Organisms and Populations Test

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Organisms and Populations Test - 81

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Weekly Quiz Competition

Question 1
1 / -0

The population size of a species over time is shown in the graph. The growth pattern demonstrated by the population at time 1 is

A
Gradual

B
Declining

C
Continual

D
Oscillating

E
Exponential

Solution

The growth pattern demonstrated by the population at time 1 is exponential. Time 1 on the associated graph depicts a steep curve of population increase over a short amount of time, which is characteristic of exponential population growth.
Exponential Growth : At a constant birth rate in population through time and is never limited by food or disease, known as exponential growth. With exponential growth, the birth rate alone controls how fast (or slow) the population grows.
Question 2
1 / -0

Which one of the following pair of animals is an example of commensalism?

A
Sacculina- Crab

B
Plasmodium- Anopheles

C
Golden Jackal- Tiger

D
Ascaris- Man

Solution

In commensalism, one organism benefits from the relationship while the other species involved neither benefits nor is harmed. The tiger can sometimes have an unknown companion in their group, the golden jackal. When the golden jackal somehow is left out of his pack they will follow around a tiger, to find food. The tiger doesn't know about the jackal due to physical appearance, this is an example of a commensalism.
Question 3
1 / -0

Which of the following could not cause a large number of density-dependent deaths in a population?

A
Winter storms

B
Disease carrying insects

C
Predators

D
Limited resources

E
Small forest fire

Solution

Density-dependent factors are the one that affects the birth and death rates of population in a density-dependent manner. These are mostly the biotic factors such as predation, competition, parasites etc. For example, low prey density affects the mortality of predator. Among the given options, winter storms affect the population in density independent manner as it can affect the individual organism. For example, winter storm causing the death of a deer regardless of deer population density. So, the correct answer is option A.
Question 4
1 / -0

Read the passage and answer the following question.
Students carry out an experiment to explore the effect of different environments on blood flow using small, freshwater fish. Each fish is placed into a petri dish. A wet cotton ball is placed over its gills to allow for the diffusion of oxygen, which will keep the fish alive. The students then place the petri dish onto the stage of a light microscope so that the thinnest part of the tail is directly under the objective lens and blood can be seen flowing in blood vessels. While focusing on a capillary, students count the number of red blood cells flowing through the vessel at 5-second intervals. After monitoring the normal flow of blood for 30 seconds, the environment in the petri dish is altered in one of five different ways. Students observe and record the change in blood flow if any. After the experiment, each fish is returned to the fish tank.

Experiment 1 - Nothing is added to this petri dish.
Experiment 2 - Water at a temperature of $$\displaystyle { 5 }^{ \circ }C$$ is added.
Experiment 3 - Water at a temperature of $$\displaystyle { 30 }^{ \circ }C$$ is added.
Experiment 4 - Ethyl alcohol is added.
Experiment 5 - Nicotine extracted from cigarette tobacco is added.

Experiment Initial average rate of blood flow Final average rate of blood flow
1 9 9
2 8 4
3 9 13
4 8 5
5 9 12

Which of the following statement is incorrect about this experiment?

A
Alcohol is a central nervous system depressant and decreases the blood flow in the capillary.

B
Nicotine is a central nervous system that stimulates and increases blood flow in the capillary.

C
Increasing the temperature increases the blood flow in the capillary.

D
The changes in blood flow in experiments 2 and 3 are temporary because a fish can adjust its body temperature.

E
Experiment 1 is the control.
Solution
- Fish is cold-blooded animal and can not control its body temperature. They cannot generate their own body heat, but they do regulate it by changing their environment.
- Therefore, this statement is not correct. All the other statements are correct.
Therefore, the correct answer is option D.
Question 5
1 / -0

The interspecific relationship which benefits one species and harms the other includes
I. Commensalism
II. Competition
III. Parasitism
IV. Predation

A
III only

B
III and IV

C
I, II, and III

D
II, III, and IV

E
I, II, III, and IV

Solution

Community interactions take many forms, including:
Competition: A relationship where both species are harmed.
Predation: A relationship where predators get benefits but harm prey.
Parasitism: A relationship where one get benefits and harms host.
Commensalism: A relationship where one get benefits but other has no effect.
Mutualism: A relationship where both gets benefits.
Thus, the correct answer is option B.
Question 6
1 / -0

The point of time in the graph when the population size reaches the carrying capacity for ecosystem is

A
3

B
4

C
6

D
9

E
12

Solution

Carrying capacity is the maximum size of population of a species that a certain environment can support for an extended period of time. Once population overshoot the carrying capacity, it starts either decreasing as at this point, the different environmental resistances start operating or remain constant but there is not increase in population size after it. In given graph, 12 represents the point with maximum population size after which there is no increase in population size. Correct answer is E.
Question 7
1 / -0

In what way a plant growing on a forest floor is adapted for its survival?

