conditions for decay absent eg fossils preserved in ice
4 of 25
what are parts of an organism replaced by when they decay?
other materials eg minerals
5 of 25
what are traces of organisms?
footprints,burrows
6 of 25
why did most organisms that dies did not leave a fossil?
because the conditions for fossil formation were not present
7 of 25
why were few traces left behind?
many early life forms had soft bodies
8 of 25
what are traces that were left likely to have been destroyed by?
geological activity eg volcanoes
9 of 25
define extinction
a species which once existed has completely died out
10 of 25
eexctinction circumstances:
new diesease;environment change; new predator; new competitor;catastrphic event; natural changes
11 of 25
what is the biggest influence on species survival?
change in environment
12 of 25
eg
climate change; too cold to breed
13 of 25
what does fossil evidence show about mass extinction?
was on a global scale
14 of 25
what may climate change cause
limites food supply as too cold or hot/we or dry
15 of 25
what caused dinosaurs to become extinct?
giant asteroid caused huge fires, earthquakes, landlsides and tsunamis; dust masked the sun - colder temperatures; plants could not grow; less food available
16 of 25
how can new species arise?
when two populations become isolated eg geographically
17 of 25
how can geographical isolation occur?
islands seperate from mainland/river seperates two ares eg mountains ranges/old craters isolate organisms
18 of 25
what may organisms in a new environment be exposed to?
new predators, different conditions
19 of 25
....... ....... will occur in both areas, but different ........... will be beneficial in the ... populations
natural selection; characteristics; two
20 of 25
when are they two seperate species?
when they cannot interbreed
21 of 25
what is genetic variation?
when each population has a wide range of alles that control their chracterustics
22 of 25
what will help an organism to survive
alleles that control the characteristics.
23 of 25
what will these organisms do?
survive and breed
24 of 25
when has speciation occurred?
when two populations can no longer interbreed
25 of 25
Other cards in this set
Card 2
Front
how can we date when different organisms exist?
Back
we can date how old rocks are
Card 3
Front
what bits of an animal will not decay easily?
Back
Card 4
Front
why have some parts of the organism not decayed?
Back
Card 5
Front
what are parts of an organism replaced by when they decay?
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