Evidence for Earth's History
What does the principle of biogenesis state?
Living organisms come from preexisting living organisms.
What is the difference between a monomer and a polymer?
A monomer is a smaller building-block molecule; a polymer is a larger molecule made from many monomers.
BONUS (100 pts): Identify the monomer and polymer of proteins.
What does the term "anaerobic" mean?
Without oxygen!
What was the Cambrian Explosion?
A period of time roughly 535-525 million years ago when many animal phyla appeared on Earth.
Put these events in order:
A. Photosynthetic organisms increase atmospheric oxygen
B. Simple early cells arise
C. More complex eukaryotic cells evolve
D. Organic molecules form through abiotic processes
D --> B --> A --> C
What is an isotope?
An isotope is an atom of the same element with a different number of neutrons.
BONUS (100 pts): What happens to the amount of radioactive parent isotope as radioactive decay occurs?
What was the purpose of the Miller-Urey experiment?
To test Oparin's hypothesis regarding the formation of organic compounds in the atmosphere of early Earth.
How does chemosynthesis allow an organism to obtain energy without sunlight?
Autotrophs that utilize chemosynthesis make their own food using inorganic chemical reactions as an energy source
A population of organisms reproduces asexually, producing offspring that are genetically very similar to the parent. What is one major disadvantage of this type of reproduction?
There is less genetic variation within the population.
Why would the formation of an ozone layer have been important for the diversification of life?
Ozone absorbs harmful ultraviolet radiation, preventing it from reaching Earth's surface and keeping living things safer.
Why is carbon-14 useful for dating some fossils but less useful for dating ancient rocks?
Carbon-14's half-life is 5,730 years, so not enough remains after roughly 75,000 years to date older rocks.
Scientists today have questioned whether the atmosphere used in the original Miller-Urey experiment accurately represented early Earth. What alternative environment has been proposed as a possible location for organic molecule formation?
Hydrothermal vents
Early photosynthetic organisms released a substance that eventually became abundant in Earth's atmosphere. What substance was it, and why was its accumulation harmful to many early organisms?
Oxygen. Oxygen can cause damage to cells and/or inhibit certain enzymes. Many early organisms did not have adaptations that equipped them to deal with increasing oxygen levels.
Name two problems organisms had to solve when moving from aquatic environments onto land.
1. How to reproduce
2. How to avoid dehydration
A scientist discovers that mitochondria contain their own circular DNA and ribosomes. Why would these observations be significant to the endosymbiotic theory?
These characteristics are similar to those of prokaryotic cells and support the idea that mitochondria originated from ancient prokaryotes that were engulfed by and then incorporated into ancient eukaryotes.
Redi, Spallanzani, and Pasteur all investigated whether living organisms could arise spontaneously. Why did Pasteur's experiment provide stronger evidence against spontaneous generation than the earlier experiments?
Pasteur's experiment utilized a curved-neck flask, which allowed air to reach the broth while preventing microorganisms from entering. This disproved the theory that there was a "vital force" in the air necessary for microorganism growth, allowing abiogenesis to be disproven once and for all.
BONUS (100 pts): Describe Redi's experiment in the pursuit to disprove abiogenesis.
A researcher places simple organic molecules in an environment where conditions favor them joining together into larger molecules. What process is the researcher attempting to model, and which scientist performed an experiment in the 1960s demonstrating that this could occur?
Polymerization; Sydney Fox
Why would the evolution of aerobic cellular respiration have been advantageous after photosynthetic organisms began releasing large amounts of oxygen into Earth's atmosphere?
Aerobic cellular respiration allowed organisms to use oxygen to obtain energy, giving organisms that could tolerate and use oxygen an advantage as oxygen became more abundant.
A plant lineage begins living on land. Over time, characteristics such as a waxy coating and vascular tissue become important to its success. Explain how these traits could help the plants survive on land.
A waxy coating reduces water loss, while vasular tissue allows the plant to transport water & nutrients to all of its cells.
Two populations of the same species become separated when a continent slowly moves and changes the geographic distribution of their habitat. Over many generations, the populations become increasingly different. What process is influencing the species, and why can it do this?
Scientists are trying to reconstruct the history of an area containing several layers of sedimentary rock. They know the layers haven't been disturbed, but they also have radioactive samples from volcanic rock associated with some layers. Why would using both relative dating and radioactive dating provide stronger evidence than relying on either method alone?
Relative dating establishes the sequence/order of events, while radioactive dating provides an estimated numerical age. Together, they can establish both when events occurred and their relative order.
Scientists discovered a group of molecules that can form droplet-like structures surrounded by a membrane-like boundary. The structures can grow and divide under certain conditions, but they do not contain genetic material. Why would scientists consider these structures important to the origin of life, even though they are not alive?
They demonstrate that some life-like properties can arise from nonliving chemical systems and could represent a step towards cellular life. However, they lack the genetic information needed for true heredity and reproduction.
A population of early organisms is exposed to gradually increasing oxygen levels. Some organisms die, while others survive and reproduce more successfully because they can use oxygen in cellular respiration. Explain how this environmental change could lead to evolutionary change in the population.
Organisms with traits that allow them to tolerate/use oxygen are more likely to survive and reproduce, causing those traits to become more common over generations.
How can a mass extinction eventually lead to an increase in biodiversity?
A mass extinction leads to unoccupied niches that must be filled. Organisms diversify to fill these niches.
Why was sexual reproduction an important evolutionary development in the history of life?
Sexual reproduction increases genetic variation among offspring. Greater genetic variation gives natural selection more variation to act on, increasing the potential for populations to adapt to changing environments.