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26 Cards in this Set
- Front
- Back
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Five agents of evolutionary change |
1. Mutation : change in DNA 2. Gene flow : the migration of alleles from one population to another 3. Non random mating : such as self fertilization in flowers 4. Genetic drift : a change in allele frequencies in a small population due to a chance event 5. Natural selection : for favourable variations |
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Mutations |
Can be created by mutagens or mistakes during replication process. Can provide genetic diversity in a species and new alleles for a gene. |
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Genetic drift |
In every generation, homozygotes of the plants in this population reproduce. When the homozygous dark pink roses in the second generation reproduce, the allele for the light pink petals was lost form the gene pool. |
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Genetic drift - bottleneck effect |
The parent population contains roughly equal numbers of yellow and blue alleles A catastrophe occurs and there are only a few survivors. Most of these survivors have blue alleles. Due to genetic drift, the gene pool of the next generation will contain mostly blue alleles. |
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Genetic drift - founder effect |
When a few individuals from a large population leave and establish a new population the allele frequencies in the new population will likely not represent the genetic diversity of the original population, and may deviate further as the population expands. |
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Natural selection |
Acts on mutations by selecting for most successful individual who has the mutation If mutation provides selective advantage -> individual lives to reproduce -> passes in mutation to offspring -> leads to evolution |
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Census |
Counting total in small area *accurate but time consuming |
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Sampling |
Representatively sample small areas and multiply by total area, assumes random distribution *less accurate and not as time consuming |
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Biotic potential |
Capacity for reproduction Regulated by 4 factors 1. Max # of offspring per birth 2. Chance that offspring will reach reproductive age 3. # if times per year organism reproduces 4. Age at which reproduction begins |
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Carrying capacity |
Ability for environment to support a population |
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Density dependent factors |
Usually biotic Affect population because of density of population Increase death and limit reproduction as population increases Disease, predation, food supply, water quality |
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Density independent factors |
Usually abiotic Affect the population regardless of density Work regardless of population size Floods, fires, drought |
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Environmental resistance |
Environmental conditions limit a species from growing out of control Influenced by abiotic factors (natural disasters, disease) |
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J curve |
Demonstrate exponential growth increase in population size at an increasing growth rate Usually occurs in closed systems Often microorganisms (or insects) with short life spans Ex, aquarium containing bacteria, algae, yeast Exception; humans |
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S curves |
Most natural population demonstrate a sigmoid shaped curve Population increases until limiting factors cause it to reach carrying capacity -> as long as resources maintained, population size stabilized Density dependent/ independent factors may initiate death phase |
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K selected strategies |
Generally slow reproduction, long life spans, longer offspring rearing, later reproductive maturity Elephants, humans, bears |
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R selected strategies |
Rapid reproduction, short life span, little to no rearing, early reproductive age Bacteria, yeast, mice, opossums, insects |
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Surviving curves |
Type 1 : large mammals, few offspring, low infant mortality, extended life span (humans) Type 2 : chances of survival or death are about the same at any age (squirrels) Type 3 : low survivorship or high mortality rates early in life (oysters) |
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Population histograms |
Useful for studying human populations to see trends and make predictions Double histograms: include age and sex of a population Often take shape of pyramid |
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Types of interactions |
Symbiosis : relationship between two or more different species Predator prey: one species preys on another Consumer producer: one species produces a resource for another Competition: individuals must compete for resources |
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Symbiosis |
Parasitism : one organism benefits and other is harmed Commensalism : one organism benefits and other is unaffected Mutualism : both organism benefit |
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Predation |
Both predator and prey have specialized adaptations to assist with survival Two ways to avoid predation 1. Camouflage 2. Mimicry (look scary) |
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Producer consumer |
Producers must be present in order to sustain the needs of consumers -> no producers = no consumers = no community |
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Competition |
Intraspecific - individuals within the same population are competing for resources Interspecific - different populations are competing for resources |
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Succession |
Pioneer species : 1st organisms to take root and build soil layer (moss, ferns, insects) Climax communities : stable end populations that develop Primary succession : communities arising from no previous living populations Secondary succession: community begins to re-establish after partial destruction |
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5 conditions required in order for a population to be at equilibrium |
1. A large breeding population 2. Random mating 3. No change in allelic frequency due to mutation 4. No immigration or emigration 5. No natural selection |
