What is a species? How do new species arise? What is the difference between the graduated and punctuated theories of speciation?
What is a species? How do new species arise? What is the difference between the graduated and punctuated theories of speciation? Speciation and evolution are topics in biology which are contentious and open to debate. New evidence is continually being found which reshapes our ideas about the mechanisms and patterns of speciation. There is much controversy over many aspects of this topic, from the question, 'what is a species?', to the pattern in which these new species arise. Darwin was the first to powerfully attack the idea of creationalism in 1959, and since this date his theory of evolution by natural selection has dominated. Darwin sparked an explosion in research in this area, and in 1972, Niles Eldredge and Stephen Jay Gould put forward the idea of punctuated equilibrium. This suggested that evolution was not a slow continuous additive process as Darwin had thought. The theory of punctuated equilibrium states that there are long periods of time where little of no morphological change occurs, punctuated by short periods of rapid change in which speciation occurs. As the fossil record grows, and more theoretical research is done, we will be able to more accurately asses the importance of Punctuated equilibrium as opposed to gradualism as the theory of speciation. There are many different definitions of the term 'species'. Creationists believe that species are discrete
) Explain how natural selction may bring about changes in a population and what conditions may be necessary to bri about speciation
a)} How may Variation Arise in Natural populations b) Explain how natural selction may bring about changes in a population and what conditions may be necessary to bri about speciation A species is a group of organisms that look alike and can reproduce successfully to produce fertile offspring. Within a species there is variation which can be caused my meiosis, random fertilisation, mutations and the natural environment. Genetic variation increases the chance for survival of a population if the environment changes. For example the introduction of a new virus in to the new environment may kill some organisms but others may be resistant to it and survive. If all the organisms had been genetically identical they may have all been killed. The species that survive are likely to live longer and pass on their useful genes to future generations. The change in a species over time is called evolution. There are two types of variation; continuous and discontinuous variation. Discontinuous variation is when there is a complete range of measurements from one extreme to the other for a normal characteristic, such as human height. Discontinuous variation is where characteristics are fit into separate categories with no intermediates such as human blood groups. During the process of meiosis each homologous pair of chromosomes aligns independently along the equator and whether the
When One Becomes Two
When One Becomes Two How can two organisms look exactly alike, yet be members of different species? This is the question that I was confronted with when studying two rodent populations of the St. Kitt's and Nevis Islands. As an expert in the field of mammalian reproductive strategies, I was hired by the Department of Nature and Island Resources of the West Indies, to investigate a previously undiscovered species of rodent.(1) The rodent population on St. Kitt's was very small and threatened. My goal was to find a way to replenish this population and help to prevent extinction. When I first arrived in the area, I observed that the population of a rodent appearing identical to the St. Kitt's rodent inhabited the island of Nevis.(1) I took note of the fact that the Nevis population was strong and healthy, relatively unaffected by the development threatening the St. Kitt's rodents. In an effort to reestablish the St. Kitt's population, I brought animals from Nevis to St. Kitt's hoping they would mate with each other and increase the population of rodents. Unfortunately, I was unable to observe a single successful reproductive event.(1) In order to understand why the two groups could not successfully mate, it was necessary that I understood the biological factors categorizing separate species. There are different ways in which biologists can define a species, one of the most
Evolution, Natural selection and Darwinism
Evolution, Natural selection and Darwinism Introduction Evolution refers to the processes that have transformed life on Earth from its earliest forms to the vast diversity that characterizes today. <Ref.1 - p414> Up until eighteenth century, biology in Europe and America was dominated by natural theology. <Ref.1 - p415> People believed that a supernatural being like God created each and every species as it is now for a particular purpose, at a particular time. However there are differences in people's interpretation of the length of the "day" mentioned in Genesis. Some Christians believe that the day was of 24hours and the world was created in 6 days. In 1650AD, Archbishop Ussher of Armagh calculated that God, created the world in October 4004BC, beginning on October the 1st and finishing with Man at 9:00am, which is not possible as we have no, archaeological evidence that suggest that a civilised life was already established in the Middle East by then. <Ref.2 - p879> Alternatively, there was the theory of spontaneous generation. A number of Greek philosophers believed in he gradual evolution of life. Amongst those philosophers, Plato (427BC-347BC) and Aristotle (384BC-322BC) influenced the western cultures the most. Plato believed in two worlds: a real world that is ideal and eternal, and illusory world of imperfection that perceive through our senses. He believed that
Evolution Revision Notes
Evolution- Revision for test 11/03/13 Specification- . define the term variation 2. discuss the fact that variation occurs within as well as between species. 3. describe the differences between continuous and discontinuous variation, using examples of a range characteristics found in plants, animals and microorganisms. 4. explain both genetic and environmental causes of variation. 5. Outline the behavioural, physiological ad anatomical (structural) adaptations of organisms to their environments. 6. Explain the consequences of the four observations made by Darwin in proposing his theory of natural selection. 7. Define the term speciation. 8. Discuss the evidence supporting the theory of evolution, with reference to fossil, DNA and molecular evidence. 9. Outline how variation, adaptation and selection are major components of evolution. 0. Discuss why the evolution of pesticide resistance in insects and drug resistance in microorganisms has implications for humans. Variation Individuals within a species have many differences; this is known as intra-specific variation. Variation within a species has two causes- an organism’s genes and its environment. Genetic Variation Some of the variations between individuals within a species are caused by differences in their genes- genetic variation. Alleles – Different varieties of a gene for a particular
Evolutionary Arms Races.
