Evolution - Home - Bixby 9th Grade Center •Theory - a well-supported, testable explanation of phenomena that have occurred in the natural world •Evolution –change in the inherited

Evolution

Antibiotic Resistance

• Bacterial infection…….

• Dr. provides you with antibiotics

• Most bacteria will be destroyed

• Some will not

• 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 Voyage

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

American Oystercatcher

•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