A
Has shallow roots

B
Requires low light

C
Has a deep ta root

D
Requires strong light

E
Requires moist soil

Solution

Plants growing on the forest floor (understorey) are adapted to lower Sunlight intensity or are shade loving. This is because, the dense canopy does not allow enough light to penetrate through and reach the forest floor. Light is the limiting factor for these plants and therefore, they are adapted to survive under low light conditions. Moisture availability and related adaptations are not of consideration. Thus, the correct answer is option B.
Question 8
1 / -0

Based on the given figure, find out the incorrect statement?

A
Rodent density is dependent on food-species diversity

B
Food- species diversity is dependent on rodent density

C
Grazing pressure maintains food-species diversity

D
Rodents are selective in their food choices

E
Rodents help prevent food-species mono cultures from developing
Question 9
1 / -0

Which of the following will be fewer in number for an invasive species in a new ecosystem?
I. Ecological niches
II. Predators
III. Suitable food sources

A
I only

B
II only

C
III only

D
I and II

E
II and III

Solution

An invasive species is an organism that is new to environment where it is not native. A key factor that makes many species invasive is a lack of predators in the new environment. This is complex and results from thousands of years of evolution in a different place. Predators and prey often co-evolve in a phenomenon called the co-evolutionary arms race. What this means is that as prey evolve better defenses, predators in turn evolve better ways of exploiting prey. The classic example of this comes from the cheetah and antelope. Faster antelope survive better because they can better escape cheetahs. The fastest cheetahs then survive better because they can better catch the faster antelope. Neither species ultimately gains an advantage because they continually evolve in response to one another. However, when a plant or animal enters a new environment, they will likely encounter predators who have not been evolving with them, which makes these predators unable to successfully exploit the prey. Defense mechanisms like venom, size or speed that have been matched by adaptation in predators are suddenly without match in the new environment. This can allow the species to proliferate rapidly as it no longer faces any predators.
Question 10
1 / -0

The given graph represents the fastest multiplication rate of bacteria when they are added to rich broth.
The following graphs represent bacterial growth under different conditions, with increasing numbers of bacteria on the $$y$$-axis and increasing time on the $$x$$-axis.
Which graph describes the result of introduction of minimal nutrients for the first six hours and then addition of surplus nutrients?

A
1

B
2

C
3

D
4

E
5

Solution

A bacterial cell undergoes several transitional changes when cultured on a nutrient media. These changes can be categorized as phases of growth. During initial stages when the bacteria adjust in the new environment, the nutrient uptake is slow due to low metabolic rate. This phase is known as lag phase. As the metabolic rate increases the nutrient uptake increases along with it and the phase is known as log phase. When all the nutrient in the solution depletes the bacteria enters the stationary phase.
Here, in the above-given graphs, Graph 5 shows slow growth rate in the initial stages. But the growth rate shoots up suddenly which clearly indicates the addition of surplus nutrient which is needed in log phase.
So, option E is the correct answer.

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Experiment	Initial average rate of blood flow	Final average rate of blood flow
1	9	9
2	8	4
3	9	13
4	8	5
5	9	12

Organisms and Populations Test - 81

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Organisms and Populations Test - 81

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SHARING IS CARING

Question 1

Gradual

Declining

Continual

Oscillating

Exponential

Solution

Question 2

Sacculina- Crab

Plasmodium- Anopheles

Golden Jackal- Tiger

Ascaris- Man

Solution

Question 3

Winter storms

Disease carrying insects

Predators

Limited resources

Small forest fire

Solution

Question 4

Alcohol is a central nervous system depressant and decreases the blood flow in the capillary.

Nicotine is a central nervous system that stimulates and increases blood flow in the capillary.

Increasing the temperature increases the blood flow in the capillary.

The changes in blood flow in experiments 2 and 3 are temporary because a fish can adjust its body temperature.

Experiment 1 is the control.

Solution

Question 5

III only

III and IV

I, II, and III

II, III, and IV

I, II, III, and IV

Solution

Question 6

3

4

6

9

12

Solution

Question 7

Has shallow roots

Requires low light

Has a deep ta root

Requires strong light

Requires moist soil

Solution

Question 8

Rodent density is dependent on food-species diversity

Food- species diversity is dependent on rodent density

Grazing pressure maintains food-species diversity

Rodents are selective in their food choices

Rodents help prevent food-species mono cultures from developing

Question 9

I only

II only

III only

I and II

II and III

Solution

Question 10

1

2

3

4

5

Solution

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