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BIOL 1001
Paula Wilson

BIOL1001 TEST NOTES 3 Persephone Greco-Otto SPECIATION (continued)  Definitions: o Anagenesis = slow accumulation of evolutionary changes in a lineage over time o Cladogenesis = the evolution of 2 or more descendent species from a common ancestor o Allopatric speciation = the evolution of reproductive isolating mechanisms between 2 populations that are geographically separated  Vicariance = the fragmentation of a continuous geographic distribution by nonbiological factors  Dispersal= the movement of organisms away from their place of origin o Parapatric speciation = speciation between populations with adjacent geographic distributions o Sympatric speciation = speciation that occurs without the geographic isolation of populations o Hybrid zone = a geographic area where the hybrid offspring of 2 divergent or populations or species are common o Secondary contact = when allopatric populations reestablish contact when a geographic barrier is eliminated o Reinforcement = the enhancement of reproductive isolation that had begun to develop while populations were geographically separated  Explain why geographic isolation does not necessarily lead to reproductive isolation. o Secondary contact o Same living conditions  Explain why islands provide such good examples of allopatric speciation. o Island conditions often very different from mainland conditions  usually reduced competition and different food sources o Reduced immigration/emigration between island and mainland allows them to become genetically very different  eventually can no longer interbreed  Explain why natural selection cannot directly promote the evolution of reproductive isolating mechanisms between allopatric populations. o Individuals in allopatric populations don’t encounter one another  no hybrids produced  Natural selection can’t select against the matings that would have produced them o No gene flow, therefore natural selection can’t directly promote speciation between allopatric populations  Describe how sexual selection and differences in mating habitat, time of mating, or food source could drive/lead to sympatric speciation. o Most frequent in insects that feed on one or two plants  carry out life activities around “host plant”  Eg. mate on host plant, eggs laid in fruit, larvae feed on host plant **separate subpopulation = host race (more likely to mate w/members of their own host race than w/members of another) o Certain organisms only fertile at times of the year  if this time is not the same, they cannot mate  eventually leads to sympatric speciation  Explain how an organism’s mobility (or mobility of their gametes) could affect the genetic relatedness of dispersed populations. o Increased mobility = increased dispersal = increased genetic relatedness  Explain the significance of polyploidy and chromosomal alterations (e.g., rearrangements, duplications) in the speciation of organisms. o Lead to reproductive isolation  Genetic divergence = genetic differences accumulate since no gene flow, no hybrids in allopatric species, reproductive isolation (minimum # of genes responsible for this) (pre and postzygotic isolating mechanisms)  Polyploidy = individuals w/ >2n sets of chromosomes  Arise from chromosome duplications (autopolyploidy  can produce tetraploid offspring, error in mitosis/meiosis  can’t reproduce w/diploid organisms sop becomes reproductively isolated) or hybridization (allopolyploidy  polyploid offspring, leads to very rapid speciation)  Chromosome alterations  Inversion, translocation, deletion, duplication all lead to postzygotic isolation  Variations accumulate over time and lead to divergence  Explain how there does not have to be a strong correlation between genetic divergence and speciation, providing examples. o **** MACROEVOLUTION  Definitions: o Adaptive radiation = a cluster of closely related species that are each adaptively specialized to a specific habitat or food source **when does this not occur? o Ecological opportunity = when an organism takes advantage of the lack of competitors in an environment and eventually deviates into its own species. o Morphological innovation = ** o Gradualism = the view that the earth and its living systems changed slowly over its history o Punctuated equilibrium = the evolutionary hypothesis that most morphological variation arises during speciation events in isolated populations at the edge of a specie’s distribution o Preadaptation (exaptation) = a characteristic evolved by an ancestral species that serves an adaptive but different function in a descendent species or population o Allometric growth = a pattern of postembryonic development in which parts of the same organism grow at different rates o Heterochrony = changes in the relative rate of development of morphological characteristics o Neoteny = the retention of juvenile features in the adult animal o Pedomorphosis = a common form of heterochrony in which juvenile characteristics are retained in a reproductive adult o Metamorphosis = a reorganization of the form of certain animals during postembryonic development HUMAN EVOLUTION  Describe the key adaptations that distinguish humans from non-human primates. o Upright posture o Bipedal locomotion o Power grip in primates and humans but humans also have precision grip o Increase in # of vertebrae and length of vertebra o Posterior concavity of individual lumbar vertebrae  stabilizes centre of mass of body over hips  Explain why humans are more correctly described as ‘sharing common ancestry with chimpanzees’, rather than the incorrect ‘descended from chimpanzees. o Chimpanzees still exist and continue to evolve o Humans diverged from chimpanzees o Humans are not more evolved than chimpanzees (simply more recent divergence)  Explain how chimpanzees are modern humans’ most closely-related species, and vice versa. o Diverged most recently o Human DNA more similar w/ chimpanzees than chimpanzees and gorillas  Hypotheses for the evolution of bipedalism in humans. o Arisen in arboreal setting that allowed ancestors of humans to move on branches o Frees hands from locomotor functions = specialization  tool use o Hands were used to swing on trees  but by becoming bipedal our hands are free for other activities  Evidence supporting African ancestry of hominins. o Neutral mutations accumulated in African populations much longer = greatest variation o All human populations contain at least one mtDNA sequence of African origin  Explain the evidence that suggests that ‘Denisova’ hominins are a separate migration out of Africa compared to Neanderthals or modern humans. o mtDNA totally different  suggests long ago divergence (not recent common ancestor)  Describe the patterns of hominin co-existence on Earth. o ******  Describe the characteristics that distinguish Homo erectus from its ancestors. o Ability to make and use sophisticated tools o Bipedal o Hunted for food (more complex diet) o Taller o Larger brain w/thicker skull and protruding brow ridges o Use of fire  Describe the two hypotheses of the relationship between H. sapiens and Neanderthals. o African Emergence Hypothesis = all modern humans are descended from a fairly recent African ancestor • H.erectus gave rise to several descendent species that