Biology Chapter: Origin and History of Life

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Questions and Answers

What did the Miller-Urey experiment demonstrate about the origin of life?

Chemical reactions are not necessary for the formation of life.

Life originated only from extraterrestrial sources.

Organic molecules can only form from other organic molecules.

Organic molecules can form from simple inorganic compounds. (correct)

Which of the following is NOT a characteristic of prokaryotes?

They are single-celled organisms.

They are simpler in structure than eukaryotes.

They lack a nucleus.

They have membrane-bound organelles. (correct)

Which class of animals is characterized by the presence of a notochord and dorsal nerve cord?

Platyhelminthes

Arthropoda

Chordata (correct)

Cnidaria

What is the main significance of the endosymbiosis theory?

It describes how mitochondria and chloroplasts originated from engulfed prokaryotic cells. Signup and view all the answers

Which of the following traits is associated with the evolution of mammals?

Mammals can be grouped into monotremes, marsupials, and eutherians. Signup and view all the answers

Which evolutionary trend is characterized by the development of complex body plans and cavities in animals?

Cephalization Signup and view all the answers

What adaptation does the amniotic egg provide for reproduction?

It offers protection and sustenance to the developing embryo. Signup and view all the answers

Which of the following statements about eukaryotic cells is true?

They are typically larger and more complex than prokaryotic cells. Signup and view all the answers

What are protobionts hypothesized to be precursors to in the evolution of life?

Simple cell-like structures Signup and view all the answers

Which of the following environmental changes contributed to the history of life on Earth?

Increased volcanic activity Signup and view all the answers

What is the main distinguishing feature of eukaryotic cells compared to prokaryotic cells?

They contain a true nucleus Signup and view all the answers

The endosymbiosis theory explains the origin of which organelles?

Mitochondria and chloroplasts Signup and view all the answers

Which group of animals is characterized by having an exoskeleton?

Arthropoda Signup and view all the answers

Which trait is a defining characteristic of chordates?

Notochord Signup and view all the answers

Which of the following represents the correct order of evolutionary transitions in vertebrates?

Jawless fish -> Cartilaginous fish -> Bony fish Signup and view all the answers

Which group of mammals is characterized by precocial young that develop inside a pouch?

Marsupials Signup and view all the answers

Study Notes

Origin of Life

Miller-Urey experiment showed organic molecules can form from inorganic compounds under early Earth conditions.
Protobionts are simple, cell-like structures, thought to be precursors to cells.
RNA was likely the first genetic material.
Early Earth conditions included environmental changes like oxygenation, volcanic activity and glaciation.
Photosynthetic cyanobacteria introduced oxygen to the atmosphere.

History of Life on Earth

Multicellularity evolved, followed by major diversification during the Cambrian Explosion.
Animals emerged 600 million years ago
Evolution included diverse body plans, digestive systems and nervous systems.
Cephalization, or development of a head region, occurred in some lineages.

Prokaryotes vs. Eukaryotes

Prokaryotes are single-celled organisms without a nucleus (e.g., bacteria, archaea).
Eukaryotes have a nucleus and membrane-bound organelles (e.g., plants, animals).
Eukaryotes are generally larger and more complex than prokaryotes.

Three Domains of Life

Bacteria, Archaea, and Eukarya are the three domains based on genetic differences.
Archaea and Eukarya share a more recent common ancestor than either do with Bacteria.

Origin of Eukaryotic Cells

Endosymbiosis theory proposes that mitochondria and chloroplasts originated from prokaryotic cells engulfed by a larger cell.

Major Animal Phyla

Cnidaria (radial symmetry, stinging cells).
Platyhelminthes (flatworms, no body cavity).
Annelida (segmented worms).
Mollusca (shell, diverse body plans).
Nematoda (roundworms, pseudocoelomate).
Arthropoda (exoskeleton, segmented bodies).
Echinodermata (radial symmetry as adults).
Chordata (notochord, dorsal nerve cord).

Evolutionary Trends in Animals

Multicellularity arose in various lineages.
Body plans and cavities become more complex.
Digestive and nervous systems diversified.
Cephalization, the development of a head region and concentration of sensory organs, evolved in some lineages.

Vertebrates

Jawless fish evolved into cartilaginous and bony fish, then amphibians, reptiles, birds, and mammals.
Key chordate traits include notochord, dorsal nerve cord, pharyngeal slits, and a post-anal tail.

The Amniotic Egg

The amniotic egg was a major adaptation allowing for terrestrial reproduction, offering protection for the developing embryo.

Evolution of Mammals

Three main groups are monotremes (lay eggs), marsupials (pouch development), and eutherians (placental mammals).

Evolution of Humans

Defining traits of humans include bipedalism, large brain size, tool use, and complex social structure.

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Description

Explore the fascinating journey from the origin of life on Earth through key events like the Miller-Urey experiment and the evolution of multicellularity. This quiz covers essentials on prokaryotes vs. eukaryotes and major developmental milestones in life's history. Test your knowledge on the building blocks of life and their progression through time.