Darwin & Evolution by Natural Selection Insect eaters Bud eater Seed eaters Cactus eater Warbler finch Tree finches Ground finches 2006-2007

Darwin & Lamarck Written by Jennifer Folsom Background Information Natural Selection is a scientific theory that has been supported by tremendous amounts of scientific evidence. In this lesson, students will be exposed to Natural Selection and an earlier alternate theory—Acquired Inheritance. Both of these theories are founded on the belief that animal species change over time and that offspring inherit traits from their parents. The two theories differ on how animals change and what traits offspring inherit from their parents. The theory of Acquired Inheritance was introduced by Jean Baptiste Lamarck. It was based on his belief that individual organisms made changes in themselves and passed those changes on to their offspring. In his theory, individual organisms had the ability to change their physical characteristics. Giraffes that needed longer necks, or elephants that needed longer trunks would use them more and they would extend them through use. Lamarck not only believed that animals could make these changes, but also that they could pass them on to their offspring. For example, when mama giraffe stretched her neck a little to reach more food, it would stay stretched, and her new baby would have that long neck too. Charles Darwin introduced Natural Selection to the scientific community. He said that organisms could neither willfully change themselves nor pass those changes on to their offspring. He said that individuals survived (or didn’t) based on the specific traits they possessed. His well-known saying “survival of the fittest” meant that out of the entire population of one type of organisms, only the fittest will survive in an environment with limited resources. Those with the best adaptations for survival stayed alive and were most likely to reproduce. When they reproduce, they passed on their beneficial traits to their offspring. Eventually, the population had a higher percentage of individuals with those more “fit” traits. If the environment changed again in some way, the process happened again. As long as environments continue to change, so will makeup of populations of organisms. Natural Selection is the driver behind evolution.

Incorrect Theories of Evolution: Lamarck Lamarck proposed an incorrect mechanism for how organisms evolve. Believed organisms could pass on aquired traits to offspring Simple life forms continually came into existence from dead matter Continually become more complex More "perfect" -- as they transformed into new species. He correctly pointed out that change in species is linked to an organism’s environment.

Charles Darwin Proposed a way how evolution works How did creatures change over time? by natural selection Collected a lot of evidence to support his ideas 1809-1882 British naturalist -Wrote the Origin of Species What did Darwin say? What evidence supports Evolution by Natural Selection? What impact did Evolution have on biology?

Voyage of the HMS Beagle Invited to travel around the world 1831-1836 (22 years old!) makes many observations of nature main mission of the Beagle was to chart South American coastline After graduation Darwin was recommended to be the conversation companion to Captain Robert FitzRoy, preparing the survey ship Beagle for a voyage around the world. FitzRoy chose Darwin because of his education, his similar social class, and similar age as the captain. Darwin noted that the plants and animals of South America were very distinct from those of Europe Robert Fitzroy

Voyage of the HMS Beagle Stopped in Galapagos Islands 500 miles off coast of Ecuador The origin of the fauna of the Galapagos, 900 km west of the South American coast, especially puzzled Darwin. On further study after his voyage, Darwin noted that while most of the animal species on the Galapagos lived nowhere else, they resembled species living on the South American mainland. It seemed that the islands had been colonized by plants and animals from the mainland that had then diversified on the different islands

Galapagos Recently formed volcanic islands. Most of animals on the Galápagos live nowhere else in world, but they look like species living on South American mainland. 800 km west of Ecuador

Darwin’s Observations Animals on the coast of S. America: Resembled those on the nearby islands Evolved differences Or Descended w/ modification after separating from a common ancestor.

Darwin found…many unique species Many of Darwin’s observations made him wonder… Why? Darwin asked: Why were these creatures found only on the Galapagos Islands?

Darwin found…clues in the fossils present day Armadillos Darwin found…clues in the fossils Darwin found: Evidence that creatures have changed over time ancient Armadillo Darwin asked: Why should extinct armadillos & modern armadillos be found on same continent?

Darwin found… more fossils present day Sloth Darwin found: Evidence that creatures have changed over time (extinct) Giant ground sloth Darwin asked: Why should extinct sloths & modern sloths be found on the same continent?

Darwin found: Different shells on tortoises on different islands Darwin asked: Is there a relationship between the environment & what an animal looks like?

But Darwin found… a lot of finches Darwin was amazed to find out: All 14 species of birds were finches… Finch? Sparrow? Woodpecker? Warbler? But there is only one species of finch on the mainland! Large ground finch Small ground finch Finch? Sparrow? Darwin asked: If the Galapagos finches came from the mainland, why are they so different now? Warbler finch Tree finch Woodpecker? Warbler?

