History of life on earth 12 Flashcards
Timeline of Earth ( PEMALMDg)
- prokaryotes
- eukaryotes
- Multicellular ( multicellular ogranism are common)
- Animals ( Cambrian explosion) ( 1st vertebrate land animals)
- land plants ( 1st flowering plants)
- mammals
- Dinosaurs
- Genus Homo
Cambrain
Period of time where life rapidly diversified and new living groups evolved. Tribolites first emerged
Stromatolites
——– are the earliest evidence of living things on earth
Prokaryotes
are cells with a circular DNA and no membrane-bound organelles
Flowering plants
the type of plant that emerged after plants that could reproduce with spores and cones
Trilobite
any member of a group of extinct fossil arthropods easily recognized by their distinctive three-lobed, three-segmented form
______I______ emerged after ______II______ via the process of endosymbiosis, whereby first ______III______ bacteria and then ______IV______ bacteria were engulfed but not destroyed by a host cell.
EUKARYOTES emerged after PROKARYOTES via the process of endosymbiosis, whereby first RESPIRING bacteria and then PHOTOSYNTHESISING bacteria were engulfed but not destroyed by a host cell.
Arthropods
is an animal without a back bone, with six or more jointed legs, a segmented body and a supporting structure on the outside.
Examples of Organism that evolved on earth during the Cambrian period
The Cambrian period was after the Precambrian era and the Ediacaran period. Describe an organism that evolved on Earth during the Cambrian period
Hallucogenia. Arthropods. Molluscs. Gastropods. Jawless fish/early vertebrates.
response:
- Trilobites evolved during the Cambrian explosion.
- They were arthropods with hard shells and a bilaterally symmetrical body plan.
Some stromatolites have been dated to 3500 mya. Would these stromatolites have been formed by prokaryotic or eukaryotic organisms? Justify your response.
- Stromatolites would have been prokaryotes, because they existed before eukaryotes evolved.
Explain why developing an oxygen-rich atmosphere was important to the development of life on Earth.
- Increasing the oxygen concentration in the atmosphere=>more living things can respire aerobically + organisms can make more energy a+larger organisms can survive.
- In addition, oxygen forms the ozone layer which protects living things from harmful UV radiation.
Using your understanding of endosymbiosis, explain how cyanobacteria were crucial for the evolution of multicellular land plants like the mountain ash.
- Once, an ancestor of mountain ash was a eukaryote that lacked chloroplasts.
- This eukaryote engulfed a photosynthetic cyanobacteria-like prokaryote,
- then used it to make glucose rather than destroying it. I
- In this way, early chloroplasts were formed inside the first eukaryotes.
- This cell replicated and evolved over billions of years, passing on its chloroplasts, until it eventually speciated into mountain ash
identify similarites and one differences between the cells of cyanobacteria and mountain ash
Other acceptable similarities include: Both have cell walls. Both have cell membranes. Both have genetic material in the form of DNA. Both have ribosomes. Both undergo respiration.
Other acceptable differences include:
Mountain ashes have differentiated cells with specialised functions, cyanobacteria do not.
Mountain ashes have membrane-bound organelles, cyanobacteria do not.
Mountain ashes are multicellular, cyanobacteria are not.
Mountain ashes have linear DNA in a nucleus, cyanobacteria have circular DNA in a nucleoid region.
Mountain ashes have cellulose cell walls but cyanobacteria have peptidoglycan cell walls.
Explain the consequences of poor replicability.
By not replicating their experiment,
- we do not know if the results are reproducible
- or if they just happened by chance.
- This means their results are not reliable
Fossils
the preserved body,
impressions, or traces of an
ancient organism
- permineralised, trace, mummified, impression
Steps in fossilation ( making a fossil) example of died dinosaur
- The organism dies in a river
- The body is covered with
sediment. The soft tissues
decompose, and the hard body
structures become fossilized by
permineralization. - The sedimentary layers
accumulate - Earth’s movements raise
the layers of the rocks to the
surface. - The rock erodes, exposing the
fossilised body structures.
Fossilation
the process by which
an organism becomes a fossil
sedimentary rock
rock that has
formed through the accumulation
of sediment and hardening under
pressure
Conditions that reduce the rate of decomposition typically increase an organism’s chance
of becoming fossilised.
- areas of rapid sediment accumulation
- constant cool temperatures
- low light availability
- physical protection from scavengers and decomposers (e.g. fungi, bacteria).
For example, as aquatic systems regularly deposit large amounts of sediment, many aquatic
animals and plants are preserved.
List 4 type of fossils
- Perminerlised fossils ( mineralised fossil)
- impression fossil
- trace fossil
- Mummified fossil
Permineralised fossil( Mineralised fossils)
formed when organic matter is gradually replaced by hard minerals. Also known as a
mineralised fossil
Impression fossil
organism is encased in material but decomposes or is removed and the gap is filled with another substance. Also known as cast and mould fossils
- they show the shape of the ancient organism but no organic material is preserved
Trace fossil
(footprints / burrows / faeces/ nest or tracks) not part of any organism, but they are preserved evidence of an organism’s activity / behaviour/ presence
Mummified fossil
List how - This occurs through factors that reduce decay
a fossil formed when the body is under conditions that slow down or stop the
decaying process
- Constant humidity,
- Cool temperatures
- Lack of decomposers or scavengers
- Low winds,
- Darkness are all factors that can reduce the rate of decay
e.g. found trap in tree sap, frozen in ice or in dry caves.
radiometric dating
- determine the absolute age of a fossil
- by measuring the relative amounts of radioisotopes to their products
- All radioactive isotopes have a fixed rate of decay – Half Life (number of years it takes for 50% of original
sample to decay)
Process of fossilisation
- Organism dies and falls to Earth’s surface
- The remains are quickly covered with sediment which minimizes scavengers and decay
- Over millions of years the sediment compiles, compacts and turns into sedimentary rock, preserving the
organism’s hard parts - Erosion exposes the fossil to be found
Absolute dating and examples
calculate the absolute age of a fossil by providing an estimate age of fossil or rock.
e. g.
- luminescence
- Electron spin
- Resonance
- Radiometric dating methods,
Relative age
- The age of a fossil is determined by comparing to other fossils with each other
- Instead of a fossil’s age in years
e. g. - fossil succession/ law of superposition and index fossil
strata
separate layers within sedimentary rock
fossil succession
- the principle that fossils of
- the same age will be in the same layer of sedimentary
rock, a - nd fossils found in a higher or lower sedimentary layer will be younger or older respectively. Also
known as the law of superposition