Presentation on theme: "27 March 2013Ecology_Nematodes.ppt1 Ecology of Free-living Nematodes."— Presentation transcript:
27 March 2013Ecology_Nematodes.ppt1 Ecology of Free-living Nematodes
27 March 2013Ecology_Nematodes.ppt2 Phylum Nematoda Body form worm-like –Slender, tapered at ends Mostly less than 2.5 mm long, 0.1 mm wide
27 March 2013Ecology_Nematodes.ppt3 Phylum Nematoda Primarily aquatic or marine, some terrestrial Many parasitic Mostly very small –Meiofauna Live in spaces between grains of soil, sediments
27 March 2013Ecology_Nematodes.ppt4 Phylum Nematoda Largest pseudocoelomate phylum –estimated 20,000 species Worldwide in all imaginable habitats –Deep sea to mountain tops –Glaciers to hot springs –Feed on all kinds of organic materials
27 March 2013Ecology_Nematodes.ppt5 Humus Partially decayed organic matter –Formed by bacteria, fungi, earthworms, and other soil organisms, including some nematodes; –Consumed by nematodes
27 March 2013Ecology_Nematodes.ppt6 Hypothesis 1 H1: Where soil contains more humus, there are more nematodes. –“More food (humus): more nematodes.”
27 March 2013Ecology_Nematodes.ppt7 Hypothesis 2 Nematodes require water in soil –Move in water films covering soil particles –Die or become dormant if soil dries out. H2: Where soil is moister, there are more nematodes. –“More water: more nematodes.”
27 March 2013Ecology_Nematodes.ppt8 Hypothesis 3 Soils differ in particle sizes and shapes –Clay soils have tiny flat particles with little space –Sandy soils have larger irregular particles with more space Nematodes can move more easily where there is more space –Find food, mates, etc.
27 March 2013Ecology_Nematodes.ppt9 Hypothesis 3 H3: Where there is more space, there are more nematodes. But, how can we measure “space?”
27 March 2013Ecology_Nematodes.ppt10 Hypothesis 3 How can we measure “space?” We can’t, but Density of rock (soil particle) ~ 3 g/ml Density of water = 1 g/ml Density of air ~ g/ml Soils with more “rock” & less space (water + air) are denser; so...
27 March 2013Ecology_Nematodes.ppt11 Hypothesis 3 H3: Where soil is more dense (less space), there are fewer nematodes; or where soil is less dense (more space), there are more nematodes –“Less density: more nematodes.”
27 March 2013Ecology_Nematodes.ppt12 3 Hypotheses H1: Where soil contains more humus, there are more nematodes. –“More food (humus): more nematodes.” H2: Where soil is moister, there are more nematodes. –“More water: more nematodes.” H3: Where soil is less dense (more space), there are more nematodes. –“Less density: more nematodes.”