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Agenda Warm-Up- Review Natural Selection and Reproduction for quiz today!!!! Notes on Evidence of Evolution Work on Vocabulary and Lab Ask questions based on 5.1 and 5.2 Quiz on 5.1 and 5.2
How do we know? The fields of anatomy, embryology, biochemistry, and paleontology have contributed the scientific evidence for the theory of evolution. Scientists study data to trace the phylogeny (evolutionary history) of a species or a group of related species. Based on this data, the theory of evolution states that all forms of life on Earth are related because the ancestry of organisms can be traced back to a common origin.
Study of the structures of organisms Involves convergent and divergent evolution Convergence: completely different organisms adapt to similar environments and develop analogous (similar) structures Divergence: a single species or two similar species evolve different structures over time Evidence has been from Homologous structures Geographical locations Anatomy
Anatomy...Homologous Structures Homologous structures: similar characteristics resulting from common ancestry The more homologous structures two organisms share, the more closely they are related Vestigial organs: structures with little or no function to the organism Important in the ancestors of that organism
Homologous Structures
Anatomy...Geographical Location If the location is different but the environment is similar, species can develop similar structures and behaviors If a species encountered a different ecosystem because of a change in geographical location, new anatomical traits come about A new species evolves with a shared common ancestor from the original population
Embryology Embryology: the study of the embryonic development of organisms Similarities in development is more similar during embryonic development versus in adults Vertebrate embryos look very similar, but vary greatly as they age and develop These similar structures may suggest that these species evolved from common ancestors Evolution may have selected for new stages at the end of embryonic development Growth and development mimics phylogeny how we are related
Biochemistry Biochemistry: study of the chemical processes in organisms Genes and proteins support biological evolution The more similar DNA and amino acid sequences in proteins of two species are, the more likely they have a common ancestor Evolutionary relationships can be traced through DNA when anatomical structures are not helpful Species may be so closely related that they don t appear to be different Species may be so diverse that they share few similar structures
Biochemistry Changes in DNA and proteins increase over time The greater the genetic similarity, the more recent the common ancestor is The time since a pair of species have diverged can be estimated under a molecular clock DNA sequence comparison may be the most reliable evidence, but there are challenges Genes evolve at different rates and it can be difficult to pinpoint divergence DNA changes (like mutations) can cause problems in aligning and comparing chromosomes Assumptions and human error may result in different phylogenetic trees Natural selection can cause convergence in molecules
Paleontology Paleontology: study of prehistoric life The fossil record provides evidence of life forms and environments along a timeline and supports evolutionary relationships by showing the similarities between current species and ancient species Comparing current and ancient species shows gradual change Fossil record tells a story of the types of organisms that have lived on Earth (including those that are extinct) and the relative ages of the fossils Fossil record is incomplete most organisms do not form fossils! Many gaps are filled as more fossils are discovered. The older the fossils, the less they look like modern species
Paleontology Fossil record shows divergence in phylogeny Transitional fossils show links in traits between groups of organisms these confirm evolutionary relationships However, fossil record is incomplete Fossils are VERY RARE and hard to form Fossil record favors species that existed for a long time, abundant and widespread, and had hard shells or skeletons Gaps in the fossil record do not indicate that it is WEAK as far as evidence is concerned, but rather points out additional research opportunities gap filling fossils are CONTINUALLY discovered
Just keep in mind... One piece of evidence does not ensure an accurate picture of the history of evolution in a particular group of organisms Scientists collect many pieces of evidence from many fields The more evidence from different fields, the more reliable the information is Evolutionary theory is a well-tested explanation that accounts for a wide range of observations made by scientists in many fields of science Evolution is not completely understood many unanswered questions remain to be studied and analyzed
Finish vocabulary and yesterday s lab. Review for 5.1 and 5.2 Quiz (Study Guide) Notebooks are DUE TOMORROW!!!! Vocabulary Cartoon sequence questions Peppered moth lab