B6e: Life in Soil

Life above ground is obvious. Life below ground is just as diverse and essential in maintaining the recycling of important elements and providing the correct conditions for plant growth. Without the action of soil life we would have to climb over dead dinosaur bodies to get to school and many important elements would be unavailable.

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What are the five main components of soil?
Water, air, living organisms, dead material and different sized mineral particles.
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Describe a typical food web in a soil.
Herbivores (slugs, snails, wire worms), detritivores (earthworms, millipedes, springtails) and finally carnivores (centipedes, spiders and ground beetles)
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Name two decomposers.
Fungi and Bacteria.
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What do decomposers do?
They help to recycle nutrients.
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Why is soil important for the majority of plants?
It provides an anchor for their roots - which absorb minerals and water from the soil.
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What two things can earthworms improve?
Fertility and soil structure.
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What is the particle size of a sandy soil?
Large
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What is the particle size of a clay soil?
Small
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What is loam soil?
A mixture of clay and sandy soil.
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What is humus?
Partially decayed organic material found in soil.
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What are the steps needed to determine the water content of a soil?
1. weigh a sample of the soil, 2. heat the soil in a warm oven, 3. re-weigh the soil, 4. repeat steps 2 and 3 until the mass of the soil does not change. The loss of mass is due to the loss of water during heating.
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How do you determine the humus content of a soil?
The weighed dry soil sample is heated strongly so that the humus burns away. The loss of mass is the mass of humus that was burnt away.
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What are the steps needed to determine the air content of a soil?
1. fill a can with soil 2. weigh the can and its contents 3. slowly add water until the water is level with the top of the soil 4. re-weigh the can & its contents. The extra mass between steps 2 & 4 is due to the water that has filled the air spaces
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Talk about air content and permeability to water in clay soil.
Air content - Low (few and small air spaces). Permeability - Low
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Talk about air content and permeability to water in sandy soil.
Air content - High (many large air spaces). Permeability - High
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Talk about air content and permeability to water in loam soil.
Air content - High (many different sized air spaces). Permeability - Medium
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Which soil tends to be waterlogged with little air content?
Clay soil
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Which soil tends to drain quickly but have plenty of air?
Sandy soil
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Which soil retains water well and has plenty of air?
Loam soil.
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Explain why some life in soil depends on a supply of oxygen and water.
All living things need water to carry ou reactions in their cells, and cannot survive without it. Almost everything needs oxygen too, for respiration. (e.g. the roots of plants need to get oxygen from the soil so they can respire)
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What is the importance of humus in the soil?
As organic material is slowly broken down by decomposers, minerals and nutrients are released into the soil. These compounds can then be used by other organisms. Humus also increases the air content of soil, making more oxygen available.
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Why are earthworms important to soil?
They bury organic material for decomposition by bacteria and fungi, this aerates and drains the soil, which mixes up soil layers and neutralises acidic soil.
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Why is aerating important?
It allows air to enter the soil - which provides the organisms with oxygen for respiration.
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Why is draining important?
If the soil is waterlogged, there's less oxygen available
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Why is neutralising acidic soils important?
Because acidic soils are less fertile than neutral or alkaline soils
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Why is mixing up soil layers important?
Because it distributes the nutrients more equally
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What did Charles Darwin realise?
That earthworms are important in agriculture.
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What did Charles Darwin realise about root cells?
oot cells need a supply of air for respiration. If the soil is waterlogged, it will contain little air. Plants will not grow well and animals living in the soil will not be able to survive.
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What did Charles Darwin realise about earthworms?
Earthworms improve soils by aerating them and improving water drainage. They also increase the depth of the fertile layer of soil by mixing the layers as they move around. Some crops do not grow well in acidic soil.
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Other cards in this set

Card 2

Front

Describe a typical food web in a soil.

Back

Herbivores (slugs, snails, wire worms), detritivores (earthworms, millipedes, springtails) and finally carnivores (centipedes, spiders and ground beetles)

Card 3

Front

Name two decomposers.

Back

Preview of the front of card 3

Card 4

Front

What do decomposers do?

Back

Preview of the front of card 4

Card 5

Front

Why is soil important for the majority of plants?

Back

Preview of the front of card 5
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