Classification and Mechanisms of Evolution

Prokaryotes

• No nucleus

• No membrane bound-organelles

• One chromosome

• Circular

• Unicellular

• Bacteria and Archaea

Eukarya

• Nucleus

• Membrane bound organelles

• Linear chromosome (multiple)

• Unicellular/Multicellular

• Protista, Fungi (don’t move), Plantae (don’t move), and Animalia (move)

What do both eukaryotes and prokaryotes have in common?

DNA

Ribosomes

Cytoplasm

Evolution

When a population changes (genetically over time).

Genetic Variation

Differences in the DNA between individual members of a population.

a. A population can only evolve to have a certain trait if the gene for that trait already exists in the population

b. Causes a genetic variation: gene flow (new individuals migration to a population and add genes) or mutation

Natural Selection

Organisms with beneficial traits survive and reproduce at a higher rate than other.

Beneficial trait?
Harmful trait?

Selected for

Selected against

Selection Pressure

Limit on survival reproduction

When does natural selection occur vs sexual selection?

Natural: Some organisms have alleles (genes) that give them an advantage in survival, allowing them to have more time to reproduce.
Sexual: Some organisms have alleles that make them more likely to reproduce than others.

Behavioral Adaptations

Behaviors that are passed down genetically that help organisms to survive and reproduce.

Fitness

An organism’s ability to pass on their gene.

How is evolutionary fitness measured?

Measured by how much an individual is able to reproduce and pass on their genes, NOT by how long an individual lives.

Why can harmful traits stay, even through evolution?

A species might evolve traits that don’t necessarily help individuals live longer but that help them mate more.