Evolution Test Notes Giulia Palazzo • THE HARDY- WEINBERG PRINCIPLE: - a mathematical equation created to predict genotype and phenotype frequencies in a population that is not experiencing any selective pressure, if model fails evolution must be occurring - Under Mendel’s model, the two alleles can be represented by... p + q = 1 (100% of the alleles in the population) where p is the dominant allele and q is the recessive allele - The genotypes can be represented by the equation (p+q)² = p² + 2pq + q² = 1 (100% of the genotypes in a population) where p² is homozygous dominant, 2pq is heterozygous and q² is homozygous recessive • FACTORS AFFECTING HARDY- WEINBERG: 1. GENETIC DRIFT- change variations in the allele frequencies of a (small) population 2. GENE FLOW- the movement of alleles into and out of a population through immigration and emigration 3. MUTATION- the creation of new (beneﬁcial) alleles through sudden, random changes in the nucleotide coding of a gene 4. SELECTION- the differential survival of individuals based on more favourable phenotypes (in a given environment) 5. FOUNDER EFFECT- genetic drift that results when a small number of individuals separate from their original population and establish a new population • TYPES OF NATURAL SELECTION: - DIRECTIONAL SELECTION - selection for individuals at one extreme of the phenotypic bell curve - DISRUPTIVE SELECTION - selection for individuals at both phenotypic extremes and against the common intermediate form - STABILIZING SELECTION - continued, or even greater selection for the common intermediate form - SEXUAL SELECTION - is a form of directional selection in which individuals of a certain gender develop traits that enhance their reproductive success - KIN SELECTION - occurs in social organisms (eg. bees) where some individuals sacriﬁce their reproductive success to enhance the reproductive success of of their close relatives. • REPRODUCTIVE ISOLATING MECHANISMS: includes various barriers that prevent one species of organism from routinely and successfully interbreeding with a related species of organism. Potential reproductive isolating mechanisms include:
- SPATIAL/ GEOGRAPHICAL ISOLATION - ENVIRONMENTAL ISOLATION A. habitat isolation= different habitats B. Niche Isolation= different niches within the same habitat - REPRODUCTIVE ISOLATION A. Pre-mating Isolation/Prezygotic mechanism a reproductive isolating mechanism that prevents interspecies mating and fertilization (for example, ecological isolation, temporal isolation, ethological and behavioural isolation) i. Temporal Isolation- different breeding times during the year (seasonal isolation), or different breeding times during the day (diurnal isolation) ii. Ethological Isolation- differences in mating behaviours or rituals iii.Mechanical Isolation- lack of compatibility between the reproductive organs iv.Gamete Isolation- lack of attraction between sex cells (particularly in externally fertilizing organisms) v. Ecological Isolation-Very similar species may occupy different habitats within a region. B. Post-mating Isolation/Postzygotic mechanism a reproductive isolating mechanism that prevents maturation and reproduction in offspring from interspecies reproduction i. Fertilization- biochemical differences preventing penetration of the egg by the sperm (pre fertilization), or preventing mitosis of the zygote (post fertilization) ii.Hybrid Inviability- breakdown of the developing embryo due to biochemical incompatibility iii.Hybrid Sterility- inability of the adult organism to produce viable sperm or egg due to genetic, chromosomal, or cytoplasmic differences iv.Hybrid Breakdown- development of sterile individuals in subsequent generations due to genetic, chromosomal, or cytoplasmic differences • MODES OF SPECIATION: Speciation, is the creation of new species. Macroevolutionary events (ie. those that produce new species) rarely result from a single phenotypic characteristic. Instead, such events generally...
Links: gaps in the fossil records; this is more likely due to punctuated equilibrium.The changes were too rapid, so the fossilization of each change in the species that led to the creation of the new species were not preserved. • MACROEVOLUTION- large-scale evolutionary changes including the formation of new species and new taxa • CUMULATIVE SELECTION- a series of rare, but beneﬁcial mutations accumulate over time to produce a complex feature where previously there was none • STRUCTURAL ADAPTATION: A characteristic in a plant or in an animal’s body that helps it to survive in its environment. Examples are protective coloration (camouﬂage) and the ability to retain water. • FUNCTIONAL ADAPTATION: ?? • TAXONOMY- the science of classifying all organisms; taxonomists classify both living and fossil species - TAXON a category used to classify organisms - KINGDOM the highest taxonomic level of the traditional Linnaean system of classiﬁcation - GENUS- a taxonomic level consisting of a group of similar species
- BINOMIAL NOMENCLATURE- the formal system of naming species whereby each species is assigned a genus name followed by a speciﬁc name; the two words taken together form the species name • PHYLOGENY: Phylogeny is the branch of taxonomy that attempt to determine the evolutionary relationships between different groups of organisms. It is based on a methodology known as cladistics, which uses the presence or absence of evolved traits in the groups being compared to determine the extent of relatedness between them. These evolved traits, or synapomorphies, can be structural,developmental, biochemical, or genetic. • EMBRYOLOGICAL DEVELOPMENT- with the exception of the most simple of multicellular organisms proceed through a series of developmental stages from the time of fertilization to the emergence of the “mature” individual. Through these embryonic stages vary tremendously in their duration and degree, they serve as a useful basis of comparison, particularly between more closely related organisms. In terms of drawing conclusions regarding the relatedness of organisms, the idea is fairly simple; the more resemblance in the embryological development of two organisms, the more closely related they should be considered to be in terms of their evolutionary history. • BIOCHEMISTRY- a term relating to the basic chemicals and chemical reactions that support life. In terms of biochemistry, the comparison between organisms can be made by modern cladistics the tend to focus speciﬁcally on he proteins found within the organisms. - ex. biochemical relatedness comes from the protein cytochrome c, one of the principle proteins involved in the process of cellular respiration. When compared to their assumed closest relative the chimpanzee, humans are found to possess an identical sequence of amino acids in terms of their cytochrome c structure. This exact match is not found between humans and any other organisms. • GENETICS- most speciﬁc point of comparison between organisms is at the genetic level. Genetic analysis of organisms may involve comparison at a more general level, such as chromosome number and/or gene location, or it may involve more ﬁne comparison of the nucleotide content of speciﬁc genes or of noncoding portions of DNA (eg. SINEs and LINEs). Organisms with more similar genetic composition are assumed to have a more common evolutionary history.
