Different scales of evolution Microevolution Macroevolution Speciation

Microevolution Change of the gene frequency in a population. Frequency – how often something happens or occurs.

Causes of Microevolution Natural Selection Migration – movement of individuals into or out of a population Mate Choice (sexual selection)– Parents select mates for a reason Mutation – causes small changes in genes. Genetic Drift – Random effects of everyday life (like being eaten, or starved)

Macroevolution Changes above the species level

Types of Macroevolution Convergent Evolution – Species living in similar environments develop similar adaptations.

Types of Macroevolution Coevolution – Species in close contact develop adaptations to each other.

Types of Macroevolution Adaptive Radiation – When new species enter an environment with few other species, they tend to change rather quickly.

Extinction All members of a species die off or fail to reproduce.

Gradualism and Punctuated Equilibrium Gradualism - Many small changes accumulate to make large changes over long periods of time. Punctuated Equilibrium – Species remain stable for long periods of time, then new species suddenly “appear.”

Gradualism and Punctuated Equilibrium

Speciation The formation of a new SPECIES through evolution

But what is a species?

A horse and a donkey can breed and create mules A horse and a donkey can breed and create mules. But mules cannot have babies. Donkeys and Horses are different species.

A Great dane and a chihuahua can breed and make babies A Great dane and a chihuahua can breed and make babies. And their babies can have babies. Great Danes and Chihuahuas are the same species.

Lions and Tigers can breed and make a liger Lions and Tigers can breed and make a liger. But Ligers cannot breed with eachother. Lions and tigers are different species.

So based on those examples and non-examples discuss with your group and write down your own definition of what a species is.

Species A group of individuals that are capable of producing FERTILE offspring in the natural environment. The key word is Fertile offspring A donkey and a horse can create a mule, but mules are infertile. Are horses and donkeys the same species?

Species These happy face spiders look different, but can interbreed and create fertile offspring so they are the same species.

There are three things you need for speciation to occur… Let’s read a couple stories to help us figure out what these are.

1st thing you need for Speciation is Isolation Separation of a formerly successful BREEDING population so they can no longer mate.

Separated PHYSICALLY from each other by topography. Geographic Isolation Separated PHYSICALLY from each other by topography. Ex: Rivers, Oceans, Mountains

Geographic Isolation

Behavioral Isolation These populations can still interbreed but they do not. They prefer their own population for a variety of reasons.

Behavioral Isolation The fruit-flies on the bananas prefer the fruit-flies on the bananas.

Temporal Isolation Animals breed at different times. Example: Different breeding seasons.

2nd Thing you need is Adaptation The isolation of populations causes them to change and adapt to their new conditions.

3rd thing you need is Reproductive Isolation : When organisms can no longer breed and create fertile offspring Rana aurora – Lays Rana boylii – Lays Eggs in streams. Eggs only in standing water.

Extinction When an entire SPECIES dies off.

Selective Breeding Also known as Artificial Selection Humans choose which traits are passed on in organisms. Examples include: Dogs, livestock, and many crops.

Artificial Selection Characteristics Process driven by humans, not nature. Humans don’t always pick the traits that are best for the organism. They pick the trait that is desirable to them. Example: Bulldogs were artificially selected for by humans. Humans wanted a short, stocky dog, with lots of wrinkles, and flat nose. This causes the dog to usually have respiratory problems and usually have poor health in general.

Then

Now

Then

Now

Then

Now

Then Removing Seeds

Then Dehorning

Now Polled

Selective Breeding In what ways is selective breeding similar to natural selection? In what ways is it different?