Unit 4: evolution Vocabulary 1. Evolution: Descent with modification; changes in the gene pool of a population over time; the idea that living species are descendants of ancestral species that were different from the present-day ones; also defined more narrowly as the change in the genetic composition of a population from generation to generation. Divergent Evolution: the process whereby organisms that have different adaptations from their recent ancestors survive in changed habitats; or, the process whereby organisms with a recent common ancestor develop different adaptations in different habitats. (Ex. Darker coloured moths survived a highly polluted area where the trees darkened while white moths died out). Convergent Evolution: Species evolve from different origins but under similar environmental conditions to have similar traits. (ex. Aardvarks and anteaters) Adaptive Radiation: when a single ancestral species evolves into a number of different species. Co-evolution: process by which species that are tightly linked with one another (ie. flower and pollinator) evolve gradually together. *The following are different pieces of evidence that support the theory of evolution: Palaeontology: the study of fossils; through fossils, many similarities of extinct organisms have been found in relation to modern day organisms. Biogeography: the study of the distribution of plants and animals in the environment; similar animals show up in different places all over the world, in places where they d never come in contact with each other. Evolution from a common ancestor would lead to these similar characteristics, as they would evolutionize differently in different environments. Heredity: similarities have been found in the genetic sequences of seemingly unrelated animals, suggesting a common ancestor. Embryology: the study of the development of an organism; many embryos in early development are almost identical to very different species. Comparative Anatomy: the study of the anatomy of various animals; many animals have similarities in structures and functions of their anatomy: o Homologous Structures: features of animals that are structurally similar but functionally different. (ex. a whales fin to a birds wing to a human arm)
o Analogous Structures: features of animals that are functionally similar but structurally different. (ex. the eyes of scallops, insects and humans). 2. Molecular Biology: The branch of biology that deals with the structure and function of the macromolecules (e.g., proteins and nucleic acids) essential to life; similarities can be found between species in their genomes. 3. Variation: differences in characteristics of a species due to genetics; some may be insignificant, while others may affect the survival of the individual. 4. Industrial Melanism: prevalence of dark-colored varieties of animals (esp. moths) in industrial areas where they are better camouflaged against predators than paler individuals. The best example of this is the peppered moth in England during the industrial revolution. Before the revolution, trees were light in color, giving light colored moths an advantage. However, after the revolution, dark colored moths were at an advantage, and today, dark moths are more common than light ones in England. This is important for three reasons: Shows that evolution is an interaction between the organisms and the environment. Shows the presence of variation within the population. Shows that evolution can act on genetic variability. 5. Catastrophism: the idea proposed by fossil hunter George Cuvier that states that catastrophes (ie. Floods, eruptions) had periodically destroyed species in one area while not affecting species in a nearby area. He drew this conclusion from the observation that new species appeared as others disappeared from the fossil record. 6. Jean Baptiste Lamarck: theologian (person who studies and makes theories) who proposed laws of evolution that were later proved to be incorrect.
o Law of Use or Disuse: If an organism uses a particular organ, it will remain active and strong. If an organism does not use a particular organ, it will eventually disappear. This law was not accepted as it suggested that a single organism could just changes its own structure to suit its needs, which is not possible. Law of Inheritance of Acquired Characteristics: The characteristics of an organism developed through the use and could be passed on to the offspring of the generation. This law was not accepted because acquired characteristics cannot be inherited; only genetics can. NOTE: All experiments conducted to support these theories failed, further disproving them. 7. Hardy-Weinberg Law of Equilibrium: this law states that a population will be in genetic equilibrium if it meets five specific conditions: (1) Large population; (2) No mutations; (3) No In of Out [no immigration or emigration]; (4) No sexual selection [random mating]; (5) No natural selection. In other words, the theory is impossible, although it does have some functions. There are two formulas with the Hardy-Weinberg theories (where p and q represent opposite alleles or genotypes): Allele Frequency Formula (p + q = 1): using this formula, you can find the frequency of one allele once give the other. (Ex. if allele R is 0.7, then allele r must be 0.3 because 0.7 + 0.3 = 1) Genotype Frequency Formula (p 2 + 2pq + q 2 = 1): in this equation, p 2 represents the homozygous dominants, 2pq represents the heterozygous, and q 2 represents the homozygous recessive. You can pair this formula with the first to answer questions about allele frequencies. o Example 1: 16% of a fruit fly population as green eyes (recessive trait). What is the allele frequency for red eyed flies? Because q 2 is used for homozygous recessive, we say: q 2 = 0.16 q = 0.4 (Allele frequency for green eyes) We now plug this in to find the other allele frequency. q + p = 1 0.4 + p = 1 p = 1 0.4 p = 0.6 o Example 2: 9% of the fruit flies have green eyes (recessive trait), 49% are homozygous for red eyes. How many are heterozygous (%)? We first find p and q, then plug that into 2pq (which represents the heterozygous). p 2 = 0.09 q 2 = 0.49 p = 0.3 q = 0.7 Plug it in: 2pq = % of heterozygous [2 x 0.3 x 0.7] = 42% Note: the percentages all add up to 100%!