Evolutionary Arms Races "...Thus I can understand how a flower and a bee might slowly become, either simultaneously or one after the other, modified and adapted in the most perfect manner to each other, by continual preservation of individuals presenting mutual and slightly favourable deviations of structure." (Origin of Species, 1857) Darwin was describing the interactions between organisms that result in reciprocal changes in traits (i.e. morphology, behaviour and physiology) over evolutionary time. He termed this phenomenon "co-adaptation". Over time, however, this term has become known as co-evolution, and the meaning of co-evolution has been refined. It defines an evolutionary change in trait(s) of the individuals in one population in response to a trait in the individuals of a second population, followed by an evolutionary response by the second population to the change in the first. This distinguishes coevolution from simple adaptations of organisms to their abiotic and biotic environment. For example, an insect herbivore that has the ability to detoxify certain secondary metabolites in the tissues of its host plant may not necessarily be "co-evolved" with that plant: the secondary metabolite might be present for a variety of reasons (i.e. not just herbivory), or the insect may have had its detoxification mechanisms in place before encountering the host plant in
The Concept of a Species.
Classification The Concept of a Species. Definition: Species (Collins Dictionary): Said "spee-sheez" NOUN a class of plants or animals whose members have the same characteristics and are able to breed with each other. There is no simple definition for a 'species'. The recently founded idea that species may 'evolve' gradually over time has changed the concept of a species. Before the idea of evolution, it was believed by almost everyone that a God created all species individually, and that they were fixed and unchanging. But later, much evidence such as the fossil record and extensive studies on the adaptations of certain creatures found by scientists, including Charles Darwin, led more and more people to believe that species have evolved very gradually over long periods of time. And because of this, the concept of a species has been modified. Ernst Mayr, one of the founders of modern evolutionary philosophy and theories defined biological species as: "Groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups". This definition is also known as the biological species concept (BSC). Advocates of the BSC say that forms that are only slightly different (for example different geographical forms) may interbreed if they had the opportunity. Therefore they should be considered as the same species. However,
Biodiversity Notes for Biology
Biodiversity, Evolution & Natural Selection Notes Biodiversity: * Variety of different organisms within a habitat. Two aspects to consider are: * Species richness: the number of different species within an area of known size at a particular time. A species is a group of organisms with so many features in common that they can mate and produce fertile offspring. * Genetic diversity: the genetic variation within a species Endemism: * Where a species is found in only one particular area * The ring tailed lemur is restricted to the island of Madagascar, so is endemic to Madagascar * Happens because the organism evolved within the region hasn’t migrated out to other areas Molecular phylogeny : * Compares the structure of a particular molecule from different organisms to discover their degree of evolutionary relatedness * The more similar the structure of the molecule, the more closely related the organisms are because changes in molecule structure generally occur slowly as they are caused by mutations * The three domains are archaea, bacteria and eukaryota Niches: * The niche of a species is the way that the species exploits its environment * If two different species are present in the same niche at the same time, there will be competition and one will out compete the other so that the better adapted will survive Types of adaptation: * Anatomical: a
The Genetic Code
The Genetic Code Essay Question The Genetic Code is made up of the nucleic acids Deoxyribose (DNA) and Ribose (RNA), which are polymers of nucleotides. A nucleotide is a section of DNA made up of three molecules, a five-carbon sugar, a phosphoric acid molecule and a nitrogen containing organic base, which are all joined by condensation reactions. DNA differs from RNA in a number of ways. Firstly DNA consists of two polynucleotide strands, which are joined together by hydrogen bonding which forms a double helix, whereas RNA consists of one single polynucleotide strand. In DNA there are the four bases in Cytosine, Guanine, Thymine and Adenine, whereas in RNA Thymine is replaced by Uracil. The bases join together according to complementary base pairing, A to T/U and C to G, because this is the correct length. The DNA helix is a store of genetic information controlling the synthesis of proteins and the development and structure of them. The sequence of three nucleotide bases is called a base triplet and each of these triplets' codes for the 20 commonly occurring amino acids in living organisms. The base triplets of mRNA are known as codons and the genetic code is degenerate because some amino acids are coded for by more than one codon. The Genetic code has to undergo DNA replication because this is essential for the growth and reproduction of organisms. DNA replication occurs
Discuss the major factors contributing to current reductions in global biodiversity.
Olivia Finch Discuss the major factors contributing to current reductions in global biodiversity. Biodiversity is the blanket term for the natural biological wealth that undergirds human life and well-being. Global biodiversity therefore covers a huge range of factors that occur on a vast spatial and temporal scale, making any assessment of biodiversity loss a complicated matter. The term biodiversity represents a complex interplay of species, genes and ecosystems, all three of which are necessary for the continued survival of species and natural communities (Primack, 2000). Any loss of biodiversity is therefore most usually manifested in species extinction and thus knowledge of extinction patterns is essential for determining rates of biodiversity loss. In 1993 the US Nature Conservancy stated that 'today, species are becoming extinct at a rate faster than at any time in the Earth's history - one species per day'. Such unprecedented and irreversible loss of species has had the effect of reducing global biodiversity. Throughout human history, species richness and global biodiversity has decreased as human populations have grown, and for this reason current reductions in global biodiversity are blamed almost exclusively on human actions. It is necessary, therefore, first to identify which human activities have affected the stability of biological populations and driven
