B2.6 Old and new species Flashcards
What is a species?
a group of organisms that share similar characteristics- two species can not successfully mate and reproduce
What is speciation?
the development of species - it takes place when an isolated population becomes so different from the original population that successful interbreeding can no longer take place
Give an example of speciation?
Australia- very isolated so has many species not found elsewhere
What is a fossil?
preserved remains or trace of dead organism
What do fossils tell us?
provide evidence about organisms that lived a long time ago and how life evolved
Name different types of fossils
casts and impressions
gradual replacement by minerals
Give an example of fossilisation taking place
insects in amber-tree sap: no oxygen,
no decay
plants or animals in glaciers-too cold for decay
peat bogs- acidic makes decaying hard as enzymes denature
Explain casting and impressions
formed when an organism is buried in soft sediment eg. clay
the sediment hardens and the organism decays leaving a cast of itself
Explain gradual replacement by minerals
things like teeth, bones etc. don’t decay easily
they eventually decay to form a rock-like substance
surrounding sediments also turn into rock
plants are soft bodied and therefore are not preserved in this way (gaps in fossil records)
Why is the fossil record incomplete?
early life forms were soft bodied–>little or no fossil evidence
fossilisation requires particular conditions–> many organisms are not fossilised
some fossils formed in rocks are often broken down by geological activity
How can we use the information from fossils?
ideas of how organisms evolved
use knowledge of living organisms to fill in gaps
use of family trees to illustrate evolutionary relationships between organisms- past and present
