporidien als Parasiten der Insekten'