• Those that are not go on to reproduce and pass on their “antibiotic resistant” characteristic to their offspring
• Eventually none
of the bacteria
will respond to
the antibiotics.
• The population
has evolved.
Evolution
• Theory - a well-supported, testable explanation of phenomena that have occurred in the natural world
• Evolution – change in the inherited characteristics of an organism over time.
• “The idea that modern organisms have descended from ancient organisms”
Differences Among Organisms• Variations – any inherited trait that makes one
organism different from another in a population• Ex: feather color, height
• Variations are caused by genetic mutations
• Adaptation – any variation that makes an organism better suited for their environment.
• Ex: Camouflage
• Help an organism survive in their environment
• May be physical, behavioral or chemical
Charles Darwin
• Born in England 1809
• Set sail on H.M.S. Beagle in 1831 for voyage around the world returning 5 years later to England
• Made numerous observations and collected evidence that led him to propose the Theory of Evolution through Natural Selection
Darwin’s Observations
•Observed a tremendous amount of diversity in plants and animals
• Noticed that plants and animals were well suited to whatever environment they inhabited
•Intrigued by which organisms survived and produced offspring
Darwin’s Observations
• He collected the preserved remains of ancient organisms (Fossils) and many current plant and animal species for that time.
Large ground-finch - Charles Darwin’s specimen
Galapagos Islands
• Small group of volcanic islands 1000 km west of South America
• Very different climates on each island
• Animals on the islands are unique
San Cristobal mockingbird
– only found on San
Cristóbal
Medium tree-finch
– only found on
Floreana
•Darwin paid particular attention to giant tortoises, marine iguanas, and finches
•He noticed that organisms varied in predictable ways from one island to another
• Ex: Tortoise shells each island had long or short neck tortoises
Warbler Finch
• Darwin proposed that animals living on different islands had once been members of the same species
• Species would have evolved from an original South American ancestor species after becoming isolated from one another
• https://www.youtube.com/watch?v=mcM23M-CCog
Evaluating Lamarck
• Lamarck’s theory of evolution is incorrect because:
• He did not know how traits are inherited.• Behavior has no effect on genetics only
mistakes that take place before fertilization are passed on.
• He was the first:
• to develop a Theory of Evolution• First to realize that groups of organisms do
adapt to their environment
Thomas Malthus – Struggle for Existence
- Population Growth
• English Economist
• Observed that babies were being born faster than people were dying.
• Malthus reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone.
• Proposed that war, famine, and disease limit the growth of human populations.
Darwin Presents His Case
• Published On the Origin of Species by Means of Natural Selection 25 years later.
• In his book, he proposed a mechanism for evolution called Natural Selection.
• Darwin stated that evolution has been taking place for millions of years, and continues in all living things.
Natural Selection• Explains how and why evolution occurs
• Organisms with inherited traits that are best suited to their environment are more likely to survive and reproduce, and pass on their “good” traits to future generations.
http://www.skeptic.com/junior
_skeptic/mixtape2009/dow
nloads/Overman_Evolutio
n_Rocks.mp3
• Natural variation: differences among individuals of a species, found in all types of organisms.
• variation in populations can be passed on to the next generation
• Artificial selection: nature provides variation among different organisms, humans select and breed for those variations that they find useful.
• Fitness - the ability of the organism to survive and reproduce in its specific environment.
• Fitness is the result of adaptations
• Adaptation - any inherited characteristic that increases an organisms’ chance of survival
• The better suited an organism is to its environment, the better chance it has at surviving. (Survival of the Fittest)
• Darwin referred to survival of the fittest as - Natural Selection