Evidences of Evolution Darwin stated that all organisms descend from a common ancestor Darwin based his theory of Natural Selection on observations of: Traits, geographical distribution, selective breeding, probably fossils
Evidences of Evolution Today, we use all the tools that Darwin used, and some others, to help us understand how different organisms have a common evolutionary history and could descend from the same once living creature.
Evidences of Evolution Fossils Embryology (or Similarities in Development) Homologous Structures (or Comparative Anatomy) Vestigial Structures Similarities in the DNA of different organisms (or Molecular Biology) Biogeography or geographic distribution not in the handout
Fossils Book page 243 - Important 1) Copy the definition of fossils 2) Copy how fossils can help scientists and how fossils can be an important evidence of evolution. 3) Conditions for fossil formation
1) Definition of fossils page 243 Remains, imprints or traces of prehistoric organisms
2) Fossils are important evidences of evolution Fossils show when life first appeared When plants and animals first moved to land When certain organisms became extinct When, where and how organisms once lived **Organisms anatomy and how it changed over time **The fossil record provides evidence of Earth s changing life
Conditions for fossil formation Usually formed in sedimentary rocks, due to the quick deposit of sediments on top of the dead organism Quick deposit of sediments protect the fossil from scavengers and agents of physical destruction such as wind and water Remains have to have hard parts. The hard parts of an organisms body will then became fossilized and included in the sedimentary rock
3) Conditions for fossil formation. Why are fossils found only in sedimentary rocks? A sedimentary rock is not formed by processes involving extreme heat and pressure like other types of rocks. Heat and pressure could destroy the remains and the fossil will not form. For fossil formation it is necessary to have organism s hard parts immediately covered by sediments that will protect the remains from any sort of destructive agent.
Fossil Evidence Development of the skull
Evolution of the whale
Dating Fossils - handout Relative dating or Principle of Superposition Radiometric dating
Principle of superposition pg 250 In undisturbed layers of rock, the rocks are at the bottom are older and the younger on top
Relative Dating of Fossils - The position of the fossil in the rock strata is a clue to when the organism lived and its age
Relative age Relative age of a rock is its age compared to the age of the layers in an undisturbed rock Relative age does not give the age in years.
Absolute Age It is the age in years To determine the age in years of a rock or a fossil scientists will use Radiometric or Radioactive Dating
Radioactive or Radiometric data Radioactive dating is a technique that analyzes the amount of radioactive material in an artifact ( fossil). Scientists know the rate of decay of radioactive materials, so they can infer the age of the fossil by the amount of radioactive material compared to the amount of non-radioactive material
Embryology or Similarities in Early Development Embryos of different species of vertebrates show similar stages during their development, suggesting a common ancestry. Ex: all vertebrates frogs, snakes, fishes, birds and mammals have a similar embryonic development, reinforcing the idea that all vertebrates have a common ancestor.
Early Development of Vertebrates
Homologous Structures or Comparative Anatomy Different species have similar body structures that are used for different functions, suggesting that these species share a common ancestor.
Vertebrates: The number and position of bones are the same, suggesting a common ancestry, but the shape and size changed over time depending on the function of the structure
Vestigial Structures- Structures found in the body of organisms that are not in use anymore. Usually they are reduced in size because they have no anatomical nor physiological importance. EX of vestigial structures in humans: Muscles of the ear, wisdom teeth, the appendix, body hair, tailbone.
Similarities in the DNA or Molecular Biology Similarities in the genes and in the amino acid sequence in the proteins, are clues to how related different species of organisms can be. species that have similar DNA and proteins could have evolved from the same ancestor. The DNA of a human is more similar to a DNA of a gorilla than to the DNA of a frog.
***Biogeography Handout
***Biogeography the study of the distribution of different species of organisms around the planet today and in the past It helps us understand that similar species inhabited the same area long time ago this can be a clue to common ancestry
There are 2 factors that affect Biogeography or species distribution: Migration Continental Drift
I-Migration: Organisms migrate for different reasons and start inhabiting different areas Organisms have to adapt to the new environment generating new species over time EX: the cases of the finches in the Galapagos islands, all descendant from a common ancestor that lived in the mainland.
II - Continental Drift - separation of continents resulting in species geographical isolation This theory suggests that organisms that lived in the same area developed into different species when separated by the continental drift When the continents separated, local conditions changed and the populations living in the area had to adapt, generating new species