write a paragraph describing how earth would be different if photosynthetic plants had not evolved.

Brief Explanations:

Photosynthetic plants produce oxygen and form the base of many food - webs. Without them, oxygen levels would be extremely low, making it hard for most aerobic life to exist. The food chain would collapse as herbivores would lack primary producers to eat, leading to a domino - effect on higher trophic levels. Also, the carbon - cycle would be disrupted as plants absorb carbon dioxide during photosynthesis. Earth's atmosphere would have a different composition, likely with higher levels of carbon dioxide and less oxygen, contributing to a much warmer climate.

Answer:

If photosynthetic plants had not evolved, Earth would have a severely depleted oxygen supply, making it inhospitable for most aerobic organisms. The food chain would break down since herbivores would have no primary producers to consume, causing a collapse of higher trophic levels. The carbon - cycle would be disrupted, leading to a different atmospheric composition with more carbon dioxide and less oxygen, potentially resulting in a much warmer planet.