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Topic 10: Population Ecology - Coggle Diagram
Topic 10: Population Ecology
This is the study of populations (organisms of the same species in the same area) and factors that define them, how they change in composition etc.
Temporal Attributes
These are characteristics of populations that change over time
Demography (the composition of the population, how many organisms are at certain ages)
We can visiually see the demography of organisms by viewing their age structure, a graph that outlines how many organisms in a population exist at a certain period of time
Note that we can use age structure to determine population dynamics as well, as you can determine if there will be an influx of births, deaths or stagnant population size based on how many indvidials are at the dying age, how many are at the reproductive age.
Columnar age structures indicate balanced populations with equal death and birth rates.
Low fertility and mortality
Pyramidal age structures with low older people, and increased younger people, indicate that there is lower healthcare for the older people to survive, and there is also a high birth rate.
Lots of younger people means there will be a growing population size
We also use survivorship curves
Survivorship is the number of indivdiuals that make it to a certain age
The curves are logarithmic so that we can see when the slope is not crazy
The y axis demonstrates the Proportion of original population
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The x-axis demonstrates the % of total life expectancy
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Life History (the general allocation of energy of organisms to reproduction, survival and growth), their life strategies.
At what point in their life they choose to do certain things.
Fecundity is the the number of female offspring produced by a population, or by a certain age, it is a measure of reproductivitiy because usually females are what limit reproduction (males can produduce millions of sperm but females but one egg a month/year/lifetime)
We can measure repreoductive strategies as tradeoffs, while investing more energy into reproduction reduces energy for growth and survival and vice versa
Low fecundity
Low numbers of reproduction
More time to take care off offspring: more survive to reproductive age
Larger organisms (more energy spent on reproduction, growth)
Fewer reproductive events
Later reproductive maturity
High preadtor and disease resistance
Long lifespan
High fecundity
High reproduction per reproductive events
More reproductive events
Smaller organisms (they allocate less energy to growth)
Low parental care, more emphasis on lots of offspring where some survive than few offspring where most survive
Low predator resistance. low disease resistance
There are many ways that we can observe these strategies
Age of maturity (when can the organism start reproducing?)
Age of highest reproduction (when is teh organism most fertile)
Morphology, are there certain types of organisms that reproduce "better" like larger lobster
Age at last reproduction
https://gemini.google.com/share/0207b718d8fa
High survivorship traits
Have predation defense mehcanisms and the energy to have them
Are long living in general (can survive many seasons, most challenges)
Can survive disease
Larger, and thus prevent preadtors because they are hard to eat, also easier to eat other organisms and gain energy
Can have intermediate strategies (organisms that exist in between)
High fecundity traits
Small organisms
Small offspring
Many offspring
Many reproductive events
Early maturity
Low parental care
The number of reproductive events
Iteroparous
These are organisms that reproduce many times, usually have access to good resources to support many reproductive scycles and ensure that offspring can survive
Semiloparous
These are when there is 1 event, and then death, usually due to not favorable conditions and thus organisms must spend most energy on 1 offspring.
Population dynamics (how the population grows and decreases)
This is the study of changes in the population size (growth and decline)
Emigration, immigration, death and birth all add to this, but the most important is birth and death
Per capita growth rate: B+I-E-D/N
BUt we simplify this to just births and deaths
The number of new individuals is B-D, And so change in population over time is the Births - Deaths per unit time
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Factors that decrease population size
Density depdendent (scaled for the size of the population, more population means more impact)
Disaease
Waste
Competition
Change in social beahviors (antogonistic, cannabalistic)
Predation
Increase in population size, increased ease of capturing prey, decrease in prey population size, predator population decreases (due to a time lang, fat stores, where the predators continues to reproduce highly before following the prey dip.
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Density independent factor
Natural disaster
Changes to habitat
Climate and temperature changes
Graphs can demonstrate population growth
The y-axis is the # of individuals in the population, the x axis is time
The slope is the population growth.
exponential graphs: this is when there is no factor slowing down growth of the population, actually the growth is increasing with every generation (constant r, increasing N at everymoment means change in poulation size is always climbing).
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Logarithmic graph: these are s shaped, and plateau around the carrying capacity of the environment
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Spacial Attributes
These are characteristics of populations that determine how they spread and take up space
Size
This is the actual population size
Can be determines absollutely (count every organism, but less likely)
Population size estimate techniques
For mobile organisms (motile)
Use mark-recapcture
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Population indices
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For sessile organisms
Transects
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Quadrats
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Ways to talk about population size
Abundance
The number of organisms in an population
Density
The numbe rof organisms in an area.
Coverage
% of the ground covered, used when you dont know how many individuals )like overlapping roots)
Dispersal
Range