EVOLUTION!

    -The word evolution means change over time.

        -We can apply this to anything. We can say that a band or musician's career has evolved. This does not mean that it got better it just means that it has changed over time.

    -EVERYTHING CHANGES

    -In biology, evolution means change of allele frequencies over time. Think of this as a change in genes over time

In order to pass on your genes you need to reproduce. Evolution is all about who reproduces

-The four mechanisms of evolution refer to who chooses who gets to reproduce

The four mechanisms of evolution

Natural Selection

    -Is when nature chooses who gets to reproduce

    -Survival of the fittest

Artificial Selection

    -Humans choose who gets to reproduce

    -How we turned wolves into Chihuahuas

Sexual Selection

    -The opposite sex chooses who gets to reproduce

    -Usually goes against natural selection

    -A peacock's feathers and a frog's croak are good examples

Genetic Drift

    -This is the only mechanism of evolution that is not a selection

    -It usually starts with an accident

    -You reproduce with what you have because they are the only options

        -The only ones in an area (Founder Effect) or a disaster kills off most of the group (Bottle Neck effect)

Speciation

    Speciation is when one species turns into another species.

History of life

    -The first cell hypothesis is the hypothesis that one cell turned into all life on earth. This is a hypothesis that uses evolution to describe how life began on earth.

Evolutionary Structures

Homologous Structures

Homologous structures are structures that share the same anatomy but could have different functions.

For example all mammals share the same anatomy besides some small differences because mammals are all related. A cat has the same forelimb bones as a human, phalanges, metacarpals, carpals, radius, ulna, and humerus. But a cats paws and a humans hands have different functions. A cat uses their paws to ruin my couch while I use my hands to play video games.

So a cats forelimbs and a humans forelimbs are homologous structures because they share the same anatomical structure even though they function differently.

Homologous structures can also share the same function. For example, a chimpanzee's hands share the same anatomy as a human's hands and they also share the same function.

Analogous Structures

Analogous structures share the same function but are very different anatomically. This is because their anatomical structures are not related. Good examples of this is comparing mammals to insects which are very different. A human eye and a fly's eye serve the same function, they are eyes, but they are made very different. Another example is a bird's wings and a fly's wings are both wings but they are not anatomically similar at all.

An analogous structure that is a little less obvious is the fins of a shark and the fins of a dolphin. They are both fins and function exactly the same, but if you look at the anatomy they are very different. A shark's fin is a solid piece of cartilage. A dolphin's fin has finger bones because it is actually a homologous structure with other mammals. 

 Vestigial Structures

Vestigial structures are a key piece of evolutionary evidence. They are left over structures from common ancestors that are no longer useful. 

For example a whale has no legs but it has a hip bone. This bone is left over from when whales were a 4 legged mammal that walked on the shore. We see vestigial structures all throughout the animals world. For example humans have a tail bone but no tail.