Life Science
Life Science on the elementary CKT exam asks you to explain core biological ideas and anticipate how children reason about them. Questions often pair content with classroom scenarios.
Core content
- Cells: Cells are the basic unit of life. Plant cells have a cell wall, chloroplasts, and a large central vacuole; animal cells do not. Mitochondria release energy from food in both.
- Photosynthesis and respiration: Photosynthesis (chloroplasts) uses carbon dioxide, water, and light to make glucose and oxygen. Cellular respiration (mitochondria) uses glucose and oxygen to release energy, carbon dioxide, and water. Plants do both, day and night.
- Ecosystems: Producers capture energy, consumers transfer it, decomposers recycle matter. Energy flows and is lost as heat at each level; matter cycles.
- Heredity: Genes come in alleles; dominant alleles mask recessive ones in heterozygotes. Inherited traits are coded by DNA; acquired traits are not passed on.
- Evolution: Natural selection requires variation, heritability, and differential survival and reproduction-not effort or need.
Worked example
Grass in a food chain stores 20,000 kcal. Grasshoppers eat grass; frogs eat grasshoppers. About 10% of energy passes to each next level: 2,000 kcal to grasshoppers, then about 200 kcal to frogs. The rest is lost mainly as heat through metabolism. The correct answer is about 200 kcal, not 2,000.
Traps
- Saying plants only photosynthesize; they also respire.
- Claiming energy cycles; energy flows, while matter cycles.
- Treating “dominant” as “most common” rather than “expressed.”
- Describing adaptation as a choice or need-driven change.