Study Guide 1- Midterm
Study Guide 1- Midterm Anth 1001
Popular in Biological Anthropology
Popular in anthropology, evolution, sphr
This 18 page Study Guide was uploaded by Jaimee Kidd on Thursday February 18, 2016. The Study Guide belongs to Anth 1001 at George Washington University taught by Shannon C. McFarlin in Spring 2016. Since its upload, it has received 100 views. For similar materials see Biological Anthropology in anthropology, evolution, sphr at George Washington University.
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Date Created: 02/18/16
What is Biological Anthropology? • Anthropology is the study of humankind in a cross cultural context Origins of Evolutionary Thought Science: An approach to gaining information about natural phenomena through observation and experimentation • Science is empirical meaning it is based on knowledge gained through observation • Scientific Method consists of an observation, hypothesis, hypothesis testing, and eventually a theory • Scientific Theory is an explanatory framework that has been repeatedly tested, is supported by an overwhelming amount of consistent evidence and has yet to be disproved. Evolution • Ancient Greek Thought ◦ Anaximander notion of change; humans and other animals descended from fish ◦ Plato species have a defining essence that is fixed and unchangeable ◦ Aristotle organized diversity into a great chain of being with humans at the top • European Middle Ages ◦ Theme: Conceptualization of a Static World; scientific knowledge was monopolized by religious institutions ▪ Argument of Design God was able to create the most perfect beings that there would be no need for them to change, examples used such as the invertebrate eye and its complexity of lenses and structure • 16th19th Century Eastern World ◦ Li ShihChen binomial system of naming organisms • Renaissance ◦ Da Vinci plays a big role in gathering extensive information on the human body, anatomy, and dissection ◦ Galileo notion of change becomes more acceptable ◦ John Ray Species defined, first person to use a biological perspective to define what a species is ◦ Carolus Linnaeus hierarchical system of classification with organisms grouped on the basis of similarities ◦ Compte De Buffon change in response to new climates ◦ Jean Lamarck first to propose a mechanism of evolutionary change to explain biological diversity ▪ theory of inheritance of acquired characteristics ◦ Georges Cuvier catastrophism ◦ Charles Lyell Uniformitarianism Basic PreDarwin Developments in Short • Appreciation of diversity in the natural world, and methods of classifying diversity • concept of species • notion of organic change • environment as an important agent of organic change • ancient origin of the natural world Darwin • Experiences that Influenced Darwin’s Thinking ◦ Observation of diversity of flora and fauna on his voyage ▪ created many and very detailed notebooks of what he had observed— although it wasn’t until years after the voyage that he understood the significance of his observations ◦ Experience of an earthquake while in Chile ▪ he became convinced that the Earth was dynamic and changing instead of the norm of thought that the earth was static and unchanging ◦ In Argentina, Darwin collected fossil bones of extinct animal forms. ◦ Observation of diversity in ground finches across the Galapagos Island chain ▪ noted that the plants and animals in the galapagos carried traits that he observed in the main land, but also carried differences as well ◦ His reading got Thomas Malthus’ An Essay on the Principle of Population (1798) ◦ Observation of the power of artificial selection by plant and animal breeders ▪ Modern day example: dog breeding Thomas Robert Malthus An Essay on the Principle of Population • Human populations have the ability to increase exponentially at a faster rate than food production ◦ However, populations around the world the dot be stable • There is a “struggle for existence" • Those that survive do because they can out compete others for the available resources Darwin concluded that individuals of a species with particularly advantageous characteristics (adaptations) would be more likely to survive in limiting conditions, and would thus reproduce more successfully than individuals with less advantageous attributes. Darwin Develops his Theory of Natural Selection 1836: Darwin returns from the voyage of HMS Beagle 1844: Darwin prepares his first lengthy “sketch” on his theory of evolution by means of natural selection. 