Terms in this set (28)
Change in species over time.
A process where modern organisms descend from
Change in the genetic makeup of a population
of a species
The earth is how many years old?
Life forms appeared how many years ago?
Geologic time scale
A representation of EARTHS HISTORY
How is the geologic time scale organized?
Organizes Earth's history by major changes or
events that have occurred.
What information do scientists use to organize
The geologic time scale?
Scientists use evidence from
fossil and geologic records.
• Largest period of time.
• Tens to hundreds of millions of years.
• Most commonly used units of time.
• Each period associated with a particular type of rock system.
Smallest unit of time
How are index fossils used to determine the age of fossils or rock layers?
Index fossils are used as markers because they are
found in the rock during the specific span of time and
geographic area in which they lived. They "tell" the
What four characteristics are best for an index fossil to
✓ easy to identify
✓ found widely around world
✓ existed for a short time
Eras & Periods:
✦ END with disappearances
✦ BEGIN with appearances
(NEW SPECIES) of
✦ Mass extinctions make
many new ecological niches
available for new species
(time without life)
makes up the MAJORITY of
Life moved onto land during the Paleozoic era
Early plants moved onto land. 1. Four-legged vertebrates (amphibians) became
2. 70 percent of land animal species at the time
became extinct by the period's end
Reptiles radiated during the Mesozoic era.
3. Dinosaurs roamed Earth
4. Earliest crocodiles arose
5. Ichthyosaurs, marine reptiles, dominated the
Evidence in evolution is found in
3. Anatomy (structures)
Preserved remains of ancient
organisms found in rocks
When an empty space is left in the rock after an organism dies and decays
Minerals in an organism are replaced by stone
Tracks in rocks (ex. Laetoli men footprints)
Amber: when insects get trapped in tree sap
Ernst Von Baer's contribution to Theory of Evolution:
Stated: The more closely related any 2 species are, the more similar their development.
Observed: vertebrate embryos
have a common design, where the adult forms are different.
Development of an individual
through a single life cycle
Vertebrate ZYGOTES are
a. similar (single cell)
b. different size of the nucleus.
EMBRYOS of closely related groups (vertebrates) resemble
more closely than the embryos of distant groups
Structures (across species) that are similar in structure
but may have a different function.
Evidence of a common
Similar in FUNCTION but different in STRUCTURE.
NOT EVIDENCE OF A
COMMON ANCESTOR. They have evolved due to a
similar environmental challenge.
Remnants (vestiges) of organs or other parts that may
be reduced in size and have little to no function. (Had a
function in an earlier ancestor.)