Currently, scientists agree with the estimate that life first appeared approximately _______ years ago.
Answer: 4 billion
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Studying Life
- The _______ hypothesis states that no difference exists due to the variable under investigation.
- Scientific investigations are based above all on the processes of _______ and _______.
- Fungi and animals both belong to the _______ domain, and their cell structure is _______.
- Multicellular organisms that are photosynthetic belong to the kingdom _______.
- A _______ tree shows the evolutionary relationships among species.
- A Pacific tree frog has the scientific nomenclature of Hyla regilla. This particular tree frog belongs to the genus _______.
- Scientists who study evolution and classification of life's diverse organisms are called _______.
- There are three domains used to categorize life forms that have evolved separately for about a billion years: _______, _______, and _______.
- Single-celled organisms that lack discrete intracellular compartments belong to the two kingdoms: _______ and _______.
- In contrast to eukaryotic cells, prokaryotes lack discrete _______ compartments.
- Some organelles in eukaryotes can be described as _______ within a cell.
- About _______ years ago, prokaryotes acquired the ability to photosynthesize.
- The ability to use energy from sunlight to synthesize complex molecules is known as _______.
- Fatlike molecules were the critical ingredient in the enclosure of biological molecules in _______ because these molecules are not _______ in water and tend to form membrane-like _______.
- The total chemical activity of a living organism is called its _______.
- ____ are structural, physiological, or behavioral traits that enhance an organism's chance of survival and reproduction in its environment.
- Most living organisms consist of one or more _______, have changed or _______ over time, and can regulate their _______ environment.
- Overfishing of the western bluefin tuna in the Gulf of Mexico breeding ground resulted in a serious decline in the population. Fishing quotas were established in the Gulf of Mexico to allow the endangered population to recover. Why did this policy fail to achieve the desired result?
- Which of the following questions cannot be answered by means of the hypothetico-deductive method?
- Which of the following statements about the experiments of Tyrone Hayes on abnormalities of male frog sex organs is correct?
- Which of the following statements represents a scientific point of view?
- Comparative experiments are designed to answer questions that require
- Which of the following statements is false?
- The advantage of controlled experiments is that