1858: Darwin receives a manuscript, in which Alfred Russel Wallace had independently conceived of evolution by means of natural selection. 1858: Darwin and Wallace present their ideas to the Linnean Society in London, detailing their proposed mechanism for evolutionary change. “On the Origin of Species by Means of Natural Selection” Charles Darwin (1859) • Main Themes: ◦ Biological evolution is fact. ◦ Common descent, with modification. ◦ Gradualism. ▪ differences between organisms evolved by innumerable small steps over time through many intermediate forms—basic idea that evolution takes time and it occurs gradually and incrementally. ◦ Natural Selection is the mechanism of evolution. Natural Selection: The Mechanism • OBSERVATION: Species produce more offspring than can be supported by available food resources ◦ DEDUCTION: Limited resources leads to competition between individuals of a species. There is a “struggle for existence" • OBSERVATION: There is biological variation among individuals of a specieis. the characteristics of some individuals appear more favorably adapted to their environments than those of tothers. ◦ DEDUCTION: Differential survival and reproduction of those individuals with more favorable or advantages traits. This leads to greater fitness. ◦ DEDUCTION: Individuals who possess favorable traits contribute more to the next generation. As favorable traits are inherited by their offspring, they become more common in the population overtime. • Fitness: Reproductive success (number of offspring) • Adaptation: Changes in response to new or varying environmental pressures. ◦ Occurs in response to particular environmental conditions. ◦ Geographic isolation may be a force int he origin of species. • Diversity observed among species is the result of evolutionary relatedness (time from common ancestor) and adaptation —> descent with modification Major Theses of Origin of Species • All organisms have descended with modification from common ancestors • Mechanisms for evolutionary change is the action of Natural Selection on individual variation Missing Pieces in Darwin’s Theory • Source of individual Variation? • Mechanism of Inheritance? Mendelian Inheritance PreDNA Concepts of Heredity: • Blending Theory of inheritance ◦ the idea that the passage of traits was directly related to the blending of the traits of parents ▪ ex. if there is a red flower and a yellow flower the child flower would be orange, as a blend of the two ◦ Parental contribution is averaged out, or blended, in offspring—exact definition ◦ Problem with natural selection, with each passing generation, the advantageous feature is “blended out" • Gregor Mendel (18221884) ◦ Undertook a systematic investigation of inheritance using very large numbers of pea plants ◦ Demonstrated Particulate Inheritance Sexual Reproduction in Plants with Flowers ▪ Although most plants are hermaphrodite (have both male and female organs), cross fertilization is achieved via cross pollination Why the Common Garden Pea Plant? 1. Easy to control pollination 2. It shows variation in a number of different traits: color and shape of pea pods, color of flowers, position of flowers, size, etc 3. Purebreeding lines could be identified Mendel’s Experiment ▪ Monohybrid Cross ▪ Purestrain parent generation (P) —> first hybrid generation (F1) ▪ Found that F1 generation: all progeny had yellow seeds, despite variation among parents; this was true for all of the cross that Mendel performed regardless of the trait ▪ Crosses F1’s with one another (second cross) ▪ Second hybrid generation (F2): wrinkled variant reappeared unchanged ▪ The trait who’s expression remained was the dominant variant, the trait that disappeared and reappeared was the recessive variant ▪ Conclusions: ▪ (1) Particulate inheritance ▪ Each hereditary characteristic is controlled by particulate unit factors, which exist in pairs in individual organisms; one factor is inherited from each parent ▪ These factors remain discreet, i.e. unchanged, regardless of external appearance ▪ (2) Dominance ▪ When 2 different unit factors relate to a characteristic, only on is expressed (dominant) while the other is not (recessive) ▪ There must be two copies of the recessive factor