* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Biology Chapter 15 notes 15-1 Evolution Concepts Theory of
Survey
Document related concepts
Natural selection wikipedia , lookup
Catholic Church and evolution wikipedia , lookup
Evolving digital ecological networks wikipedia , lookup
Punctuated equilibrium wikipedia , lookup
Hologenome theory of evolution wikipedia , lookup
Evidence of common descent wikipedia , lookup
The Descent of Man, and Selection in Relation to Sex wikipedia , lookup
Saltation (biology) wikipedia , lookup
Theistic evolution wikipedia , lookup
Genetics and the Origin of Species wikipedia , lookup
Transcript
Biology Chapter 15 notes 15-1 Evolution Concepts Theory of evolution states that species change over time. Fossils provide one form of evidence for evolution. Other evidence includes: similarities in morphology and development; DNA, RNA and protein sequences. Fossils Fossil – trace of a long-dead organism. Sedimentary fossils are formed when sediment covers the decaying organism. Over time hard minerals replace the organisms remains, leaving a fossil Mold – fossil that is an imprint of the shape of an organism. Cast – a mold that has filled in with hard minerals. Robert Hooke in 1668 published his conclusion that fossils are remains of plants and animals. Nicolaus Steno in 1669 proposed the law of superposition – states that successive layers of rock or soil were deposited on top of one another by wind or water. The lower stratum is the oldest, top stratum the most recent. Fossils in a single stratum are from the same age. Under Steno’s law, someone could establish a relative age of a fossil. (one fossil is relatively older than a fossil above it) The fossil’s absolute age could be established from the amount of sediment deposited above the fossil. Succession of Forms According to the fossil record, some organisms lived a while, then disappeared – extinct Fossil records also indicate mass extinctions – brief periods where a large number of species disappear. Mass extinctions probably resulted from drastic changes in the environment, possibly from volcanic activity that filled the atmosphere with ash and blocked out the sun for long periods of time. Biogeography - the study of the geographical distribution of fossils and of living organisms. Comparison of recently formed fossil types with types of organisms in the same area shows that new organisms arise in areas where similar forms already lived. Armadillos appeared in North and South America, where glyptodonts lived in the past. Burgess Shale 800 m above sea level in the Canadian Rockies lies the Burgess Shale. Contains a very diverse fossil bed from the Cambrian period 550 million years ago. It is considered an explosion of life from the Precambrian Era, which only had simple eukaryotic and prokaryotic cells. Many of these animals are not similar at all to modern day animals. 15-2 Biological evolution is the change of populations of organisms over many generations. Population –group of organisms of one species that interbreed. Early scientists observed that new life-forms appeared to be modifications of fossil forms found in the same geological area. This suggests a natural modification process is at work. - a glyptodont is a fossil form of an armadillo. Lamarck’s Ideas French scientist Jean Baptiste de Lamarck proposed that species undergo modifications over time. His belief was that similar species descended from a common ancestor – living species came from fossil forms. To explain how species change, he hypothesized that acquired traits were passed to offspring. Acquired traits are not determined by genes. Acquired traits arise from a result of the organism’s experience or behavior. An example he used: Over time the webbed-feet of water birds resulted from repeated stretching of the membrane between the toes. So the trait was preserved. Although this idea was disproved, it lead the way for the evolution theory. IMPORTANT – individual organisms do NOT evolve, populations evolve over time. Modern Evolutionary Thought Mid 1800s –Charles Darwin and Alfred Wallace independently proposed the idea that species were modified by natural selection. Natural Selection – when organisms that are best suited for their environment reproduce more successfully than other organisms. Natural Selection Example of natural selection – bacterial resistance to antibiotics. Overtime strains of bacteria become resistant to antibiotics, because they have the right gene that makes the bacteria resistant to the antibiotics. As those bacteria with the gene reproduce, eventually the entire population is resistant. A No-no of Natural Selection Question: Why do leopards have spots? No-no: “Leopards evolved their spots IN ORDER TO survive better in their environment.” More Accurate: “Spots are a beneficial trait that have arisen from generations of populations of leopards.” IMPORTANT – Evolution is not active! Charles Darwin In 1831 was hired as a naturalist on the ship H.M.S. Beagle for a five-year expedition to collect specimens from South America and the South Pacific. In 1859 he published his ideas of evolutionary theory in his book “The Origin of Species.” 