Which of the following choices is evidence that present-day vertebrates shared common ancestors? a. they all have hearts and feet

b. they display similar embryo development and share common genes that control development.

c. they have many bone structures that are unique to each species

d. they all thrive in a single ecosystem
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This is a coral reef ecosystem. many biotic and abiotic factors affect the health of this ecosystem. which set correctly pairs a biotic factor and an abiotic factor?

25) a student takes four samples of a white crystalline solid and places each in a well plate. on top of each sample, she carefully places 20 drops of clear mystery liquids a, b, c and d. her results for each well are: liquid a: the solid dissolves quickly. liquid b: the solid appears unchanged. liquid c: a brownish colored liquid is produced. liquid d: fizzing occurs and the well becomes warmer. in which well does a physical change occur?

Which of these statements are true about scientific theories and hypothesis