present for a recessive form to be expressed ▪ (3) Law of Segregation ▪ During formation of the sex cells (gametes), the paired unit factors, separate, or segregate, randomly, such that each sperm or egg receives one of the other factor with equal likelihood ▪ Dihybrid Cross ▪ 2 traits considered in combination ▪ (4) Law of Interdependent Assortment ▪ The distribution of one pair of factors into the gametes does not influence the distribution of other factors. Factors controlling for two different traits assort independently of each other. ▪ Mendel’s Postulates Summar ▪ (1) Particulate Inheritance ▪ (2) Dominance ▪ (3) Law of Segregation ▪ (4) Law of Interdependent Assortment Defining Terms Phenotype The observable or detectable expression (e.g. appearance) of a trait Genotype The full set of genetic factors that interact in determining the phenotype Homozygous When two copies of the same genetic factor controlling a trait are present in an individual (true breeding lines) Heterozygous When two different genetic factors for a trait are present in an individual (hybrid) Genetics: Cells and Molecules Chromosome Cells and Cell Division Eukaryote Cell • organelles surrounded by membrane, each organelle has a specified function DNA deoxyribonucleic acid Chromosomes are made up of DNA Anatomy of a Chromosome • Gene Genetic material that encodes for the expression of a particular trait • Locus Location of a gene on a chromosome • Allele: alternative versions of a gene one gene, but two or more alleles • One strand of chromatid before reproduction, then duplicates and replicates DNA to form two chromatids • Karyotype ◦ allows us to visualize all of the chromosomes, recognize matching chromosomes, and recognize diagnosable aspects of anthropology ◦ Human karyotype ▪ 46 chromosomes (23 pairs) ▪ First 22 pairs of these 23 are autosomal ▪ Sex chromosomes one pair of sex chromosomes ▪ pair 23 (X and Y) ▪ Females: XX ▪ Males: XY • All chromosomes exist as pairs— homologous pairs (one from the mother, and one from the father) ◦ homologous chromosomes of a pair may carry different alleles for the same trait ◦ Both chromatids in an identical chromosome are identical (the result of the replication of the DNA molecule) ◦ Both homologous chromosomes in a pair are different (one comes from the father and one from the mother) They have the same loci, may have different alleles • Each species has a particular number of chromosomes in somatic cells ◦ Examples: ▪ indian fern=1260 ▪ garden peas=14 • Chromosome numbers evolve Cells • 2 Types of Cells ◦ (1) Somatic Cells ▪ Components of body tissue ▪ 23 chromosomes pairs (46 chromosomes) in humans ▪ Diploid: contain both members of each chromosome pair ◦ (2) Sex Cells (Gametes) ▪ Ova: egg cells produced in female ovaries ▪ Sperm: sex cells produced in male testes ▪ 23 chromosomes in humans ▪ Haploid: contain only on member of each chromosome pair ▪ Zygote union between a sperm and an ovum Cell Division • Mitosis ◦ Mitosis is cell division in somatic cells ◦ Occurs during growth and repair/replacement of tissues ◦ The result of mitosis is two identical daughter cells, which are genetically identical to the original cell (2 diploid cells) ◦ Several basic events that need to happen before cell division can take place ▪ genetic material replication or duplication ▪ material needs to be separated from its parent copy ◦ Phases: ▪ (1) Interphase ▪ DNA replication happens during interphase right before the rest of cell division is initiated ▪ (2) Prophase ▪ Chromosomes visible with 2 identical sister chromatids (sister chromatids because they are representative of the same chromosome and thus possess the same DNA) ▪ (3) Metaphase ▪ Nucleus disappears ▪ Chromosomes line up single file along equator of cell ▪ one sister chromatid containing one copy of the deny positioned on one side of the equator and the other sister chromatid positioned on the other side ▪ preparing to be pulled apart ultimately ▪ (4) Anaphase ▪ Sister chromatids separate ▪ The two copies of DNA are thus separated ▪ (5) Telophase ▪ Results in two daughter cells (diploid) with identical copies of genetic material (each have their own nucleus, one copy of DNA) • Meiosis ◦ Production of gametes (sex cells) ◦ Characterized by two rounds of division that result in four daughter cells, each of which contains 23 chromosomes (4 haploid