why there is less earthworms in in the soil which has mostly gravel in it ?
Answers
Answer:
Have you ever dug a hole in the soil and noticed earthworms wriggling out of your way? Not only are earthworms good for birds and fish to eat, but these little animals actually work hard to help put food on your table, too. By adding nutrients to the soil they live in, earthworms are continually working to keep soil healthy so that most plants can grow well in it. To do their important work, earthworms prefer certain types of soils over others.
Background
Here's a riddle for you: What has five hearts, no eyes and helps feed all the people on Earth? The earthworm! This amazing animal is important for keeping soil rich in nutrients. Just as you need vitamins to stay healthy, such as the vitamin C you get from fruits and vegetables, plants need nutrients to grow properly as well—and they get them from the soil. The earthworm is able to transform dead plants and leaves (also called plant matter) into nutrients for the soil. Earthworms can make food for living plants from dead ones. They leave this food (the nutrients) behind in the soil where growing plants can absorb it.
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In less than a day an earthworm can eat its entire weight in dead plant matter. So, for example, if you were an earthworm and weighed 50 kilograms, you'd need to eat about 50 kilograms of food every day! During this moving feast, an earthworm is also loosening and aerating (letting air get into) the soil to make it easier for many beneficial plants to grow in it.
Materials
• A cool area that is not brightly lit
• Measuring cups
• Dry sand (1.5 cups)
• Dry gravel (1.5 cups)
• Dead leaves, crumbled (1.5 cups)
• Dry potting soil (1.5 cups)
• Mixing bowl
• Spray bottle
• Water
• Spoon or fork
• Empty plastic box with a sealable lid, larger than a shoe box, but smaller than a laundry basket
• Earthworms (at least five); available at a bait shop; or use a small hand trowel or shovel to dig up earthworms from the ground (usually in shady, moist soil); or find them on the ground after it has rained
• A small container with a lid in which to hold the earthworms; put some damp soil and dead leaves inside the container for the worms, and keep them in a cool place until you are ready to do the activity
Preparation
• You can test this activity indoors or outside. Choose a location that is cool and in the shade (if you are testing outside) or in a dimly lit room (if you are testing indoors). If the plastic box is transparent, use an especially dark location, such as a closet.
• Put 1.5 cups of sand into the mixing bowl. Spray the sand with water (counting the squirts as you go) until it all feels wet, stopping before puddles of water appear; mix the moistened sand with a spoon or fork.
• Transfer the wet sand from the mixing bowl to one corner of the plastic box. Make sure the sand does not spill out over one quarter of the area of the bottom of the box.
• Rinse out and dry the mixing bowl. Spray the other "soils" (gravel, dried leaves and potting soil) in the mixing bowl (each separately) just as you did the sand. Use the same number of sprays of water for each soil type as you did for the sand. When each soil has been sprayed, transfer it in its own corner of the box. How wet does the sand feel compared with the gravel, dried leaves and potting soil?
Observations and results
Were most of the earthworms in the leaves? Were some in the sand and potting soil? Were none in the gravel?
Earthworms eat dead plant matter, such as fallen leaves, and transform it into a nutritious substance that plants can absorb more readily. So, if they want a tasty meal, they would most likely be in the leaves. However, if there is organic matter (dead plant matter or animal matter, which they also eat) in the other soil types tested, the earthworms might be attracted to those soils as well. But just because an earthworm is in one of the soils does not mean that it is its ideal environment or that it wants to eat that soil. For example, you may find one or more earthworms in the gravel, but this could be due to factors other than the earthworm searching for a food source—the gravel's humidity, for example, might be more appealing or there may be possible chemoattractants on the gravel.
Explanation:
I hope it is useful