“Evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection.”The hypothesis of evolution depends on the idea that all species are related and change over time.Example of natural selection/evolution: The first types of giraffes had short necks. The considered average giraffes with the long necks, which we have today, were also around the same time as the short neck giraffes.
The short neck giraffes would feed on short trees and shrubs while the “average” giraffe would feed on tall trees. Over the years, the short trees in which the short neck giraffes would feed on got taller and taller and eventually those giraffes began to die because they could not reach the higher food in the trees, and other animals would eat the berries in the leftover short trees and shrubs, leaving them with no food. —The endosymbiosis theory states that eukaryotic cells may have evolved from prokaryotic cells.
Eukaryotic cells may be the descendants of prokaryotic cells.Evidence: The mitochondria and chloroplast have their own cell membranes, just like a prokaryotic cell doesMitochondria and chloroplasts divide by binary fission, just like bacteria doesMitochondria and chloroplast ribosomes are similar in size to prokaryotic ribosomesPart B: Contributing ScientistsJean Baptiste Lamarck vs Charles DarwinLamarck- said change is made by what the organisms want or need- believed evolution happens according to an arranged plan and the results had already been decidedLamarck: Said body parts that are not being used, ex: human appendix or toes, will gradually start disappearing due to the non-usage of them, and eventually people will be born without these parts. Darwin- believed that the desires of animals had nothing to do with how they evolve- believes evolution does not happen according to any sort of planDarwin: Said organisms even of the same species are all different, and those who happen to have alternatives that help them survive in their environments survive and have more offspring. The offspring would be born with their parents helpful traits, and as they reproduce, individuals with that trait make up more of the population.—Thomas Malthus made observations that the human race would be likely to overproduce if the population was not kept under control.He focused his studies on the human raceThe main idea of Malthus’ work was that population growth would always overpower food supply growth, creating constant conditions of hunger, disease, and struggle. Darwin believed that populations grew until they were aligned with existing resources, and then stabilized. Malthus’ work encouraged Darwin to refine natural selection-Georges Cuvier studied elephant fossils.
He did not believe the idea that living members of these fossil species were hanging about somewhere on earth; he claimed that they were separate species that had vanished. Cuvier studied many other big mammal fossils and demonstrated that they too did not belong to any species alive today.The fossil evidence led him to suggest that periodically the earth experienced sudden changes, each of which could wipe out a large number of species. Cuvier noted extinctions as a fact that any future scientific theory of life had to explain. In Darwin’s theory, species that did not adjust to changing situations or withstand the opposition of other species faced annihilation.
Darwin also doubted that species went extinct in great “catastrophes”. Cuvier happened to be correct in this argument. About 99% of all species that ever existed on earth are now extinct. Several times over the past 600 million years, life has experience mass extinctions which may have included volcanic eruptions, asteroids or relatively fast changes in sea level. These extinctions mark some of the greatest transitions throughout everyday life, when new groups of species got the opportunity to take over the place of old ones. Us humans are the “children” of extinctions.Part C: ExtinctionEnd-Triassic ExtinctionThe end-Triassic extinction was a global extinction event occuring at the end of the Triassic Period that resulted in the death of 76% of all marine and terrestrial species, and about 20% of all taxonomy species. The reason for the end-Triassic extinction comes down to a selection of theories.
Many scientists suggest it was caused by climate change and rising sea levels resulting from the sudden release of carbon dioxide. Others suggest the relatively modest heating caused by the release of carbon dioxide in the atmosphere could have liberated massive amounts of methane trapped in permafrost and undersea ice. Methane is a much more effective greenhouse gas than carbon dioxide, it could have then caused earth’s atmosphere to warm significantly. Some maintain that the mass extinction was triggered by the impact of an extraterrestrial body (such as an asteroid or comet). -K-T Extinction or Cretaceous-TertiaryThe K-T extinction was a global extinction event that abolished approximately 80% of all species of animals 66 million years ago.
It was characterized by the expulsion of many lines of species that were vital elements of the Mesozoic Era(252.2 million to 66 million years ago), including nearly all of the dinosaurs and many marine invertebrates. “The only lines of archosaurs – the group of reptiles that contains the dinosaurs, birds, and crocodiles – that survived the extinction were the lineages that led to modern birds and crocodiles.
