Lamarck vs. Darwin Introduction to change in organisms

What is a theory? The most probable explanation for a large set of data based on the best available evidence Summarizes a hypothesis or group of hypotheses that have been supported with repeated testing

What is a species? What is a population? Species – group of a single type of organisms that interbreed and are reproductively isolated White-tailed deer Population – refers to a group of organisms of a particular species living in a certain area. White-tailed deer on Mt. Nebo

Lamarck’s Theory Jean Baptiste Lamarck: 1800’s Believed: Change Occurs Over Time inheritance of acquired characteristics  acquired changes were passed to offspring Law of Use and Disuse  If a body part were used, it got stronger  If body part NOT used, it deteriorated Examples: Body builders or pierced ears

Lamarck’s Theory of Evolution Giraffes all had SHORT necks originally Giraffe’s Necks got LONGER from stretching for food “Acquired” trait (long necks) then passed to offspring Giraffe population became long-necked

Lamarck’s Theory of Evolution More examples Traits Acquired During Ones Lifetime Would Be Passed To Offspring Clipped ears and tails of dogs could be passed to offspring!

Lamarck’s Mistakes Was he correct?? NO! Traits are passed down from one generation to the next by GENES, not by an individual’s life experiences or activities Lamarck did NOT know how traits were inherited (Traits are passed through genes) Genes Are NOT Changed By Activities In Life Change Through Mutation Occurs Before An Organism Is Born

Voyage of the Beagle Charles Darwin Born Feb. 12, 1809 Joined Crew of HMS Beagle, 1831 Naturalist 5 Year Voyage around world Astounded By Variety of Life

Voyage of the Beagle During His Travels, Darwin Made Numerous Observations And Collected Evidence That Led Him To Propose A Revolutionary Hypothesis About The Way Life Changes Over Time

Darwin’s Belief’s Survival of the fittest OR natural selection Food and resources are limited So organisms have to COMPETE to get them (lions fight for food, space, mates …) OVER PRODUCE too many organisms Not all offspring will survive only the MOST FIT (not always the strongest!)

What happened to the giraffe’s? Survival of the fittest or natural selection Natural selection said the giraffes with short necks had less food to eat Why?  the food resources changed to leaves only on the upper branches What happened?  short necks could not reach upper branches and did not survive (couldn’t pass on genes)  Long neck giraffes survived & reproduced because they were able to reach the food

Evolution is the slow, gradual change in a population of organisms over time… a looooooooong time!

Where do we see this change? unequal ability of individuals to survive and reproduce … When there is an unequal ability of individuals to survive and reproduce … This leads to a gradual change in a population with favorable characteristics accumulating over generations This leads to a gradual change in a population with favorable characteristics accumulating over generations Most fit “naturally” selected Most fit “naturally” selected New species evolves New species evolves

Natural Selection How does Selection occur? Selection of the most fit can occur from several factors: Variations exist among individuals in a population Competition for limited resources Overpopulation Predation/Disease

Example of Natural Selection A classic example of natural selection is the Peppered moths during Industrial Revolution in Europe