left Africa . H.sapiens arose in Africa much later and migrated  archaic humans became extinct o Multiregional Hypothesis = after archaic humans migrated from Africa to many regions on Earth, their different populations evolved into modern humans simultaneously • Populations of H.erectus and archaic humans migrated by 0.5MYA, H.sapiens evolved from archaic humans  were geographically isolated and had gene flow = one species (H.sapiens)  Explain the evidence that suggests that some modern-day Africans represent an earlier migration back from Europe. o Phylogeny ****  Explain the pattern of evidence that suggests that the Americas have only recently been colonized by modern humans. o ****  Concept of ‘mitochondrial Eve’. o The woman from whom all living humans today descend, on their mother's side, and through the mothers of those mothers and so on, back until all lines converge on one person o Descent to each person alive today includes precisely one purely matrilineal line o Other women were alive at the time but may have only had sons  Describe and explain some examples of past human lineages traced by nuclear DNA from the Y chromosome. o ***  Describe and explain some examples of phylogenetic analyses of non-human species to reconstruct past human history. o ***  Describe traits formerly attributed solely to humans that are found in other species. o Intelligence, learning, language POPULATION ECOLOGY  Definitions o Ecology = the study of the interactions between organisms and their environment o Ecological organization  Organismal = a living thing; one member of a species  Population = all of the organisms of one species that live in a certain area  Community = all the populations of organisms that occupy a certain area  Ecosystem = all the living (communities) and non-living organisms (abiotic factors) in a given area o Geographic range = The total area occupied by a population o Habitat = specific environment in which an individual lives o Population size = all individuals of a single species that live together in the same place  3 different methods: o Population density = number of individuals per unit are **more informative than population size o Population dispersion = spatial distribution of individuals within the geographic range  Clumped = individuals are grouped more closely to each other than if they are randomly dispersed  Random = organisms are distributed independently of each other  Uniform = individuals are more widely separated from each other than they are if they’re randomly distributed o Age structure = the relative proportion of individuals in each age group in a population o Generation time = The time period from birth to average age of reproduction o Sex ratio = The ratio of the number of males to the number of females in a population o Reproducing proportion = proportion of individuals in a population that are reproducing o Metapopulation = a group of neighboring populations that exchange individuals o Species distribution = the manner in which a biological taxon is spatially arranged  Social animals, easy to locate, cooperative raising of young, feeding, defense from predators, clumped when species reproduce by asexual clones that remain attached to the parents, seeds/eggs/larvae, resources in short supply, allelopathy (chemical warfare), territorial behaviour  Describe the relationship between an organism’s size and its population density, and an organism’s size and its generation time. o Larger organisms tend to have lower population densities (fewer individuals), larger organisms tend to have an increased generation time  Describe how the age structure (and relative proportion of pre/post reproductive) of a population impacts population growth in a shrinking population, a zero-growth population (ZPG) and a rapidly growing population. o ZPG = a circumstance in which the birth rate of a population equals the death rate o As the population ages, the population shrinks  post reproductive/dying o ZPG would occur when the age structure is equal between pre and post reproductive age o Growing pre-reproductive = growing population (will all reach sexual maturity around same time and produce lots of offspring = population spike)  Describe how a country’s stage of economic development is related to its pattern of population growth (i.e., birth/death rates and resulting population growth). o Lower economic situation = higher birth and death rates o Higher economic situation = lower birth and death rates  As counties move from third to first world status, the populations grow since death rate decreases but birth rate is still high (cultural influence)  Describe the effects of altered sex ratios on a population’s size for species with different mating strategies (e.g., monogamy, polygyny, etc.) o ****  Describe how an organism’s different life stages can reduce intraspecific competition. o **** LIFE HISTORY  Definitions: o Life table = a chart that summarizes the demographic characteristics of a population o Cohort = a group of individuals of similar age o Age-specific mortality = the proportion of individuals alive at the start of an age interval that died during that age interval o Age-specific survivorship = the proportion of individuals alive at the start of an age interval that survived until the start of the next age interval o Age-specific fecundity = the average number of offspring produced by surviving females of a particular age o Life history = the lifetime pattern of growth, maturation, and reproduction that is characteristic of a population or species o Energy budget = the total amount of energy that an organism can accumulate and use to fuel its activities o Passive parental care = the amount of energy invested in offspring – in the form of the energy stored in eggs or seeds or energy transferred to developing young through a placenta – before they are born o Active parental care = parents’ investment of time and energy in caring for offspring after they are born or hatched o Semelparity = characterized by a single reproductive episode before death (big bang reproduction) o Iteroparity = characterized by multiple reproductive cycles over the course of its lifetime (repeated reproduction) o Survivorship curve = graphic displays of the rate of survival of individuals over a species’ life span  Type I: high survivorship until late in life, large animals that produce few young  Type II: relatively constant rate of mortality in all classes, steadily declining survivorship  Type III: high juvenile mortality, followed by a period of low mortality once offspring reach a critical age and size o Density-dependent factors = description of environmental factors for which the strength of their effect on a population varies with the population’s density o Density-independent factors = description of environmental factors for which the strength of their effect on a population does not vary with the population’s density  Describe how natural selection shapes life history traits and the different trade-offs (e.g., fecundity vs. parental care; number of times to breed; age at first reproduction) in reproductive life history traits. o ***  Explain, with respect to life history tradeoffs, why spaying/neutering may be beneficial for your pet.
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