Development of Life on Earth Flashcards
Earths current atmosphere is rich in…
nitrogen, oxygen, argon, and carbon dioxide.
what was Earth’s early atmosphere composed of?
gases that came from volcanic eruptions
What gases are emitted from volcanic eruptions?
water vapor, nitrogen, and carbon dioxide, almost no oxygen
As the water vapor in the air _____ it formed the Earth’s early oceans
condensed
What formed as water vapor in the air started condensed?
Earth’s early oceans
about 2.5 billion years ago what increased in the atmosphere?
oxygen
Why did oxygen increase in the atmosphere 2.5 billion years ago?
the development of a single-celled bacteria called cyanobacteria (algae)
Another name for cyanobacteria is…
algae
Cyanobacteria were some of the first species to undergo…
photosynthesis
Oxygen levels in the atmosphere _______ as soon as cyanobacteria developed and started to undergo photosynthesis
increased
As oxygen levels rose, did carbon dioxide levels drop or rise along with it?
drop
What is photosynthesis?
the process by which plants use carbon dioxide, water and energy from the sun to create oxygen as well a carbohydrates that are used to make the plants structure
_______ is the process by which _____ use carbon dioxide, water, and energy from the sun to create oxygen
photosynthesis, plants
In photosynthesis, what do plants use to create oxygen?
carbon dioxide, water, and energy from the sun
Oxygen has been steadily _____ since the development of photosynthesis 2.5 billion years ago
rising/increasing
In the beginning of the Cenozoic Era there is a sharp increase of oxygen content that corresponds to the…
number and diversity and size of mammals.
In the beginning of the Cenozoic Era there is a sharp _____ of _____ content that corresponds to the ____ and ______ and ____ of mammals
sharp, increase, number, diversity, size
There seems to be a link between the amount of ______ in the atmosphere and how may _______ are developing on the Earth.
oxygen, mammals
For most of Earth’ history we don’t find any evidence of _____ or ______
life, bacteria
In order for life to survive it must have the ability to ______ itself
replicate
What do all forms of reproduction require?
DNA
A living thing must be able to…
metabolize
what does metabolize mean?
to make energy for oneself
What does metabolism require?
some sort of cellular structure that allows food and energy to be exchanged
Metabolism requires some sort of cellular structure that allows ____ and _____ to be exchanged
food, energy
What are the earliest signs of bacterial life on Earth?
stromatolites
stromatolites are…
calcium carbonate deposits formed by cyanobacteria
Stromatolites are _______ ______ deposits formed by cyanobacteria
calcium carbonate
Cyanobacteria are bacteria that underwent ________, and as they developed what?
photosynthesis
- shells of calcium carbonate from secretions of calcium carbonate (kind of how coral is formed) and the calcium carbonate builds up over years and years so we see a fossilized remnant of cyanobacteria
all bacteria are ______ celled organisms
single
What are all single celled organisms called?
prokaryotes
Prokaryotes have no _____ separating their DNA from the rest of the cell contents
nucleus
What are Eukaryotes?
Organisms that have a clearly defined nucleus as well as organelles within the cell
organelles are things like ________ in animals and _______ in plants
mitochondria, chloroplasts
Indirect evidence suggests that the earliest Eukaryotes developed between ____ and _____ billion years ago
2.7 and 1.4
Eukaryotes are different from Prokaryotes because they have an ______ metabolism
aerobic
What does an aerobic metabolism mean?
they use oxygen from the atmosphere
Since oxygen provides for more ______ energy production, eukaryotes were able to become bigger and more _______
efficient, complex
Any multi celled organism is a…
eukaryote
When did the earliest multicellular eukaryotes appear?
around the end of the Proterozoic eon
How many years ago was then end of the Proterozoic eon?
630 million years ago
The mulitcellular eukaryotes from the end of the Proterozoic eon did not have any ____ ____ making there fossils hard to find. Why are they harder to find?
hard parts (shells, bones)
- because there soft parts are less likely to be fossilized
do we have a fossil record of how the huge jump from unicellular organisms to multicellular organisms occurred?
