The Basics Behind Population Growth
Part A, #1
What is population growth? What is population ecology?
Population growth is the change in the number of individuals of a species in an area over time
Population ecology is the area of ecology that works to understand the patterns and processes of change over time (or space) for populations of a single species.
Part A, #7
Give a general equation in the note for calculating population growth rate.
Population Growth Rate (ΔN/ΔT) = birth rate + immigration rate – death rate – emigration rate
OR just...
Population Growth Rate (ΔN/ΔT) = birth rate – death rate
Part A, #10
With the ____________________ , the rate of population growth is directly proportional to its current population size.
exponential growth model
Part A, #15
What does ‘carrying capacity’ mean?
The particular point in time where the limiting factors and other factors slow the growth such that the population reaches a maximum size (more or less with often constant fluctuating) is called the carrying capacity.
Part A, #2
Give an example of any rate. Give an example of a rate that relates to population.
Claire makes 3 pancakes every 6 minutes. The rate is 3 pancakes per 6 minutes.
If 50 human births occur per year per 1000 women, the fertility rate is 50.
(Other answers are possible!!!)
Part A, #8
Why are there more than one equations given for calculating population growth rate?
It depends on whether immigration and emigration are a factor or not.
Part A, #11
For the exponential growth equation, NT+1 = (1+r) NT , identify what each variable means.
NT+1 means population size in the following time generation.
NT means current population size.
r means growth rate per capita (per individual).
Part A, #16
Compare and contrast the plotted curves for exponential growth and logistic growth.
Exponential curve is a J-shaped curve
Logistic curve is S-curve.
Logistic curve includes exponential curve within it.
Part A, #3
What is the difference between birth rate and fertility rate? Give an example too.
Birth Rate- is the number of offspring per 1000 individuals in some population per year
Fertility Rate- is the number of offspring per 1000 females in some population per year.
Ex. There are 1000 females and 2000 individuals in total. If 100 babies are born in a year then…
Birth rate = 100 / 2000 = 50 / 1000
Fertility rate = 100 / 1000
Part A, #9
Calculating how long it takes for bacteria to increase their population by twice as much is ____________ _______________________.
doubling time.
Part A, #14
Give one or more reasons why the exponential growth model is often less realistic than the logistic growth model.
In real life there will often be multiple limiting factors that can affect the growth rate and eventually stop it from exceeding some number. The exponential growth model does not account for these factors but the logistic growth model does by including the carrying capacity in its equation.
What is the equation for logistic growth?
dN/dT = (r) [(K-N) / K] (N)
Part B, #1
Schuhlsville is an island of 5000 square miles off the coast of Jabooty. There are currently
250 000 inhabitants of the island. Last year, there were 12 000 new children born and
10 000 people were recorded as deceased
What are the birth and mortality rates?
Birth Rate = 4.8 %
Death Rate = 4%
Part B, #3
The doubling time of a population of plants is 12 years. Assuming that the initial population is 300 and that the rate of increase remains constant, about how large will the population be in 37 years?
300 >> 600 >> 1200 >> 2400 in around 37 years
Part B, #9a
One dandelion plant can produce many seeds leading to a high growth rate for dandelion populations. The population of dandelions is currently 40 individuals and r = 0.2 dandelions / month.
a. What is the exponential growth rate at that time of population?
= 0.2 (40)
= 8 So this means the population of 40 has currently increased by 8.
BONUS. Your team only gets the points automatically!!!
:) :) :)
Part B, #8
Suppose that 50 fish are born in year 1. There are only 36 left in year 2 and 22 left in year 3. What is the mortality rate between years 2 and 3? Round to the nearest hundredth.
36 in year two
…… 36- 22 = 14 die after year 2
So death rate during year 2 = 14/36 = 0.389
Part B- #5
In April of 2010, the US population was 308 745 538 and had been growing by about 0.97 %. Assuming a constant growth rate, what was the population in 2020?
(308 745 538)(1+0.0097)^10
= 340 035 494
Part A, #9b
One dandelion plant can produce many seeds leading to a high growth rate for dandelion populations. The population of dandelions is currently 40 individuals and r = 0.2 dandelions / month.
b. Predict how many dandelions would be added to this population after 2 months.
= 40(1+0.2)^2
= 58 is the population .
So 58 – 40 = 18 individual dandelions would have been added.
Part B, #10
(challenge) Suppose a population of butterflies is growing according to the logistic equation. If the carrying capacity is 500 butterflies and r = 0.1 individuals/(individual*month), what is the maximum possible growth rate for the population?
dN/dT = (0.1) [(500)-250 / 500] (250)
= 12. 5 So 12.5 is the maximum growth rate and occurs when N is half of K
(ie. when N is 250 butterflies)