Bio Chapter 14

When Earth formed

4.6 billion years ago

When solid crust formed

500 million years ago

Densest elements

elements pulled by gravity to the center of the planet

Early atmosphere

water vapor, carbon dioxide, sulfur dioxide, carbon monoxide, nitrogen, and hydrogen

Minerals

the oldest known rocks to suggest that the early atmosphere had little to no free oxygen

Fossil

preserved evidence of an organism

Fossil formation

Fossils are formed in sedimentary rock that builds up until it covers the organisms remain until minerals replace the original matter leaving behind an impression of its body

Paleontologists

scientists who study fossils

Relative dating

a method used to determine the age of rocks by comparing them with those in other layers

Law of superstition

what relative dating is based on which states that younger layers of rocks are deposited on top of older layers

Radiometric dating

uses the decay of radioactive isotopes to measure the age of a rock

Half life

the time it takes for half of the original isotope to decay

Original preservation

remains of plants or animals that have been altered very little since death which is uncommon, ex: mummification, freezing, amber

Altered hard parts

hard parts of organisms becoming fossils, ex: shells, bones

Mineral replacement

actual hard par minerals eventually getting replaced with new minerals

Permineralization

pore spaces filled in with minerals from groundwater, ex: petrified wood

Recrystallization

hard parts subjected to changes in temperature and pressure, original minerals transformed into a new mineral

Mold

when sediments cover the original hard part of an organism and the hard part is later removed to leave a hollowed-out impression

Cast

a material that fills a mold and makes a 3-D replica of the hard part of an organism

Trace fossils

can provide information about how an organism lived, moved, and obtained food, ex: burrows, footprints

Index fossils

fossils that are easily recognized, abundant, widely distributed geographically, and lived for a relatively short period of time

Geologic time scale

a model that expresses the major geological and biological events in Earth’s history

Epochs

smallest units of geologic time (less than a million years)

Periods

two or more epochs (10m years)

Eras

two or more periods (100m years)

Eon

largest unit in geologic time, can be billions of years

Precambrian

4 billion years ago including 90% of earth’s history, when life first appears and autotrophic prokaryotes bring oxygen to the atmosphere, first animals appear

Paleozoic Era

first life on land, mass extinction ended the era taking out 90% of marine organisms

Cambrian explosion

when most major animal groups diversified

Mesozoic Era

dinosaurs, birds, and mammals evolved, meteorite impact changed the climate and wiped out dinosaurs and many other species, iridium is rare

K-T boundary

a layer of material in between the rocks in the Cretaceous and Paleogene periods with unusually high levels of iridium

Plate tectonics

describes the movement of several large plates that make up the surface of the Earth which move atop a molten layer of rock

Cenozoic Era

mammals become dominant. humans appeared recently in the Neogene Period

Spontaneous generation

an early idea that suggests life arises from nonlife such as mud

Theory of biogenesis

states that only living organisms can produce other living organisms

Louis Pasteur

scientist that designed an experiment to show that biogenesis was true even for microorganisms

Simple organic molecule formation

life originated

Primordial soup hypothesis

Suggests if the Earth’s atmosphere had a mix of certain gases, organic molecules could have been synthesized

Miller and Urey

the first to show that inorganic compounds could produce simple organic molecules, including amino acids

How proteins could have been made

if amino acids were bound to a clay particle

RNA

considered life’s first coding system, can act as a ribozyme that might have carried out early life processes

Clay crystals

potentially could have provided an initial template for RNA replication

Formation of membranes

important step in the evolution of life

The first cells

simple prokaryotes

Cyanobacteria

photosynthesizing prokaryotes that evolved not long after archaea-like life forms that eventually produced enough oxygen to make the ozone layer

Endosymbiont theory

proposed by Lynn Margulis saying that ancestral eukaryotic cells absorbed prokaryotic cells