Lecture 1 1 1 Biodiversity the variety of life Biodiversity can refer to habitat diversity species diversity and genetic diversity Genotype set of genes carried by an individual Phenotype expression of a trait in an individual influenced by both genes and the environment they experience Most important discovery of a unifying principle of life was the theory of evolution by natural selection by Charles Darwin and Alfred Wallace in the 19th century There are between 1 5 and 2 million species that have been named Largest number of species of life are members of the insect group Particularly diverse groups of species include beetles insects in general over 1 000 000 named species and plants over 300 000 species There are only 50 000 species of vertebrates Species population or group of populations of organisms that are very similar to one another and share a recent evolutionary history No single definition of a species in biology Reasons Different biological characteristics of different types of organisms Don t form instantly Amount of information about species is different in different situations Linnean system of classification organizes species into larger named groups and given several named ranks Given name known as a binomial two names Genus first name and Species second name Three domains of life bacteria archea and eukarya For the majority there are more species in the tropics than in temperate or polar regions The closer to the equator in general the more species there are Species richness number of species occurring in a particular area Scientists think of diversity as a composite of both the number of species and the evenness of abundance of the different species Ultimate explanation for biological diversity is evolution Evolution typically follows a branchlike pattern known as a phylogeny Usually evolution doesn t result in one species replacing the other but rather one species becoming two different species Every species of life is dependent on other species in their ecosystem as well as the abiotic non living environment Species are often defined by the ability to interbreed Ecosystem services different species take on different roles in an ecosystem Oxygen fresh water or food that is provided by an ecosystem 1 2 1 3 1 4 Biophilia attraction to elements of the natural world Comparative method biologists compare different forms of life to reveal the relationship between form and function New use of the comparative method is part of the field of genomics Genomics is the study of the molecular structure of many genes at the same time Genome entire set of genetic material in a cell Differences in genes are the fundamental basis for biodiversity Allele particular version of a gene having different alleles for particular genes is the source of genetic variation among individuals A gene is made of a DNA sequence consisting of a particular set of molecules called nucleotides that are strung along the DNA in a particular order The sequence is related to the function of the gene To sequence a genome means to work out the order of all nucleotides for all the genes and other parts of the DNA Mass extinction events periods in which biodiversity has dramatically declined Causes of the mass extinctions are not known with certainty but they are associated with fairly sudden changes in the climate of earth Human made changes such as habitat loss from human activities degradation of habitat due to pollution movement of invasive species around the world exploitation of natural populations for human use and climate change Lecture 2 2 1 Population groups of individuals of the same species living in the same area Two main measurable characteristics of population are mean and standard deviation measure of the amount of variation in a population Populational each individual in a population is being influenced by many factors that interact in complicated ways Typologically assign things to categories and expect them to fit into those Population variation can make the link between cause and effect less than categories straightforward Charles Darwin evolution by natural selection Sailed on the Beagle to South America and the Galapagos Islands Alfred Russel Wallace learned about biodiversity through his travels to the Amazon and Southeast Asia 1 6 1 7 1 8 2 2 2 3 2 4 2 5 2 6 3 1 3 2 Darwin had two major contributions to the concept of evolution 1 natural selection 2 branching pattern of evolution from a common ancestor Variation among individuals in a population is the fundamental basis of Darwin s ideas Darwin had the following types of evidence available to him life on islands homology comparative anatomy fossil record and selective breeding Natural selection doesn t act on characteristics that don t occur in nature Three different ways natural selection can act on a population are stabilizing directional and disruptive selection Stabilizing individuals with characteristics close to the mean are the most successful and have the most offspring Directional individuals at one end of the distribution are more successful and individuals at the other end are less successful Disruptive individuals close to the mean do the worst and those at the extremes do best one way of producing two forms of life from one Another way of producing divergence is geographic separation Species are most commonly formed through geographic isolation Evidence for the formation of species comes from several sources fossil record 1 2 Species on islands 3 Observations of populations in the process of speciation 4 5 Genetic similarity Instantaneous speciation DNA data was an important test of the idea of evolutionary descent from a common ancestor Lecture 3 Second source of diversity ecological interactions Ecology study of interactions between organisms and their environment Temperature seasonality and rainfall determine the climate of any particular spot on earth other than oceans Mediterranean climate temperatures highest in summer and almost all precipitation is in winter Arid or desert climate most precipitation falls during summer The effect of local factors such as shade soil type and slope are called micro Seasonality is important in distinguishing the desert and Med habitats climate Areas of the world with similar climates have similar habitats biomes 3 3 3 4 3 5 3 6 Ecological niche particular set of environmental conditions that each species has in which it normally occurs specific types of organisms live in
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