Download 2) Homologous structures

Evidence of Evolution
Vocab:
1) Vestigial Structures – Use to have a function but no longer does.
Ex: Appendix/ Snakes have structures that resemble hipbones
Ex: eyes on cave fish that are blind
2) Homologous structures – Same in structure and possibly the same in function
Ex: Human arm and fore leg of dog.
3) Analogous structures – Same in function but different in structure.
Ex: Insect wing and bird wing
Homologies
Evolutionary theory predicts that related organisms will share similarities that are derived
from common ancestors. Similar characteristics due to relatedness are known as
homologies. Homologies can be revealed by comparing the anatomies of different living
things, looking at cellular similarities and differences, studying embryological development,
and studying vestigial structures within individual organisms.
4 of fields of study leading to the evidence that supports Evolution:
1. Embryology: -Study of Embryos
-The embryos (which are the earliest stages of growth in plants and animals) of fish,
reptiles, birds, and mammals cannot be told apart.
-they all have gill slits, tails, and notochord
-Fish/Chicken/Pig/Human
2. Comparative Anatomy: -The study of living and extinct species anatomy (body
structures)
-Wooly Mammoth vs. an Elephant
3. Biogeography: The study of Geographical distribution of living things
4. Molecular biology:
Genetics-All organisms have DNA/RNA
Purines:A G (Aggies are pure)Primidines:TCU
Fossil Records
-Physical evidence of an organism that lived long ago
-Not all fossils have been found
-Bases of the geological time scale (marks mass extinctions)
Types of dating Fossils:
-Relative Dating: layers of rock with the youngest fossils on top and the oldest
in the bottom layers. One can conclude that the land could’ve been a completely different
environment at different points in time.
-Absolute Dating/ Radiometric dating: Potassium 40 is used to date over a
million years old, carbon 14 is used for less than 50,000 years old. (Isotopes/ Half-life)
Natural Selection:
Survival of the Fittest: Those best “fit” for their environment will survive the best and
reproduce the most
Camouflage - concealment by some means that alters or obscures the appearance.
Mimicry – The close external resemblance of an organism, the mimic, to some different
organism, the model, such that the mimic benefits from the mistakes the identity, as seeming to
be unpalatable or harmful.