Lab Quiz 1 Flashcards
Define evolution.
Any genetic change, and resulting phenotypic change, in organisms of a species from generation to generation.
How does evolution occur?
gradually through processes such as mutation, migration, and especially natural selection.
What is the substance of evolutionary change?
Variation in the allelic frequencies within a population
What are Darwin’s six ‘rules’ of natural selection?
(1) There is overproduction of organisms (biotic potential for exponential growth)
(2) But, population size remains more or less constant over the long term (most populations show logistic growth)
(3) Thus, there must be. struggle for existence
ALSO
(4) Individuals in a population vary in their characteristics, and these variations are inherited (at least in part) by their offspring
(5) Favourable variation will slowly accumulate in a population by means of natural selection
(6) Consequently, the population slowly adapts to its environment
What is biotic potential?
The characteristic of all populations to produce more individuals than are required to replace those already existing.
Biotic potential defines the maximum rate at which a population will grow if conditions are ideal.
What is the reason for overproduction?
If a population failed to produce enough offspring to replace itself each generation, it would decline to extinction.
Populations must have the potential to increase, or overproduce, in order to recover from catastrophes that occur in the natural world.
In populations that reproduce sexually, what four factors in female life history determine the biotic potential of a species and determines the maximum rate of growth for a given species?
(1) The length of time a female reproduces
(2) Female age specific survivorship
(3) Average female births per female per reproduction
(4) Delay of reproduction; the time between birth and production of the average number of female offspring (the generation time T)
What is exponential growth?
Where resources are unlimited, the rate of growth is constant, and the amount of increase is proportional in the initial population size
What is the purpose of plotting values on a logarithmic scale?
To scale the values so that proportional changes in population size appear equal in magnitude on the graph
What does exponential growth look like on a semi-log plot?
The population growth rate is constant through time so this type of plot will result in a straight line relationship
What is the formula for determining the rate of growth (r) for exponential growth specifically?
ln (population size at t) - ln (population size at t0)
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t - t0
Describe a J-shaped growth curve.
The “J-shape” refers to the first part of the curve
The growth curve increase more or less exponentially for a time and then abruptly stops and crashes to extinction or near extinction.
The crash occurs either because the population exhausts the resources necessary for its continued existence, or there is an environmental change which drastically reduces the population.
This is seen in several species of algae and insects
Describe a sigmoid (S-shaped) growth curve.
A natural population exhibiting sigmoid growth continuously adjusts its rate of growth as its density increases and resources become more limited.
The carrying capacity is a population density or biomass that can be sustained indefinitely by the environment.
What is the relationship between the population growth rate (r) and population density?
The population growth rate (r), or the slope of the graph, is negatively related to the population density. As the population reaches greater densities, the growth rate slows.
In the process of evolution through natural selection, we are concerned about the _________ growth rates of different phenotypes and genotypes in populations.
relative
Define a population.
A population is a group of individuals of the same species which can potentially all interbreed with one another.
What is the gene pool?
all the alleles (of all the genes) in a population
Define fitness.
The ability of an individual to pass on its genes to the next generation; relative to that of other individuals (i.e. survive and produce viable offspring)
