Across
- 2. What helps reduce the oxygen levels in water?
- 5. How many factors affect natural selection?
- 7. A natural process in which take place is a?
Down
- 1. Who's work did Wallace read?
- 3. When water is unhealthy the fish have nowhere to ___
- 4. If all offsprings survived what would happen?
- 6. A difference in color,size or patterns is what?