Darwin VS. Lamarck Chapter 15-2
First to propose the theory of evolution. Lamarck claimed that species are descendents from early ancestors. Fossil records supported his findings. Jean Baptiste de Lamarck (1744-1829)
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 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. Charles Darwin (1809-1882)
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.
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
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.