Scientists estimate that the Sun formed from a nebula with 71.1% hydrogen and 27.4% helium. Current measurements of the outermost layer of the Sun, the photosphere, indicate that this layer is made up of 74.9% hydrogen and 23.8% helium. However,

the core of the Sun contains about 38% hydrogen and 60% helium.

Which conclusion about the Sun is best supported by this information?

To confirm when to exclude children from school it’s recommended that you refer to guidelines from which of the following organizations

Which of the following is an example of competition a. the leaves of a tree prevent a small shrub from getting sunlight. three species of birds feed a different heights in the same tree. b. three species of birds feed at different heights in the same tree c. zebra and giraffe’s feed on different grassland plants d. cats living in two different homes eat the same brand of cat food.

1. in what ways have non-native species been beneficial? 2. what are some of the hypotheses for the collapse of honeybee colonies? 3. distinguish between regional and functional extinction. 4. why is it difficult to measure background extinction rates? 5. what three factors are most important in causing extinction rates to climb?