Introduction to Evolution Biology – Ch 16 Where did all organisms come from? Why such variety? These are questions that scientist have discussed for 1000’s of years.

Darwin’s Voyage Darwin’s voyage took j5 years to complete Five year voyage around the world collecting 1000’s of specimens & recording 1000’s pages of notes

Darwin’s Observations Patterns of Diversity Different parts of the world exhibited slightly different, but similar organisms Similar phenotypes Africa and South America Galapagos Islands – see next slide! Fossil evidence Ancient similar organisms? Culminate in “Theory of Evolution”

Galapagos Tortoises Different islands = different tortoise shells Each island had a different climate. Why would different shell shapes allow tortoises to survive differently on each island?

Galapagos Finches Each island had different climates and vegetation. How would various beak shapes help birds to survive?

Some finch skull samples. Focus on the different beak sizes and shapes.

Darwin’s Influenced by others The world is ancient and continually changing MUCH older than previously thought Continually changes – not fixed Populations grows faster than the environment can support them Leads to competition for existing resources: food, shelter, locations Characteristics are inherited, not acquired during a lifetime Characteristics that allow organisms to survive better can reproduce more offspring The “survival” trait gets passed on to offspring Geologists helped show that the world is much older than previously thought. Mathematicians and economists help show that populations tend to grow faster than the natural resources can support. Scientists showed that traits don’t really change in one individual, but can change over time in a population.

Darwin’s Concepts Inherited Variation Observed that members of any species vary from one another in nature Observed that breeders are able to get desired traits in animals by breeding together those animals that exhibit the wanted traits The traits randomly occurred in nature Named “Artificial selection” since “helped by humans

Struggle for existence Organisms produce more offspring than can naturally survive Produces a “struggle for existence” – resources, space, mates Those are fish and people on a train.

Survival of the Fittest Struggle for existence led to only the most “fit” surviving and having offspring The ability of an individual to survive and reproduce in an environment is “fitness” Anatomical Structural Behavioral Darwin’s quote is the BEST way to remember “survival of the fittest”. (The BEST definition)

Descent with Modification With time, natural selection results in changes in the inherited traits of a population. These changes can increase a species’ fitness in an environment. Descent with Modification Over a vey long period of time, natural selection produces organisms that have different structures, establish different ways of surviving, or occupy different habitats so that organisms today look different from their ancestors

Evolution Evidence Fossils – showed that organisms have been around and changing for millions of years Geographical distribution of living species – similarity of species around the world in similar environments Homologous structures of living organisms – similar anatomical structures in different species led to the idea that they may have had a common ancestor Similar embryonic development – embryos of many animals with backbones look similar

Fossil Evidence Fossils were found that resemble modern-day organisms and were slightly different.

Geographic Distribution of Living Organisms

Homologous Body Structures

Similar embryonic development In early embryoinc development, all of these organisms look similar.

Summary of Darwin’s Theory Individual organisms differ - some of these variations are heritable Organisms produce more offspring than can survive. Some survivors do not reproduce Due to “overcrowding” in an environment, there is competition for limited resources Each organism has unique characteristics that can help it survive or not. Individuals that have characteristics that allow them to survive and reproduce successfully, produce more offspring and pass along these traits to their offspring. (Survival of the fittest) Species alive today have descended, and changed, from ancestors in the distant past (Descent with modification) Understand and know this summary fo Darwin’s theory