15.2 Evidence of Evolution

Transcription

1 15.2 Evidence of Evolution I. Support for Evolution - theory of evolution states that all organisms on Earth have descended from a common ancestor a. The fossil record i. Fossils provide evidence of evolution ii. Ancient species share similarities with current species iii. Fossil record important for determining ancestry of organisms and patterns of evolution iv. Archaeopteryx fossils provide evidence of characteristics that classify it as a bird, but shows retention of dinosaur features v. Derived traits newly evolved features (feathers) that do not appear in fossils of common ancestors vi. Ancestral traits primitive features (teeth, nails) that do appear in ancestral forms b. Comparative anatomy vertebrate forelimbs have different functions but appear to be constructed of similar bones in similar ways (shared ancestry) i. Homologous structures anatomically similar structures inherited from a common ancestor 1. Not evidence of evolution, they are an example for which evolution is the best available explanation

2 ii. Vestigial structures structures that are reduced forms of functional structures in other organisms 1. Evolutionary theory predicts that features of ancestors that no longer have a function for that species will become smaller over time until they are lost iii. Analogous structures can be used for the same purpose and can be superficially similar in construction, but are not inherited from a common ancestor

3 c. Comparative embryology i. Embryo an early, pre-birth stage of an organism s development ii. Vertebrate embryos exhibit homologous structures during certain phases of development but become totally different structures in adult form iii. The embryos shown below have a tail, pharyngeal pouches (fish=gills, reptiles, birds, mammals=parts of ears, jaws, throats) iv. The shared features suggest that vertebrates evolved from a shared ancestor d. Comparative biochemistry common ancestry can be seen in complex metabolic molecules that different organisms share i. Cytochrome c enzyme essential for respiration and highly conserved in animals (it has changed very little over time) ii. The more closely related a species is, the greater number of amino acid sequences shared e. Geographic distribution i. Darwin observed animals in South America were more similar to other animals in South American than those in similar environments in Europe ii. South American mara occupied a niche similar to the rabbit in Europe South American Mara English Rabbit

4 II. iii. Biogeography the study of distribution of plants and animals around the world iv. Evolution is linked with climate and geological forces, especially plate tectonics, which helps explain many ancestral relationships and geographic distributions seen in fossils and living organisms today Adaptation a. Types of adaptation a trait shaped by natural selection that increases an organism s reproductive success i. Fitness measure of the relative contribution an individual trait makes to the next generation. Often measured as the number of reproductively viable offspring that an organism produces ii. Camouflage morphological adaptations that allow them to blend in with their environments, allows organisms to become almost invisible to predators Leafy Sea Dragon Malaysian Orchid Mantis iii. Mimicry one species evolves to resemble another species, increases an organism s fitness, mimics are protected because predators can t always tell them apart Monarch Butterfly Viceroy Butterfly

5 Western Coral Snake California Kingsnake iv. Antimicrobial resistance species of bacteria that have developed a drug resistance, some diseases that were thought to be contained, re-emerge in a more harmful form b. Consequences of adaptation i. Spandrel example 1. Some features in organisms are like spandrels, because even though they are prominent, they do not increase reproductive success ii. Human example 1. Human baby helplessness is not an adaptive purpose, merely a consequence of big brains and upright posture due to human pelvic structure