Darwin VS. Lamarck Chapter 15-2

Jean Baptiste de Lamarck (1744-1829) First to propose the theory of evolution. Lamarck claimed that species are descendents from early ancestors. Fossil records supported his findings.

Lamarck’s Theory Lamarck claimed that species changed over time due to an acquired trait. Acquired trait- A trait not determined by genes but acquired through a life time. Lamarck’s theory was later proven false.

Charles Darwin (1809-1882) Charles Darwin came up with a different theory to explain how evolution takes place. Darwin collected evidence for his theory on his journey around the world on a ship called the H.M.S. Beagle.

Natural Selection Darwin’s theory was based on the idea of what he called natural selection. Natural selection- Organisms best suited to their environment reproduce more successfully than other organisms. Thus passing down their favorable traits to their offspring.

Voyage of the Beagle One of Darwin's most famous collections from his trip was the collection of finches from the Galapagos islands.

The Finches Darwin collected 13 different species of finches from the island. Each bird had a distinct bill specialized for a particular food source. Darwin later concluded that these 13 species came from one common ancestor. Darwin thought that the original ancestors had migrated from the nearby coast of South America.

The Origin of Species Darwin later published his findings in a book titled the Origin of Species.

Survival of the Fittest We often use the term “survival of the fittest” What does this mean?

Survival of the Fittest Animals with favorable traits will survive and pass those genes to the offspring. The contribution of genes an organism gives to the next generation is called fitness.

Fitness As more favorable genes are contributed to the population the organisms will change over time. This is Darwin’s idea of natural selection. The process by which a population becomes better suited to its environment is known as adaptation.

THE FORMATION OF A NEW SPECIES Chapter 15-3 and 16-3 Notes

Homologous Structure Homologous Structure- Similar features that are found in a shared ancestor.

Vestigial Structures Vestigial Structure- Structures that were useful to ancestors now have no purpose.

Vestigial Structures

Vestigial Structures

Similarities in Embryology The early stages of different vertebrate embryos are strikingly similar to each other. The similar appearance provides further evidence that species originated from a common ancestor.

Similarities in Macromolecules Darwin based many of his conclusions on the physical similarities between organisms. Darwin was unable to examine similarities at a molecular level. Scientists have later studied the molecular similarities between different organisms.

Molecular Similarities The similarity in amino acid sequence can determine how closely related two species are. And how long ago they branched off the evolutionary chain and developed a new species.

Analogous Structures When organisms that vary greatly anatomically evolve similar structures that serve similar functions. Example: bird wing and insect wing Example: bird beak and giant squid beak Share very distant relatives.

Co- Evolution The change of two or more species in close association with each other is called co-evolution. Example: Bat and flower

Some flowers and bees have coevolved in a way that their existence depends on each other.

Convergent Evolution Selection that causes two species to become very similar to each other even though they have very different ancestors. Example- Dolphin and Shark

Convergent Evolution

Divergent Evolution Two or more related populations or species become more and more dissimilar. Divergence is nearly always a response to differing environmental factors and can ultimately result in new species. The rate of divergent evolution among dogs has been increased by artificial selection in humans.

Speciation Speciation- Is the formation of new species which results in many related populations of organisms.

Biological Species Concept The Biological Species Concept states- A species is a population of organisms that can successfully interbreed but can not breed with other groups.

Biological Species Concept The biological species concept works great for living organisms but is difficult for organisms that have since become extinct.

Speciation In order for speciation to occur there must be isolation. In isolation two parts of formerly interbreeding populations stop interbreeding. Why is isolation important for speciation to occur?

Speciation Two major types of isolation frequently drive speciation Geographic Isolation Reproductive Isolation

Geographic Isolation Geographic Isolation- Is the physical separation of members of a population. Examples Canyon formation Shrinking ponds - Islands

Reproductive Isolation Reproductive Isolation- Reproductive isolation results from barriers to successful breeding between population groups in the same area.

Reproductive Isolation Examples Offspring does not survive to reproduce Mating call that is not recognized Different mating times Selective mate