Evolution and Scientists

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Unit 2 – Evolution

Steps Leading Up to Charles Darwin’s Theory
ü Around the world, there is an enormous diversity of life

Each species has its own set of characteristics
Arctic animals – have characteristics that help them survive in the cold, harsh environment Desert animals – have characteristics that help them survive in the extreme heat ü Theory is a set of statements that explains a group of facts or phenomena

Tested repeatedly and supported by evidence
Can be used to make predictions about natural phenomena
ü In the 19th Century, Charles Darwin developed a theory

Designed to explain:
Diversity of life on earth
How all organisms are related to one another and to the environment in which they live Sought to explain evolution
It is the idea that all species are descendants of ancient species that were different from modern-day species Biological history of life on Earth, from the earliest micro-organisms to the diversity of modern-day organisms Two ideas before Darwin’s time

Species are fixed/permanent – do not change over time
Earth is less than 10 000 years old and also relatively unchanging Changing Ideas About the Natural World
ü James Hutton

Scottish geologist
Proposed that rock formations are being continually formed
Molten material is forced up to Earth’s surface to form rock Studied the rates of present-day erosion and sedimentation and the thickness of bands of sedimentary rock Concluded that it must have taken millions of years, not thousands, to form the current landscape Supported the theory of uniformitarianism

States that Earth was formed by slow-moving processes, such as erosions and sedimentation, and still continues to shape our landscapes ü Charles Lyell

English geologist
Popularized and expended on Hutton’s ideas of uniformitarianism in his book Principles of Geology Found more evidences to support the idea that rock formations were formed by incredibly slow processes that are still at work today ü Georges Cuvier

French naturalist
Compared the bones of modern-day elephants and fossilized mammoths Concluded that the mammoth’s skeleton was different enough from an elephants’ that mammoths had to be considered a different species and that the mammoth had become extinct Another example – T. rex

ü Jean-Baptiste Lamarck

French naturalist
Recognized that species are not permanent
Proposed that species evolve, or change, over time
Explained that evolution as a process of adaptation
Adaptation is an inherited characteristic that improves an organism’s ability to survive and reproduce in a particular environment Also proposed a hypothesis to explain how changes in species happen Realized that organisms were adapted to their environment

Had 3 ideas:
By using, or not using, certain body parts, an organism develops certain characteristics Ex) giraffes need to reach vegetation high up in the trees à developed long necks These enhanced characteristics would be passed onto the offspring Called this idea “inheritance of acquired characteristics” All organisms have a “tendency towards perfection”

Organisms continuously change and acquire features in order to be more successful in their environments ALTHOUGH IT SEEMED LOGICAL AT THE TIME, OUR KNOWLEDGE OF DNA AND ITS ROLE IN THE INHERITANCE OF TRAITS DOES NOT SUPPORT LAMARCK’S HYPOTHESIS An acquired characteristic would have to somehow change the DNA of particular genes in order to be inherited Nonetheless, he was important in analyzing the role of the environment and explaining evolution as a process of adaptation to the environment Darwin’s Observation

ü In 1831, the HMs Beagle set sail on a voyage around the world

As a naturalist, Darwin collected many fossil records and samples around the world His main interest was to study the geology, plants, and animals encountered on the voyage ü Patterns in Diversity

Species Vary Globally
Distantly related species living in similar habitats in different parts of...
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