Evolution Part 2 Evidence & Types

Common Descent with Modification Darwin proposed that organisms descended from common ancestors Organisms change over time, diverging from the common form Caused speciation: evolution of new species

Descent With Modification Takes Place Over Long Periods of Time Natural Selection Can Be Observed As Changes In Body Structures Ecological Niches (role of the organism in its environment) Habitats

Descent With Modification Implies All Living Organisms Are Related Single Tree of Life DNA, Body Structures, Energy Sources Common Descent - All Species, Living & Extinct, Were Derived From Common Ancestors

Theory of Evolution Today Supporting Evidence

Evidence of Evolution 1. Fossil Record: Fossil = any preserved remain or imprint of once-living organisms found in layers of sedimentary rock strongest evidence

The fossil record is the ordered arrangement in which fossils appear within sedimentary rocks. These rocks record the passing of geological time and provides an actual record of the Earth’s past life forms

DETERMINING FOSSIL AGE Relative Dating = estimating a fossil’s age compared with that of other fossils Gives an approximate age of fossils Fossils in lower layers are older than fossils in top layers Radiometric Dating = calculating the age of a sample based on the amount of remaining radioactive isotopes it contains Half-life = the length of time required for half of the radioactive atoms in a sample to decay

Evidence of Evolution 2. Homologous structures Structures that are similar because of common ancestry (comparative anatomy) Scientists Noticed Animals With Backbones (Vertebrates) Had Similar Bone Structure May Differ In Form or Function Limb Bones Develop In Similar Patterns Arms, Wings, Legs, Flippers

Evidence of Evolution 3. Analogous structures Structures that are similar NOT due to a common ancestor but instead a common environment or habitat Type of comparative anatomy

Evidence of Evolution 4. Vestigial Structures Structures that are no longer used by the organism that have decreased in size and/or function Examples: whale leg, ostrich wing, human appendix

Evidence of Evolution Comparative Embryology Study of structures that appear during embryonic development. Organisms that are of a common ancestry will develop in a similar fashion

Evidence of Evolution 6. Geographic Distribution of Life forms Different Animals On Different Continents But Similar Adaptations To Shared Environments

Evidence of Evolution 7. Molecular biology (biochemistry): Study of DNA and proteins (amino acids) Organisms that are more closely related will have DNA that is more similar

Types of Evolution Microevolution – the change of allele (DNA/gene) frequencies with in a population; small scale Exp: Peppered Moths Macroevolution – large scale evolutionary changes 5 Patterns of macroevolution Mass extinctions Adaptive Radiation Convergent Evolution Coevolution Punctuated Equilibrium (and gradualism)

5 Patterns of Macroevolution 1. Mass Extinctions More than 99% of all species that ever lived are now extinct Mass extinctions wiped out food webs and ecosystems Exp: Dinosaurs were killed by an asteroid. Could have been many factors (volcanoes & continental drift)

5 Patterns of Macroevolution 2. Adaptive Radiation (Divergent evolution) A species or group of species evolves into many new species with different adaptations Exp: Darwin’s finches

5 Patterns of Macroevolution 3. Convergent Evolution Unrelated species may evolve to resemble one another if they live in very similar environments. Show analogous traits Example: 1. Ostrich (Africa) and Emu (Australia). 2. Shark, and dolphin (have streamlined bodies that allow them to swim rapidly)

5 Patterns of Macroevolution 4. Coevolution Evolutionary change, in which one species act as a selective force on a second species, inducing adaptations that in turn act as selective force on the first species. Example: Humming birds and plants with flowers with long tubes

5 Patterns of Macroevolution 5. Punctuated Equilibrium Patterns of rapid evolution after long periods of equilibrium (balance) Why? Migration, mass extinctions, isolation

5 Patterns of Macroevolution How does it appear that GRADUALISM is different? Gradualism is selection and variation that happens more gradually.