Evolutionary Biology: Origins and Domains

Life on Earth ranges from complex multicellular organisms to single-celled species. All life is believed to have descended from a common ancestor, leading to the formation of three domains: Bacteria, Archaea, and Eukaryotes. Bacteria, defined 3.5 billion years ago, are single-celled and metabolically diverse, playing both beneficial and harmful roles. Archaea, discovered in the 1970s, thrive in extreme environments and are not harmful to humans. Eukaryotes emerged from a symbiotic relationship between bacteria and archaea, leading to complex multicellular life forms like plants and animals. Despite their complexity, eukaryotes are not more evolved than bacteria or archaea, which have adapted to survive as single-celled organisms.

What is believed to be the origin of all life on Earth?

• Multiple ancestors

• A single common ancestor

• Spontaneous generation

• Extraterrestrial origins

Into how many major domains did life split during early evolutionary history?

• Five

• Three

• Two

• Four

Which domain is characterized by tremendous metabolic innovations?

• Bacteria

• Archaea

• Protists

• Eukaryotes

What is a unique feature of some bacteria that allows them to thrive in deep oceans?

• Producing oxygen

• Feeding on sulfur

• Photosynthesis

• Living in colonies

When were Archaea recognized as a separate domain?

• 1950s

• 1960s

• 1970s

• 1980s

Which environments are some Archaea known to survive in?

• Tropical forests

• Deserts

• Extremely hostile environments

• Urban areas

What significant event led to the origin of Eukaryotes?

• A bacteria merging with an archaea

• A new form of photosynthesis

• A mutation in bacteria

• A volcanic eruption

What is a defining feature of eukaryotic cells?

• Presence of a nucleus

• Ability to live in extreme environments

• Single-celled structure

• Lack of nucleus

Which domain includes fungi, plants, and animals?

• Protists

• Bacteria

• Archaea

• Eukaryotes

What ability did some eukaryotes acquire from bacteria?

• Fermentation

• Photosynthesis

• Respiration

• Nitrogen fixation