Microscopic Life in Soil

[Music] soil is not an entirely lifeless substance it contains much more than can be seen with the naked eye while soil is composed partly of inorganic or non-living materials it is also composed of organic materials anything living or anything that was once alive among the living organic materials are many microscopic plants and animals magnified here several hundred times these microorganisms are important to the balance of life on Earth for they continually work upon other soil materials making them useful for plant growth the same soil may contain different microorganisms at different times the population depends partly upon moisture water is an inorganic part of soil many microorganisms live here even in the microscopic droplets attached to other soil materials they are best seen in this liquid medium the amoeba is a typical example the amoeba belongs ons to the class of animals called protozoa the entire animal consists of just one cell the amoeba moves by flowing or streaming other protozoans move by means of cyia tiny hairlike projection which surround their bodies protozoans feed on smaller microorganisms many protozoans and other single celled organisms reproduce by dividing called reproduction by fishing this protozoan is now in the process of dividing it forms two independent individuals when these two reach a certain size they will divide again different kinds of bacteria are found in soil bacteria are also single celled organisms many kinds of bacteria form colonies visible to the naked eye each of these spots is a colony composed of millions of bacteria colonies of microscopic fungi a simple non-green plant live in soil these single celled organisms are usually classified as plants at this level of Life plants and animals are often hard to tell apart the green chlorophyll in their bodies is characteristic of higher forms of plant life unlike more complex green plants however these microscopic plants can move about these tiny organisms are links in the chain of life for they provide food for other forms of life such as certain protozoans roopers are more complex microscopic animals their bodies are composed of many cells the cyia are for food procurement as well as locomotion even more complex in structure are the nematodes found in soil in great numbers these microscopic round worms often appear to the naked eye as fine threads nematodes help stir up the soil and they form tiny tunnels which allow air and moisture to penetrate when soil conditions become unfavorable such as a reduction in moisture a period of total rest occurs in many microorganisms some of the single celled organisms form cysts a cyst is a thickening of the cell wall in which the organism remains alive but dormant when conditions become favorable the the cyst wall will break and the organism will become active again microscopic fungi reproduce by means of spores masses of which develop within a specialized container called a sporangium the sporangium when opened reveals numbers of individual spores each one capable of producing a new plant spores also can withstand poor soil conditions for long periods of time and still develop when conditions again are favorable in addition to moisture favorable soil conditions include the presence of dead organic material which is the food of many microorganisms this can be demonstrated by inoculating an AAR plate with a little soil the aggar is rich in dead organic matter and the soil contains many microorganisms this time-lapse picture covers a period of 48 Hours see how rapidly certain microorganisms not visible in the soil multiply to form visible colonies in this suitable environment all these microorganisms and millions more exist in soil certain of them profoundly influence all higher forms of life for instance soil microorganisms rid the Earth's surface of dead organic materials in doing so they perform an even more important function a leaf as an example is composed partly of inorganic soil materials decomposing the leaf into its original materials is essential so that other forms of life can use these materials if a leaf is placed in a jar with some damp soil for a few days the process of decomposition can be observed dark areas soon appear these are colonies of microscopic fungi the fungi are helping to reduce the leaf into its original soil materials eventually the leaf becomes a part of the soil other forms of life can now use the basic materials once contained in the leaf plowing the stubble of a crop into the soil makes this organic material available to microorganisms so that they can perform their valuable work while some microorganisms decompose matter others build matter up for example every plant requires nitrogen for growth nitrogen must be taken in through the roots of higher forms of plant life as soil nitrates this is nitrogen gas it can't be seen for its colorless this is a soil nitrate manufactured from nitrogen gas this is the nitrogen material higher plants require air is 78% nitrogen gas it's changed chemically into soil nitrates by microorganisms living in the soil the roots of certain higher plants like alphalpha Clover and soy beans house colonies of these microorganisms they live within these tiny nodules and are called nitrogen fixing bacteria a cross-sectional microscopic scene shows the root of this plant and a colony of the bacteria attached each little section is an individual microscopic plant which functions to change nitrogen gas into soil nitrates because these bacteria form on the roots of certain plants such as alphalpha this crop is often rotated with other crops such as cotton which does not attract the bacteria when the cotton is harvested Alfalfa will be planted again soil nitrates will be added through the action of the bacteria and so improve the field for the next cotton crop soil then is not entirely lifeless it contains countless numbers of microscopic plants and animals many of the Single Cell microorganisms reproduce by fishing some withstand adverse environmental conditions by forming cysts and others by forming spores the reproductive device of these microscopic plants moisture and dead organic materials influence the development of many microorganisms breaking down dead organic materials and making them usable to other forms of life is a function of some microorganisms others are Builders changing nitrogen gas into soil nitrates these are only a few of the many ways in which soil microorganisms are essential to the balance of life on Earth [Music]