Theory of Evolution Data Driven Process Supported by Evidence
TEKS (7) The student knows evolutionary theory is a scientific explanation for the unity and diversity of life. The student is expected to: (A) analyze and evaluate how evidence of common ancestry among groups is provided by the fossil record, biogeography, and homologies, including anatomical, molecular, and developmental; (B) analyze and evaluate scientific explanations concerning any data of sudden appearance, stasis, and sequential nature of groups in the fossil record;
Essential Question How do an organism s traits help to determine its survivability in nature?
Vocabulary Evolution Ancestor Descended Offspring Fossil record Biogeography Radioactive dating Homology Anatomical homology Homologous Structure Analogous Structure Developmental homology Embryology Molecular homology DNA sequence Genome map Phylogenetic Native Genus Species
What defines a Theory? The term theory when used in science does NOT mean guess, educated or otherwise. In science: Theory a logically connected group of ideas that explain a set of facts or phenomena in the natural world which can be repeatedly confirmed through experimentation or observation.
Darwin s Theory of Evolution by Natural Selection A species, not an individual, that has changed over time and has members related through decent from a common ancestor. (A species is a group of individuals who are genetically similar enough to reproduce with each other) The change in the species population is driven by Natural Selection. Natural Selection is the ability of the natural world to apply pressure/stresses to a population, and only those with beneficial traits will survive to reproduce (and pass on favorable traits to the next generation).
Evidence for the relatedness of life Hypothesis: All living species have descended from common ancestor(s) and changed over time. Prediction: There should be evidence that shows the relatedness of species Geographic distribution/fossil record Homologies
Fossil Evidence Fossils are preserved evidence of an organism. There are basically 5 types of fossil evidence: 1. Mold-and-cast bones or shells dissolve and leave a depression 2. Trace impressions of movement (footprint, burrows, toothmarks, etc) 3. Body entire body is preserved 4. Compression organism is compressed and leave a dark imprint. 5. Petrification minerals replace organic matter
How is a fossil evidence? Fossils can tell us about time sequences. When used with radioactive dating of the rocks fossils are found in, paleontologists can create a timeline according to the fossil s age, they show successive Evolutionary Change. Fossil intermediates are transitional fossils that have been found between amphibians/reptiles, reptiles/birds, and reptiles/mammals
Evolution of horses as an example Horse fore limb fossils have been well documented to show evolutionary connections to modern horses.
The fossil record is Incomplete During Charles Darwin s studies, the fossil record was VERY piece mail. Since the 1800 s many more fossils have been found making connects, but it is far from complete. Reasons: 1. Soft tissues are rarely preserved 2. Tectonic movement of Earth s crust has destroyed man fossils. 3. Fossilization only takes place in certain types of environments. 4. Paleontologists have not dug up every place on earth. The fossil record does not show gradual change, it shows sudden appearances followed by stasis.
Homologous Evidence Homologies are similarities in structures. There are 3 main types of homologies: 1. Anatomical 2. Developmental 3. Molecular
Anatomical Homologies Comparing structures between organisms. Homologous structures same structure, different function (ex: the forelimbs of animals)
Anatomical Homologies Comparing structures between organisms. Analogous structures different structure, same function (ex: wings of birds, bats, butterflies, etc)
Homology vs. Analogy Natural selection appears to have favored similar adaptations in unrelated organisms in similar environments these structures are analogous. Flight is a good adaptation to have, so wings evolved in many different animal lines independently of each other.
Vestigial Structures A feature or trait that exists, but has not apparent function. (ex: hindlimb bones in whales)
Vestigial Structures in Humans Some examples in humans: Wisdom teeth, appendix and tailbone. Wisdom Teeth Tailbone Appendix
Developmental Homologies Embryology the study of how related organisms tend to develop in very predictable stages.
Dog Fetus Bat Fetus Human Fetus
Molecular Homologies The best evidence of evolution is coming from today s ability to map genomes and compare gene sequences. All living organisms share the same genetic code, DNA.
What similarities exist between humans and other animals? Chromosomes and gene similarities between species show evolutionary similarities. Human chromosome 2 Telomere sequences Centromere sequences Chimpanzee chromosomes Telomere-like sequences Centromere-like sequences 12 Human chromosome 16 Mouse chromosomes (a) Human and chimpanzee chromosomes 13 7 8 16 17 (b) Human and mouse chromosomes
Cytochrome C protein similarities Cytochrome C is a protein found in the inner membrane of the mitochondria. It is understood that all organisms on the planet descended from prokaryotes. If the prokaryotic DNA is not mutated much then connections can be made to the evolution of organisms.