There are many types of crabs in the sea. most of them have shells made from chitin, which is different from calcium carbonate (it's actually the same stuff that your fingernails are made of). however, hermit crabs live in shells that are made from calcium carbonate. where do these "houses" come from? do the crabs make them?

What does polymerase chain reaction (pcr) do? o a. separates dna fragments by size o b. cuts a dna sample into fragments o c. provides an overall picture of a person's chromosomes o d. makes more copies of a sample of dna

Atree root breaking a rock into smaller fragments is an example of both and mechanical weathering. when rocks are exposed to heat, they which can contribute to thermal stress. when harmful gases, such as sulfur dioxide and nitrogen oxide, react with water in the atmosphere, they can produce the agent of erosion involved in stream erosion is when the ground is so saturated that it can't absorb rainfall or when rain falls so quickly that the ground can't absorb the water, forms. a/an is a huge, heavy, moving body of ice that picks up rocks and sand and erodes the ground beneath it as these materials scrape across it. hot arid climates are prone to erosion by rows of trees and shrubs planted to protect fields from wind erosion are known as

Color blindness is a recessive trait. the gene for color blindness is on the x-chromosome. the family tree below shows the trait of color blindness. theonly unknown is the father in the first generation.