No
what are our only clues to the history of life on Earth?
fossils
How do most fossils form?
when an organism has a hard part, such as a shell or bone, and it is quickly buried in sediment.
Most fossils form when an organism has a hard part that is quickly _______ in _______.
buried, sediment
Once a hard part of an organism is buried, what happens?
a cast is made of its shell or bones, and so we have evidence of that organism
Ins special circumstance soft parts of an organism may be preserved as well, this preservation can occur in…
tree sap, or amber, or through the process of mummification if its in a dry area
Mummification of organisms can only happen in a very _____ area
dry
What is mummification?
drying out before decomposition
when was the Cambrian period?
The Paleozoic era started with the Cambrian period 542 million years ago
What happened during the Cambrian period?
bio-diversity exploded.
Geologically, right about 542 million years ago, all of a sudden there are tons of ______ in the rocks
fossils,
called an explosion because there were little to no fossils beforehand and all of a sudden there are tons of fossils
Is why the explosion occurred well understood?
No
what are some hypothesis for why the biodiversity explosion occured?
- sexual reproduction increased rate of evolution
- more oxygen available for larger organisms
the hypothesis for why biodiversity exploded lean towards…
into the development of sexual reproduction.
In the Cambrian period there is evidence of more…
hard-shelled organisms such as trilobites
which type of hard shelled organism is the most diverse group of extinct organisms?
trilobites.
found trilobite fossils ranging in size from 3mm to 70 cm (over 2ft)
over 20,000 species
Trilobites lasted how many years on Earth?
270 million years,
longest lived group in Earth’s history
Why are trilobites well preserved?
They have a hard shell and an easily recognizable body shape
Most of the living organisms found in the Cambrian period lived in _______
water, marine life
During the Paleozoic era and into the Cambrian period, plants began to develop the capacity to survive on ______
land
Plants developing on land require an internal aquatic environment to keep a _____ environment for the ______ system
moist, reproductive
Continuing into the Cambrian period we see the first fossils of chordates. What are chordates?
organisms which developed a spinal chord
What is the earliest chordate fossil found?
a jawless fish, jaws developed next and fish became larger: first sharks
The first amphibians may have evolved from ______
fish
The first fish to develop on land evolved into the first ______
amphibians
What happened at the end of the Paleozoic Era?
a mass extinction
During the mass extinction of the Paleozoic era only ____ branch of amphibians is thought to survive. What did these amphibians evolve into?
one, reptiles
Reptiles lay ______ eggs and are therefore freed from living in _____ for some of their life
watertight, water
Throughout the Mesozoic era _______ are the biggest creatures on earth
reptiles
Reptiles during the Mesozoic era proliferated in the new environment and grew in ____ and ______
size, number
small ______ existed alongside dinosaurs
mammals
Near the end of which period did birds begin to appear?
Jurassic (middle of Mesozoic era)
At the end of the Mesozoic era, dinosaurs as well as other species were wiped out in a…
mass extinction
after the mass extinction of dinosaurs we enter into the the Cenozoic era, known as the _____ ____ ______. what happened during this era?
age of the mammals
- mammals grew larger and more diverse with larger brains
what are hominids?
human-like species that walked upright
The earliest hominids were ____ in size
small
Hominids never travelled out of _______
Africa
Which type of hominid fossil ha been found more widely spread?
homo erectus
There is evidence that homo Erectus were able to fashion and use _____
tools
When did Homo Erectus disappear?
300,000 years ago
we don’t see anymore Homo Erectus fossils in the rock record.
what species of hominid do we see in fossils of in the rock record after the Homo Erectus?
Neanderthals
homo neanderthalensis
there is evidence that neanderthals practiced _____ and perhaps ______
rituals, religion
about 30,000 Neanderthals disappeared, but we start to see the development of ____ ____
Homo sapiens
Homo sapiens are modern ______
humans
