chap 10- changes in species over time Flashcards
what is a fossil
any evidence of life from the past
what are the two types of fossil
body fossils and trace fossils
what are body fossils
made from whole or part of an organism
what are trace fossils
rocks that have preserved evidence of biological activity of organisms.
when are fossils likely to form in animals
-when they have hard bones
-when they live near water sources where sediments can be easily deposited on them.
- animals that are rapidly buried
- animals with low chance of disturbance, low oxygen levels and low temp
what are mass extinctions
a collection of fossil animals and plants in a stratum layer giving way abruptly to a completely different collection of fossils in the next stratum due to substantial changes in global environmental conditions.
these sudden changes in global environmental conditions meant that the habitat was no longer suitable for some organisms and they were wiped out
what are index fossils
fossils that are representative of a specific geological time.
what are index fossils used for
dating and correlating the strata in which it is found
what are transitional fossils
fossils that bear features of both an older ancestral life form and a younger descendant.
what do transitional fossils provide evidence for
evolution (can show how a species may have been able to adapt to new conditions)
what is relative dating
looking at the ordering of rock layers and index fossils to determine the relative age of a fossil
what is relative age
the age of an object compared to the age of another object. does not provide exact age of an object
what is absolute dating
assigns a numerical age in years to a fossil or rock
what is the most common form of absolute dating
radiometric dating
what is radiometric dating
based on predictable rates of decay of naturally occuring radioactive isotopes rock or fossil (carbon/potassium/uranium) present in a fossil
what are the 3 isotopes of carbon
carbon-12, carbon-13, carbon-14
what is the half-life of carbon
5730 years
when is carbon-14 radiometric dating thought to be accurate up until
60,000 years
what is evolution
the change in the genetic composition of a population over time
what are mutations
a permanent change in a genetic sequence which can either have a beneficial effect, no effect or a harmful effect on the survival ability of an individual
what are selection pressures
external agents which contribute to selection of variants in alleles that can affect an organisms ability to survive in a given environment
what is a fragmented population
organisms in a population being separated from other groups of the same species
what are isolating mechanisms
refer to the ways in which groups of organisms can become separated for long enough to develop into different species.