Glossary of Biology Vocab and Key Concepts for Chapter 17 The History of Life

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scientists who study fossils
fossil record
information about past life; organisms grouped together and arrange them in the order in which they lived from oldest to most recent
species died out
relative dating
age of a fossil determined by comparing its placement with that of fossils in othe layers of rock
index fossil
used to compare the relative ages of fossils; exist short period but have had a wide geographic range
length of time required for half of the radioactive atoms in a sample to decay
radioactive dating
use of half-lives to determine the age of a sample
geologic time scale
represents evolutionary time- Precambrian time, Paleozoic, Mesozoic, Cenozoic
division of the time between the Precambrian and the present into three eras
eras subdivided
what can be learned from the fossil record?
the fossil record provieds evidence about the historyof life on Earth. it also shows how different groups of organisms have changed over time.
which type of dating provides an aboslute age for a given fossil? describe how this is done.
in radioactive dating, scientists calculate the age of a sample based on the amount of remaining radioactive isotopes it contains.
how are eras and periods related?
after precambrain time, the basic divisions of the geologic time scale are eras and periods.
proteinoid microsphere
tiny bubbles formed by large organic molecules under certain conditions; similar to living cells
microscopic fossils
endosymbiotic theory
eukaryotic cells formed from a symbiosis among several different prokaryotic organisms
what substances probably made up Earth's early atmosphere?
Earth's early atmosphere probably contained hydrogen cyanide, carbon dioxide, carbon monoxide, nitrogen, hydrogen sulfide and water
what molecules were the end products in Miller and Urey's experiments?
Miller and Urey's experiments suggested how mixtures of the organic compounds necessary for life could have arisen from simpler compounds present on a primitive Earth
How did the addition of oxygen to Earth's atmosphere affect life of that time?
the rise of oxygen in the atmosphere drove some life forms to extinction, while other life forms evolved new, more efficient metabolic pathways that used oxygen for respiration.
according to the endosymbiotic theory, how might chloroplasts and mitochondria have originated?
the endosymbiotic theory proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms.
mass extinction
many types of living things became extinct at the same time; affected plants and animals
where did life exist during the early Paleozoic Era?
early in the paleozoic era, the fossil record became rich with evidence of many types of marine life.
what evolutionary milestone involving animals occurred during the Devonian Period?
During the Devonian, animals began to invade the land.
what are the two key events from the Mesozoic era?
events during the mesozoic include the increasing dominance of dinosaurs, the mesozoic is marked by the appearance of flowering plants.
what happened during the cenozoic era?
during the cenozoic, mammals evolved adaptations that allowed them to live in various environments- on land, in water, and even in the air.with some climate changes from warm in Tertiary and an ice age in the quaternary
large scale evolutionary changes that take place over long periods of time
adaptive radiation
a single species or a small group of species has evolved into several different forms that live in different ways
convergent evolution
unrelated organisms come to resemble one another
two species evolve in response to changes in each other over time
punctuated equilibrium
pattern of long, stable periods interrupted by brief periods of more rapid change.
describe patterns of macroevolution
mass extinctions, adaptive radiation, convergent evolution, coevolution, puncuated equilibrium, developmental genes
how did hox genes help reveal how evolution occurred?
1st-molecular studies show that homologous hox genes extablish body plans in animals as different as insects and humans
2nd-major evolutionary changes may be based on hox genes
3rd- small changes in timing of genetic control during embryonic develpment makes difference between long legs and short ones- variation involved in natural selection

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