• CLADOGRAMS- the relationship between the groups of organisms being considered as summarized in a phylogenetic tree, or cladogram. Cladograms not only predict relatedness but they can also indicate: - “when” synapomorphic traits were developed - Whether a group is extinct or “extant” - The rate of evolutionary change- i.e. whether the divergence of the groups was slow and gradual or more abrupt • ARTIFICIAL SELECTION: directed breeding in which individuals that exhibit a particular trait are chosen as parents of the next generation; artiﬁcial selection is used to produce new breeds or varieties of plants and animals - Artiﬁcial selection is limited by the genetic variability within the breeding population. - Artiﬁcial selection methods can reduce the overall genetic diversity of the population and therefore contribute to the loss of biodiversity. • HOMOLOGOUS FEATURE a structure with a common evolutionary origin that may serve different functions in modern species (for example, bat wing and human arm) • ANALOGOUS FEATURE a structure that performs the same function as another but is not similar in origin or anatomical structure; for example, bird and insect wings • VESTIGIAL FEATURE a rudimentary and non-functioning, or only marginally functioning, structure that is homologous to a fully functioning structure in closely related species • DARWIN’S OBSERVATIONS1. Individuals within a population vary in their displayed characteristic 2. Many displayed characteristics are heritable 3. Organisms produce more offspring then are able to survive 4. Resources available to a population are limited 5. Populations of organisms do not increase in size indeﬁnitely From there observations he concluded: - there is competition within a population for the limited resources - individuals with more beneﬁcial characteristics have a greater chance of surviving and reproducing ; Darwin referred to this as “ﬁtness” - Ultimately, more beneﬁcial characteristics increase in frequency of future generations
• DARWIN’S EVIDENCE FOSSIL EVIDENCE: - increasing complexity through time - procession of forms GEOGRAPHICAL DISTRIBUTION - related, but distinct forms on oceanic islands - relatedness between island and continental forms ANATOMICAL FEATURES - homologous structure (divergent evolution) - vestigial structure - analogous structure (convergent evolution) ARTIFICIAL SELECTION • SCIENTISTS THAT INFLUENCED DARWIN JEAN-BAPTISTE LAMARK - ﬁrst principle was that of use and disuse. He believed that structures an individual used became larger and stronger, while structures that were not used became smaller and weaker. Evidenceathletes train and their muscles respond by getting stronger and increasing in size. - Lamarck’s second principle was the inheritance of acquired characteristics. Lamarck believed that individuals could pass on to their offspring characteristics they had acquired during their lives. He believed, for example, that if an adult giraffe stretched its neck during its lifetime, then its offspring would be born with slightly longer necks. GEORGE CURVIER - ﬁrst one to document extinction - theory of catastrophism: catastrophes happen and species go extinct, God replaced the extinct forms with new forms CHARLES LYELL (father of modern geology) - revolutionized geology with his theory of uniformitarianism/actualism - uniformitarianism the theory that geological changes are slow and gradual and that natural laws and processes have not changed over time - gave a much longer time frame (life span) in terms of the existence of the earth ARISTOTLE
- “ladder of life” every species has their place on the change, it is set by God and can not move from the chain of being (unchanging position of species). Hierarchy of species.
AUGUSTINE OF HIPPO - believed in God, but said that the creation stories should not be taken literally - organisms were created by God, but the organisms were able to adapt - decomposition theory- current organisms decompose to become new organisms AL- JAHIZ - was all about the environment, realized the struggle of existence between organisms - struggle of existence, the environment (environmental pressure) would determine who is stronger and therefore who could survive ROBERT MALTHUS - studied populations, said that there is a struggle for existence - at some point the population is going to over power (there is a maximum number of species in a population) the availability of resources - the population grows at an exponential rate CAROLUS LINNAEUS - father of taxonomy, came up with the binomial nomenclature - did not believe in the changeability of species JAMES USHER - deﬁned creation october 23, 4004 B.C., by studying the bible - he thinks that Earth is less than 6000 years old - theory of creationism **Mr. Kerr thinks species change**
Summarize in one sentence Darwin’s theory of natural selection: Individuals who are more able to survive pass on their traits to future generations.
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