Download Evolution Notes

Geologic Time and Evolution Notes
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Evolution – a scientific theory that explains how modern organisms evolved (changed) over long periods of time through
descent from common ancestors
o Developed by Charles Darwin after his five year voyage on the HMS Beagle
o Theory is based on the following principals:
 Adaptations – an inherited characteristic that increases an organisms ability to survive and reproduce in
its environment
 Fitness – how well an organism can survive and in the environment in which it lives
 Natural Selection – the process by which organisms with variations most suited to their local
environments survive and leave more offspring
o Evidence for Evolution:
 The Earth is old enough for evolution to have occurred (about 4.6 billion years old)
 Fossil Evidence – recently discovered fossils form series that trace the evolution of modern species from
extinct ancestors
 Homologous Structures – structure adapted to different purposes as a result of descent with modification
from a common ancestor; ex. Similar bones in the leg of a frog, alligator, chicken wing, and horse
 Vestigial Structures – inherited from ancestors but have lost much or all of their original function due to
difference environments of the descendent (ex. Wings in flightless birds)
 Biochemical Evidence – Amino Acid Sequences (the DNA/RNA code) is nearly identical in all organisms,
including bacteria, yeasts plants, fungi, and animals
o Divergent Evolution – when two or more related species become more and more different
o Convergent Evolution – similar structures and characteristics in distantly related organisms
Evolutionary Classification – grouping species into larger categories that reflect lines of evolutionary descent, rather than
overall similarities and differences
o Clade – a group of species that include a single common ancestor and all descendents of that ancestor both living
and extinct
o Cladogram – links groups of organisms by showing how evolutionary lines, or lineages, branched from a common
ancestor
Geologic History
o Fossil record – by studying the fossil record, paleontologists learn about the structure of ancient organisms, their
environment, and the ways in which they lived
o Relative Dating – to determine if a fossil is older or younger than other fossils
o Geologic Time Scale
 Era - a division of geologic time – divided into Paleozoic, Mesozoic, and Cenozoic
 Period – subdivisions of eras
 Mass extinction – when many species become extinct over a relatively short period of time
o Rate of Evolution – evolution has proceeded at different rates for different organisms at different times over the
history of the Earth
 Gradualism – slow and steady evolution
 Punctuated equilibrium – brief periods of more rapid change
Advantages of Sexual Reproduction and Asexual Reproduction
 Sexual Reproduction - Genetic material comes from two parents
 Lots of genetic diversity
 Increases likelihood of adapting to a new or changing environment
 Asexual Reproduction – The production of genetically identical offspring from a single parent; An
organism duplicates genetic material and passes it on to offspring
 Efficient – a survival mechanism to reproduce quickly in an unchanging environment
 Genetic variation is restricted