Mastering Astronomy Chapter 18 – Life – Tutorials Aid

The history of the universe can be divided into seven major phases. Taken together, these phases make up the cosmic evolutionary scheme—the continuous transformation of matter and energy that has led to the appearance of life and civilization on Earth. Rank the phases in the history of cosmic evolution from earliest to most recent. -Particulate -Galactic -Steller -Planetary -Chemical -Biological -Cultural

Somewhat surprisingly, there is not a single generally accepted definition of life. Depending on the set of criteria used to define life, some generally accepted non-living things might fulfill all of the criteria and be categorized as living. Likewise, some generally accepted living things might fail to meet all of the criteria and be classified as non-living. For example, one working definition of life requires that living things exhibit the following four characteristics. This working definition fits the easy cases of things that are obviously alive, but does not always hold up in all cases. Use these four characteristics as a working definition of life to see which generally accepted living and non-living things from the table would be considered alive based on these characteristics. 1. They can react to their environment and can often heal themselves when damaged. 2. They can grow by taking in nourishment from their surroundings and processing it into energy. 3. They can reproduce, passing along some of their own characteristics to their offspring. 4. They have the capacity for genetic change and can therefore evolve from generation to generation and adapt to a changing environment. From the descriptions and the working definition of life, determine which things do and do not exhibit these characteristics -trees -dogs -rocks -stars -viruses

As the mass of the central star increases, the distance to the habitable zone __________ and the size (width) of the habitable zone __________. Select from the choices in the format first blank / second blank. A) increases / increases B) decreases / increases C) decreases / decreases D) increases / decreases

Suppose that our Sun was cool enough to include Mercury in its habitable zone. Which of the following would be true in that case? A) Only Mercury would be in the Sun's habitable zone. B) Mercury and Venus would be in the Sun's habitable zone, but Earth and Mars would not. C) Mercury, Venus, and Earth would be in the Sun's habitable zone, but Mars would not. D) All the terrestrial planets would be in the Sun's habitable zone.

Scientists think it is very unlikely that complex and large forms of life could evolve on planets that orbit stars that are much more massive than the Sun. Why? A) The habitable zone of a massive star is too far from the star to allow for the evolution of complex life B) The habitable zone of a massive star covers too wide a range of distances from the star to allow for the evolution of complex life C) The expected lifetime of a massive star is too short to allow for the evolution of complex life

Currently, astronomers are observing the universe across many different regions of the electromagnetic spectrum, from gamma rays to radio waves. One of the primary issues when considering communication with potential life outside our planet is how an extraterrestrial signal would be distinguished from natural radiation sources. Sort the following source properties by whether they might be considered as originating from intelligence or simply be natural phenomena. Drag the appropriate items to their respective bins. -constant, unchanging signal -random radio fluctuations -single strong visible light burst that fades away over months -identical repetitive pulses -sequence of pulses varying over time

In searching for signs of intelligence elsewhere in the universe, scientists begin with assumptions based on biological and chemical properties of Earth. They also examine how signals from Earth might appear to an observer in space. Select the statements that correctly describe what an extraterrestrial observer outside our Galaxy might see when viewing Earth. Select all that apply. A) a strong constant radio signal B) a pulsating radio signal that varies in intensity during each cycle C) spectral evidence that hydrogen and oxygen are the most abundant gases D) spectral evidence that nitrogen and oxygen are the most abundant gases E) natural emissions maximized in the 18-cm to 21-cm wavelength range, called the "water hole" F) natural emissions minimized in the 18-cm to 21-cm wavelength range called the "water hole"