Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Evidence of common descent wikipedia , lookup
Hologenome theory of evolution wikipedia , lookup
Precambrian body plans wikipedia , lookup
The Expression of the Emotions in Man and Animals wikipedia , lookup
Saltation (biology) wikipedia , lookup
Vestigiality wikipedia , lookup
Genetics and the Origin of Species wikipedia , lookup
The eclipse of Darwinism wikipedia , lookup
The Descent of Man, and Selection in Relation to Sex wikipedia , lookup
Diversity and Change over Time Please place homework in the basket. Pick up notes. Be ready for Testprep questions. There are millions of different organisms that live on the Earth They vary in size, shape, color Atelopus frog found in rain forest of South America They vary in….. • habitat (environmental conditions in which they can survive) • how they obtain energy, the method of reproduction, and lifespan •All this variation is known as the diversity of life E.coli Fossil records indicate there are other organisms that existed in the past Some fossils are similar to creatures found today, but others are very different Variation occurs within the same species. Individuals of the same species living together are referred to as a population In every population variation exists within the inherited traits of the individuals An organism’s phenotype may influence its ability to find, obtain, or utilize resources (food, water, shelter, oxygen) and may affect the organism’s ability to reproduce Phenotypic variation is controlled by genotype and environmental influences Despite all of the variation, there are some similarities between all living things 1) All living things have nucleic acids (DNA/ RNA) 2) All living things use the same 20 amino acids to make proteins 3)Transcription and translation occur in all life forms on Earth 4)All organisms pass genetic information to offspring through reproduction Also, recall that all organisms are made of cells and that cells come from other cells (life arises from other life) Charles Darwin made observations that led him to devise an explanation for the diversity of life, how living things are related, and how life changes over time Darwin made many of his observations while traveling on a ship , the H.M.S. Beagle Charles Darwin was born on the same day as Abraham Lincoln, Feb 12, 1809 He came from a family of doctors When Charles started medical school, he found he did not like it He went to theological school to become a minister He had an interest in nature and also took courses in biology and geology He accepted a 5 year job on the H.M.S. Beagle where he worked as a naturalist and was an educated companion for the captain Darwin Left England in 1831 Darwin returned 5 years later in 1836 12 One place he visited was the Galapagos islands located west of South America The islands are close together, but have different climates and thus a different environment Small brown birds (finches) living on the islands were similar, but had very different beaks Tortoises were similar, but had different shell shapes Ideas that Shaped Darwin’s Thinking Darwin lived in a time when explorers were traveling the world and challenging long-held views about the natural world The old views were that the Earth and all life were only a few thousand years old and that neither the planet nor life had changed through time Theories of Geologic Change Geologists in Darwin’s time began suggesting that the earth was much older. James Hutton proposed that the Earth is shaped by geological forces that take place over millions of years (gradualism) Charles Lyell stressed that past geological processes are the same processes that continue to shape the Earth today (uniformitarianism) Examples of geologic processes are: Erosion (such as water carving out mountains forming canyons) Underwater Volcanoes erupt and release lava that can form islands Earthquakes cause land to be lifted up and form mountaintops These processes helped shape the Earth over millions of years, and we can continue to observe them today Darwin asked: If the Earth can change over time, can life change as well? If the earth was extremely old then it allowed for a great deal of time for life to change Malthus Thomas Malthus was an economist who published a book about population growth He proposed that resources are limited and that if the human population continued to grow without limits that eventually food and space would be insufficient Darwin applied this concept not only to humans, but to all living things He reasoned that if all offspring from every organism survived, that they would overrun the world This hasn’t happened because most of the offspring die, and of those that live, not all are successful in reproducing Darwin wondered what caused so many deaths and what factors contributed to survival and reproduction These questions became central to Darwin’s explanation of evolutionary change Lamarck Jean-Baptiste Lamarck was one of the first scientists to believe that change over time occurred in populations. Lamarck’s method of how evolution occurred was flawed, but he paved the way for future scientists such as Darwin Lamarck Lamarck’s idea involved the “inheritance of acquired traits”. This meant that changes in an individual that occurred during their lifetime would be passed on to their offspring He felt that if an organism used or did not use a particular body part, that the part would be enhanced or eliminated in the offspring (the law of use and disuse) Example, if you work out and build big muscles, your children will have big muscles Giraffes who stretch their necks to get higher leaves will have offspring with longer necks 22 Lamarck For example, birds developed wings by trying to use their front limbs for flying and then passing on the “improved” limbs to their offspring If wings were not used, then wings would decrease in size until they were lost altogether Problem with Lamarck’s Theory Darwin’s Findings In 1859, Darwin published the results of his work and observations his book called “On the Origin of Species” He presented the mechanism for evolution known as natural selection and included that evolution has been taking place over millions of years and continues in all living things In Darwin’s time, genetics was not yet understood, but it was clear that variation existed within a population For example: some cows gave more milk than others, some strawberry plants gave larger strawberries Humans then selectively bred the organisms to achieve desired traits Darwin called this “artificial selection” Natural selection was based on the “survival of the fittest” in nature The struggle for existence