Biology 1111 Notes Chapter 22 Descent with Modification A Darwinian View of Life Evolution descent with modification as Darwin proposed that Earth s many species are descendants of ancestral species that were different from the present day species or change in the genetic composition of a population from generation to generation viewed as a pattern and process pattern of evolutionary change revealed by data from scientific disciplines biology geology chemistry and physics facts of observed of natural world process of evolution consists of mechanisms that produce the observed pattern change mechanisms represent natural causes of natural phenomena we observe Darwin developed his revolutionary proposal over time influenced by others Scala Naturae and Classification of Species Greek Philosopher Aristotle 384 322 BCE viewed species as fixed unchanging recognized affinities among organisms concluded that life forms could be arranged on scale of increasing complexity scalanaturae each form of life was assigned to its own step Carlous Linnaeus 1707 1778 Swedish physician and botanist who sought to classify life s diversity for the greater glory of God developed binomial format for naming species such as Homo spaiens for humans adopted a nested classification system grouping similar species in increasing general categories opposed evolution Ideas About Change over Time Darwin drew sources of information from the work of scientist studying fossils the remains or traces of organisms from the past many found in sedimentary rocks formed from the sand and mud that settle to the bottom of seas lakes and swamps new layers of sediment cover older ones and compress them into superimposed layers of rock called strata stratum singular Paleontology was developed by French scientist Georges Cuvier 1769 1832 Examined strata and noticed that older the stratum the more dissimilar its fossils were to current life forms new species appeared while others disappeared through each layer Opposed the idea of evolution but believed in the extinctions Each boundary between strata suggested that catastrophe has occurred such regions were populated with different species due to immigrations from other areas In 1795 James Hutton Scottish Geologist 1726 1797 proposed that Earth s geologic features could be explained by gradual mechanisms such as valleys being formed by rivers Charles Lyell 1797 1875 incorporated Hutton s thinking into his proposal that the same geologic processes are operating today as in the past at the same rate 1 Biology 1111 Notes Both of these ideas influenced Darwin s thinking he agreed that geological change results from the slow continuous actions rather than from the sudden events then Earth must be much older than accepted age later reasoned that similarly slow and subtle processes could produce substantial biological change gradual change to biological evolution Lamarck s Hypothesis Jean Baptiste Lamarck was first to propose mechanism for how life evolved PublishedPhilosophieZoologique 1809 describing two basic theoretical principles to explain evolution Use and Disuse the idea that parts of the body that are used are extensively become larger and stronger while those that are not used deteriorate giraffe stretching its neck Inheritance of acquired characteristics stated that organism could pass these modifications to its offspring reasoned that muscular neck of the living giraffe had evolved over many generations as giraffes stretched their necks even higher Proposed that organisms have innate tendency towards increasing complexity perfection Darwin was recommended to Captain Fitzroy for survey expedition on HMS Beagle it was a 5 year circumnavigation of world Darwin Descent with Modification Darwin s Focus on Adaptation Adaptations inherited characteristics of organisms that enhance their survival and reproduction in specific environments Finches beaks Natural selection a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits Tree of life Darwin s metaphor for history of life branching tree with multiple branching from common trunk to tips of living twigs Symbolic of diversity of contemporary organisms Extinct lineages help explain morphological gaps between related groups of organisms Artificial selection selective breeding of domesticated animals and plants to encourage the occurrence of desirable traits Darwin argued that Artificial selections similar process occur in nature also saw connection between natural selection and the capacity to over reproduce Observation 1 Members of a population often vary in their inherited traits 2 Biology 1111 Notes Observation 2 All species can produce more offspring than their environment can support and many of these fail to survive and reproduce Inference 1 Individual whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals Inference 2 The unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations Thomas Malthus contended that much of human suffering disease famine and war resulted from the human population s potential to increase faster than food supplies and other resources Similarly Darwin recognized that capacity to overreproduce was characteristic of all species only tiny fraction of offspring survive or develop the rest are unable to tolerate physical conditions of the environment such as salinity or temperature An organism s heritable traits can influence not only its own performance but also how well its offspring cope with environmental challenges ex Passing trait to offspring such as escaping predators obtaining food etc advantages like these increase the number of offspring Over time natural selection can lead to increase in the proportion of favorable traits in a population Summary of Natural Selection 1 2 It occurs through interactions between individual organisms and their environment individuals do notevolve it is the population that evolves over time It can amplify or diminish only those heritable traits that differ among the individuals in a population Thus even if a trait is heritable if all the individuals in a population are genetically identical for that trait evolution by natural selection cannot occur 3 Environmental factors vary from place to