Unit 11 - I. Evidence of Evolution

Fossils

the preserved/traces of remains of ancient organisms

Absolute dating

process of determining age of remains based on content & decay rate of radioactive isotopes

Relative dating

process of determining age of remains based on position in rock strata

Law of Superposition

in any undisturbed sequence of rocks deposited in layers, the youngest layer is on top & the oldest on bottom

Index fossil

• widely distributed fossil

• of narrow range in time

• regarded as characteristic of a given geological formation

Biogeography

geographic distribution of organisms on Earth indicates evolution & movement of tectonic plates over geological time

Comparative anatomy

• homologous structures

• analogous structures

• vestigial structures

Homologous structures

• structurally similar features in different organisms suggesting common ancestry

• structures perform different functions

• may suggest divergent evolution

Analogous structures

• similar features found in unrelated organisms that have evolved to perform the same function

• structurally dissimilar

• no common ancestry

• suggest convergent evolution

Vestigial structures

an anatomical feature that no longer seems to have a purpose in the current form of an organism

Comparative Embryology

• study of similarities & differences in development of embryos of different species

• similarities in embryos are evidence of common ancestry

Molecular evidence

comparing DNA sequences & protein sequencing between species to determine relatedness

Molecular clock

using the # of changes in sequences of biomolecules (mutations) to deduce time in prehistory when 2 or more life forms diverged

• mutation rate is relatively constant, therefore history can be inferred