Evolution Notes Chapters 15-17

Theories have some important properties They explain a wide variety of data and observations They can be used to make predictions They are not absolute, they serve as a model of understanding the world and can be changed as the world view changes

Scientists Charles Lyell - geologist who proposed that the earth is changing. Alfred Russel Wallace - reached the same conclusion as Darwin but didn’t publish as quickly.

Lamarke's Theory of Acquired Characteristics Some thought that you would gain or lose features if you overused or didn't use them, and you could pass these new traits onto your offspring. This was known as the Inheritance of Acquired Characteristics A lizard that didn't use it legs would eventually not have legs and its offspring wouldn't have legs A giraffe stretched its neck to reach higher leaves, and this stretched neck would be a trait inherited by its offspring Lamarke's Theory was eventually discarded - PROVEN TO BE WRONG! Why? Logically it doesn't work. Imagine if you were in a car accident and had a leg amputed. This does not mean that your children will only have one leg. Features gained during life are not passed on to children.

A giraffe stretched its neck to reach higher leaves, and this stretched neck would be a trait inherited by its offspring Lamarke's Theory was eventually discarded - PROVEN TO BE WRONG! Why? Logically it doesn't work. Imagine if you were in a car accident and had a leg amputed. This does not mean that your children will only have one leg. Features gained during life are not passed on to children.

Charles Darwin (1809 – 1882) Author of the ‘Origin of Species’ Stated that evolution occurs by natural selection Diversification of life through a lengthy process of change by adaptation

Darwin's Theory of Evolution by Natural Selection Natural Selection = a mechanism for change in populations that occurs when organisms with favorable variations for a particular environment survive, reproduce, and pass these variations on to the next generation. In nature, there is a tendency toward overproduction of offspring. Ex) Fish lay thousands of eggs but not all survive. In any population, individuals will exhibit slight variations. fish may differ slightly in color, fin and tail size as well as speed. 

Natural Selection Continued 3) Individuals with variations favorable for a particular environment are more likely to survive and pass those variations on to the next generation than those with less favorable variations. 4) Gradually, offspring of survivors will make up a larger proportion of the population. Depending upon environmental factors, after many generations, a population may come to look entirely different

Adaptation any change in a species that makes them better suited to their environment. Those not suited to the environment do not survive - “Survival of the fittest” The result of adaptation… Change within a species leads to replacement and extinction

Structural Adaptations 1) Mimicry – a structural adaptation that provides protection for an organism by copying the appearance of another species. Ex) the bee orchid is a flower that mimics the appearance of female bees in order to attract the male bees for pollination Ex)Another example is the Viceroy butterfly and the Monarch butterfly. monarch viceroy

Structural Adaptations 2) Camouflage – a structural adaptation that enables an organism to blend in with its surroundings. Ex) The markings of a flounder and the color of the ocean floor Ex) The coloring of the artic hare or artic fox and its environment.

Physiological Adaptations changes in an organism’s metabolic processes. Ex) Bacterial resistance to antibiotics; Ex) Weeds and insects build resistance to pesticides

Evidence for Evolution Geological Record - Radioactive Dating estimates Earth to be 4.6 Billion years old. Fossil Evidence We have tons of fossils of creatures that no longer exist but bear striking resemblance to creatures that do exist today. Carbon dating--gives an age of a sample based on the amount of radioactive carbon is in a sample. Archaeopteryx. An animal intermediate between two living animal groups. (Teeth like reptile, feathers like bird) Fossil record---creates a geologic time scale.

Evidence from Living Organism Homologous Structures = Similar in structure and/or function. Ex) Flipper or a dolphin & hand of a human. The pentadactyl limb is a perfect example of a homologous structure

Analogous Structures = Body structure that is similar in function but different in structure. Ex) Wings of a bird and wings of a butterfly.

Vestigial Structures = Body structure reduced in function but may have been used by an ancestor. Ex) Hipbone in a whale; Appendix and Tailbones in humans.

3. Embryological Development studies Ex) Presence of tails and gills in early vertebrate embryos supports fossil record that aquatic, gill-breathing vertebrates preceded air-breathing, terrestrial species.  DNA comparison studies = comparing biochemical similarities such ad DNA

Evolution of Species 1) Gradualism - the idea that species originate through a slow build-up of new adaptations. 2) Punctuated Equilibrium - When speciation occurs in quick, rapid bursts with long periods of stability in between.

Patterns of Evolution 1) Divergent Evolution = the pattern of evolution in which species once all similar to an ancestor become more and more distinct. Ex) Adaptive Radiation = The diversification, over evolutionary time, of a species or group of species into several different species (where a species occupy different niches - the role an organism plays in its community) 2) Convergent Evolution = situation in which distantly related organisms evolve similar traits. Ex) The sleek body of a seal and the similar body shape of a penguin.

Speciation the formation of new species. Changes in related organisms to the point where they are different enough to be considered separate species This occurs when populations of one species are separated and adapt to their new environment or conditions (physiological, geographic, or behavioural). Ecological races are the first step in a new species evolving from an ancestor. Ex: Darwin’s Finches- Due to isolation, chance, different climates and natural forces such as food availability and type, they evolved into thirteen different species of finch

Examples of Evolution 1. industrial melanism (Kettlewell's moths) 2. dog breeds 3. viruses & vaccines 4. bacteria & antibiotics 5. elephant tusks

Unifying Theory of Biology The Theory of Evolution is considered a Unifying Theory of Biology, because it answers many of these questions and offers and explanation for the data. Why do so many different animals have the same structures, the arm bones in a human are the same bones as a flipper in a whale? Why do organisms have structures they no longer use, like the appendix in a human? Non functioning wings in penguins Why are there bones and fossil evidence of creatures that no longer exist? What happened to these creatures? Why do so many organisms' morphology and anatomy follow the same plan? Why is the sequence of DNA very similar in some groups of organisms but not in others? Why do the embryos of animals look very similar at an early stage?