Nuclear envelope, endoplasmic reticulum, the Golgi apparatus, lysosomes, and vesicles
Answer:
Two characteristics are a notochord, and a dorsal hollow nerve cord.
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Answer:
by the process of photosynthesis
The seasons are caused as the Earth, tilted on its axis, travels in a loop around the Sun each year. Summer happens in the hemisphere tilted towards the Sun, and winter happens in the hemisphere tilted away from the Sun. As the Earth travels around the Sun, the hemisphere that is tilted towards or away from the Sun changes.