8. Charles Darwin: a theologian that traveled the world on the HMS Beagle studying evolution, particularly the finches of the Galapagos Islands. The only weakness in Darwin s theories was that they did not account for how these changes happen (genetics). As that was later proven by Mendel, it became an accepted theory. Malthus Essay: an essay on the principles of human population that helped with Darwin s conclusions. It stated that the ever increasing human population was exceeding the food supply needed to feed it; to keep a balance between the need to food and the supply for food, millions of individuals died by disease, starvation or war. Darwin realized that this competition is true of all organisms. Selective Breeding: the selection of who breeds with who, whether in nature or with human interference; Darwin realized that this could affect a population over time. Charles Lyell: a geologist that proposed that the earth was very old and ever changing. This theory is known as uniformitarianism. This idea led Darwin to think that organisms was be changing in the same way. Observations: Darwin noted many things, such as larger beaks for birds that ate larger nuts. His theories are accepted today as the correct facts of evolution. This led him to believe that these animals adapted to their needs. *Below are Darwin s Final Conclusions. Overproduction: most species produce more offspring than are needed because many of them will likely die. Competition: all organisms compete for food and living space. Variation: Individuals of species have their own minor differences from one another, and these variations may affect the individual s chances of survival. Adaptations: because of variations, traits that are more likely to help an individual survive will be passed on to offspring, adapting the species over time. Natural Selection: survival of the fittest; individuals with the best advantages to survival will reproduce. Speciation: over time, adaptations will make an organism so different from what it was that it will be designated a new species. 9. Alfred Wallace: another theologian that came to many of the same conclusions as Darwin around the same time period. 10. Lamarck vs. Darwin: Darwin s theory won over Lamarck s, however their theories did have some similarities as well as differences. Similarity: both believed that evolution was related to the environment. Differences: Lamarck believed that individuals evolved, while Darwin believed that species evolved as solid populations. Also, Lamarck believed that an individual would decide on the
change after an event, whereas Darwin believed that we were ever changing with variation as the environment was ever changing. 11. Relative Dating: because most fossils are formed in sedimentary rock, we can determine the relative age of a fossil by examining the rock in which it was found. Generally, those found deeper are older, and those found higher are younger. 12. Radioactive Dating: the most accurate way to age fossil and rock; it is based off of the radioactive decay of isotopes that an organism accumulated in their lifetime; the rate of this break down is called half-life (the amount of time it requires to breakdown half of the originally accumulated isotopes and having it replaced by one half decay product). The easiest way I ve found to find the age of a rock is by using the following formula: Age = t known half-life log 10 (current amount original amount) log 10 (1/2) EXAMPLE 1: The half life of uranium-238 is about 4.5 billion years. A rock containing uranium is found with only ½ of the original amount of uranium-238. The age of this rock in billions of years is approximately what? Age = t known half-life log 10 (current amount original amount) log 10 (1/2) Age = 4.5 log(0.5 1) log(0.5) Age = 4.5 log(0.5) log(0.5) Age = 4.5 4.5 billion years old
EXAMPLE 2: If the half life of radioactive carbon (C14) is 5730 years, what is the age of a bone with 4% C14 (a modern bone has 16%)? Age = t known half-life log 10 (current amount original amount) log 10 (1/2) Age = 5730 log 10 (0.04 0.16) log 10 (0.5) Age = 5730 log 10 (0.25) log 10 (0.5) Age = 11460 11460 years old 13. Biodiversity: the variety of life in the world or in a particular habitat or ecosystem. Biodiversity is supported by 5 main factors: Mutations: a mutation will alter gametes that are handed down to later generations. Genetic Drift: in small populations, frequencies can be severely altered by chance (ie. more red bugs just happen to get eaten then green bugs). Because the population is so small, this could have a strong effect on the gene pool, leading to more biodiversity. o Bottleneck Effect: when chance greatly reduces a population (ie. natural disaster, overhunting, habitat destruction). This leaves certain alleles in the gene pool some other alleles may have disappeared entirely. Original Population Bottleneck Effect Surviving Reproduction of Population Survivors o The Founder Effect: when a small number of individuals colonize a new area who do not carry all of the traits of the original parent population (ex. all of the red haired individuals decide to colonize a new area therefore, nobody in the new colony will ever have brown hair, even if their parents did).
