Chapter 22 Aristotle 1 Species are fixed 2 There are certain affinities among organism 3 Organisms can be arranged on a ladder of increasing complexity Scala Naturae Scale of Nature 1700s Organisms match to their environment is evidence that the Creator designed each species for a particular purpose Carolus Linnaeus 1707 1778 Swedish physician and botanist developed two part Binomial format for naming species in the 1750s Contrast to linear hierarchy Scala Naturae Binomial is a nested classification system similar species are grouped into increasingly general categories similar species are groups in same genus and family Resemblances of species is related to pattern of creation not evolutionary kinship Darwin Classification should be based on evolutionary relationships Drew from the work of scientists Hutton and Lyell studying fossils If geologic change results from slow continuous actions instead of sudden events then Earth must be much older than a few thousand years It could also produce substantial biological change Fossils Remains or traces of organisms from the past Usually found in sedimentary rock formed from the sand and mud that settle to the bottom of seas lakes and swamps Allows a glimpse of some of the organisms that populated Earth at the time the layer was formed Strata Singular stratum composed of compressed new layers of sediment over older layers into superimposed layers of rock Paleontology study of fossils Developed by Georges Cuvier Cuvier older the stratum more dissimilar its fossils were to current life forms Extinction is common Opposed idea of evolution Species don t evolve Each boundary between strata represented a sudden catastrophic event that destroyed many of the species living in that area The regions were later repopulated by different species immigrating from other areas James Hutton Earth s geologic features could be explained by gradual mechanisms Valleys being formed by rivers Lyell used Hutton s thinking in his proposal that the same geologic processes are operating today as in the past and at the same rate Lamarck known for the incorrect mechanism he proposed not for visionary recognition that evolutionary change explains patterns in fossils and the match of organisms to their environment Found several lines of descent chronological series of older to younger fossils leading to a living species Used 2 principles 1 Use and disuse idea that parts of the body that are used extensively become larges and stronger while those that aren t used deteriorate Ex Giraffe stretching its neck to reach leaves on high branches 2 Inheritance of acquired characteristics organism could pass modifications to its offspring Ex long muscular neck of giraffe evolved over generations Evolution happens because organisms have an innate drive to become more complex Darwin rejected this idea but thought that variation was introduced into the evolutionary process through inheritance of acquired characteristics Noted that organisms are well suited for life in their environments explained by gradual evolutionary change Experiments show that traits acquired by use during an individual s life aren t inherited in the way proposed by Lamarck Descent with modification by natural selection explains that adaptations of organisms and the unity and diversity of life physical evidence didn t support the traditional view that Earth was only a few thousand years old Darwin Galapagos was colonized by organisms that had strayed from South America and then diversified giving rise to new species on the various islands Adaptation inherited characteristics of organisms that enhance their survival and reproduction in specific environments Adaptation to the environment and origin of new species are closely related Natural selection individuals that have certain inherited traits tend to survive and reproduce at higher rates than do other individuals because of those traits Origin of Species Descent with modification used instead of evolution It led to the rich diversity of life Organisms share many characteristics which is why there is unity in life All organisms descended from an ancestor that lived in the remote past Descendants of that ancestral organism lived in various habitats and gradually accumulated diverse modification adaptation that fit them to specific ways of life History of life is like a tree with multiple branching from a common trunk Each fork on the tree represents the most recent common ancestor of all the lines of evolution that subsequently branch from that point Many evolutionary branches are dead ends 99 of all species that have ever lived are now extinct Darwin thought branching and past extinction events could explain the large morphological gaps that exist sometimes between related groups of organisms Ex Asian elephant and 2 species of African elephants The two have the same line of descent until a recent split from the common ancestor There are no living species that fill the morphological gap between the elephants and their nearest relative hyraxes and manatees Artificial selection humans modifying species over many generations by selecting and breeding individuals that possess desired traits Causes crops and animals to have no resemblance to their wild ancestors Darwin s Observations and Inferences a Observations 1 Members of a population often vary in their inherited traits b Observation 2 All species can produce more offspring than their environment can support and many of these offspring fail to survive and reproduce c Inference 1 Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than do other individuals d Inference 2 This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations There is a connection between natural selection and the capacity of organisms to over reproduce It is characteristic of all species Organisms either die when born or eaten starved diseased unmated or unable to tolerate physical conditions of the environment such as salinity or temperature Organisms heritable traits can influence its performance and how its offspring cope with environmental challenges
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