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Life: From the First Organism Onward
Terms in this set (48)
Determines about how long ago a fossil organism lived. This gives the fossil an approximate age in years. Absolute dating is often based on the amount of carbon-14 or other radioactive element that remains in a fossil.
Occurs when a species completely dies out and no members of the species remain.
The preserved remains of organisms that lived in the past. The soft parts of organisms almost always biodegrade, but sometimes the hard parts- mainly bones, teeth, or shells - remain long enough to mineralize and form fossils.
The record of life that unfolded over four billion years and was pieced back together through the analysis of fossils.
geologic time scale
Divides Earth's history into divisions (such as eons, eras, and periods) that are based on major changes in geology, climate, and the evolution of life. It organizes Earth's history and the evolution of life on the basis of important events instead of time alone
last universal common ancestor
Scientists think tht only one early cell (or group of cells) eventually gave rise to all subsequent life on Earth. That one cell is called the Last Universal Common Ancestor. It probably existed around 3.5 billion years ago, and was one of the earliest prokaryotic cells. It would have lacked a nucleus and other membrane bound organelles.
Uses DNA sequences (or the proteins they encode) to estimate how long it has been since related species diverged from a common ancestor. /////////////////////////////////////////////////// Molecular clocks are based on the assumption that mutations accumulate through time at a steady average rate for a given region of DNA. Species that have accumulated greater differences in their DNA sequences are assumed to have diverged from a common ancestor.
Determines which of two fossils is older or younger than the other, but not their age in years. Relative dating is based on the positions of fossils in rock layers. Lower layers were laid down earlier, so they are assumed to contain older fossils.
RNA world hypothesis
Some scientists speculate that RNA may have been the first organic molecule to evolve. In fact, they think that early life was based solely on RNA and the DNA and proteins evolved later. RNA can encode genetic instructions (like DNA), and some RNAs can carry out chemical reactions (like proteins).
when did the world form? when was life? and what time frame did human life come into play?
4.6 billion years ago, life was about 3.5/4 billion years ago, human life was on the last minute
how do fossils form
they must be quickly covered with sediment, then they remain long enough to mineralize and form fossils
how did earth itself form
The solar system began as a rotating cloud of stardust. Then, a nearby star exploded and sent a shock wave through the dust cloud, increasing its rate of spin. As a result, most of the mass became concentrated in the middle of the disk, forming the sun. Smaller concentrations of mass rotating around the center formed the planets, including Earth.
how did its atmosphere and oceans develop?
At first, Earth was lava and lacked an atmosphere and oceans. Gradually, the planet cooled and formed a solid crust. As the planet continued to cool, volcanoes released gases, which eventually formed an atmosphere. The early atmosphere contained ammonia, methane, water vapor, and carbon dioxide, but only a trace of oxygen. Water from rain (and perhaps comets and asteroids that struck Earth) eventually formed the oceans.
describe miller and urey's experiment? what did it attempt to prove
Scientists think that lightning sparked chemical reactions in Earth's early atmosphere. They hypothesize that this created a "soup" of organic molecules from inorganic molecules. Miller and Urey used their imaginations to test this hypothesis. They created a simulation experiment to see if organic molecules could arise in this way. They used a mixture of gases to represent Earth's early atmosphere. Then, they passed sparks through the gases to represent lightning. Within a week, several simple organic molecules had formed.
why were the earliest cells considered heterotrophs
Most likely they got their energy from other molecules in the organic "soup."
when did photosynthesis evolve
3 billion years ago, organisms that did this were autotrophs
After photosynthesis evolved, oxygen started to accumulate in the atmosphere. This has been dubbed the "oxygen catastrophe." Why? Oxygen was toxic to most early cells because they had evolved in its absence. As a result, many of them died out. The few that survived evolved a new way to take advantage of the oxygen. This second major innovation was cellular respiration. It allowed cells to use oxygen to obtain more energy from organic molecules.
describe the first cells
how organic molecules such as RNA evolved into cells is not known for certain
scientists speculate that lipid membranes grew around the organic molecules. the membranes prevented the molecules from reacting with other molecules, so they did not form new compounds. in this way, organic molecules persisted, and the first cells may have formed.
