Evolution by Natural Selection and Systematics

Systematics: Classification System

3 Domains of life: Eukarya, Archaea, and Bacteria

2 to 8 million species1.5 million named

Maybe billions of species! Maybe billions of species!

More go extinct than are identified on a daily basis

Binomial nomenclature (how we name things in science so

there’s no confusion)

Homo sapiens Corvus corax Corvus brachyrhychosHomo neanderthalensis

genus

specie

s

Convergent Evolution

Hawkmoths

Sunbirds

Hummingbirds

Evolution via natural selection

What would happen if all of the trees and dinosaurs were the same size?

Individual variation is necessary for natural selection to occur.

What would happen if all the dinosaurs produced just one offspring?

Differential fitness is necessary for natural selection to occur.

What would happen if offspring never resembled their parents?

Parents:

Offspring:

✖

Traits must be heritable for natural selection to occur

✖Parents:

Offspring:

Conditions required for natural selection to occur:

Individual variation: members of a species differ in their characteristics

Differential fitness: some individuals leave more offspring than others due to their special inherited traits

Mode of inheritance: parents pass on some of their traits to their offspring

Organisms do not “try” to change. It happens by random chance!

Change in population occurs because of differences in reproductive success.

Total offspring + future generations = “fitness”

Organisms do not evolve because they want or need to change.

Tomorrow!

• We’re going to the PL Wright Museum – this is the most important collection of specimens between Seattle and Chicago.

• While looking at the specimens, can you think of adaptations that enable the species to thrive? • What do the teeth of herbivores look like? How are they different from carnivores?• Why do zebras have stripes? Is it adaptation?

• What is your favorite species and why? • Can you identify other species in the same family? What sets this species apart from others?

• Show up on-time in this class. We will walk over together. Bring your notebooks and something to write with.