Describe tools used to determine student preconceptions:
Before beginning this unit, have your students draw and label a plant (any plant they choose is fine) and write what they think plants need in order to live and grow. Provide students with a sheet of paper and instruct them to fold it in half. On the left side of the folded paper, have students write their names and be sure to have them write the date. After students draw and label a plant and write what they think plants need in order to live and grow, collect the papers. At the end of this unit, hand the papers back to the students, have them draw and label a plant on the right side of the folded paper, and write what they now think plants need in order to live and grow. Make sure they include the date. Comparing the before-and-after work will serve as a graphic example of what students have learned.
KWL charts, Student science notebooks, class discussions, and student comments and questions are also tools used to determine student preconceptions.
Description of a student preconception (naïve conception, misconception, incomplete conception):
A common misconception of students is that plants have flowers so that bees can make honey.
Correct conception by the end of the unit:
By the end of the unit, students should have a solid understanding that plants have flowers so they can make seeds so that more plants will grow. The bees need flower nectar and pollen for food. Bees don't know they are pollinating flowers while they are collecting their food. Flowers benefit because they are pollinated and bees benefit because they collect food for the hive. This is called a symbiotic relationship, or interdependence of organisms.
Description of a student preconception (naïve conception, misconception, incomplete conception):
Pollen sticks to bees because bees are sticky.
Correct conception by the end of the unit:
Pollen clings to the tiny hairs on the bees' body. Bees are not sticky.
Additional Background: Plants pollinated by insects produce pollen with tiny hooks or spines that cling to hairs on the insect's body. Sometimes the pollen also has a sticky coating. These types of plants are referred to as "entomophilous" or insect-loving. Plants whose pollen is lightweight and dispersed by the wind are referred to as "anemophilous" or wind-loving.
Description of a student preconception (naïve conception, misconception, incomplete conception):
The reason plants need water is so they don't wilt and die.
Correct conception by the end of the unit:
Plants need water to carry out the process of photosynthesis. Plants need light, air (carbon dioxide), and water to make their own food (glucose). Water also provides turgidity, or firmness to the tissues of the plant by stretching against the cell walls.
Description of a student preconception (naïve conception, misconception, incomplete conception):
Plants get their energy from water.
Correct conception by the end of the unit:
Water is necessary for photosynthesis, but the energy that plants store and use comes from the sun.
Description of a student preconception (naïve conception, misconception, incomplete conception):
Plants need oxygen to live and grow, like animals do.
Correct conception by the end of the unit:
Oxygen is a waste product of photosynthesis, rather than a necessary ingredient. Carbon dioxide is the component of air used by plants to store energy from the sun.
Additional Background: Photosynthesis uses energy from the sun to build glucose and other carbon molecules (carbohydrates), thereby "storing" the energy from the sun in those molecules. The carbon chain molecules are built using carbon dioxide and water molecules; the resulting carbohydrates make up the bulk of the plant's tissues. Oxygen (O2) is a by-product of photosynthesis.
Cellular respiration is the process by which cells break down carbohydrate molecules to release the energy for cellular work. Cellular respiration uses oxygen to breakdown carbohydrate molecules, and carbon dioxide and water are the by-products of the breakdown. Cellular respiration is often thought of as the opposite of photosynthesis: breaking down molecules and releasing energy as opposed to using energy from the sun to build molecules.
Plants release far more oxygen through photosynthesis than they take in oxygen through cellular respiration. Therefore, plants are often said to "take in carbon dioxide and release oxygen." Animals, on the other hand, perform no photosynthesis and a great deal of cellular respiration. Therefore, animals are often said to "take in oxygen and release carbon dioxide."
Description of a student preconception (naïve conception, misconception, incomplete conception):
Seeds are not alive.
Correct conception by the end of the unit:
Seeds are alive and waiting for proper conditions (moisture and warmth) to begin growing (germinating) into a tiny plant (seedling).