1. History of Life & Evolution
Vocabulary Words
History of Life
& Evolution

2. Cambrian Explosion
When ancestors of most major animal groups diversified in the space of just a few million years at the start of the Paleozoic era. This is known as the Cambrian explosion.

3. K-T boundary
A layer in between the rocks of the Cretaceous period and the Paleogene period that occurred 65 million years ago. The layer contains high levels of Iridium. This is evidence of a meteorite impact on earth 65 million years ago.

4. Plate Tectonics
Describes the movement of several large plates that make up the surface of the earth

5. Relative dating
A method used to determine the age of rocks or fossils by comparing them with those in other layers

6. Law of superposition Radiometric dating
States younger layers of rocks are deposited on top of older layers
Radiometric dating
Uses the decay of radioactive isotopes to measure the age of a rock

7. Spontaneous Generation
Half-life
The amount of time it takes for half of the original isotope to decay
Spontaneous Generation
The idea that life arises from non-life

8. Biogenesis Endosymbiont theory
The theory that states only living organisms can produce other living organisms
Endosymbiont theory
The theory that early eukaryotic cells developed organelles such as mitochondria and chloroplasts from prokaryotic cells that were ingested or lived as parasites inside the eukaryote.

9. artificial selection natural selection
The process of selective breeding of animals or plants
natural selection
Darwin’s theory that nature selects the best adapted individuals for survival based on four principles:
Individuals in a population have variation
Variations can be inherited
Organisms produce more offspring than can survive on available resources
The Variations that allow for improved survival in an environment will survive and reproduce more

10. Evolution Derived trait
Cumulative heredity changes in groups of living organisms over time
Derived trait
New evolved features such as feathers that are not present in fossils of common ancestors

11. Ancestral trait Homologous structure
Features such as teeth and tails that also appear in ancestral forms
Homologous structure
Anatomically similar structures inherited from a common ancestor (example: birds wings and reptile forearms)

12. Vestigial structure analogous structure
Reduced form of a functional structure that includes shared ancestry (tail bone in humans, pelvic bone in snakes, your appendix)
analogous structure
Structures used for the same purpose and superficially similar but not inherited from a common ancestor (Bird wings vs. bat wings or insect wings)

13. mimicry
When one species evolves to resemble another species of plant or animal
camouflage
Morphological adaptations that allow an organism to blend with their environments.

14. Hardy-Weinberg Principle
States that allelic frequencies in populations stay the same unless they are affected by a factor that causes change
Directional Selection
Shift of a population towards an extreme version of a beneficial trait

15. Founder Effect
Can occur when a small population is separated from the main population and interbreeds producing unique allelic variations

16. Punctuated Equilibrium
Evolution that occurs rapidly and results in sudden periods of speciation followed by long periods of stability

17. Gradualism
The theory that evolution proceeds in small, gradual steps

18. Prezygotic Isolation
Geographic, ecological or behavioral barriers or differences that make mating and fertilization unlikely between a species

19. Allopatric speciation
Occurs when a physical barrier (such as an ocean or mountain range) causes the separation of a species and thru natural selection two separate species form over time

20. Sympatric speciation
When a species evolves into a new species without a physical barrier (due to feeding habits or polyploidy in plants for example)

21. Postzygotic isolation
Co-evolution
When the evolution of one species affects the evolution of another (mutualism or parasitic dependency)
Postzygotic isolation
When fertilization has occurred but a hybrid offspring can not develop or reproduce (ex: A horse and donkey create a mule or a lion and tiger create a liger. Neither offspring is fertile)