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Ecology Chapter 17-1& 17-4 BIO Cheat Sheet by

help study for bio exam

Fossils and Ancient Life

- paleon­tol­ogists are scientists who study fossils
- they collect inform­ation about fossils and put it into a fossil record -> shows how species lived and have changes over time
- 99% species on earth are extinct

How Fossils Form

1) water carries small rock particles to lakes and seas
2) as layers of sediments build up over time, dead organisms sink to the bottom and become buried
3) the layers of sediment compress and turn into rock -> fossils
4) the fossils are later discovered and studied

Interp­reting Fossil Evidence

paleon­­to­l­o­gists determine a fossil's age using two techni­­ques: relative and radioa­­ctive dating

Radioa­ctive & Relative Dating

- in relative dating, the age of one fossil is determined by comparing its placement with other fossils in other layers of rock
- scientists use index fossils to compare the relative ages of fossils
- index fossils are species that are easily recognized and have existed for a short period of time but have had a wide range of geographic range
- in radioa­­ctive dating, half-lives are used to determine the age of a fossil
- a half-life is the radioa­­ctive atoms in a fossil to decay
- age is calculated based on amount of remaining radioa­­ctive isotopes contained

Geologic Time Scale

- geologic time scale is divided into eras and periods
- eras are Cenozoic, Mesozoic, Paleozoic, and Precam­brian Time
- periods range from tens of milions of years to less than two million years


- macroe­­vo­l­ution are large scale evolut­­ionary pattens and processes that occur over large periods of time
- this includes:
1) extinction
2) adaptive radiation
3) convergent evolution
4) coevol­­ution
5) puncuated equili­­brium
6) changes in develo­­pm­ental genes


- extinction happen b/c of compet­­ition for resources & enviro­­nm­ental changes
- some species extinc­­tions are caused by natural selection
- mass extenc­­tions have wiped out ecosystems b/c enviro­­nment was collapsing
- mass extinc­­tions are caused by volcano eruptions, shifting contin­­ents, and sea level changes
- mass extinc­­tions provide opport­­un­ities for new species and surviving species

Adaptive Radiation

-periods of evolut­ionary change in which groups of organisms form many new species whose adapta­tions allow them to fill different niches in their enviro­nment
- diversity of life fueled by adaptive radiation
- large scale changes; ex: dinosaurs -> reptiles today

Convergent Evolution

- when adaptive radiation occurs -> natural selection molds different body structures
- the process where unrelated organisms come to resemble one another is convergent evolution
- ex: dolphin and sharks body structure; penguin and dolphin nose and mouth


- the process where two species evolve in response to changes in each other over time is called coevol­ution
- ex: snakes and rats; snakes evolve -> more poison, rats evolve -> more resistance

Punctuated Equili­brium

- punctuated equili­brium is the pattern of long, stable periods interupted by brief periods of rapid change

Develo­pmental Genes and Body Plans

- changes in the expression of develo­pmental genes can explain differ­ences in evolution
- one type hox genes provide positional inform­ation in an animal embryo
-small changes in regulatory sequences of particular genes can lead to major changes in body form


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