Ch 15- Darwin’s Theory of Evolution

• Evolution- change over time– Process by which modern organisms have

descended from ancient organisms• Theory- well supported explanation of

phenomena that has occurred in the natural world

• Evolution is a theory that has been well tested concept that is supported by evidence

Voyage of the Beagle

• What was Charles Darwin’s contribution to science?– Made numerous observations and collected

evidence-led to revolutionary hypothesis about the way life changes over time

– Now supported by large body of evidence• Pattern of diversity– Grassland in Argentina, Australia, and Europe all

supported different sorts of organisms

• Fossils- preserved remains of ancient organisms– Resembled organism living today, others were like no

other organisms– Why had so many of these species disappeared?

• Galapagos Islands- 1000 km west of South America– Close together, very different climates

• Observed the characteristics of many animals and plants varied noticeably among the different islands of Galapagos– Birds’ different shaped beaks

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Lamarck’s Evolution Hypotheses• Proposed that by selective use or disuse of

organs, organisms acquired or lost certain traits during their lifetime– Traits could be passed on to offspring– Over time this process leads to change in species

• One of first scientists to develop scientific hypothesis of evolution

Origins of Evolutionary Thought

• Hutton and Lyell- suggested Earth was old enough for evolution to have occurred

• Thomas Malthus- suggested human population would continue to grow but sooner or later living space would be insufficient

Sec 3- Darwin Presents His Case

• 1859 Darwin published his findings in his book, On the Origin of Species- natural selection was the driving force behind evolution

• Artificial selection- selection by humans for breeding of useful traits from the natural variation among different organisms– Nature provided the variation, and humans

selected the variation they found useful

Evolution by Natural Selection

• Struggle for existence- members of each species competes regularly to obtain food, living space, and other necessities of life– Predators that are faster can catch more prey– Prey that are faster, better camouflaged can avoid being caught

• Fitness- the ability of an individual to survive and reproduce in its specific environment

• Adaptation- any inherited characteristic that increases an organism’s chance of survival– Structural characteristics, physiological processes, behavior in

animal in which they hunt in groups

• Survival of the fittest- individuals that are better suited to their environment survive and reproduce most successfully= natural selection

• Over time natural selection results in changes in the inherited characteristics of a population– These changes increase a species fitness in its environment– Cannot be seen directly, observed as changes in population over

many successive generations• Welcome to Discovery Education Player• Descent with modification- species descend with changes

from other species over time– Natural selection produces organisms that have different

structures, establish different niches, occupy different habitats– Common descent- all species, living and extinct, were derived from

common ancestors

Evidence of Evolution

• Darwin argued living things have been evolving on Earth for millions of years

• Evidence– Fossil record– Geographical distribution of living species– Homologous structures of living organisms– Similarities in early development, or embryology

Homologous Body Structures

• Homologous structures- structures that have different mature forms but develop from the same embryonic tissues– Provide strong evidence all four limbed

vertebrates have descended with modifications from common ancestors

• Vestigial organs- organs in animals reduced in size that serve little to no function– Miniature legs, tails