Theory of Evolution // KAFIL

Theory of Evolution

The theory of evolution is the foundation of all biological sciences. Charles Darwin was the most famous contributor to the theory, bringing together his natural selection and evolution ideas. His work was greatly inspired by the work of many scientists across several disciplines, including geology, paleontology, taxonomy, demography, and evolutionary biology. The theory of evolution was defined as "descent with modification," the idea that species change over time, give rise to new species, and share a common ancestor.

Geology

Scientists knew that the Earth was old, and that it had changed remarkably over time.

Paleontology

Fossils found showed scientists that there was proof of remains that were once living. Fossils of extinct animals provided a record of the history of life.

Taxonomy

Classification of life forms; Scientists knew it was important to be able to identify biological relationships. Life evolves over time.

Demography

The influences on population size and the competition between living animals for limited resources. The amount of adults in a specific population will usually remain the same as time goes by.

Evolutionary Biology (What We Now Know It As)

Groups of species that were interconnected helped scientists clarify evolutionary history.

Charles Darwin

Darwin's key contribution to the theory of evolution was the principle of natural selection. Three principles allowed him to conclude that natural selection was the primary driver of evolution:

• The number of adults in a population tends to remain the same over time, even though, for most organisms, parents tend to produce multiple and sometimes many offspring.
• variation exists in members of different populations.
• some individuals that have the variation that boosts their survival and reproduction increase in relative frequency.

Early Life

Charles Darwin came from a wealthy and cultured family, raised to respect hard work and education. He spent his time as a kid walking through his home's countryside in England to watch the natural world around him. He used this time to begin his study on the variation of plants and animals.

College Days

Darwin attended medical school at the University of Edinburgh, where he became interested in natural history. After attending one lecture by the American ornithologist, John James Audubon, his interest in birds and wildlife sparked. He also learned of Lamarck's hypothesis about species changing over time. Darwin left the University of Edinburgh and enrolled in Cambridge University, where he set on his journey to pursue natural history.

Seeing The World

John Stevens Henslow, English geology, archaeology, and botany pioneer, impressed with Darwin's work, suggested he serve as a naturalist on the HMS Beagle to South America. Darwin jumped for the opportunity and took on the journey. Darwin recorded his observations throughout the rainforests, deserts, and mountains in South America. He learned about Lyell's ideas about uniformitarianism. He collected bones, fossils, animal skins, and preserved plants, shipping them back to England. He also studied tortoises, lizards, and mockingbirds (now known as Darwin's finches) on the Galapagos Islands. On the journey back home, he concluded that species were not stable after studying the variation in birds. D

Darwins Ideas

In 1837, Darwin wrote that all forms of life had "transmuted" from a single life form. He found the connection between fossils and living descendants. In 1838, he used the work of Thomas Malthus, who argued that the human species was far too large to be supported by current resources, and connected it to the lives and deaths of plants and animals.

Darwin knew that his findings would be challenged, so he decided not to publish them. To Lyell, Joseph Dalton Hooker, and Thomas Henry Huxley, he showed his 230-page writings that stated his natural selection and evolution ideas in general. He spent the next fifteen years in his home, working and developing a major treatise on evolution. His time was spent studying barnacles and seed dispersions, and breeding pigeons to study the variation of their bones throughout generations.

Darwins Work Made Public

Alfred Russel Wallace heard of Darwin, read the same work from Malthus, and came to similar conclusions of natural selection. In 1858, the two teamed up and presented their ideas to the Linnean Society of London, and published them that year. Darwin published his book, On the Origin of Species by Means of Natural Selection. The book sold out and started the modern era of biology and what would later be known as biological anthropology.

Major Contributions

Pre-Darwinian Theory and Ideas: The Groundwork for Evolution

John Ray (1660)

Pioneered taxonomy based on physical appearance; Created the first scientific classification of plants and animals.

Robert Hooke (1665)

Proved that fossils are organisms remains; Revealed that fossils would provide the history of past life.

Carolus Linnaeus (1735)

Wrote Systems of Nature; Presented the binomial nomenclature taxonomy of plants and animals.

James Hutton (1788)

Calculated Earth's age as millions of years; Provided geologic evidence necessary for calculating time span of evolution.

Erasmus Darwin (1794)

Posited that characteristics are acquired via inheritance; Advanced the notion that physical changed occurred in the past.

Georges Cuvier (1796)

Extensively studies fossils; Revealed many variations in the fossil records.

Thomas Malthus (1798)

Founded demography: only some will find enough food to survive; Provided the concept of characteristics advantageous for survival.

Jean-Baptise Lamarck (1809)

Posited that characteristics are acquired via inheritance; Provided the first serious model of physical traits passing from parents to offspring.

Charles Lyell (1830)

Rediscovered and reinforces Hutton's ideas; Provided more geologic evidence.

Our Understanding; How It Changed

Many things have happened in the development of our understanding of evolution since Darwin. Gregor Mendel discovered the principles of inheritance, which is now our basis for understanding how physical characteristics are passed from parents to their offsprings. His declarations of these qualities being passed as genes laid the groundwork for our current understanding of cell biology and chromosomes. Scientists now understand that evolution, which is the genetic change in a population or species, has one or more of these causes; natural selection, mutation, gene flow, and genetic drift. They also now understand that every chromosome in the cell of an organism consists of DNA molecules, which are the blueprint for all biological attributes.