“Many theories/hypotheses have been suggested over the years to explain dinosaur extinction, but only a few have received serious attention. Proposed causes include heat waves, disease, freezing cold spells, x-rays from a nearby exploding supernova. Since the early 1980s, the “asteroid theory” has received a lot of attention; this theory states that a bolide (meteorite or comet) impact may have triggered the extinction event by ejecting a huge quantity of rock debris into the atmosphere. Another theory people have in mind is one of the same theories in the end-Triassic extinction. That would be the release of carbon dioxide theory. They believe that the carbon dioxide created a global greenhouse effect that greatly warmed the planet (causing horrific heat waves).Others have noted that tectonic plate movements caused a major rearrangement of the world’s landmasses.
The climatic changes resulting from such continental drift could have caused a gradual deterioration of habitats favourable to the dinosaurs and other animal groups that suffered extinction.—The Sea MinkSea minks were semi aquatic animals that lived around the coasts of New England and Atlantic Canada, as far north as Nova Scotia. They used to occupy rocky areas along the coastal lines. This animal is the only other terrestrial mammal species in the order Carnivora to go extinct in historic times; aside from the Falkland Islands wolf. The cause of the extinction of sea minks was by an act of people hunting them for their fur.
They were announced extinct in the 1860s. -Tasmanian TigerAustralia was the home of one of its most fabled species, the tasmanian tiger, also known as the thylacine. The animal went extinct on the continents mainland around 100 years ago.
A small population of thylacines endured in Tasmania when Europeans arrived in Australia. The species was immediately viewed as a pest and a dangerous threat, though many of these claims were highly exaggerated. Over 2000 bounties were paid by the government between 1888 and 1909 to eliminate the species. A sudden decrease in the thylacine population was reported in the early 1900s, and then the species was declared extinct in 1936.Part D: PhylogenyThe WhaleThe modern whale began life as a land animal fifty million years ago. The whale’s ancient ancestor named pakicetus faced a survival crisis. It was the shape, size and weight of a modern wolf, and it lived on a diet of plants and small animals; climate change was wiping out its food supplies.
It had to find a new food source, its only other option was to hunt for fish in shallow waters. And that is how its food crisis was solved.The pakicetus disappears a number of years later and evolves into a new species. How did it evolve into a new species? – Its poor swimming skills made the pakicetus vulnerable, so it adapts in three key ways to swim better; his tail develops muscles and flattens like that of an otter, his back leg shortened and widened to act like flippers, and it becomes more streamlined. This new species is named ambulocetus, which means the walking and swimming whale.Sometime in the ancient past, a whale ancestor evolves the skills to live permanently in the oceans.
If a land animal drinks seawater, it can be lethal.To live in the ocean, the ambulocetus had to adapt to cope with the seawater.When studying teeth you can really get a good idea of lots of different aspects of the life of the animal, such as its diet, where they were living.. in water or on land, and which waters they were drinking. Modern whales can drink seawater, their ancestors with land mammals were freshwater drinkers (the evidence has been proved by the studies done on their teeth), so somewhere that transition had to happen moving from freshwater to seawater. The ambulocetus was a poor swimmer, just like the pakicetus had been.
It would struggle to escape predators and struggle to hunt. This species now evolves a series of adaptations to swim better; it now has a shorter neck more powerful neck better for diving, its rear legs widen and become flipper like, and its tail develops muscles.This new whale lives permanently in the sea – the first whale that took to sea. This new species of whale is named rodhocetus.
The rodhocetus is about ten feet tall. The ancestor of this whale 3 million years earlier had only been able to drink freshwater, now this new species lives in the ocean and spreads out across the globe. The ear is the key to help the rodhocetus escape predators; a vital organ inside of the ear called the organ of balance. The organ of balance consists of three canals at right angles filled with fluid.
The fluid moves when the head moves, nerve cells register and send signals to the brain, the brain instantly decodes these signals and adjusts the body’s balance so it doesn’t fall over. However, acrobatic behaviour causes the liquid in the inner ear to slosh around, ending scrambled messages to the brain which causes dizziness. The inner ear controls balance, but how did it till the balance of survival in favour of the ancient whale? Well, the whales inner ear is so small that the liquid inside barely moves, this allows them to turn and twist at high speeds without getting disoriented.
