Species, Variation, Adaptation, Natural Selection and Evolution Including an overview of Florida’s imperiled species.
Darwin was a naturalist, a scientist who studies the natural world. He was a collector of natural specimens including, plants, animals, rocks and fossils. After his 5 year voyage, Darwin studies his notes on his observations and the specimens he collected. This led him to his theory of how species change over time, or evolve. This process of change over time in species is called evolution.
Alfred Russell Wallace also studied natural history. He spent years on the island of Borneo Where he observed unique adaptations to the environment. Wallace submitted his theory of change over time to Charles Darwin. He asked Darwin to publish his ideas. When Darwin realized they shared the same ideas, they presented their theory together in London, England.
What observations led to Darwin and Wallace’s ideas of changes over time? Darwin observed that birds called finches on the Galapagos Islands were all descendants of one species of finch from South America. Each Galapagos finch had adapted to the type of food found on different islands. Wallace made many observations over 8 years in Borneo. He is credited with discovering many new species. One of the most famous was the “flying frog” of Borneo. Its unique adaptation helped lead Wallace to his theory of natural selection and evolution.
Often, species change when they become isolated. Members of a species become isolated when they are completely separated from each other. Rivers, canyons, mountains other geologic features can isolate members of a species. 25 millions YBP, there was no connection between North and South America. The Atlantic Ocean and the Pacific Ocean flowed together. When the Isthmus of Panama formed, it isolated snapping shrimp on the Pacific side from snapping shrimp on the Atlantic side, resulting in speciation, the creation of new species. This resulted in a greater biodiversity, or the number of different species. Today 25 million ypb
Both Darwin and Wallace combined studies of living organisms and fossils, the remains of once living organisms that are preserved in some way.
The bones of the front limb (arm) of many vertebrates are homologous structures. These are structures that we share with other living organisms and ancestors now extinct. Notice that each limb contains the same bones in modified form. They all have a humerus (tan), a radius (white) and an ulna (red). What do you think about the yellow and brown coded bones?
Variation in a species drives natural selection. Here are examples of variation in the phenotypes of two species: zebras and orchids. How could these trait variations change the species? Why might one phenotype be favored over another?
A classic example of natural selection! In England, peppered moths were adapted to grey colored tree trunks. When coal pollution coated the trucks black, predators selected the gray moths instead of the rare black form (phenotype). Can you see why? Now that coal is “scrubbed of pollution”, what do you predict will happen to the moths? The peppered moth is adapted to grey colored tree trunks. One variation is black. When soot from pollution covered the grey bark, the moths lost the advantage of camouflage and were replaced by the black variant. Can you see the grey moth at the tip of the yellow arrow?
Let’s summarize. Read the summary and then copy down the bold face terms. In your own words, explain what the terms mean. Discuss the terms with a friend until you have decided on a written meaning.
Both Darwin and Wallace noticed that isolated organisms become different from their ancestors over long periods of time. They described what we now call genetic variation as a factor that allowed organisms to adapt to changes in the environment. They used homologous structures and fossils for evidence of these changes in related species. Organisms having beneficial traits, were more likely to reproduce and pass the traits along. They described this process as natural selection. Today we know that genetic variation and natural selection lead to biodiversity . Organisms that are not able to adapt to changes in the environment may go extinct. Extinction is a natural process with >99% of all known species now extinct. The theory of evolution is anaccepted explanation of how organisms change over time, as evidenced by fossils, DNA/Protein analysis, homologous structures and developmental patterns of embryos.
Extinction occurs when all individuals of a species disappear from the Earth. The collage at left shows some species that are now extinct. In the picture below, a Haast eagle attacks it’s primary food source, a Moa. What happened to the Haast eagle when the Moa went extinct? PSSsst! A Moa was a flightless bird 6 feet tall!
Here is a review of some of the species in Florida that may become extinct very soon. When a species is close to becoming extinct they are referred to as threatened or endangered.
Remember that extinction is a natural process. In time, all species seem to disappear or become extinct. Still, the biodiversity of allspecies isa treasure chest of genetic variation needed for DNA based life forms on Earth to survive. How would Florida be different if they disappeared? What would it be like for us? Is Florida’s story of life different from the rest of the Earth? Could extinctionbe a factor in our own existence?
Look at the scene below. How many of the animals you can identify. Where do you think this habitat is located?
Giant Ground sloth Horse Beaver Bird from Heck Alligator Blue heron North Florida!!!!! Giant armadillo Short face bear Mastodon Condor Zebra Hyena Saber toothed cat Most ofthese species are now extinct in Florida, except for a few. Which ones?