<span>True plankton are low in the food chain</span>
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Answer:
Observers ahead of the wave observe an apparent increase in wave frequency
Explanation:
This is the Doppler Effect. The frequency of a wave increases when the source approaches the observer and decreases as the source recedes.
B, C, and D are wrong. Observers behind the source notice a decrease in frequency.
Around 4.1 billion years ago the first single celled organism appeared
Answer:
Brain structures called the hypothalamus and pituitary gland control the menstrual cycle.
Explanation: