When polymerase binding causes transition to the open complex and initiates transcription. This gives a low level of constitutive expression called the basal level. 

Binding of RNA polymerase is the rate-limiting step in this case.

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#Unit 10. Ecological Principles

λ represents the finite rate of population change over some time interval, often a year

λ = N1/N0

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#Unit 10. Ecological Principles

Populations grow when R0 or λ>1, populations decline when R0 or λ<1, and are at equilibrium when R0 or λ=1

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#Unit 10. Ecological Principles

The simplest method to measure population density is to visually count the number of organisms in a population in a given habitat.

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#Id: 5369

#Unit 10. Ecological Principles

Quadrats - A square frame often, but not always, measuring 50 × 50 cm. 

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#Id: 5371

#Unit 10. Ecological Principles

Pitfall traps set into the ground catch wandering species such as beetles and spiders. These have rain covers to prevent the animals from drowning

 

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#Id: 5372

#Unit 10. Ecological Principles

Baited snap traps, Population density can thus be estimated as the number of animals caught per trap or per unit area where a given number of traps are set.