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Population
a group of organisms that belong to the same species and live in a particular space
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Size estimation
by sampling a small area and multiplying by the whole
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Density
- How crowded it is
- *individuals/ km^2
- Japan- high density
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Dispersion
Spatial distribution
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Clumped
- groups are clustered due to:
- food, living spaces
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Uniform
consistent space between each organism
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United States
- Birth rate: 4 million/year
- Death Rate: 2.6 million/year
- Life expectancy: male-24 years, female- 80 years
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Age structure of a country
High % of young people= high potential for growth (vise versa)
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Survivor ship
3 types of curves
- Type 1- small chance of dying until very old- human, elephants
- type 2- equal chance of dying at any time in life- robins, sparrow
- type 3- good chance of dying young, but live long if make it- salmon
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Add to a population
Birth and immigartion
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Subtract from a population
Death and emigration
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Exponential model of population growth
- population grows slowly at first then pop. will add a larger # of individuals with each generation
- It is realistic
- Because only under certain conditions and for limited periods of time
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The Logistic model
accounts for the influence of limiting factors
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carrying capacity
- # of individuals the enviornment can support over a long period of time
- Death rate= birth rate when pop. size is at carying capacity
- fluctuates with number of prey- predators
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Density Independent Limiting Factors
weather, flood, fire
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Density Dependent Limiting Factors
shortages of food, shortages of nesting sites
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Population Fluctuations
- all populations fluctuate in size
- ex. lynx and snowshoe hare
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Small Populations
vulnerable to extinction, increased liklihood of imbreeding, decrease in genetic variation
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Original human population
small nomadic groups, hunter gatherer lifestyle, low growth rate, high mortality rate
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Agriculture Revolution
(10,000- 20,000 years ago)
- domesticated animals, cultivated plants
- result: stabilized food supplies, human population grew
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Population Explosion
- After 1650
- better sanitation
- control of disease
- more food
- drop in growth rate can be decieving because it doesnt mean the population will stop growing
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Developed Country
better educated, healthier, live longer
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Developing Countries
poorer, populations growing faster
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predator
- eats all parts of another species
- adaptations: sticky web, flesh cutting teeth, speed
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prey
adaptations: deceptive markings, chemical defenses, mimicry
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herbavores
form of predation
adaptations: same as predator
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Batesian mimicry
harmless animal trying to look like harmful one
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Mullerian mimicry
when two or more dangerous or distasteful species look alike
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plants
adaptations: sharp thorns, spines, sticky hairs, tough leaves
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Secondary compounds
- chemical defenses of plants (poisonous, irritating)
- ex, strychnine, nicotine
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interspecific competition
2 species struggle for same limited resource
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Competitive Exclusion
one species eliminated from a community because competition for same limited resource
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character displacement
- evolution of differences in characteristics due to competition
- ex. beaks of galapagos finches
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resource partitioning
- species avoid competition by dividing up the resource
- ex. 5 species of warbler divide up diff. parts of tree
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symbiosis
close long term relationship between two organisms
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Parasitism
the parasite benefits and host is harmed
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ectoparasite
- outside
- ex. aphid, lice, ticks, mosquitoes, leeches
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endoparasite
- inside
- ex. tapeworm, heartworm
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mutualism
- both species benefit
- ex. ants and acacia tree
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commensialism
- one species benefits, other is not affected
- ex. cape buffalo and cattle egret
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ecological succession
gradual, sequantial regrowth of a species in an area
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pioneer species
- species of organisms that predominate early in succesion
- characteristics: small, grow quickly, reproduce quickly
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climax community
- community that reached a stable end point
- stability does not last forever
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