The finches cinched it! different beaks are inherited variations serve as adaptations that help birds compete for food these birds survive & reproduce pass on the genes for those more fit beaks over time nature selected for different species with different beaks Darwin found: The differences between species of finches were associated with the different food they ate. Finch? Sparrow? Woodpecker? Warbler? Darwin said: Ahaaaa! A flock of South American finches were stranded on the Galapagos… Large ground finch Big seed eater Small ground finch Small seed eater Insect eater Warbler finch Leaf & bud eater Tree finch

Relationship between species (beaks) & food

Darwin’s finches Darwin’s conclusions variations in beaks differences in beaks in the original flock adaptations to foods available on islands natural selection for most fit over many generations, the finches were selected for specific beaks & behaviors offspring inherit successful traits accumulation of winning traits: both beaks & behaviors separate into different species

From 1 species to 14 species… Warbler finch Woodpecker finch Small insectivorous tree finch Large insectivorous Vegetarian Cactus finch Sharp-beaked finch Small ground finch Medium ground finch Large ground Insect eaters Bud eater Seed eaters Cactus eater Warbler Tree finches Ground finches natural selection for best survival & reproduction variation

Growth of Populations Darwin was influenced by Thomas Malthus He wrote: Populations grow as much as the environment allows.

Evolution by Natural Selection The process of: “Survival of the Fittest” Organisms that adapt to their environment survive while those that do not adapt disappear N.S. leads to adaptations in a population.

ADAPTATIONS LEAD TO FITNESS Living things that are well adapted to their environment survive and reproduce. Those that are not well adapted don’t survive and reproduce. An adaptation is any characteristic that increases fitness, which is defined as the ability to survive and reproduce.  YOU CANNOT AQUIRE AN ADAPTATION, MUST BE AN INHERITED TRAIT.

Natural Selection Video Label Paper: Genetic Variation a. b. Overproduction of Offspring a. Struggle for Existence a. Differential Survival & Reproduction a. Natural Selection Video http://www.pbs.org/wgbh/evolution/library/11/2/e_s_4.html 6 min 39 sec

SUMMARY: Individuals best suited to their environment survive and reproduce most successfully. The characteristic that make them best suited to their environment are passed on to offspring. Individuals whose characteristics are not as well suited to their environment die or leave fewer offspring.

Species change over time. This is natural selection. Over long periods of time, natural selection causes changes in the characteristics of a species, such as in shape and form. New species arise, and other species disappear.

African wild Ancestral canine Species alive today have descended with modifications form species that lived in the past. African wild dog Jackal Fox Fox Thousands to millions of years of natural selection Coyote Wolf Ancestral canine These five canine species evolved from a common ancestor through natural selection

Darwin’s Ideas Updated 1) Change Within Populations N.S. causes the frequency of certain alleles in a population to change over time. 2) Species Formation Under certain conditions, change within a species due to reproductive isolation can lead to new species. 3) The Tempo of Evolution Gradualism is a process of evolution in which speciation occurs gradually Punctuated Equilibrium is a process in which speciation occurs rapidly between periods of little or no change.

Examples of Evolution-- Natural Selection at Work 1) Factors in Natural Selection Organisms w/traits helping them survive—reproduce & pass genes. 2) Evolution of Antibiotic Resistance Experiments show that evolution through N.S. has occurred within populations of antibiotic-resistant bacteria Tuberculosis bacteria 3) Evolution in Darwin’s Finches Experiments show that evolution through N.S. has occurred in beak size in Darwin’s Finches.

Formation of New Species 1) Speciation Speciation begins as a population adapts to its environment. 2) Forming Subspecies Populations of the same species that differ genetically b/c of adaptations to different living conditions are called: subspecies. Newly formed subspecies are on the road towards speciation. 3) Maintaining New Species Reproductive isolation through barriers keeps species from breeding with one another.

Speciation Geographic isolation of populations Can lead to Reproductive isolation of population New Species (unable to breed when together)

Geographic Isolation Members of a population may become isolated from one another by geographic boundaries like mountains, rivers or even oceans

Reproductive Isolation

Convergent Evolution

Divergent Evolution (Adaptive Radiation)

Dichotomous Keys Tool used when new species is found Used to categorize different species based on physical characteristics Classification is a way of separating a large group of closely related organisms into smaller subgroups. A Dichotomous Key is a listing of characteristics, such as structure and behavior, organized in such a way that an organism can be identified or classified.