Where does a starfish have its water vascular system?
Options:
- (A) salt and water.
- (B) Chlorophyll
- (C) the environment
- (D) in its arms
- (E) on the rocks
- (F) in its eyes
- (G) Epidermis
- (H) in the ocean
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Let's think first: Echinoderms have a unique water vascular system with tube feet. Each starfish arm is lined with tube feet. Each starfish arm contains part of the water vascular system.... So the answer is [(D)]

_ are an essential nutrient for animals.
Options:
- (A) Energy
- (B) Chemicals
- (C) trees
- (D) potatoes
- (E) Acids
- (F) allow growth
- (G) store
- (H) Proteins
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Let's think first: All animals are heterotrophs. Proteins are an essential nutrient for heterotrophs . Proteins are an essential nutrient for animals.... So the answer is [(H)]

Nitrogen depletion is a condition of some:
Options:
- (A) bushes
- (B) humans
- (C) animals
- (D) soils
- (E) disease
- (F) legumes
- (G) mammals
- (H) Birds
--
Let's think first: Soil can be depleted of nutrients. An important nutrient commonly added to soil is nitrogen. Soil can be depleted of nitrogen.... So the answer is [(D)]

The penetration of the egg by a sperm takes place where?
Options:
- (A) salt and water.
- (B) an area swollen with pus
- (C) By wind and rain
- (D) outside the body
- (E) Earth revolving around the sun
- (F) inside the prostate
- (G) inside the female organism
- (H) inside the male organism
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Let's think first: Fertilization takes place inside the female organism. Fertilization is the penetration of the egg by a sperm. The penetration of the egg by a sperm takes place inside the female organism.... So the answer is [(G)]

What is it called when male gametes are propelled because of muscle contractions?
Options:
- (A) competition
- (B) rapid expansion
- (C) intercourse
- (D) thrusting
- (E) a wave
- (F) reproductions
- (G) A Greek letter
- (H) ejaculation
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Let's think first: Ejaculation occurs when muscle contractions propel sperm from the epididymes. Male gametes are called sperm. Ejaculation occurs when muscle contractions propel male gametes from the epididymes.... So the answer is [(H)]

What is a main component of a virus?
Options:
- (A) Something that causes allergies
- (B) Leptospirosis
- (C) Localized damage
- (D) heat produced
- (E) deoxyribonucleic acid
- (F) Chemical energy
- (G) direct damage to the lungs
- (H) It helps them survive
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Let's think first: Viruses contain DNA but not much else. DNA DNA is deoxyribonucleic acid. Viruses contain deosyribonucleic acid, but not much else.... So the answer is [(E)]