How do humans obtain the nitrogen they use in their bodies?
1. by consuming plants or other animals
2. by absorbing ammonia from bacteria growing in the roots of plants
3. by breathing the nitrogen present in the atmosphere
4. by absorbing nitrogen found in the soil

What happens during the heat transfer within earth

The table shows dates and appearance of index fossils. which rock layers can be dated most precisely? a) a layer containing both a fossil 4 and a fossil 3 b) a layer containing both a fossil 2 and a fossil 3 c) a layer containing both a fossil 1 and a fossil 4 d) a layer containing both a fossil 1 and a fossil 2

Which of these transport mechanisms moves glucose from the blood into a cell? active transport diffusion facilitated diffusion osmosis