15-3 Darwin’s Voyage Uniformitarianism – principle that geological structures of the Earth resulted from cycles of observable processes and that these same processes operate continuously through time. So rivers form the same way they did millions of years ago. While on his voyage Darwin incorporated the idea of uniformitarianism into his works on natural selection. (If geological processes take a long time, maybe changes in environments take a long time too.) Darwin discovered fossil shells of marine organisms in rock beds above 14,000 feet in elevation in mountains. Darwin reasoned that the formation of mountain ranges would slowly change habitats, requiring organisms that lived there to adapt to these changes. Darwin’s Finches Darwin found 13 similar species of finches on the Galapagos Islands. Each bird had a bill specially designed for its food. But similarities implied the birds came from a common ancestor. Because the Galapagos Islands are young islands (about 5 million years old), Darwin assumed that the offspring of the original finches have been adapting to different environments for a relatively short time. Darwin reasoned that over millions of years, many large differences could accumulate between species. The Origin of Species In 1858 Alfred Wallace sent Darwin his studies on evolution. This prompted Darwin to finish his studies on natural selection and present both his and Wallace’s works side by side to the Linnaean Society. The following year in 1859 Darwin finished his works On the Origin of Species by Means of Natural Selection. Darwin’s Theories Two ideas of evolution Darwin presented: Descent with modification Natural selection Descent with Modification The newer forms appearing in the fossil record are actually the modified descendents of older species. Similar to Lamarck’s idea, but he included that all species had descended from one or a few original types of life. Modification by Natural Selection - Explains how evolution occurs Thomas Malthus published a paper on human populations that observed that the growth of the human population was limited by factors like war, disease or supply of natural resources. Darwin figured that the environment limits the growth of populations by increasing the rate of death and/or decreasing the rate of reproduction. Organisms with a greater number of favorable traits tend to leave a larger number of offspring than organisms with fewer beneficial traits. Darwin called that different degrees of reproduction among organisms in a population natural selection. A population of organisms adapts to their environment as their proportion of genes for favorable traits increases. In an evolving population, a single organism’s genetic contribution to the next generation is termed fitness. An individual with high fitness is well adapted to its environment and reproduces more successfully than an individual with low fitness. A favorable trait is said to give the organism an adaptive advantage. A favorable trait that does not enhance reproductive success does not contribute to evolution. 15.3 Evolution in Process Evolution Thoughts The environment dictates only the direction and extent of evolution (shows where organisms came from and how much organisms have changed). Natural selection changes species over time. Since natural resources are limited, all organisms must compete for resources. Evidence of Evolution Beaks are modifications of a feature found in an ancestor common to all birds. Similar features that originated in a shared ancestor are called homologous structures. Limbs can look different and vary in function (wing and an arm), but are derived from the same structures in the embryo. Presence of homologous structures in different species indicate a recent ancestor. Analogous structures serve identical functions, look somewhat alike, but have a different embryological development. Example: the hummingbird and the humming moth. Both hover to suck nectar from flowers, but do not share anatomical or embryological similarity between their wings (Their wings are not the same.) Vestigial Structures Features that serve no function that were useful to the ancestor. Example: human tailbones and whale pelvic bones. The human tailbone is homologous structure to functional tails of other vertebrates. Species that have evolved from a common ancestor should have certain characteristics in common. Embryological Similarities Early stages of different vertebrate embryos are extremely similar to each other. These similarities fade as the embryo develops. This is another indication that vertebrates share a common ancestry. Molecular Similarities Darwin was unaware of genetic similarities like RNA, DNA or homologous proteins. Amino acid sequences in human blood and gorilla blood differ by one amino acid. Frog blood amino acid sequences and humans differ by 67 amino acids. The number of differences in amino acids in homologous proteins of two species is proportional to the length of time that has passed since the two species shared a common ancestor. Coevolution – the change of two or more species in close association with each other. Species can coevolve, like parasites and their hosts or plants and the animals that pollinate them. Convergent Evolution organisms that look similar, but ancestral types are different. It occurs because the environment selects similar phenotypes. Example – sharks and dolphins. Divergent Evolution Two or more related populations or species become more and more dissimilar, often resulting in a new species. This is usually due to differing habitats – open niches. Adaptive Radiation A type of divergent evolution where many related species evolve from a single ancestral species. Example: Galapagos finches Artificial Selection Process of speeding up divergence artificially by selective breeding. Example: Domestic dogs