12.6 Earth's First Life

What organic compounds are essential for DNA and RNA to form?

• hydrogen sulfide

• ammonia and methane

• carbon dioxide

• oxygen

• amino acids

The most common Precambrian fossils are ________, layered mounds of calcium carbonate.

• prokaryotes

• chert

• trilobites

• eukaryotes

• stromatolites

Answer explanation

Stromatolites formed from secretions by photosynthetic organisms (cyanobacteria). The organisms would deposit the sediment in layers.

Tags

NGSS.MS-LS4-1

Scientists have found evidence that life existed at least 3.5 billion years ago ________.

• in northern Siberia

• on the Gulf Coast

• throughout North and South America

• in Kenya

• in several locations around the world

Tags

NGSS.MS-LS4-1

Which of the following is would be considered a hypothesis for how life began?

• ) Methane and hydrogen sulfide from deep-sea hydrothermal vents and hot springs like those at Yellowstone National Park provided the necessary materials.

• Asteroids and comets brought amino acids to Earth.

• Outgassing and related volcanic materials brought proto amino acids to the surface of the earth.

• Methane and ammonia in the early atmosphere combined with the help of lightning or ultraviolet light to produce the first amino acids.

A distinctive characteristic of prokaryotes is ________.

• their thick cell walls that separate the DNA from the rest of the cell

• their lack of a separation between the DNA and the rest of the cell

• their oxygen based metabolism

• their methane based metabolism

• their ability to produce sugars

Which type of bacteria thrive in environments that lack free oxygen?

• aerobic

• placental

• anaerobic

• foraminifera

• photosynthetic

Tags

NGSS.HS-LS2-3

A class of organic molecules that provide the primary structural material for life and contribute to the functioning of cells.

Tags

NGSS.HS-LS1-1

A cell or an organism such as bacteria whose genetic material is not enclosed in a nucleus.

Structures that are deposited by algae and consist of layered mounds of calcium carbonate.

Answer explanation

Stromatolites formed from secretions by photosynthetic organisms (cyanobacteria). The organisms would deposit the sediment in layers.

An organism whose genetic material is enclosed in a nucleus; plants, animals, and fungi are eukaryotes.

Tags

NGSS.MS-LS4-2