List the different levels of an organisms organization from a cell up:

Abird flies by moving its wings up and down. which two systems are most directly responsible for the movement of a bird's wings? a. skeletal and muscular systems b. respiratory and muscular systems c. skeletal and digestive systems d. respiratory and digestive systems

If a keystone species is removed from an ecosystem

The term autotroph refers to an organism that: a. uses co2 for its carbon source. b. must obtain organic compounds for its carbon needs. c. gets energy from sunlight. d. gets energy by oxidizing chemical compounds. e. does not need a carbon source