Classification Five kingdoms Binomial system of nomenclature system
Classification Five kingdoms:
Binomial system of nomenclature: system devised by Carl von Linné giving organisms two names, the genus and another specific name Species: species refers to individuals that can interbreed to produce fertile offspring. Variations: Different form of something. Variations that increase chances of survival may also be thought of as adaptations.
Biodiversity Variation in the many different communities and their environments on Earth Species diversity: the number of different species within an ecosystem Genetic diversity is important because it codes for variations of phenotypes, some of which may better suit the individual organism to a particular environment than others, giving it an increased chance of survival.
Mutation can occur in all organisms and is the source of new genetic variation. A change in the genetic code in DNA can lead to a change in the protein that is coded for and produced by that segment of DNA. This can change the organism’s characteristics.
Variation between individuals Variation can occur during meiosis due to crossing over of sections of maternal and paternal chromosomes. The combination of gametes that fuse together during fertilisation provides another source of variation The selection of a particular mate causes the variation as well.
Learning Intentions: To be able to understand different type of adaptations and How organisms adapt themselves to the environment for survival.
Adaptations An adaptation may be considered to be a special feature or characteristic that improves an organism’s chance of survival in its environment. There are three types of adaptations: Structural adaptations Functional adaptations Behavioural adaptations
Structural adaptations: Structural adaptations are physical adaptations. They can take many forms. Many animals are camouflaged to blend with their background so that predators cannot see them. Some animals resemble objects such as leaves, twigs or even bird droppings. Some extremely colorful animals look like they would be easy prey. These animals usually sting, taste bad or are poisonous and their bright appearance warns predators to stay away With some animals it is difficult for a predator to tell which end is which. The predator attacks the wrong end, giving the prey a chance to escape. A tricky variation is the ‘mimic’. The mimic is not dangerous to predators, but has copied the colorings of another dangerous animal, so that predators avoid it. Some animals have features that make them look larger and more frightening to predators; for example, the neck frills of some lizards can be opened to make the head seem like that of a much larger lizard.
Functional adaptations affect how the internal functions of an animal work. Their internal function changes depending on their immediate environment. For example, the chameleon changes color to blend with changing backgrounds e. g. ability to produce concentrated urine to conserve water
Behavioral adaptations involve the way an animal acts. They too can take many forms. Some animals sit very still or move slowly to avoid predators Others are active only at certain times of the day or year to avoid unfavorable conditions such as extremes of heat or cold Some collect and store food for future use. Many larger animals form herds to provide some protection from predators. Some have learnt to use tools to access food that is hard to get at; for example, chimpanzees commonly use broken twigs to extract termites.
Theory of evolution A theory about how change occurs in the inherited characteristics of a group of organisms
Natural selection Darwin’s theory was different from others in that it included a process by which evolution could occur. Although this process is often referred to as ‘survival of the fittest’, he called it natural selection. He believed that by this process a single species could have given rise to many new species, and that these new species were much better suited to the environment in which they lived.
Natural selection proposes the following: There is variation of inherited characteristics in a species and some of these variations will increase the chances of surviving in a particular environment. In the struggle to survive, those members with favourable traits will have an increased chance of survival over others. Surviving members have an increased chance of reproducing and passing on their inherited traits to their offspring. Over time and many generations, organisms will possess traits that are better suited to their environment and increase their chances of survival.
Natural selection Survival of the fittest is more than having muscles, being tough or working out at the gym. It’s about being better suited to a particular environment and having an increased chance of surviving long enough to be able to have offspring that will take your genes into the next generation. Can you see the butterfly in this image?