Gene Flow: the movement of alleles in and out of a population via emigration and immigration. This may lead to two slightly different populations slowly having less and less differences from one another. Non-Random Mating (Sexual Selection): individuals tend to mate with individuals that they feel will give their offspring the best chance of survival. Natural Selection: A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits. o Stabilizing Selection: a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value; Mode of natural selection by which intermediate phenotypes in the range of variation are favoured and extremes at both ends are eliminated. o Directional Selection: directional selection occurs when natural selection favours a single phenotype and therefore allele frequency continuously shifts in one direction. (ex. brown beetles living in mud will outlive green beetles living in mud). o Disruptive Selection: describes changes in population genetics in which extreme values for a trait are favoured over intermediate values. 14. Speciation: the formation of a new species through adaptation. Adaptation: any trait that enhances an organism s ability to survive that is passed down through generations. Biological Species: a group of organisms that can interbreed and produce fertile offspring and who breed at the same times of the year. o Hybrid Species: an organism that successfully develops from two different species but who is sterile (ex. donkeys and horses can make mules) Transformation: when one whole species evolves into another. Divergence: when two or more species arise from one parent species o Allopatric Speciation: divergence whereby the species is separated by a physical barrier (Ie. Mountains, island, etc.) and evolve individually.
o Sympatric Speciation: when individuals within the population can no longer successfully breed with one another, the two fertile groups separate. Prezygotic Barriers: when fertilization cannot occur between two individuals. Behavioural Isolation: when the reproductive behaviour (ie. a mating dance) differs from another to the point that they will not mate. Habitat Isolation: when two species live in different habitats or niches. Temporal Isolation: when mating times of the year differ from that of other species, and will therefore not mate. Mechanical Isolation: anatomy makes fertilization impossible (ex. a Chihuahua and a Great Dane) Gamete Isolation: when gametes are chemically unable to fuse. Postzygotic Barriers: when a fertilized egg cannot produce a successful and fertile organism. Hybrid In-Viability: zygote never fully develops because of incompatible genes. Hybrid Sterility: organism is produced but is sterile (ie. donkey and a horse make a mule) Hybrid Breakdown: if the first generation is successful but the second or third is weak and dies. 15. Gradualism: the belief that species arise through gradual changes accumulated over time (Darwin); the opposite of punctuated equilibrium. 16. Punctuated Equilibrium: the belief that species remain constant for long periods of time and then arise into new species in a short period of time, interrupting the original equilibrium and bringing about a new equilibrium (Gould and Eldridge); the opposite of gradualism. 17. The Origin of Life: there are many theories of where life began. Panspermia Theory: theory that life on earth originated from a migrating species from outer space, either brought here by accident or by an intelligent being.
Intelligent Design: the concept that all biological origins on earth have followed a pattern which set out as a product of some intelligent cause, concluding that life is too complex to be by chance. Gaia Hypothesis: the suggestion that Earth is one huge, living, self-regulating system; proposed by James Lovelock. Lynn Margulies Hypothesis (Symbiogenesis): the theory that mitochondria and chloroplasts (major organelles in cells) used to be single-celled prokaryotes and later fused into cells, creating a symbiotic relationship. Haldane-Oparin Hypothesis (Heterotrophic Hypothesis): the widely accepted theory that suggests that the first organic compounds were formed by natural chemical processes on the primitive earth and that the first life like structures developed from large heterotrophic protein molecules that resulted from those reactions. They suggest that the world had to of been very hot and consisting only of Hydrogen, Water, Ammonia, and Methane; the oceans were near boiling temperature; energy from UV ray, lightening and volcanoes would be enough to begin the necessary reactions to make the first cell like structures. This theory works with the theory of Symbiogenesis as well. Once these reactions began to take place, oxygen became a by-product (as cells learned to photosynthesize), which eventually led to the world we know today. o Miller and Urey: conducted an experiment that proved that the Haldane-Oparin Hypothesis was physically possible. They took the assumed materials of the primitive Earth (water, hydrogen, methane and ammonia), placed them in a flask, and exposed the mixture to sparks (to mimic lightening). The flask then produced tiny organic compounds that could build a cell.