Tag: growth rates and conditions for growth

Questions Related to growth rates and conditions for growth

The sequence of various components of a growth curve are

biology plant growth growth rates and conditions for growth population ecology growth and development

  1. Lag, log, stationary

  2. Log, lag, stationary

  3. Log, stationary, lag

  4. Stationary, log, lag

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Correct Option: A
Explanation:
Growth curve is divided into four phases, namely lag phase, log phase, stationary phase and death phase. In lag phase, there is very little or no bacterial growth. In this phase, bacteria are adjusting to environment and synthesizing biochemicals and nutrients. In log phase, the number of bacterial cells doubles at an exponential rate. The maximum growth phase is log phase. In stationary phase, the rate of cell death is equal to the rate of cell division. In death phase, there is decrease in the bacterial population due to lack of nutrients and high toxin concentration.
Thus, the correct answer is 'Lag, log, stationary'.

Maximum of growth occurs in

biology plant growth growth rates and conditions for growth population ecology growth and development

  1. Exponential phase

  2. Decline phase

  3. Stationary phase

  4. Lag phase

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Correct Option: A
Explanation:
Bacterial growth is divided into four phases, namely lag phase, exponential phase, stationary phase and decline phase. In lag phase, there is very little or no bacterial growth. In this phase, bacteria are adjusting to environment and synthesizing biochemicals and nutrients. In exponential phase, the number of bacterial cells doubles at an exponential rate. The maximum growth occurs in this phase. In stationary phase, the rate of cell death is equal to the rate of cell division. In decline phase, there is decrease in the bacterial population due to lack of nutrients and high toxin concentration
So, the correct answer is 'Exponential phase'

A tracheid is distinguished from a vessel elements on the basic of.

biology plant growth growth rates and conditions for growth population ecology growth and development

  1. Length

  2. Thickness

  3. Side-wall pitting

  4. End-wall perforation

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Correct Option: A

What is the maximum period of growth?

biology plant growth growth rates and conditions for growth population ecology growth and development

  1. Slow growth rate

  2. Steady growth rate

  3. Speedy growth rate

  4. Senescence phase

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Correct Option: A

If division and differentiation are cocurrent then growthi will be 

biology plant growth growth rates and conditions for growth population ecology growth and development

  1. Geometric

  2. Logistic

  3. Linear

  4. Infinite

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Correct Option: B
Explanation:

There are two types of population growth, geometric growth and logistic growth. Geometric growth is also called as exponential growth. Logistic growth is S shaped growth. Arithmetic growth is a linear growth. During cell division, cell divides into two. It increases cell number. During cell differentiation, cell specializes into different cell type. If division and differentiation are cocurrent then there will be negative control. It will regulate the cell division. Hence, the growth will be logistic.

Thus, the correct answer is option B.

In signoid growth curve, upper asymptote represents period of

biology plant growth growth rates and conditions for growth population ecology growth and development

  1. Establishment

  2. Negative acceleration

  3. Positive acceleration

  4. Equilibrium

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Correct Option: D
Explanation:

In a sigmoid growth curve, there are three phases, lag phase, exponential phase and steady state phase. The upper limit of the curve is called as upper asymptote. It represents the period of equilibrium. At this stage, birth rate and death rate are at balance. It is said to be at equilibrium because at this stage, there is equilibrium between biotic potential and environmental resistance.

Thus, the correct answer is option D.

State whether the following statements are true or false.
Ethylene stimulates leaf release, while auxin keeps leaves from falling.

biology plant growth growth rates and conditions for growth population ecology growth and development

  1. True

  2. False

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Correct Option: A
Explanation:

Ethylene is a gaseous hormone which stimulates the transverse growth but inhibits the longitudinal growth. Auxin delays the abscission of young leaves and provides nutrition to it so that they do not die down while ethylene increases the senescence of leaves and flowers and produces more gas which leads to loss of leaves.

So, the correct statement is 'True'.

Which of the following is not a feature of a J-shaped growth form of population?

biology plant growth growth rates and conditions for growth population ecology growth and development

  1. It is found in stable type of population.

  2. Exponential phase is very rapid.

  3. A crash phase occurs at the end of the growth.

  4. Environmental resistance does not operate.

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Correct Option: A
Explanation:

J-shaped growth curve is a curve on a graph that records the situation in which, in a new environment, the population density of an organism increases rapidly in and exponential or logarithmic form, but then stops abruptly as environmental resistance or some other factor suddenly becomes effective. The actual rate of population change depends on the biotic potential and population size. It may be summarized mathematically as 

                                           dN/dT= rN (with a definite limit on N)
where, N is the number of individuals in the population
t is time
and, r is a constant representing the intrinsic rate of increase (biotic potential) of the organism concerned.
The population grows exponentially, and after attaining the peak value, the population may abruptly crash. This increase in population is continued till large amount of food materials exist in the habitat.
So the correct option is 'it is found in stable type of population'.

 Because of the which of the following reason/s, growth stops completely during the stationary phase?

biology plant growth growth rates and conditions for growth population ecology growth and development

  1. Lack of nutrients

  2. Saturation of nutrients

  3. Over availability of nutrients

  4. None of the above

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Correct Option: A
Explanation:

The stationary phase is the phase in which the growth of lant generally stops and the plant proceeds towards maturity it may occur due to the lack of nutrients majorly seen in the unfavourable season.

So, the correct option is 'Lack of nutrients'.

Incorrect about geometrical growth

biology plant growth growth rates and conditions for growth population ecology growth and development

  1. After mitosis both daughter cells retain the capacity of division

  2. Growth pattern follows sigmoid curve

  3. Less common than arithmetic growth in the plants

  4. Growth rapidly increases

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Correct Option: D
Explanation:

In geometrical growth both the progeny cells following mitotic cell division retain the ability to divide and continue to do so. However, with a limited supply of nutrients, the growth becomes slow which lead to the stationary stage. A sigmoid curve is the characteristic of organism living is the natural environment.

So the correct option is 'growth rapidly increases'