cells) in humans ◦ Fertilization restores the full complement of chromosomes (diploid number of 46) to the zygote ◦ Phases: ▪ Characterized by two phases of division ▪ (1) First Division (Reduction) ▪ Interphase DNA Replication ▪ Prophase I Crossing over (genetic recombination) ▪ as chromosomes condense, homologous pairs of chromosomes find each other, this provides an opportunity for crossing over to occur, each member of homologous pairs, come together and cross over exchanging genetic material ▪ after crossing over occurs, the mother chromosome actually traded genetic information with the father’s chromosome ▪ Metaphase I ▪ Chromosomes align in homologous pairs ▪ Random assortment of chromosome members with respect to either side of the equator ▪ Anaphase I ▪ Members of chromosomes pairs separate (Reduction Division) ▪ Telophase I further separation ▪ Interkenesis I ▪ Two haploid daughter cells, which are genetically dissimilar; no DNA replication ▪ Results of Meiosis Division 1 ▪ Each daughter cell inherits half as many chromosomes as the original cell, only one member of each homologous pair (i.e. haploid) ▪ Each chromosome has two chromatids, but they are different because of crossing over ▪ There has been recombination of genetic material from the mother and father ▪ (2) Second Division ▪ Prophase II ▪ No further replication of DNA ▪ Metaphase II ▪ Chromosomes line up single file at the equator (similar to metaphase of mitosis ) ▪ Anaphase II ▪ Telophase II ▪ Daughter Cells ▪ 4 Haploid Gametes, genetically dissimilar ◦ Nondisjunction of Autosomes during Meiosis ▪ One daughter cell receives two copies of the chromosome, and the other daughter receives no copies ▪ In the next phase of Meiosis, these copies with continue to replicate ▪ Usually these nondisjunction events are lethal and the organism does not survive ▪ Non lethal disjunction event ▪ trisomy 21 Downs Syndrome ◦ Mendel’s Laws of Particular Inheritance ▪ Law of Segregation ▪ Paired hereditary factors segregate randomly during formation of gametes ▪ Law of Independent Assortment ▪ Factors controlling for inheritance of different traits assort independently of one another ▪ exception* Applies to genes located on different chromosomes, but genes located on the same chromosome (linkage) may be exceptions ◦ Evolutionary Significance of Meiosis ▪ Meiosis increases genetic variation: ▪ Crossing over (genetic recombination) ▪ Random assortment (genetic recombination) ▪ Mutation (source of new variants) ▪ only mutations occurring during MEIOSIS are heritable ▪ Provides the raw material for natural selection to act upon Genotype to Phenotype Biological Role of Genetic Material 1. Accurate Replication 2. Stable Structure 3. Capable of coding for diverse information, including proteins 4. Capable of transmitting this information, to regulate development and normal cell functioning—coordinate the activity of those proteins The Building Blocks of DNA: Nucleotides • Deoxyribonucleic acid (DNA) is a nucleic acid ◦ Resides in the nucleus of the cell ◦ Stores and transmit information ◦ Made up of smaller molecules called nucleotides • Chargaff’s Rule ◦ A=T and G=C • Rosalind Franklin’s Xray diffraction photos provided clues to the structure of DNA showing that DNA was a helical structure DNA: Deoxyribonucleic Acid • Double Helix Structure • Compromised of Nucleotides: ◦ (1) Phosphate ◦ (2) Sugar (deoxyribose) ◦ (3) Nitrogenous base ◦ (Phosphate and sugar form the background) • Located in the nucleus of the cell • Complimentary base pairing: ◦ Adenine = Thymine ◦ Cytosine = Gamine • Implications of DNA Structure: ◦ Complimentary polynucleotide chains (specificity of base pairing) provides a mechanism by which the molecule can replicate itself ▪ one strand forms the template for the creation of the other strand ◦ The sequence of nucleotide bases caries and contains important information (i.e. the genetic code…) • Functions: ◦ Replication (cell division) ◦ Protein Synthesis (genotype to phenotype) • DNA Replication ◦ Occurs during Cell Division ◦ All of this occurs inside the nucleus of the cell ◦ Prior to Cell Division, special enzymes break hydrogen bonds between nucleotide bases resulting in ultimately an unzipping got the molecule somewhere along its length continuing towards both ends of the molecule ◦ Original polynucleotide strands separate, leaving their bases