Consider the two species competition model given by da/dt=[lambda 1a/(a+K1)]−rab*ab−da, db/dt=[lambda 2b∗(1−b/K2)]−rba*ab, t>0, for two interacting species denoted a=a(t) and b=b(t), with initial conditions a=a0 and b=b0 at t=0. Here lambda 1, lambda 2, K1,K2, r_(ab), r_(ba) and d are all positive parameters. (a) Describe the biological meaning of each term in the two equations. => A series expansion of 1/(a+K1), gives

Kamila Frye

Kamila Frye

Answered question

2022-10-16

Consider the two species competition model given by
d a d t = [ λ 1 a / ( a + K 1 ) ] r a b a b d a ,                     ( 1 )
d b d t = [ λ 2 b ( 1 b / K 2 ) ] r b a a b ,               t > 0 ,                 ( 2 )
for two interacting species denoted a=a(t) and b=b(t), with initial conditions a=a0 and b=b0 at t=0. Here λ , λ 2 , K 1 , K 2 , r a b , r b a and d are all positive parameters. (a) Describe the biological meaning of each term in the two equations.
=> A series expansion of 1/(a+K1), gives
1 a + K 1 K 1 a K 1 2 + O ( a 2 )
Now,
d a d t = [ λ 1 a × a + K 1 K 1 2 ] r a b a b d a ,
λ1 a represents the exponential growth of population
da represents the exponential decay of population
λ1 is the growth rate
d is the decay rate
what does r_(ab) ab represent?
The first term of RHS equation 1 : [ λ 1 a × a + K 1 K 1 2 ] represents logistic growth at a rate λ1 with carrying capacity K1.
d b d t = [ λ 2 b × 1 b K 2 ] r b a a b ,
λ2 b represents the exponential growth of population
λ2 is the growth rate
what does r_(ba) ab represent?
The first term of RHS equation 2 : [ λ 2 b × 1 b K 2 ] represents logistic growth at a rate λ2 with carrying capacity K2.

Answer & Explanation

Theresa Wade

Theresa Wade

Beginner2022-10-17Added 9 answers

A typical Interspecific competition between two species a and b can be represented by the following equations:
dadt=λ1a[1−ak]
This is the logistic population growth model in the absence of competing species b.
Now ,
dadt=λ1a[1−ak1−β12bk1]
is the logistic population growth model for a under the presence of species b. Now we are going to add one more term to the model to represent the decay by exponential decay model.
Exponential decay model is
dadt=−λda
Add this term to the original equation, we get
dadt=λ1a[1−ak1−β12bk1]−λda
Now to define each of the term in the above model (ODE).
λ1 = logistic population growth rate.
k1 - Carrying capacity of species a
**β12b - can be thought of as the decrease in growth rate of species "a" due to the presence of species "b"
λd = exponential decay rate.
Similarly,
dbdt=λ2b[1−bk2−β21ak2]
Now to define each of the term in the above model (ODE).
λ2 = logistic population growth rate of b.
k2 - Carrying capacity of species b
**β21a - can be thought of as the decrease in growth rate of species "b" due to the presence of species "a".
This is typically the interspecific competition model. In your original equation, you have β12 to be rab

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