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Population
- These are the same species, same place and same time
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Gene pool
- - These are all the alleles in a population.
- - both dominant and recessive
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Hardy Weinberg Principle
- - This is when all the factors remain constant the gene pool will remain constant generation after generation that leads to genetic equilibrium.( no evolution)
- - This equation calculates what a non involving frequency should be but if we see something different than the equation we know micro evolution has occurred
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Conditions in which Hardy Weinberg works
- - Large populations.
- - Random mating ( no selective breeding )
- - No mutations
- - No migrations
- - no natural selection
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Gene flow
- - This is the net movement of alleles from one population to another.
- - That results in an increase in diversity and helps protect this organisms against diseases
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Non( not ) random mating
- - this is a selective advantage which one mate have over the other.
- - it is unlikely because you have preferred phenotypes and some other organisms like plants usually do inbreeding ( self fertilization )
- - you are not being picky it’s kind of like selective breeding
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Genetic drift
- - This is the change in allele in a population due to random events.
- - This is when small populations lose certain alleles due to lack of mates to mate with or disease.
- - This results in a lack of diversity
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Types of genetic drifts
- - Founder effect( includes movement )
- - Bottleneck effect
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Founder effect
- - A population or gene pool that is formed by a small group of individuals that carry representations of the originals population genes.
- - Intially it starts out bad but as time goes on it gets better
- - it has movement
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Bottle Neck drift
- This is when quick reduction of an organisms population due to environmental resistance ( natural disasters, diseases ) that results in the surviving population producing a new generation that does not have that much diversity.
- - There is no movement in this drift
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natural selection
- - some individuals are better able to survive and reproduce than others . Furthermore, this results in the offspring carrying the successful genes.
- - An example is sickle cell Anemia
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Modes of selection
- - Stabilizing selection - average phenotypes have a selective advantage over the extreme phenotypes.
- - Disruptive or bimodal selection- both extreme are favored over the intermediate phenotypes.
- - Directional selection- phenotype at one extreme has a selective advantage over those at the other extreme
- - Sexual selection- leads to bimodal selection and this is extreme differences between 2 genders
- - Artificial selection- humans select breeding
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distribution of populations
- - these are determined by a type of organism and resources
- - Random- no order or attraction or repulsion ( large amount of resources )
- - Uniform - order , territories competition among individuals for factors such as moisture space )
- -Clumped - grouped in patches, or asexual reproduction
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factors affecting population growth
- - biotic potential ( r) - this is the maximum amount of offspring that can be produced in ideal conditions. ( good )( maturity, life span)
- -Environmental resistance- factors that tend to limit population growth such as emigration, climate change, disease)
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J curve vs S curve
- - J = this is unrestricted growth for animals like bugs ( r factor )
- - S = Logistic ( this is restricted growth), it has a point of maximum growth and a carrying capacity ( K)
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population histograms ( Age pyramid)
- - they are useful to study animals to see if the population will grow, stabilize or decline.
- - allows to study populations based on it's age, structure and proportion of males to females.
- - does not show immigration or migration numbers.
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limiting factors in populations
- - Shelford's law = too much or too little can be harmful to an organism.
- - law of the minimum= in all of the essential substances for growth in an organism, the shortest supply controls population numbers.
- - density dependent = increase in population sizes results in higher chances of disease, parasites ( biotic= living )
- - Density independent = will affect the population regradless of size eg floods, drought ( abiotic )
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R species
- - they are highly reproductive but limited by a short life span.
- - Mature quickly
- - large number of offsprings
- - small bodies such as bugs, bacteria, beetles, bees
- -not much parents
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k selective species
- - they are limited by the carrying capacity ( maximum species they can have )
- - long lifespans
- - long time to mature
- - few offspring
- - big in size such as bears blue whales
- - parents are present
- - normal an s curve
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intraspecific competition
- Density dependent competition between same species for resources
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interspecific competition
- between different species for the same resources.
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gause's law
- if 2 populations have the same niche one will be eliminated.
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