The rodhocetus survives and evolves. Basilosaurus, an 18 m long 50 foot long whale. Exceptional eyesight, improved underwater hearing, and a long thin body shape to hunt in shallow waters. Weighs in at 13,900 pounds, from the hunted to the hunter. Dorudon also evolved from rodhocetus, most resembles a modern dolphin.
16 feet long, much smaller than basilosaurus, powerful vertebral column, tell fluke, and short flipper shape limbs. To protect themselves from predators, they’d swim in pods.Only one of these species survives to become an ancestor to the modern whale. The large basilosaurus dies out. The cause: 35 million years ago, planet earth is changing dramatically.
Oceans continue to cool, Antarctica has split from South America and develops a permanent ice cap. Water that once flowed down into the oceans remains frozen at the poles, this causes a dramatic drop in global sea levels; shallow coastal waters disappear, forcing the basilosaurus to hunt in deeper waters. Its eel like body struggles in deeper water, it lacks the power to dive. The short and muscular durudon has no such problems, and is the whale species that is left to inherit the earth. For the dorudon species to escape predators such as sharks, they would make their way to polar seas.
They have warm blood so they can handle the cold water, unlike sharks which are cold blooded.Part E: Mechanisms of EvolutionGradualism is selection and transition that happens more gradually. Small transitions that fit an organism slightly better to its environment are selected for : a few more individuals with a greater amount of the accommodating characteristic survive, and a few more with less of the characteristic die. Gradually, over some time, the population changes.
Change is slow, steady and consistent. Ex: a bird is born with a longer beak than others in its population, which allows it to more easily forage for insects inside trees, offering it an advantage over its shorter-beaked relatives. The shorter baked birds die off due to hunger since they cannot scavenge easily with their short beaks.Ex: changes occur among a group of tree frogs which include colour patterns that help them hide from predators and poisonous skin secretions that block predators from seeking them out as a food source. The population of the frogs without these traits would decrease because they were easily visible to predators.
As time progresses, these traits become standard in the population of tree frogs.-Punctuated Equilibrium states that evolution only takes place in bursts of time that are rapid. There is a period of next to no change, and after that one or a couple of enormous changes happen, often through transformations or mutations of the genes of a few individuals. Mutations are unplanned changes in the DNA that are not acquired from the past age, but are passed on to ages that take after. In spite of the fact that mutations are often harmful, the transformations that result in punctuated equilibrium are very helpful to the individuals in their environments. Since these mutations are so distinct and very helpful to the survival of those that have them, the extent of individuals in the population who have the transformation/characteristic and the ones who don’t changes a lot over a short period of time. The species changes very promptly over a few ages, then settles down again for a period of little to no change.
Ex: a species of birds exists in stasis for many thousands of years. Suddenly, a bacteria causes their primary tree of sheltering choice to die. The birds must adapt to trees that are much higher requiring more wing strength. Some birds die, the remaining birds’ bodies adapt as necessary and they return to a state of stasis. Ex: a species of sea animals lives, breeds, and dies for thousands of years. Suddenly, the level changes and the animals must adapt.
Their bodies develop in order to accommodate the environmental change. And from then on are evolutionary different from their ancestors.Part F: Modern EvolutionAcinetobacterAcinetobacter is a group of bacteria that is mainly found in soil and water.
There are many types of Acinetobacter and all can cause human diseases. This bacteria is the cause for about 80% of reported infections. Acinetobacter causes a variety of diseases and infections: pneumonia, meningitis, necrotizing fasciitis, urinary tract infections, bacteremia and sepsis.The bacteria can pass between people on dirty hands or through contact of a contaminated surface or object. Once it is inside the body, a person with an already weakened immune system, like a hospital patient, are most likely to become infected.
People with the conditions such as diabetes, lung disease, or autoimmune disorders have an increased chance of getting infected. Antibiotic resistance in acinetobacter is increasing rapidly. The bacteria possesses two intrinsic beta-lactamase genes, in addition to weak permeability and efflux systems, that together confer a natural reduced susceptibility to antibiotics. Numerous acquired mechanisms of resistance have been identified in acinetobacter.