Over the past 500 million years, there have been ________ mass extinctions, and each time, at least ________ of the species on Earth became extinct
A) two; 25%
B) five; 25%
C) five; 50%
D) twelve; 96%
Answer: C
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Which of the following choices represents the
correct sequence? a. microspores >>> meiosis >>> gametophyte >>> sperm b. meiosis >>> microspores >>> gametophyte >>> sperm c. gametophyte >>> meiosis >>> megaspores >>> eggs d. meiosis >>> gametophyte >>> megaspores >>> eggs e. gametophyte >>> mitosis >>> megaspores >>> eggs
Why might increased nutrient availability result in increased species diversity in aquatic systems while it results in decreases in terrestrial systems?
A) Aquatic systems have weaker competitive interactions. B) Aquatic systems have stronger competitive interactions. C) Nutrients are diluted too rapidly in aquatic systems. D) Nutrients are always abundant in terrestrial systems.
Some dinosaurs and birds share characteristics that make flight possible such as
A. a short tail. B. a horizontal back. C. an upright stance. D. All of the answer choices are correct. E. hollow bones.
Which of the following biomolecules interact with toll-like receptors (TLRs)?
A) bacterial LPS B) immunoglobulins C) major histocompatibility complex proteins D) none of these