The mechanism for evolution Darwin and Wallace’s theory of evolution included the suggestion that the mechanism for evolution was natural selection. The three key terms that help us to understand this idea are variation competition and selection
Variation More individuals are produced than their environment can support and that individuals within populations are usually different from each other in some way — they show variations. Some of these variations will provide an increased chance of survival over other variations. In other words, some variations will provide individuals with a competitive advantage. Individuals that possess a favourable variation (or phenotype) will have an increased chance of reproducing and passing on this variation (through their genes) to their offspring. Inheritance of this variation (or phenotype) will also increase the chances of survival of the offspring and hence the possibility that they will contribute their genes into the next generation. Over time and many generations, if this variation continues to provide a selective advantage, the number of individuals within a population that show the favourable variation will increase. Individuals that have less favourable variations or that are not as well suited to their environment will not be able to compete as effectively. They may die young or produce few or no offspring. Therefore they will have a limited contribution to the gene pool of the next generation. This will lead to a decrease in the number of individuals with that particular variation within the population.
Selection Organisms live within ecosystems, which are made up of various living (biotic) and non-living (abiotic) factors. These factors contribute to selecting which variations provide the individual with an increased chance of surviving. It is for this reason that these factors may be referred to as selective pressures or selective agents. Biotic factors that may act as selective agents include predators, disease, competitors, prey and mating partners. Examples of abiotic factors include temperature, shelter, sunlight, water and nutrients.
Competition Individuals within a population compete with each other for resources such as food, shelter or mates. Those with a selective advantage over other individuals are better able to compete for the resource. There may be situations in which competing is not about resources, but about competing to not be eaten by a predator or killed by a particular disease. In this case, individuals with a particular variation that reduces their chance of being eaten or killed will have a higher chance of survival.
Evolution is the gradual development of different species from a common ancestor. Modifications and adaptations in species over a period of time. The theory of biological evolution states that life on Earth has changed over time.
Early theories of evolution Up until the late 1700 s, most scientists believed that the different types of organisms and their characteristics had been fixed for all time French naturalist Georges Buffon (1707– 88), suggested that species could change. Erasmus Darwin (1731– 1802), also suggested that one species could change to another, but he had no evidence to support his ideas.
Lamarck’s theory French naturalist Jean Baptiste Lamarck (1744– 1829) thought that the species were evolving. Lamarck believed that organisms adapted through their struggle to survive. In 1809 he suggested that: Organs are improved when used repeatedly and weakened when not used. These changes are called acquired characteristics. Working out at the gym develops the acquired characteristic of larger muscles. Playing music or computer games develops the acquired characteristic of improved hand– eye coordination Any improvements (or weaknesses) developed due to the environment are passed on through reproduction to the next generation of individuals.
Lamarck suggested that the long necks of giraffes, for example, developed because giraffes stretched their necks to reach food high in the trees. The acquired characteristic of a long neck was then inherited by their offspring, which would then be born with long necks. Is it true?
Darwin’s theory On the Galapagos Islands, Darwin marveled at the diversity in the flowers, tortoises, iguana and birds found there. Much of the wildlife differed in small but significant ways from island to those on the mainland The islands were effectively isolated from one another by strong ocean currents, and there were no winds blowing from one island to another. Darwin found fourteen species of finches, all with similar colorings, calls, nests, eggs and courtship displays. They differed, however, in habitat, diet, body size and beak shape. Darwin believed these fourteen species had come from a common ancestor, and proposed the process of natural selection to explain it.
He suggested that a few finches had arrived at the islands at some time in the past. These finches showed natural variation in their beak shape. On one island, those with beaks of one shape were better able to feed on the cacti found there. Finches with other beak shapes found it difficult to survive. On other islands, other beak shapes gave some finches a feeding advantage. The birds most suited to their island survived to produce offspring, which inherited that beak shape. This is sometimes called survival of the fittest. The ‘fittest’ were the birds that were able to feed and reach breeding age. The beak type that gave particular birds on a particular island an advantage was ‘selected for’. Over many generations, the birds on different islands became sufficiently different from each other to be recognised as a different species.
Darwin’s theory can be restated in terms of modern genetics. Evolution is natural selection based upon the natural genetic variation that appears in all populations
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