Darwin VS Lamarck Chapter 15 2 Jean Baptiste

Darwin VS. Lamarck Chapter 15 -2

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

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

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

Natural Selection l Darwin’s theory was based on the idea of what he called natural selection. l 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 l One of Darwin's most famous collections from his trip was the collection of finches from the Galapagos islands.

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

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

Fitness l As more favorable genes are contributed to the population the organisms will change over time. l This is Darwin’s idea of natural selection. l 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 l Homologous Structure- Similar features that are found in a shared ancestor.

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

Vestigial Structures

Vestigial Structures

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

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

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

Analogous Structures l l 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 l The change of two or more species in close association with each other is called coevolution. l Example: Bat and flower

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

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

Convergent Evolution

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

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

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

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

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

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

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