Concerning your heart, that's the circulatory system
Your lungs are the respritaory system
Answer: All birds are warmblooded, or endothermic, animals. Birds are vertebrates because
they have backbones. All birds have a four-chambered heart, a
characteristic they share with mammals. All birds lay hardshelled eggs. Birds have only two legs. Their forelimbs have
become modified into wings for flying. All modern birds evolved
from ancestors that could fly.
Explanation:
Answer:
photosythesis
Explanation:
I only know one which is photosynthesis
1. Atoms and molecules
2. Cells
3. Tissue
4. Organ systems
5. Organs