1. GMAS Practice Question
Permafrost, soil that remains permanently frozen all year, can be found in which biome?
Taiga
Grasslands
Tundra
Temperate deciduous forest

2. GMAS Practice Question
Permafrost, soil that remains permanently frozen all year, can be found in which biome?
Taiga
Grasslands
Tundra
Temperate deciduous forest

3. Clues About Evolution

4. Standard S7L5
Students will examine (look at) the evolution (change over time) of living organisms through inherited (present at birth; from parents) characteristics (uniqueness; individuality) that promote (help; encourage) survival of organisms and the survival of successive (later) generations (age groups) of their offspring (babies; children).

5. Essential Question
What evidence do scientists have to support evolution?

7. Essential Question
What evidence do scientists have to support evolution?

8. 5
Clues

9. 1st Clue Fossils provide most of the evidence for evolution
Fossil: The remains, an imprint, or a trace of a prehistoric organism.
Most fossils come from sedimentary rock.

10. Fossils are found more often in limestone than any other kind of sedimentary rock.
The fossil record provides evidence that living things have evolved.

11. Determining a Fossil’s Age
Two basic methods, relative dating & radiometric dating, can be used alone or together to estimate the age of rocks and fossils.

12. Relative Dating: A way to find the approximate age of fossils found within a layer of rocks.
-Based on idea that in undisturbed areas, younger rock layers are deposited on top of older rock layers
- Provides only an estimate of a fossil’s age
- Made by comparing the ages of rock layers found above and below the fossil’s layer

13. Radiometric Dating: Obtaining a more accurate estimate of the age of a rock layer by using radioactive elements (gives of a steady amount of radiation as it slowly changes to a non-radioactive element).
-Each radioactive element gives off radiation at a different rate.
-Scientist can estimate the age of a rock by comparing the amount of radioactive element in the rock with the amount of non-radioactive element in the rock.

14. Fossils & Evolution
Fossils provide a record of organisms that lived in the past.
The fossil record has gaps because of incomplete rock record, and because most organisms don’t become fossils.
From a study of the fossil record, scientist concluded that 99% of all organisms that have ever existed are extinct now.

15. More Clues About Evolution
Sometimes evolution can be directly observed:
-cross-breeding to produce genetic changes in plants, antibiotic resistance in bacteria, pesticide-resistant insect species
Indirect evidence also exists:
-Similarities in embryo structure, DNA, the way an organism develops into an adult

16. 2nd Clue Embryology: The study of embryos and the development
An embryo is the early growth stage of an organism
A tail & gills or slits are found at some point in embryos of fish, reptiles, birds, and mammals
These similarities suggest an evolutionary relationship among all vertebrate species.

18. 3rd Clue
Homologous Structures: Body parts that are similar in origin and structure.
Homologous structures and also be similar in function.
Homologous structures often indicate that two or more species share common ancestors.

20. 4th Clue
Vestigial Structures: Structures that don’t seem to have function.
Provide evidence for evolution.
Manatees, snakes, and whales no longer have back legs, but they still pelvic bones.
Body parts that once functioned in an ancestor.

22. 5th Clue
DNA: The molecule that controls heredity and directs the development of every organism.
Scientist compare DNA from living organisms to identify similarities among species.
Provides additional evidence of how some species evolved from their extinct ancestors.