Fossils Flashcards
What is a fossil?
Evidence of past life in the form of remains or imprints of a once living organism that has been preserved in rock or another substance
What are the 5 types if fossils?
- permineralisation
- casts and moulds
- carbonisation
- trace fossils
- fossilised resin
What is permineralisation?
- original material is hardened by minerals deposited by the ground
- also called petrification
What are casts and moulds?
Casts- a rock with the shape of an organism protruding
Moulds-a rock that has an impression (hollow) of an organism
What is carbonisation?
- Often indicated by shiny black texture of an organism
- e.g plant leaves or anthropod
What are trace fossils?
Remains of trackways, burrows, eggs and eggshells, nests and droppings
What is fossilised resin?
- also called amber fossils
- formed when tree sap solidifies
- traps insects
What is absolute age?
- estimate of the age of the fossil
- based on radioactive decay of materials
- carbon dating - determined by comparing the amount of original isotype
What is relative age of a fossil?
- whether it is younger or older than other fossils or rocks
- older layers of sedimentary rock at bottom and newer at top
- fossils will be same age as rock its formed in
What was lamarcks theory?
- THEORY OF ACQUIRED CHARACTERISTICS
- improvement with repeated use and weakened with disuse
- these improvements could be passed on to child
- unsupported by evidence
What was darwin/wallaces theory?
- THEORY OF NATURAL SELECTION
- within species, variation of characteristics (char) already exist
- favourable char. help an organism survive its environment
- supported by modern studies of genetics
What is variation?
Within any species, individuals can have inherited characteristics and be similar to others but not identical
What is adaptation?
- organisms can adapt to their environment
- stuctural - physical characteristics
- behavioural - how they act
- functional - internal changes
What is VESP and whose theory is it?
Variation, environmental pressures, population and survival of the fittest
Darwin and wallace
What is variation within natural selection?
Individuals with favourable variations are more likely to survive longer and produce more offspring
What is environmental pressures within natural selection?
Competition for resources, predators
What is population within natural selection?
Favourable characteristics passed on, so it becomes more common in the population
What is survival of the fittest?
- individuals best adapted to their environment have better chance of surviving
- have advantage when competing for resources
- e.g galapogos finches
What is the convergent evolution?
Over time two species become more alike due to similar selection pressures and similar variations selected for
What is divergent evolution?
A barrier isolates population of a species and over time they change due to different selection pressures and different variations selected for
What is the evidence for evolution?
- fossil record
- comparative anatomy
- comparative embryology
- molecular biology
Fossil record - evidence
- shows organisms living on earth have become increasingly complex
- shows some species become extinct
- shows gradual change to species
- eg fossils of ancient horses
Comparative anatomy - evidence
-similarity in characteristics from common ancestry
Homologous
Similarity in anatomical signs- eg similar forearms of mammals
Analogous structures
Perform same role but have different evolutionary origins
Comparative embryology
- organisms go through similar stages in their embryonic development are believed to be closely related
- gill slits - fish and all
Molecular biology - evidence
- closer match in dna sequences, the more recent their common ancestor and hence the more closely they are related
- human and chimpanzees