The Paleozoic Era began with a spectacular burst of new life, called the Cambrian explosion. This followed the precambrian mass extinction
This literally means the era of "modern life." It is also called the age of mammals, which took advantage of the extinction of dinosaurs. They flourished and soon became the dominant animals on Earth. The Cenozoic began 65 million years ago and continues to the present.
when many or even most species abruptly disappear from the earth.
this occurred at the close of the precambrian 544 million years ago, and there have been five in the world's history, some think we're going through a 6th
regardless, the precambrian extinction paved the way for a burst of life during the paleozoic era
what caused the Precambrian mass extinction
a combination of climatic and geologic events was probably responsible
The era of "middle life." It is also known as the age of dinosaurs. It lasted from 245 to 65 million years ago and is divided into three periods. The Mesozoic began with the supercontinent Pangaea. Then during the era, Pangaea broke up and the continents drifted apart. The movement of continents changed climates. It also caused a lot of volcanic activity. Mass extinctions occurred at the end of the Triassic and Cretaceous Periods. The first extinction paved the way for a dinosaur takeover. In the second extinction, the dinosaurs finally disappeared.
The era of "old life." It lasted from 544 to 245 million years ago and is divided into six periods.
The Paleozoic Era ended with the biggest mass extinction the world had ever seen. This is known as the Permian extinction.
Describe geologic and climatic changes that occurred during the late Precambrian.
1) The geologic and climatic changes that occurred during the late Precambrian: continents drifted, carbon dioxide levels fluctuated, and climates changed. Some could not survive the changes and died out, while others developed adaptations, and survived. These adaptions include sexual reproduction, cell specialization, and multi-cellularity.
3. What is the relationship between the Precambrian extinction and the Cambrian explosion?
the precambrian extinction paved the way for a new burst of life, called the cambrian explosion
List several important evolutionary events that occurred during the Paleozoic Era.
During the Paleozoic Era, invertebrate animals diversified in the oceans. Plants, amphibians, and reptiles also moved to the land.
Describe how the continents shifted during the Mesozoic Era.
5) The Mesozoic era began with the supercontinent Pangaea. Then, during the era, Pangaea broke up and the continents drifted apart, causing change climates and volcanic activity
What explains why mammals were able to flourish during Cenozoic Era?
6) Mammals took advantage of the extinction of the dinosaurs. They flourished and soon became the dominant animals on Earth. During the Tertiary Period, mammals evolved to fill virtually all niches vacated by dinosaurs. Many mammals increased in size. Mammals called primates evolved, including human ancestors.
TIMELINE OF MESOZOIC AND CENOZOIC ERA
FILL IN LATER
evolutionary appeal of sexual reproduction
8) Sexual reproduction created much more variety among offspring. This increased the chances that at least some of them would survive when the environment changed. It also increased the speed at which evolution could occur.
evolutionary appeal of multicellularity
Multi cellularity meant that they formed an organism that was bigger, more efficient, and able to do much more than any single-celled organism ever could.
Compare and contrast the Tertiary and Quaternary Periods of the Cenozoic Era.
During the tertiary period, earth's climate was generally warm. During the quaternary period, earth's climate cooled, leading to a series of ice ages.
Perhaps the single greatest contribution Linnaeus made to science was his method of naming species. This method, called binomial nomenclature, gives each species a unique, two word Latin name consisting of the genus name and the species name.
A group of organisms that includes an ancestor and all of its descendants. Clades are based on cladistics, which is a method of comparing traits in related species to determine ancestor-descendant relationships. They are represented by cladograms.
A taxon that is larger and more inclusive than the kingdom. Most biologists agree that there are three domains of life on Earth: Bacteria, archaea, (both single celled prokaryotes) and eukaryota (eukaryotes with dna and membrane bound organelles)
Closely related species are grouped together in a genus.
The largest and most inclusive grouping. It consists of organisms that share just a few basic similarities. Examples are the plant and animal kingdoms.
linnaean classification system
All modern classification systems have their roots in the Linnaean classification system. It was developed by Swedish botanist Carolus Linnaeus in the 1700's. He tried to classify all living things that were known at his time. He grouped together organisms that shared obvious physical traits, such as number of legs or shape of leaves. For his contribution, Linnaeus is known as the "father of taxonomy."
Phylogeny is represented by a phylogenetic tree.
The evolutionary history of a group of related organisms.
The species is the smallest and most exclusive grouping. It consists of organisms that are similar enough to produce fertile offspring together.
the linnaean system of classification consists of several different ways of grouping, called taxa (singular, taxon). Taxa range from the kingdom to the species.
The science of classifying life organisms is called taxonomy. This is an important step in understanding the present diversity and past evolutionary history of life on Earth.
kingdoms under the eukaryota domain
protista, plantae, fungi, animalia
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