relates back to Malthus’s overpopulation problem. It means that each individual competes for food, space, and resources Those who are better able to compete, obtain the resources, and are more likely to survive The better suited an organism is to its environment, the greater the chance of survival is Fitness is the ability of an individual to survive and reproduce in its environment More “fit” individuals are more likely to survive Adaptations are any inherited characteristic that increases survival Adaptations can be in the anatomy of the individual or in it’s behavior. Think of examples of adaptations… Birds build nests to protect their eggs Wolves hunt in packs Walking leaf insect http://videos.howstuffworks.com/discovery/28 313-dirty-jobs-malaysian-walking-leaf-insectvideo.htm As more “fit” individuals out-survive and outreproduce less “fit” individuals, certain traits increase over time Over time the population changes (just as in artificial selection) and these changes increase a species’ fitness in its environment Given enough time, natural selection will produce organisms that have different physical characteristics and occupy different habitats than their ancestors Though related, these new organisms are somewhat different than the species from which they came from Darwin termed this principle as “descent with modification” Please pick up a copy of the notes. Be prepared to answer the Testprep questions. Quiz next class session on Evolutionary Theory. Evidence used to by Some Biologists to Support Evolutionary Theory Evidence for evolution is sited by evolutionists in these scientific fields: Paleontology Anatomy Embryology Biochemistry Paleontology/Fossil Record By comparing fossils from older rock layers with fossils from younger rock layers, evolutionists believe the fossil record provides evidence of change in life forms along a timeline Transitional fossils are fossils that show links in traits between groups of organisms and are used to show intermediate stages of evolution of a species Even though millions of fossils have been discovered, many environmental conditions must be met in order for a fossil to form Fossils are more likely to be found for species that existed for a long time, were abundant and widespread, and had hard shells or skeletons It is rare that an organism will form a fossil, so gaps in the fossil record occur when intermediate fossils have not yet been discovered These gaps are sometimes referred to as “missing links” As more and more fossils are discovered, the gaps are filled and the understanding of how particular species evolved increases Fossil Distribution Law of superposition was proposed by Nicolaus Steno in 1669. States that successive layers of rock and soil were deposited on top of one another with wind and water. The oldest stratum (or layer) is on the bottom and newest is on top. This law has been used to give relative age to fossils. (the age of a fossil compared to another fossil-younger or older). Absolute age can be determined through radioactive dating. Radioactive Dating Radioactive Dating – Technique used to establish the age materials. Atoms of the same element but differ in the number of neutrons are isotopes. Radioactive Dating Certain isotopes (radioactive isotopes) have unstable nuclei that may undergo radioactive decay. The nucleus releases particles or radiation or both causing the isotope to decay. One example is carbon. Carbon exists as both Carbon-12 and Carbon-14 (12 and 14 denote the mass number (the total number of protons and neutrons). Carbon-14 undergoes radioactive decay while carbon-12 does not. Radioactive Dating Cont….. Living things constantly take carbon in and the ration of carbon-14 to carbon-12 is a known quantity. After death, production of carbon halts and the decay of carbon-14 begins. Overtime carbon-14 decays with respect to the stable carbon-12. Radioactive Dating Cont… After 5,730 years, half of the carbon-14 present in the organism will have decayed. Therefore the half-life of carbon-14 is 5730 years. Carbon dating is limited to materials that are less than 60,000 years old. Other isotopes that might be used: Thorium-230 Potassium-40 Uranium-238 Half life 75,000 Half life 1,300,000,000 Half life 4,500,000,000 Anatomy/Homologous Body Structures Anatomy is the study of structures of organisms To the evolutionist, the greater the number of shared structures between species, the more closely the species are related Structures that have different mature forms, but that develop from the same embryonic tissue are called homologous An example of homologous structures are the forelimbs of different creatures Vestigial organs- are structures with little or no apparent function to the organism. Evolutionists believe these are remnants of structures that existed in their ancestors. Common examples that are often sited are the appendix and the tail bone. Often vestigial organs of one species are homologous with structures in a related species in which the structure has remained functional Anatomy and Geographic Distribution Species located in different geographical locations reveals that species in different locations, but under similar ecological conditions developed similar structures and behaviors Structures that have a similar function, but different evolutionary origins are known as analogous to evolutionists. If a species encountered a different environment due to a change in geographical location, different adaptations were favored This could eventually lead to a new species with a shared common ancestor to the original population Embryology The study of how an embryo develops is a field called embryology Sometimes similarities in the patterns of development of structures that are not obvious in adult organisms become evident when embryonic development is observed The embryos of vertebrates are very similar in appearance early in development, though they grow into different adult structures Cells develop in the same order and in similar patterns to produce tissues and organs of all vertebrates These common cells and tissues will produce homologous structures Similarities in embryonic develop are believed by evolutionists to support that these species evolved from common ancestors Biochemistry The study of chemical processes examines genes and proteins The more similar the DNA of two species, the more likely they are to be related Looking at DNA evidence has been very helpful when studying relationships that are not easy based on physical characteristics Examples: if species are very closely related and share many structures Or if species are so diverse that they have a lot of variation in structures