Natural Selection

What was Darwin’s reasoning? Plants and animals that arrived on the Galapagos faced environmental factors that were different from the mainland. Species gradually changed over many generations and became better adapted to the new environment.

What is evolution? The gradual change in a species over a long period of time

What is a species? A group of similar organisms that can mate and produce fertile offspring.

What is selective breeding? The practice by which humans select plants or animals for breeding based on desired traits. Ex: dogs

What is natural selection? The process in which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species.

What are four factors that affect natural selection? Example: Sea Turtles! Environment → Adaptations 1. 2. 3.

Overproduction organisms produce more offspring than can survive. Ex: too many sea turtles!

2. Variation Each individual has its own unique combination of traits. Similar but not identical. Ex: some turtles are faster than others

3. Competition (Struggle to Survive) Some may get caught by predators or starve or get disease. Only some make it to adulthood. Ex: not enough food + predators

Selection Turtles that are best adapted to their environment are likely to have many offspring that survive.

Can natural selection lead to evolution? YES! Over a long period of time natural selection can lead to change. Helpful variations increase while harmful variations decrease. Nature “selects” characteristics.

What are environmental factors? Things in the environment that can affect an organism’s ability to survive. Ex: predators and food supply

What about genetic variation? Individuals need to be different for natural selection to work, otherwise, all individuals would have an equal chance of survival!

Example of natural selection: Peppered moth variation: black form and white form environment: trees in England