W18 L2 - Macroevolution and the Origin of Life

Flashcards about the beginning of life on Earth

What were the main topics discussed regarding speciation?

Prezygotic and postzygotic barriers that prevent hybridization between species, and the causes of speciation, including allopatric and sympatric speciation.

What main topics will be covered regarding the bigger picture of the beginning of life on Earth?

From macromolecules to the evolution of complex functions like the eye, and an overview of mass extinctions.

What are the key macromolecules discussed, and what are their building blocks?

Proteins, DNA, and RNA, composed of amino acids and nucleotides, respectively.

What were the initial conditions on Earth regarding its atmosphere and age?

The Earth formed around 4.6 billion years ago with an atmosphere of water vapor and various chemicals but lacking oxygen.

What is abiogenesis?

The formation of small organic molecules from inorganic substances without life, in the absence of enzymes.

What did the Miller-Urey experiments demonstrate?

Experiments simulating early Earth conditions that produced amino acids from inorganic materials like methane, ammonia, and hydrogen without any enzymes.

What is the panspermia hypothesis?

The hypothesis that amino acids and nucleotide bases were brought to Earth by meteorites.

What are ribozymes, and what role do they play in the RNA world hypothesis?

RNAs that have enzymatic functions and can cut other RNA molecules, promoting the RNA world hypothesis.

What does the RNA world hypothesis suggest?

That life started with RNA instead of DNA, as RNA can act as reacting and adopting different structures.

How could RNA polymers have formed without enzymes or a life?

RNA polymers could have formed by shaking nucleotides on clay surfaces.

What are protocells?

Precursors of cellular life consisting of RNA inside a lipid membrane.

How did protocells form membranes?

Formed through the binding of fatty acids present in the earth's original compounds.

What are stromatolites?

They are rocks formed by layers of bacteria and are the oldest known fossils, dating back 3.5 billion years ago.

What was the oxygen revolution and what caused it?

A massive increase in atmospheric oxygen produced by photosynthetic cyanobacteria, leading to the extinction of anaerobic species.

What is the endosymbiosis theory?

The theory that eukaryotic cells evolved from prokaryotes engulfing other bacteria, which became mitochondria and chloroplasts.

What are the advantages of being multicellular?

Allows for specialized cells, teamwork, more functions, and the evolution of complex structures like the eye.

How did the eye evolve?

Different eye systems have evolved over millions of years with increasing complexity, from recognizing dark and bright to focusing and seeing colors.

Give an example of conversion evolution

The eye of the squid and the human eye

What is a mass extinction?

A high rate of extinction that kills at least 50% of all species.

What likely caused the Permian mass extinction?

Volcanic activity, increased CO2, and rapid global warming led to a 95% reduction in species.

What caused the KT mass extinction?

Caused by an asteroid impact, killing 80% of the species, including dinosaurs.

What do current calculations say about the sixth mass extinction?

That the current rate of extinction is 100 to 1,000 times the typical background rate due to human activity.

What are the effects of mass extinctions on species and ecological communities?

Mass extinctions alter ecological communities and niches, leading to adaptive radiation.