Charles Darwin (1809-1882) Sailed around the world 1831-1836

What did Darwin’s Travels reveal The diversity of living species was far greater than anyone had previously known!! These observations led him to develop the theory of evolution!!

How did tortoises and birds differ among the islands of the Galapagos? Each island had its own type of tortoises and birds that were clearly different from other islands

Galapagos Turtles

Evolution is when organisms change over time Evolution is when organisms change over time. So, modern organisms descended from ancient ones

Malthus Reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone

Darwin finally published his ideas in 1859 Other naturalists were developing the same theory that Darwin did. Even though he was afraid of the Church’s reaction to his book he wanted to get credit for his work.

Artificial Selection nature provides variation, humans select variations that are useful. Example - a farmer breeds only his best livestock

Natural Selection The traits that help an organism survive in a particular environment are “selected” in natural selection

Natural Selection and Species Fitness Overtime, natural selection results in changes in the inherited characteristics of a population. These changes increase a species fitness (survival rate)

Descent with Modification Each living species has descended with changes from other species over time

Summary of Darwin’s Theory 1. Organisms differ; variation is inherited 2. Organisms produce more offspring than survive 3. Organisms compete for resources 4. Organisms with advantages survive to pass those advantages to their children 5. Species alive today are descended with modifications from common ancestors

Natural Selection Does not act directly on genes, but on phenotypes Affects which individuals having different phenotypes survive and reproduce and which do not. Reproducing individuals add to the population Non-reproducing individuals die without passing on their genetic material (genes).

Types of Natural Selection SBI 4U: Metablic Processes Types of Natural Selection Directional selection – The environment favours individuals with an extreme variation of a trait. Occurs when organism moves to a new environment ex. gill nets and salmon fishing in 50s and 60s Gill nets in the 1050s were made of hemp and had larger mesh size (e.g. only catching larger fish) therefore large fish (an extreme variation of a trait) were selected against while average – smaller sized fish were able to swim through and survive Section 1.3

Types of Natural Selection Stabilizing selection – the extremes of a population are selected against and the average is favored. Once well adapted to environment, selection pressures tend to prevent them from changing ex. baby weights (3kg)

Types of Natural Selection Disruptive selection – selects for extremes and against the average.

SBI 4U: Metablic Processes Disruptive selection Taste good Taste bad Section 1.3

Sexual selection Favours the trait that influences mating success Usually based on female choice and/or male vs. male competition Male competition Male competes against other males for territory, or access to females Anything that gives him an advantage makes him more likely to pass on his genes

SBI 4U: Metablic Processes Female selection (or male selection) Leads to sexual dimorphism (physical differences between males and females) Male must prove he is genetically good enough Plumage, gifts, nesting site or mating rituals Selection makes many organisms go to extreme lengths for sex: peacocks (top left) maintain elaborate tails, elephant seals (top right) fight over territories, fruit flies perform dances, and some species deliver persuasive gifts. Section 1.3