| Your Results | Global Average | |
|---|---|---|
| Questions | 5 | 5 |
| Correct | 0 | 3.19 |
| Score | 0% | 64% |
Which of the following is the primary difference between a comet and an asteroid?
comets orbit the Sun |
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asteroids contain frozen water |
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comets have an atmosphere |
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asteroids have a coma |
A comet is a loose collection of ice, dust, and small rocky particles that, in contrast to an asteroid, has an extended atmosphere surrounding the center. When passing close to the Sun, this atmosphere warms and begins to release gases forming a visible coma or tail.
Which of the following describes the Earth's outer core?
solid |
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primarily solid |
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makes up most of the Earth's volume |
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liquid |
The Earth's core is divided into the liquid outer core (1,430 miles or 2,300 km radius) and the solid inner core (745 miles or 1,200 km radius).
Which of blood component fights infection?
platelets |
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plasma |
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red blood cells |
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white blood cells |
Blood is created in bone marrow and is made up of cells suspended in liquid plasma. Red blood cells carry oxygen, white blood cells fight infection, and platelets are cell fragments that allow blood to clot.
Within DNA, a variety of a particular gene is called a(n):
heterozygous |
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allele |
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homozygous |
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chromosome |
The gene is the base unit of inheritance and is contained within DNA. A gene may come in several varieties (alleles) and there are a pair of alleles for every gene. If the alleles are alike, a person is homozygous for that gene. If the alleles are different, heterozygous.
This skeletal system is common in arthropods like insects, spiders, and crustaceans.
vertebrate |
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bone |
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endoskeleton |
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exoskeleton |
An exoskeleton (external skeleton) is common in arthropods like insects, spiders, and crustaceans.