Natural Selection

Classifying or grouping organisms in certain ways allows scientists to better understand how they interact in nature. vocabulary word! species – a group of organisms that can reproduce only with one another.

population – a group of organisms of the same species that live in the same place. vocabulary word!

The more variation in a species, the healthier it is genetically. variation – the differences that occur in individuals within a species. The more variation in a species, the healthier it is genetically. vocabulary word!

Why are variations good? Sometimes, certain variations increase an organisms chance at surviving. sexual reproduction – many variations are possible asexual reproduction – no variations are possible

Running faster, being able to reach or catch food easier, longer legs, longer neck, taller trunk, colors, patterns etc. are all examples of variations. Variation can begin as a mutation

Peppered Moths In England there is a species of peppered moth They come in two color variations Light dark The trees they lived on had a light bark color During the industrial revolution, factories were built that produced soot The soot stained the tree bark black

Peppered Moths Which moths were better adapted to the trees before pollution? Which moths were adapted to the trees after the pollution? light dark

Elephant Example Let’s say a group of elephants had mostly short trunks But a few of the elephants in the group had slightly longer trunks than others When food and water became scarce, the elephants with longer trunks could reach higher for food and deeper into holes for water

Elephant Example Elephants with shorter trunks would die of thirst and starvation Elephants with longer trunks would survive and reproduce passing on their longer trunks Over time, the group would consist mostly of long trunked elephants

Elephant Example

Charles Darwin (1809-1882) Studied biology. The HMS Beagle docked at the Galapagos Islands off the coast of South America.

Charles Darwin (1809-1882) Based on fossil evidence, Darwin knew plants and animals change over time. Believed organisms had changed slowly over time and would keep changing. The environment and adaptability of the organisms controlled the changed.

evolution – process by which populations gradually change over time. vocabulary word!

What he saw in the Galapagos…

What he saw in the Galapagos… Each island had similar animals with slightly different traits. Long or short necked tortoises depending on the plant height.

What he saw in the Galapagos… Finches had many different beak sizes and shapes depending on diet.

vocabulary word! natural selection – process by which organisms that inherit helpful traits tend to reproduce more successfully.

Natural Selection Organisms with traits that help them survive grow and reproduce passing on those traits to their offspring. Organisms with traits that don’t help them survive are usually eaten or die and don’t pass on their traits.

Natural Selection There are four parts to the natural selection process: overproduction genetic variation selection adaptation

overproduction - more offspring are usually born than an environment can support

genetic variation - greater genetic variation increases the chances a population will survive.

selection - nature weeds out the weak or the organisms with variations that do not help them survive.

adaptation - once a variation proves it helps a species survive, it can become an adaptation that is common to all of the population.

Create this table in your notes: More organisms are born than survive Variations within a species allow for options Organisms with better variations survive Variation becomes an adaptation in the species

Which Beak is Best Lab When Charles Darwin explored the Galapagos Islands, he discovered 31 different species of ground finches with many different beak sizes and shapes. He theorized that that over time, different groups of finches adapted to their food source by changing their beak shapes. Each beak shape could be matched to the type of food the bird ate.

Which Beak is Best Lab Procedure Look at the shapes of the bird beaks in the chart. Under each bird’s picture, give at least two things you think it might eat based on the shape of it’s beak.

Which Beak is Best Lab

Which Beak is Best Lab On each table there is a spoon, tweezers and an eyedropper. These items are your beaks. Decide which beak is best suited to catch and eat each type of food.

Which Beak is Best Lab