8 History of Life Flashcards
Define Half-Life
the amount of time from when half the parent isotope atoms will have decayed into the daughter isotope
Given the half-life of a radioactive isotope, be able to roughly estimate how much of the isotope would remain after a given number of half-lives.
Isotope X has a half-life of 400 years. You measure a sample and find that 1/8 of the original amount of Isotope X is still present.
- How many half-lives have passed for this sample?
- How old is this sample in years?
To do this, divide by 2 every half-life.
400/2 = 200 years, 1 half-life (1/2 of 400)
200/2 = 100 years, 2 half-lives (1/4 of 400)
100/2 = 50 years, 3 half-lives (1/8 of 400)
*3 half-lives have passed for this sample (2^3)
400yrs x 3half-lives = 1200 years
*The sample is 1200 years old
Given the half-life of a radioactive isotope and the proportion of parent or daughter isotope present in a sample, calculate the age of the sample.
- Determine half-lives by using proportion given (ex: 1/32, notice 2^5 = 32)
- Calculate (sample age = half-life # of half-lives passed)
Describe what kinds of samples for which carbon-14 dating vs uranium dating are appropriate
- Carbon-14 dating is useful for recent organic things
- Uranium dating is useful for old rocks, starts when rock solidifies
Identify what starts the “clock” for carbon-14 vs uranium dating samples
- Carbon-14 dating, clock starts when organism dies
- Uranium dating, clock starts when rock solidifies
Name the biological process that has produced most of Earth’s atmospheric oxygen. Explain what cyanobacteria were and why they were important to the history of early life on Earth (PRECAMBRIAN)
- Photosynthesis
(H20 + Carbon –> O2 + C6H12O6) - Cyanobacteria were a photosynthetic organism that performed photosynthesis
- Cyanobacteria were important to history of early life on Earth because it is responsible for the rise of aerobic organisms. They performed photosynthesis, where oxygen that was produced gradually made up the majority of the atmosphere and ocean.
Describe Stromatolites (PRECAMBRIAN)
Stromatolites are some of the oldest fossils. They are made up of layers with cyanobacteria and sediment together. They are the first form of life
Explain the origin of mitochondria and the bacterial traits that modern mitochondria still retain their bacterial traits. What is mitochondria’s job in eukaryotic cells? (PRECAMBRIAN)
- a prokaryotic cell (before nucleus) engulfed another prokaryotic cell (had function of mitochondria) and gained the functions of a mitochondria, making it a eukaryotic cell.
- mitochondria’s job is to produce ATP (energy) for the cell to carry out its cellular functions
Explain what the Cambrian “explosion” in the fossil record was and give the approximate date for it. Discuss reasons why phyla that evolved long before the Cambrian Period first appeared in the fossil record in the Cambrian (PALEOZOIC)
- Cambrian “explosion” was where over half of extant phyla appeared in fossils. It was the time animals were no longer soft bodied, developing techniques of predation and defense (jaws, joints, limbs, spines). This made it easier for organisms to become fossilized
Briefly describe these events and correctly identify them as having happened during the Paleozoic Era - Colonization of land by Plants (PALEOZOIC)
ORDOVICIAN PERIOD where big geological events happened like landmasses forming one big continent and mountain formations. Marine life flourished.
Briefly describe these events and correctly identify them as having happened during the Paleozoic Era - Evolution of terrestrial vascular plants PALEOZOIC)
SILURIAN PERIOD
Adaptations
- Spores to retain water
- Roots to help absorb nutrients
- More solid structure allowing them to stand upwards
Briefly describe these events and correctly identify them as having happened during the Paleozoic Era - Colonization of land by arthropods (PALEOZOIC)
EARLY DEVONIAN PERIOD
Arthropods began to colonize land. This event marked a significant transition in Earth’s history as organisms moved from water to land. Shaped early evolution of life on Earth
Briefly describe these events and correctly identify them as having happened during the Paleozoic Era - Colonization of land by vertebrates (PALEOZOIC)
LATE DEVONIAN PERIOD Vertebrates started transitioning from water to land. They evolved limbs and better respiratory systems, stronger bodies to adapt to life on land. This led to development of diverse vertebrates
Briefly describe these events and correctly identify them as having happened during the Paleozoic Era - Radiation of terrestrial amphibians and bony fish (PALEOZOIC)
LATE DEVONIAN PERIOD, terrestrial amphibians and bony fish experienced rapid increase in diversity and spread. Led to colonization of diverse habitats
Briefly describe these events and correctly identify them as having happened during the Paleozoic Era - Development of the amniotic egg, allowing reproduction on land and leading to reptiles (PALEOZOIC)
Development of amniotic egg allowed reptiles to reproduce on land. They didn’t need the water anymore. Reptiles started to diverse and emerge into various reptilian groups
