NSCI 1403 Lecture Notes - Lecture 9: Survivorship Curve, Delta N, External Fertilization
9 Jul 2016
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Population Ecology 4/25/2016 7:36:00 PM
Chapter 55:
Biological species concept: when two animals are able to mate and
reproduce viable offspring
Population: group of organisms belonging to the same species belongs to the
same geographic area at some point of time. (always space and time)
Population Biology: concerned with factors which increase or decrease size
and describe rates of change.
• Rate of change (r): change in numbers ÷ time interval
• r = delta N / delta t
• factor that go into change in numbers:
o birth rate/ natality rate (b)
o death rate/ mortality rate (d)
o emigration: move away, go somewhere else
o immigration: move in, come to this location
o just ignore immigration and emigration- assume them to be 0
o r=b-d rate of population as a whole is the difference between
the birth and death rates
• “ideal” environment: no predators, unlimited food and water, no
disease, etc
o Malthus showed algebraically what would happen :
2,4,8,16,32,64,128,256…
o population explosion
o when graphed there would be a ‘j’ shaped curve
o shape of the curve is reliant on:
▪ death and birth rates depending on the organism itself
▪ number of offspring per female
▪ gestation time
▪ age at sexual maturity
• Biotic potential: in a construct what is the potential species based
on biological factors to increase
• At some point populations have to level off
• Realistic environment there will be a sigmoidal S curve
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o maximum individuals supported in an environment is known
as the carrying capacity of the environment (K)
▪ OF THE ENVIRONMENT because the population is not
self regulating, the available food resources or nesting
environment limits the carrying capacity
Predicting Growth Rates:
• we want to collect the data we need to make the projections
• humans:
o easy to start with humans, we can determine the date in
which we die
o we have census data of the number of people born on a
certain day and follow that data to the day they meet their
end
o assume male and female numbers are equal
o Born 1910 – cohort of individuals
▪ 100% survivors
o 1920 – 95% survivors
o 1930 – 90% survivors
o 1980 – 40% survivors
o 1990 – 15% survivors
o 2000 – >1% survivors
o plot a survivorship curve (type a or I)
•
• There are animals that reproduce through external fertilization and
no parental care. These eggs and larva become fish food
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o Their highest mortality will be in the early ages, but once it
get to larval stages
o plot a morality curve (type c or III)
• Third possibility depends on the age of the individual
• mortality is not strongly correlated with the age of individual ex:
song birds
• plot a survivorship curve (type b or II)
•
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Biological species concept: when two animals are able to mate and reproduce viable offspring. Population: group of organisms belonging to the same species belongs to the same geographic area at some point of time. (always space and time) Projections about future trends and differences between nations. Growth of human population graph shows an exponential curve. What accounts for more people to survive: society becomes more developed, hunting and gathering as opposed to agriculture, food shortage. Things we need to know to make predictions on the following years: birth rate: 2 per female, mortality rate, societal reasons such as people tending to have fewer or no children at all. Competition of limiting resources: interspecific interactions involving members of the same species for some resource, intraspecific: competition between different species. Examples of limiting resources: resources of shorter supply, not oxygen or water. When there are 2 different species competing for supplies, time energy effort expended makes it harmful for both species.
