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Charles Darwin (1809-1882) was an English scientist who sailed all over the world on the HMS Beagle. Darwin became curious about the diverse creatures that he saw and the possible relationships between them. Natural Selection occurs when organisms with certain traits survive, reproduce, and pass on those traits to the next generation. Ex: A faster fish may be better suited for escaping predators and live to produce offspring with that same variation This is often described as “Survival of the Fittest” Overproduction of offspring – having many offspring raises the chance that some will survive 2. Variation and Adaptation 1. 1. A heritable trait that increases and organisms ability to survive is an adaptation. Survival of the ‘Fittest’ 3. 1. Those best suited for an environment will survive and reproduce. Descent with Modification 4. 1. More individuals will have the successful traits in future generations, as long as those traits are beneficial. All the genes, including different alleles, in a given population is called the “gene pool” Diversity within a species makes it more likely that the right adaptation could be present – therefore, an increase in diversity increases its chances of survival **How do you get diversity in a population…???** 1. Genetic Drift - the random change in the frequency of alleles of a population over time. Due to chance, rare alleles in a population will become eliminated; other alleles will increase in frequency and become fixed. 2. Gene Flow - the movement of genes into or out of a population. 3. Non-random Mating – Mating among individuals with favorable traits » such as coloration in plants and animals, competitive strength, courting behaviors etc. 4. Mutations – changes in DNA increase the frequencies and types of allele 5. Natural Selection – Since only the ‘fittest’ organisms survive, they will influence which genes are passed down to future generations. Speciation is the process of forming a new species by biological evolution from a preexisting species Adaptive Radiation/Divergent Evolution: - a number of different species diverge (split-off) from a common ancestor. in different niches. Convergent Evolution – Unrelated organisms in similar environments may evolve adaptations to similar niches. Coevolution - when two or more species living in close proximity change in response to each other. The evolution of one species may affect the evolution of the other. Extinction - the elimination of a species often occurring when a species cannot adapt to a change in its environment. This can be gradual or rapid. Gradual extinction - occurs at a slow rate and may be due to other organisms, changes in climate, or natural disasters. Mass extinction - occurs when a catastrophic event changes the environment very suddenly (such as a massive volcanic eruption, or a meteor hitting the earth causing massive climatic changes). It is often impossible for a species to adapt to rapid and extreme environmental changes. The changes in inherited traits in a species over time is called biological evolution. Microevolution occurs on a small scale affecting a single population Macroevolution occurs on a large scale affecting changes in species across populations The species we see today evolved from species of former periods of time. Other Evidence of Evolution Paleontology Anatomy Embryology Biochemistry Paleontology is the study of prehistoric life Fossils are preserved remains of organisms that lived many years ago The fossil record provides evidence of life forms and environments and supports evolutionary relationships by showing the similarities between current species and ancient species. Anatomy is the study of the structures of organisms 1. Homologous Structures have similar characteristics resulting from sharing common ancestry The greater the numbers of shared homologous structures between two species, the more closely the species are related2. 2. Analogous Structures reveal that species living in different locations under similar ecological conditions may evolve similar ex. Butterfly and Bird Wings 3. Vestigial Structures serve little or no function in the organism The vestigial organs of one specie are often homologous with structures in a related specie that still uses the organ. Embryology is the study of embryo development in organisms The could include pre-birth, pre-hatching, or pre-germination Studying the structures of embryos can lead to clues of possible ancestors The embryos of fish, reptiles, birds, and mammals all have a tail and gill slits even though they may not exist on the mature organism The more similar the DNA and amino acid sequences in proteins of two species, the more likely they are to have diverged from a common ancestor All citrus trees can produce citric acid and therefore may have developed from a common ancestor The study of the ability of different species to synthesize similar substances is called comparative biochemistry the relationship of different organisms believed to have a common ancestor based on taxa (groups) Branches from an intersection show those with a common ancestor You can see that the snail, earthworm and insect have a more recent common ancestor than the snail and sea star Time A Phylogenetic Tree shows All living things can be classified as belonging to one of 3 Domains Bacteria - Archaea - Eukarya All living things can be classified as belonging to one of the 6 Kingdoms of Life Archaeabacteria Eubacteria Protista Plantae Fungi Animalia Biologists identify and organize organisms through Taxonomy- a classification of organisms based on shared characteristics. To work, the system needs to be universal across the scientific community and everyone needs to follow the same rule for naming a specie. At first, scientists tried to use Greek or Latin but the interpretations often didn’t work well. Carolus Linnaeus developed a two-part naming system called Binomial Nomenclature. It uses the Genus and Specie of an organism to identify it. EX: Polar Bear would be called Ursus maritimus Red Fox Organism Kingdom Animalia Animalia Animalia Animalia Animalia Phylum Chordata Chordata Chordata Chordata Chordata Class Mammalia Mammalia Mammalia Mammalia Mammalia Order Carnivera Carnivera Carnivera Carnivera Rodentia Family Felidae Canidae Canidae Canidae Geomyidae Genus Felis Vulpus Canis Canis Thomomys Species domesticus fulva familiaris lupus bottae A dichotomous key is a tool that allows the user to determine the identity of items in the natural world, such as trees, animals, or rocks. Keys consist of a series of choices that lead the user to the correct name of a given item. "Dichotomous" means "divided into two parts". Therefore, dichotomous keys always give two choices in each step. 1. a. wings covered by an exoskeleton ………go to step 2 b. wings not covered by an exoskeleton ……….go to step 3 2. a. body has a round shape ……….ladybug b. body has an elongated shape ……….grasshopper 3. a. wings point out from the side of the body ……….dragonfly b. wings point to the posterior of the body ……….housefly When there is no change in the allele frequencies in a species, the population is in genetic equilibrium. This concept is known as the Hardy-Weinberg Principle. To sustain equilibrium, the must be: A very large population with no genetic drift No movement into or out of the population Random mating No mutations with the gene pool No natural selection Godfrey Hardy (1877-1947) Wilhelm Weinberg (1862-1937)
