Early life likely began a. in the atmosphere b. in the ocean c. on the Earth’s surface
All kinds of life are made of a. very similar chemicals b. very different chemicals c. an equal mix of similar and different chemicals
Life probably began when molecules bonded to form a. RNA b. DNA c. mRNA
Discussion/essay questions
The origin of life on Earth is one of humanity’s most important and controversial questions. Why do you think this is? Do you think religion and science have the same purpose?
Transcript
Abiogenesis is the process that causes non-living materials to become living things. Abiogenesis is one of the greatest mysteries in science. Early life likely began in a “chemical soup” in the ocean. Scientists have observed that all kinds of life are made of very similar chemicals. People, plants, animals, and bacteria all share a common ancestor, which lived about 4.2 billion years ago. Most scientists agree that life probably began when molecules in the chemical soup bonded to create RNA. RNA can cause the chemical reactions that made early life possible, and it can also store information. This allows it to replicate itself. Some scientists have tried to begin the process of RNA bonding in labs. However, no one has ever observed abiogenesis. Because all life is made of the same chemicals, many scientists believe that abiogenesis has only happened once on Earth.
The biosphere is a. the surface of the Earth, where there is plenty of light and oxygen b. the areas of the Earth where most plants and animals live c. all of the areas on Earth that can sustain life
Microbes that can live in environments without much water, sunlight, or oxygen are called a. eukaryotes b. extremophiles c. eubacteria
The “shadow biosphere” hypothesis suggests that a. life on other planets is probably very similar to life on Earth b. new types of bacteria are evolving very quickly underground c. Earth may contain microbes that have very different chemical structures from us
Discussion/essay questions
Do you believe in life on other planets? Why or why not? Why do you think we haven’t found any?
Transcript
The biosphere is all of the areas on Earth that can sustain life. Most complex plants and animals need lots of water, oxygen, and sunlight to survive. When scientists look for life on other planets, they seek places that have the potential to provide these things. On Earth, however, certain microbes thrive in environments that are low in these essential ingredients. These microbes are called extremophiles. They live in volcanoes, deserts, and Antarctic ice. Some extremophiles survive because they can use unusual chemicals to sustain themselves. It is possible that Earth contains microbes with chemical structures that are very different from our own. This hypothesis is called the “shadow biosphere.” A shadow biosphere would be made up of life that is chemically unrelated to life as we know it. If this type of life exists, there may be more habitable planets than we think.
Astronomers look in Goldilocks zones to find a. planets that humans could travel to b. planets with rare chemical compositions c. planets that might be able to produce life
Venus is not habitable because a. it is outside of the Sun’s Goldilocks zone b. its atmosphere is too thin to support liquid water c. greenhouse gases make it too hot for liquid water
Life may be possible outside of stars’ Goldilocks zones because a. some stars are hotter than others b. alien life forms may use a liquid other than water to survive c. some systems contain multiple stars
Discussion/essay questions
Do you believe there is life on other planets? Why do you think we haven’t found any?
Transcript
The Goldilocks zone, or habitable zone, is the place in a star system where a planet can reach the right temperature to have liquid water on its surface. Because life on Earth requires liquid water, astronomers look for exoplanets in Goldilocks zones in case they are also capable of producing life. However, not every planet in a habitable zone is actually habitable. Besides Earth, the Sun’s habitable zone also contains both Venus and Mars, which are either too hot or too cold to sustain much liquid water. This is because Venus has an atmosphere full of greenhouse gases, while Mars has barely any atmosphere at all. It is also possible that life made of different chemicals than life on Earth could develop outside of a star’s Goldilocks zone. These life forms would use a liquid other than water to survive.
Why do you think so many religious people rejected the theory of evolution? Is it possible to believe in both religion and evolution?
Transcript
Charles Darwin was an English naturalist. He is known for forming the theory of evolution, a scientific explanation for the origin of life on Earth. Darwin was born in 1809 in Shrewsbury, England. In 1831, he got a job on a ship called the HMS Beagle, which was taking a five-year trip around the world. Darwin got to visit many countries and study different plants and animals. He started to form his theory while studying birds on the Galápagos Islands. In 1859, he published a book called On the Origin of Species, which stated that all life on Earth may have evolved from one organism. This theory was unpopular at the time, because society was very religious. However, over time, more people started to accept Darwin’s ideas. Darwin died in 1882, at age 73.
Human fossil fuel use is a big issue. Carbon dioxide levels are getting higher, and climate change is going to affect the world in many ways. Are there any changes you’ve made in your life to help the environment? Are there changes you’d like to make in the future?
Transcript
Carbon dating is a process that scientists use to find out the age of a fossil. All living things consume forms of carbon throughout their lives. A rare type of carbon called carbon-14 is radioactive, which means that it decays over time. Living things usually absorb carbon-14 through natural carbon dioxide in the atmosphere. Since every radioactive substance decays at a specific rate, scientists can use a substance’s half-life to find out how long it has existed. Carbon-14 has a half-life of 5700 years. Scientists can estimate an age for any fossil that has enough carbon-14 left to measure. However, carbon dating may become more difficult as humans continue to use fossil fuels. Oil and coal put more stable carbon dioxide into the atmosphere, which affects the amount of carbon-14 that living things absorb. If a plant or an animal does not contain enough carbon-14 to measure, then finding its age will be much harder.
