Sensorimotor stage: birth to 2 years. Preoperational stage: ages 2 to 7. Concrete operational stage: ages 7 to 11. Formal operational stage: ages 12 and up.

At four years, preschoolers know hundreds of words and can use 5-6 words or more in sentences. You’ll be able to understand what your child is saying all the time. By five years, preschoolers can speak more clearly and will know, understand and use even more words, often in more complex sentences of up to nine words.

1 Reversibility is an important step toward more advanced thinking, although at this stage it only applies to concrete situations. In other words, they are able to understand that other people have their own thoughts.

Tasks. Conservation tasks test a child’s ability to see that some properties are conserved or invariant after an object undergoes physical transformation. Piaget proposed that children’s inability to conserve is due to weakness in the way children think during the preoperational stage (ages 2–6).

Preschool attendance is linked to improvements in social and emotional development, less grade repetition, less special education placement, and higher levels of high school graduation. The evidence and research consistently show that preschool allows children to develop skills that will serve them all of their life.

Conservation. Conservation is the understanding that something stays the same in quantity even though its appearance changes. To be more technical conservation is the ability to understand that redistributing material does not affect its mass, number, volume or length.

The importance of soil conservation also relates to water supply, and earth layers function as natural filters to improve water quality. In its turn, water is necessary to dissolve nutrients for plants.

Soil carries out a range of functions and services without which human life would not be possible. It provides an environment for plants (including food crops and timber wood) to grow in, by anchoring roots and storing nutrients. It filters and cleans our water and helps prevent natural hazards such as flooding.

The impact of poor soil use, meanwhile, goes beyond food production. Wind can carry thinned topsoil off fields and onto large bodies of water. Through a process known as eutrophication, the excess nutrients hasten plant growth and algae bloom, sucking up oxygen in the water and killing fish and other marine fauna.

Soil and Water Conservation Measures

• to control runoff and thus prevent loss of soil by soil erosion, to reduce soil compaction;
• to maintain or to improve soil fertility;
• to conserve or drain water;
• to harvest (excess) water (Tidemann 1996).