The background rate of extinction for birds is estimated to be about 1 species every 400 years. The current estimate for actual loss during the last 800 years is somewhere between 200 and 2,000. Explain what exactly background extinction rate is and hypothesize at least two specific factors that are contributing to the current rate.

anthropod traits:

a well-developed collarbone

rotating shoulder joints

partially rotating elbow joints

opposable thumb

similar dental formula

answer; the male's sperm cells have mitochondria, but because the sperm contributes dna but no cytoplasm, no mitochondria are passed to the egg at ferilization;

answer; /// the shaft of the hair consists of dead cells;