Biology Unit 7 Notes: Evolution & Natural Selection

Unit 7: Evolution

&Natural Selection

(1) Genetic Variation

• Genetic Variation / Diversity Organisms inherit different variations of traits, giving them different strengths and weaknesses.

• Genetic Variation allows for some individuals to succeed + survive.

(2) The Struggle for Existence

• Living things are always competing to stay alive AND pass on their genes:– There is limited food, water, shelter.– There are changes in climate, disease

transmission, etc.

• Those who can survive and reproduce during tough times are best suited/adapted to their environment.

(3) What does it mean to Adapt?

• To have the traits necessary to remain living and sexually attractive during times of change.

• It does NOT mean:To change/grow body parts so that you can survive that moment.

(4) Evolution

• A change in the allele frequency of a population of living things, over a period of time.– “Allele Frequency” = How often a certain trait

shows up in the population.

(5) NOT Evolution

• Sudden, quick physical changes to individuals so that they can survive.

• Change in populations so that only the “more perfect” versions live on.

• Humans “coming from” monkeys.

(6) What causes/drives Evolution?

• Genetic variation in a population.

• Changes in the environment/resources.

• Changes in sexual preference.

• The dying/extinction of certain populations.

(7) Evolution Mechanisms (EM)

• All evolutionary changes and mechanisms are still driven by natural selection.

• But there are different types of events that can drive evolution.

• End Result is ALWAYS the same:– There will be a change in the allele frequencies in the

population.

– Could produce a new species (a group of organisms that can only reproduce with each other).

(8) Natural Selection

• As the environment changes, certain characteristics amongst living things will help them to survive (Survival of the Fittest).

• If you don’t have these characteristics, you will not reproduce, or will die.

(9) Genetic Drift

• The random removal of certain traits (alleles) from a population.

• “Wrong Place, Wrong Time.”

(10) Genetic Migration

• When organisms with different traits move into new regions and populations, and reproduce with the original organisms.

(11) Geographic Isolation

• When a diverse population is separated and isolated by some geographic barrier (land, water, climate).

Natural Selection video

Hummingbirds YouTube Video

Now Let’s Watch This Video…