exposed ◦ Original strands become templates for attracting complimentary bases and bond to them to create a new polynucleotide molecule ◦ End result: two identical copies of the DNA molecule Protein Synthesis (from genotype to phenotype) • Genotype= underlying genes • Phenotype= physical outcome • Proteins may serve as structural components of body tissue and play active roles • Amino Acids, Polypeptide Chains and Proteins ◦ Amino Acid subunits are linked together to form linear polypeptide chains ▪ 20 different amino acids ▪ Create an unlimited amount of proteins based on the sequence of the amino acids ◦ Different polypeptide chains can be associated to form complex (multimeric) proteins • The Genetic Code ◦ Information to make proteins is encoded in the nucleotide base sequence ▪ CODON= a sequence of three nucleotide bases, which code for one amino acid ▪ Amino acids are specified by three nucleotide bases ◦ 4 nucleotide bases can combine to produce 64 sequences—coincide with only 20 amino acids ◦ Only 20 amino acids (redundancy). Many amino acids specified by more than on codon sequence ▪ because of this, many mutations still result in functionality ◦ gene: sequence of DNA bases that carries information for synthesizing a particular protein, and occupies a specific chromosomal locus • Protein synthesis takes place outside of the nucleus • DNA needs to be carried outside of the nucleus by ribosomes to begin protein synthesis ▪ Ribonucleic acid RNA ▪ single stranded ▪ ribose sugar ▪ uracil base ▪ DNA ▪ double stranded ▪ deoxyribose sugar ▪ thymine base • Stages (2) ◦ (1) Transcription ▪ Happens inside the nucleius ▪ DNA splits in the region of gene and attracts complementary ribonucleotides to assemble a messenger RNA molecule ▪ Complimentary messenger RNA (mRNA) strand is synthesized. This mRNA will leave the nucleus and travel to the ribosome for protein synthesis ▪ DNA: AAA CGC ▪ mRNA: UUU GCG ◦ (2) Translation: ▪ When the mRNA binds to the ribosome, protein synthesis is initiated. As each codon in the mRNA sequence is “read” a tRNA brings the corresponding amino acid to the ribosome ▪ happens outside the nucleus at the ribosome ▪ Transfer RNA (tRNA) molecules bind the the complementary mRNA strand at the ribosome, bringing with them amino acids specified by the mRNA codon ▪ As amino acids are brought to the ribosome, they bind together to from he amino acid chain of synthesized protein • REVIEW: ◦ DNA: ATA GAT CGC TTA ◦ mRNA: UAU CUA GCG AAU DNA Mutation • = an alternation in the genetic code; source of new variants ◦ Chromosomal Mutations ◦ Point Mutations —> when a single base is incorrectly replication ◦ Duplication —> when multiple strands are replicated incorrectly ◦ Inversion —> when a strand is replicated backwards ◦ Deletions —> when a nucleotide or series of nucleotide gets incorrectly deleted • When mutation occurs at the level of the nucleotide base, it may or may not alter function • Mutations occur at random; they may also be included by other agents • Mutations may be functionally irrelevant; of those that are functionally significant , many are lethal or have negative consequences. Others may be neutral. • A small proportion may be beneficial and confer selective advantages. • If the mutation occurs during meiosis, it may be passed to the next generation. Genetics Beyond Mendel • Mendelian Inheritance: ◦ single gene, autosomal dominantrecessive model ◦ useful for examining traits with qualitative variation (discrete changes) ▪ examples: ppea seed color, ABO blood system, albinism, cystic fibrosis ◦ Codominance ▪ Both alleles in the heterozygous condition are fully expressed, with neither being dominant over the other. ▪ ABO Blood System ◦ Sex Linkage (Xlinked Traits) ▪ Controlled by genes on the X chromosome, more commonly expressed in males. As males (XY) have only one X chromosome, any allele will be expressed, whether dominant or recessive. ▪ Examples of recessive Xlinked traits: Hemophilia, redgreen color blindness • Traits that do not follow Mendel’s rules ◦ Polygenic traits ▪ Traits with quantitative (continuous) variation, influenced by two or more genes ▪ Stature, skin color, eye color ◦ Pleiotropy ▪ A single gene influences the expression of multiple traits simultaneously ▪ Marfan syndrome ◦ Environmental effects ▪ many aspects of the phenotype are influenced by the interaction of