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BIOL 1001 MIDTERM III NOTES LOS's part 3.docx

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BIOL 1000
Hernan Humana

H Human Evolution H1. Describe key adaptations that distinguish humans from non-human primates. Describe hypotheses for the evolution of bipedalism in humans. Describe traits formerly attributed only to humans that are found in other species. [Comprehension]  Upright posture and bipedal motion are key adaptations distinguishing hominids from apes. Primates have power grip, humans have power grip and precision grip. Increase in # of vertebra.  The African Emergence Hypothesis: proposes that modern humans first evolved in Africa and then dispersed to other continents; all modern humans are descended from a fairly recent African ancestor. They drove archaic humans to extinction.  The Multiregional Hypothesis: proposes that after archaic humans migrated from Africa to many regions on Earth, their different populations evolved into modern humans simultaneously. Geographically isolated, but may have experienced differentiation; gene flow prevented reproductive isolation.  Neanderthals were culturally and technologically sophisticated. Made tools, built shelters, hunted and buried their dead H2. Explain why humans are more correctly described as ‘sharing common ancestry with chimpanzees’, rather than the incorrect ‘descended from chimpanzees.’ *Comprehension, Analysis]  Chimpanzees still exist and continue to evolve independently. Humans diverged from chimpanzees; a more recent divergence  Sequence variations: contain no genes and do not go through natural selection. Result only from random mutations and serve as molecular clock, Only 3 sequences mutations found among 5 people of varying ethnic backgrounds. Chimps, however had 207 differences from humans. Limited genetic diversity and recent ancestor confirms they are all from Africa. H3. Explain and describe the evidence, from both humans and other organisms, supporting African ancestry Of hominins, and the pattern of migration of humans over their evolutionary history, relating evidence to founder events. Describe evidence of the relationship between H. sapiens and Neanthertals. [Knowledge, Comprehension]  African ancestry of hominins: neutral mutations accumulated in African populations much longer = greatest variation. All human populations contains at least one mtDNA sequence of African origin I Population Ecology 1. Identify characteristics of a population and what they tell us about a population, specifically: why population density is more informative than population size; three methods to estimate population size and density, providing advantages and disadvantages of each; difficulties in accurately determining population size; the relationship between an organism’s size and its population density, its generation time, and its rmax; and different patterns of population dispersion. [Comprehension] Population density: number of individuals per unit area/volume of habitat Population size: number of individuals comprising the populations at a specified time Density > size provides more information about its relationship to the resources it uses. 3 ways to measure: 1. Simple head count: easy in small populations compared to bigger 2. Mark-release-recapture: assume mark has no effect on survival; individuals mix randomly, no migration, and equal chance of being caught for all. 3. Random sampling? Difficulties in accurately determining population size:  Measuring population size in organisms that are clones The relationship between organisms’ size and population density, generation time, and rmax:  Whether the spatial distribution of a population appears to be clumped, uniform, or random depends on size of organisms and study area. Oak seedlings may be randomly dispersed on a spatial scale of few metres, but over an entire mixed forest, it would appear to be clumped.  Generation time: average time between birth of organism, and birth of its offspring. Usually short in species that reach sexual maturity at small body size; population size grows rapidly because of speedy accumulation of reproductive individuals = high population density  Rmax: maximum per capita growth rate; intrinsic rate of increase…population size increases very rapidly. Different patterns of dispersion:  Clumped: individuals are grouped more closely to one another  Random: organisms are distributed independently of each other  Uniform: individuals are more widely spread separate from one other a. Predict given a description of an organism and its environment: which method would be most useful/feasible to determine its population size; and the type of dispersion it most likely exhibits. [Application, Analysis]  Refer above b. Describe how age structure (and relative proportion of pre/post reproductive members) of a population impacts population growth in a population that is: shrinking, zero-growth, or rapidly growing. [Comprehension]  Age structure: statistical description of the relative number of individuals in each age class  Pre-reproductive: younger than age of sexual maturity  Post-productive: older than the maximum age of reproduction  Structure reflects recent growth history, and predicts future growth potential  Those with more many pre-reproductive grew rapidly in recent past, and population will continue to grow as young individuals mature and reproduce  Shrinking: birth rate lower than death rate  Zero-growth: birth rate equals death rate  Rapidly growing: birth rate exceeds death rate c. Describe how an organism’s different life stages can reduce intraspecific competition. [Comprehension]  Intraspecific competition: the dependence of two or more individuals in a population on the same limiting resource  At different stages of life, they have different needs, this prevents entire population from vying for same resource 2. Describe what a survivorship curve represents. Given general information about a species’ pattern of survivorship and mortality, identify or draw the type of survivorship curve (I, II, or III) a population would exhibit. [Comprehension, Application]  Survivor ship curve: displays the rate of survival for individuals over the species average life span  Type 1: high survivorship until late in life. Typical of large animals that produce few young and provide extended care, reducing juvenile mortality.  Type 2: relatively constant rate of mortality in all age classes, pattern that produces steadily declining survivorship. E.g., lizards. Face mortality from predation, disease, starvation…  Type 3: high juvenile mortality followed by low mortality once offspring reach a critical age and size. E.g. 1 million seeds produced, fewer than 1000 germinate, only about 40 survive first year. Once established, survival is higher probability. E.g. insects and fish 3. Describe how natural selection shapes life history traits, and the different trade-offs (e.g., parental care vs. fecundity; number of times to breed; age at first reproduction) involved in reproductive life history traits. [Knowledge, Comprehension]  Passive parental care: amount of energy invested in each offspring before it is born: yolk in an egg, nutrients crossing placenta  Active parental care: amount of energy invested in each offspring after it is born: nursing child  Fecundity: potential reproductive capacity of individual  Number of times to breed: some devote all stored energy to a single reproductive event, whereas others reproduce more than once, and devote some energy to reproductive with balance allocated to maintenance and growth. Later results in greater fecundity at a later age.  Age at first reproduction: those that first reproduce at the earliest possible age stand a good chance of leaving surviving offspring. But energy they use in reproduction is not available for maintenance and growth…thus early reproducers may be smaller and less healthy in comparison to others.  Individual that delays reproduction may increase its chance of survival and future fecundity by becoming larger and more experienced. But possibility that it will die before next breeding season and leave no offspring. Thus, finite energy budget and the risk of mortality establish a trade-off in the timing of first reproduction.  Delayed reproduction is favoured by natural selection if a sexually mature individual has good chance of surviving to an old age.  Early reproduction favoured if adult survival rate are low. 4. Describe the relationship (and differentiate) between the exponential and logistic growth models, making reference to why exponential growth cannot continue indefinitely. Provide the exponential and logistic growth equations, identify all terms, and explain how the terms change relative to one another.  Exponential: population size increases steadily by a constant ratio…e.g. bacteria. As population grows, uses more resources, leads to shortening, individuals have less energy available for maintenance and reproduction, which causes decrease in per capita births and rise in deaths. Energy in food is not always equally available…changes cause population growth to slow dN/dt = rmax N population growth rate = intrinsic rate of increase x population size  Logistic: population growth slows as the population size approaches K (carrying capacity: max number of individuals the environment can support. Populations grow slowly at low and high population size: low – few individuals reproduce, high – per capita growth is low. Grows quickly at intermediate when good amount of individuals breeding. Assumes vital resources ecome increasingly limited with growth dN/dt = rmaxN (K-N)/K population growth rate = intrinsic rate of increase x population size (carrying capacity-population size)/carrying capaity  R decreases as population size approaches K a. Explain: how r changes when b>d, bd: r has a positive value, population grows  B
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