Crossword puzzle

123456
Across
  1. 1. The process by which plants make their own food using sunlight.
  2. 4. The study of living organisms and their interactions with the environment.
  3. 5. The layer of Earth where all life exists.
Down
  1. 2. The practice of washing hands to prevent the spread of germs.
  2. 3. A book that tells a story, often with characters and a plot.
  3. 6. The organ in the human body that pumps blood.