genes and the environment ▪ Genotype sets limits and potential for developmental processes • The Complex Genome ◦ Types of Genes ▪ Structural Genes ▪ Regulatory Genes ▪ Homeotic Genes ◦ Introns and exons ▪ Intron region or stretch of region that is not translated into a known protein ▪ Exons opposite ◦ Splice Variation ◦ Nonprotein coding regions ▪ Introns ▪ Pseudogenes ▪ formally functioning genes that have been subsequently rendered as nonfunctional due to a mutation ▪ Primates, especially humans, have a higher proportion of olfactory pseudogenes than other mammals ▪ Variable number tandem repeats & short tandem repeats The Forces of Evolution and the Formation of Species Population • = A group of organisms potentially capable of successful reproduction ◦ Individuals of a population tend to choose mates from within the group ◦ The largest reproductive population is the species Genes in Populations • The population is the unit of evolution • Evolutionary change over time are not changes that occur during the lifetime of a population, but within the phenotypic structure of these organisms and species overtime ◦ Result is the change of an appearance of the trait or genetic substructure of the trait • Gene Pool= The sum of all alleles carried by the members of a population • Evolution= A change in allele frequencies from one generation to the next • Genetic Equilibrium= no changes in the allele frequencies, i.e. no evolution is occurring in the population HardyWeinberg: Model of Genetic Equilibrium • Used to determine whether or not evolutionary forces areoperating on the population, for a given genetic locus • Measure observed genotype frequencies for specific traits, and compare them against predicted genotype frequencies assuming no evolution is occurring ◦ In other words, Hardy Weinberg provides a genetic model (or null hypothesis) against which we can compare observed genotype frequencies in a population to determine whether evolution is occurring at a given genetic locus • Two alleles: Dominant (A), Recessive (a) • Frequency of alleles: Dominant (p), Recessive (q) • p + q = 1 • To calculate expected proportions in a specific population we calculate the probability of each possible genotype combination ◦ (Chances of A combining with A to form Genotype AA) p x p = p^2 ◦ (Chances of A combining with a or a combining with A to form Aa or aA) p x q + p x q = 2pq ◦ (Chances of a combining with a to form aa) q x q = q^2 ▪ p^2 + 2pq + q^2 = 1 • Assumptions made in this model ◦ Mating is random ◦ No new alleles are being introduced Forces of Evolution • Factors occurring in natural populations that cause changes in gene frequencies over multiple generations ◦ (1) Mutation ◦ (2) Natural Selection ◦ (3) Genetic Drift ◦ (4) Gene Flow ◦ (5) nonrandom mating ▪ Hardy Weinberg assumes that these are not occurring • (1) Mutation ◦ An alteration in the genetic material ◦ Mutations are chance events ◦ rare events ◦ give rise to new alleles ◦ add variation to the gene pool ▪ most important thing because they are the only force that adds variation to the gene pool • (2) Natural Selection ◦ Alleles that confer an increased likelihood of survival to reproduction will be passed on to the next generation with greater frequency ◦ Different types of selection: ▪ Stabilizing: maintains a certain phenotype by selecting against deviations from it (normal looking graph, up then down) ▪ Directional: selection fro greater or lesser frequency of a given trait (shift in graph) ▪ Disruptive: maintains extreme values in the population (dip in the graph, two humps) • (3) Genetic Drift ◦ = Change in gene frequency in a population over time, caused entirely by random factors ◦ Assumes that we are taking information on a population that is infinitely large ◦ Sampling error effects: more likely to change the frequency of alleles in a small population ▪ Population bottlenecks: severely reduces population is and genetic diversity ▪ limits genetic variation ▪ losing variation ▪ Founder Effect: involves an element of geographic isolation such that the new population becomes a variation of the parent generation ▪ in humans this is seen with migration, groups of people that migrate to a new area tend to be closely related so that their genes are close to the same • (4) Gene Flow ◦ = movement of individuals and their genes between populations ◦ Makes