5.1 - Life On Earth Top Down Flashcards
How many advanced civilisations could there be in the Milky Way that are capable of communication?
It is difficult to determine the exact number of advanced civilizations that could exist in the Milky Way capable of communication, as it depends on a number of factors that are currently unknown.
The Drake Equation, a probabilistic argument used to estimate the number of communicative civilizations in the Milky Way, takes into account factors such as the rate of star formation, the fraction of stars with planets, the fraction of planets that are habitable, the likelihood of life arising on those habitable planets, the likelihood of intelligent life arising on those planets, and the average lifespan of a communicative civilization.
Based on the latest estimates of these factors, some scientists have suggested that there could be anywhere from a few dozen to tens of thousands of communicative civilizations in the Milky Way. However, until we detect evidence of extraterrestrial life or communication, any estimates of the number of advanced civilizations in the galaxy remain speculative.
What is the Drake equation?
The Drake Equation is a probabilistic argument used to estimate the number of communicative civilizations that may exist in our galaxy, the Milky Way. It was developed by American astronomer Frank Drake in 1961, during the first scientific search for extraterrestrial intelligence.
The equation takes into account several factors that are thought to be important in the development of intelligent life and its potential for communication with other civilizations. These factors include the rate of star formation in the galaxy, the fraction of stars that have planets, the number of habitable planets around those stars, the probability of intelligent life evolving on those planets, the fraction of those intelligent civilizations that would develop technology capable of communication, and the length of time those civilizations would last before they become extinct.
The Drake Equation is expressed as: N = R* x fp x ne x fl x fi x fc x L, where N is the number of communicative civilizations in our galaxy, R* is the rate of star formation, fp is the fraction of stars with planets, ne is the number of habitable planets per star, fl is the fraction of habitable planets where life actually arises, fi is the fraction of life-bearing planets where intelligent life evolves, fc is the fraction of intelligent civilizations that develop communication technology, and L is the length of time that such civilizations last.
While the Drake Equation is not a definitive calculation and relies on many assumptions, it remains a useful tool for exploring the possibility of extraterrestrial life and the search for intelligent civilizations beyond Earth.
When was the first intentional radio wave sent into space?
Yes, in 1974 a message called the Arecibo message was broadcasted into space from the Arecibo Observatory in Puerto Rico. The message was aimed at a star cluster known as Messier 13, located approximately 25,000 light years away from Earth.
The message was composed by a team led by American astronomer Frank Drake and contained basic information about human beings and Earth, such as our numerical system, the chemical elements that make up life, our DNA structure, and the Arecibo telescope itself. The message was transmitted in the form of a binary code, a series of 1s and 0s that could be interpreted as images or sound.
The transmission was a symbolic gesture to demonstrate the capabilities of the Arecibo Observatory and to celebrate its recent renovation. It was also an attempt to initiate contact with extraterrestrial intelligence and to raise awareness of the search for extraterrestrial life.
The Arecibo message is not expected to receive a reply, as it will take 25,000 years for the message to reach its intended destination, and another 25,000 years for any potential reply to reach Earth. Nonetheless, the transmission of the Arecibo message was an important milestone in the history of the search for extraterrestrial intelligence.
How do we know about the history of life on earth?
Because of direct fossil evidence preserved in sedimentary rocks
What is ancillary fossil evidence?
Ancillary fossil evidence refers to fossils that are not direct evidence of the organism or organism’s body part being studied, but are still useful in understanding aspects of the organism’s biology or environment.
For example, trace fossils, such as footprints or burrows, provide evidence of an organism’s behavior or movement. These fossils do not preserve the actual organism itself, but can still provide important information about how the organism lived and interacted with its environment.
Another example of ancillary fossil evidence is the study of coprolites, or fossilized feces. Coprolites provide information about an organism’s diet and digestive system, and can be used to reconstruct food webs and ecological relationships in ancient ecosystems.
Other types of ancillary fossil evidence may include pollen or spores, which can provide information about the ancient environment and the types of plants that were present. Additionally, isotopic analysis of fossilized teeth or bones can provide information about an organism’s diet or migration patterns.
Overall, ancillary fossil evidence can provide important insights into the biology, behavior, and ecology of ancient organisms and ecosystems, even when direct fossil evidence is not available.
What trace fossil can be found at fife coastal path?
The trace fossil of a giant scorpion tracks, 330 million years ago
What is a hominid?
It is a primate or family which includes humans and their fossil ancestors and also (in recent schemes) at least some of the great apes.
Originated 6 million years ago in the great Rift Valley - savannah habitat
- hominids diverged from chimpanzees 6 million years ago
When did mammals originate?
Synodonts or mammal like reptiles ruled the earth millions of years before the dinosaurs came on the scene. They weren’t true mammals but nature was on track for possibly having mammals come right out of reptiles and become the dominant life on earth. Then the Permian extinction killed them off and dinosaurs, starting from small creatures, bloomed into the great age of reptiles, while true mammals arose at the same time but as small, nocturnal burrowing things hiding in dinosaur’s shadows before getting their pown chance to spring forth to dominance after the Cretacious-Terciary extinction event killed most of the dinos.
- Mammals originated in Triassic period (201 to 252 million years ago)
The origins of forests in the late Devonian
Archaeopteris grey 375 Ma and is an extinct tree with fern-like leaves. It is a useful index fossil, this tree is found in strata dating from the Late Devonian to Early Carboniferous (383 to 323 million years ago), the oldest fossils being 385 million years old and had global distribution.
Until the 2007, many scientists considered Archaeopteris to be the earliest known tree.
There were widespread forests from the Devonian 375 Ma, until about 40 Ma when grazers evolved.
The earliest trees in the mid Devonian
The earliest trees known in the fossil record are Wattieza trees which formed around 385 Ma.
They were more like a fern than a tree. They grew up to 8m high.
What was prototaxites?
Prototaxites were a fungus from 420-370 Ma.
Researchers found that the carbon ratios from the different fossil samples of the fungi differed much more than would have been expected of a plant from that era, strengthening the evidence that Prototaxites is a fungus that absorbed some of its carbon from sources other than the air. (It was supported by variable C isotope composition)
Prototaxites became extinct as vascular plants rose to prominence. The organism could have used its tall columnar structure for spore dispersal.
When were leaves and root fossils found?
From the late Silurian = 420 million years ago
Baragwanathia related to modern clubmosses
- They had small leaves (microphylls) and proper roots
When were vascular plant fossils found?
Fossils were found from the mid Silurian = 425 Ma
They maintained internal water pressure (homiohydric)
- they had tubes with rigid cell walls (xylem) to allow capillary action to draw up water against gravity
- Transportation took place through stomata
- Phloem distributed products of photosynthesis in solution
They had no leaves or roots.
When were the earliest land plants?
The earliest land plants were from the Ordovician
Ordovician spores grew from 475 Ma.
The spores were found in groups of 4 (tetrads) and the Trilete (Y) marks on them indicated desiccation-resistance spores
The first fragments of plants could be found from about 450 Ma such as bryophytes.
How much evidence for life on land covers earths history?
Evidence for life on land only covers 1/10th of earths history
Ordovician = earliest land plants (only marine life earlier than this)
Devonian = first forests
Triassic = mammals
Beginning of tertiary = primates
End of tertiary = hominids