populations more similar to one another ◦ Counteracts the evolutionary forces that cause populations to diversity • (5) Nonrandom Mating ◦ Inbreeding ▪ raises the frequency of homozygous genotypes at all loci ▪ decreases the frequency of heterozygous genotypes at all loci ▪ also increases the likelihood that negative recessive alleles will build up ▪ ex. build up of hemophilia in royal families of England ◦ Assortative Mating ▪ Negative AM: increases frequency of heterozygous genotypes for particular loci ▪ Positive AM: increases frequency of homozygous genotypes for particular loci Microevolution vs Macroevolution • Microevolution: Small changes occurring within a species, such as changes in allele frequencies. • Macroevolution: Large changes produced after many generations, such as the appearance of new species. ◦ Micro and macro are part of the same continuum of evolutionary processes Definition of Species • Biological Species Concept ◦ Groups of interbreeding natural populations, which are reproductively isolated from other such groups. Ability to produce fertile offspring. ▪ Reproductive isolation ▪ Physical Barriers: ex. geographic ▪ Intrinsic Barriers: ex. physiology, behavior ▪ Reproductive Isolating Mechanisms ▪ Premating Mechanisms ▪ Habitat Isolation ▪ Temporal Isolation ▪ Behavioral Isolation ▪ Mechanical Incompatibility ▪ Postmating Mechanisms ▪ SpermEgg Incompatibility ▪ Inviability of ZygoteFetus or Offspring ▪ Offspring Sterility • Recognition Species Concept ◦ Emphasized unique traits or behaviors that allow individual members of the same species to recognize each other for the purposes of mating ▪ According to this, individuals from separate species should not recognize one another as viable mating partners ▪ Natural selection should favor those traits that are active in species recognition for mating • Ecological Species Concept ◦ A group of organisms exploiting a single ecological adaptation ▪ Assumes that there is an adaptive gap separating ecological zones that allow intermediate type of species from being successful ▪ If the intermediates or hybrids are always going to be outcompeted over the normal species, than the hybrid species frequency will not prevail largely,especially since they are unable to exploit their resources and environment to best serve mating purposes • Evolutionary Species Concept ◦ Defines species as evolutionary lineages (ancestral descendant sequences of populations) with their own unique identity ◦ Has been criticized for its vagueness ◦ Oen criterion on which these species are rectified is based on phenotypical identity, how similar they look, etc. ◦ Also important to keep in mind the time on a historical framework that the beings exist to concur whether or not they are defined a species, as well as the space they take up, geographically speaking ▪ Ultimately it is based on, do they live in a similar time span, in a similar geographical location, do they look alike? • Morphological Species Concept ◦ Defines species based on anatomical similarities ▪ Not very reliable because some species can be polymorphic and different species can be very similar ▪ But sometimes is the only one that can be used (paleontology) ▪ Similar to Evolutionary Concept, except there is no concept of time and space Major Modes of Speciation • Two Modes of Speciation ◦ Anagenesis ▪ One species evolves into another over time, basically a line of species ▪ When one species becomes another, the previous species no longer exists ▪ Difficulty: picking out the boundaries between different species ▪ Chronospecies each species within an anagenetic line ◦ Cladogenesis ▪ One species splitting off into multiple species ▪ The first species can die out, but also can continue to live on ▪ More of a splitting kind of evolution • Processes of Speciation ◦ Allopatric Speciation ▪ Speciation occurring via complete geographic isolation ▪ Some kind of physical barrier appears, such as a river, this serves to separate one or more segments of a population off from the parent population ▪ Thus, these segments experience a slightly different environment and speciation occurs ▪ No more gene flow between the isolate and parent population allowing for isolate populations to continue to diverge further ◦ Parapatric Speciation ▪ Speciation involving only partial geographic isolation ▪ Divergence ▪ Natural Selection, combines with partial geographic overlap to create a new species, so there is still some gene flow although it still allows for variations from natural selection ▪ differential natural selection on the outer most isolated areas, which further pulls apart species ▪ Prevents complete speciation of individuals, however, the two different remote ends of the populations look very different but where their geographic range overlaps the species look more similar than not (this area is the hybrid zone, capable of interbreeding) ▪ ex. Baboons ◦ Sympatric Speciation ▪ Speciation occurring in the absence of geographic isolation ▪ Very strong section favoring different phenotypes can create speciation affects ▪ Requires one population diverging from another population in the same environment ▪ Can also occur in an area with limited resources, where different aspects to use resources help select the survival of certain species ▪ Could happen through chromosomal mutations Patterns of Adaptive Change • A niche is how a species “makes a living,” which includes how it interacts with its environment, with other species in its community, and how it utilizes resources in its habitat ◦ each species has a unique role in their environment • Species that live together in the same habitat must have different niches in order to avoid being in direct competition with other species—no two species can occupy the same niche, or one would outcompete the other inevitably • Adaptive Radiation ◦ When a single kind of organism diversifies to fill many available niches. Tends to follow the origin of an evolutionary novelty. ▪ Each species has some sort of variation of that novelty and can exploit the environment in a new way ▪ Allows them to diversify Tempo of Speciation • Gradualism ◦ Evolutionary change proceeds gradually through accumulated small scale changes • Punctuated Equilibrium ◦ Evolutionary change proceeds through long periods of stasis and rapid periods of change ▪ long periods of stasis punctuated by rapid change during speciation Principles of Classification • Systematics = the study of the diversity of life and the relationships at all levels in the hierarchy ◦ Kingdom animals ▪ Phylum possess a nerve cord (major body plans) ▪ Class warmblooded with mammary glands ▪ Order ▪ , Family, Genus, Species • Taxon = a group of organisms assigned to a particular level in the classification • Species: basic unit of biological classification ◦ Binomen: Homo sapiens ▪ Genus name is Homo ▪ Species name is sapiens • What Criteria Do We Use? ◦ Similarities are a good starting point. ▪ Similarities must reflect descendant from a common evolutionary ancestor ▪ Some similarities arise for other reasons, so not all similarities are equally informative ◦ Analogy ▪ Structures that are similar among organisms in properties (e.g. superficial appearance and function) but evolved independently and are inherited from different precursors ▪ These are similarities in function, not in common ancestry ▪ Separate adaptations that have evolved independently ▪ Homoplasy ▪ ex. wings, bats and birds are not related although they both evolved wings ◦ Homology ▪ Similarities that are shared between organisms because they were inherited from the same structures in a common ancestor ▪ We avoid analogous traits, and use homology to reconstruct evolutionary relationships ▪ Derived vs. Ancestral Homology ▪ Not all homologies are equally informative for reconstructing evolutionary relationships ▪ Ancestral Homology: symplesiomorphy, shared with the other descendants of common ancestry, such as all primates having mammary glands, or presence of hair, these traits do not distinguish them as primates, but is shared with their common ancestors of mammals ▪ Derived Homology: synapomorphy, used to define clades (groups with a common ancestor), distinguished group from other common ancestors, uniquely evolved, traits that are not present in other common ancestors and are telling of their species, newly evolved features that provide their evolutionary distinctiveness ▪ Reconstructing Phylogeny ▪ phylogenic trees are built using large sets of traits (for extant and recent fossil species, DNA sequences can be used) ▪ shows degrees of relationships between related groups of taxa ▪ Cladogram: if we add geological time, we get a phylogeny
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