Population Ecology MCQ Quiz in मल्याळम - Objective Question with Answer for Population Ecology - സൗജന്യ PDF ഡൗൺലോഡ് ചെയ്യുക

The correct answer is At point B, population of species N increase while that of species M decreases

Explanation:

Isoclines: The zero-growth isocline for a species represents the conditions under which the population of that species remains constant (neither increases nor decreases).
The graph shows two isoclines: one for species M and one for species N.
Carrying Capacity: K_M and K_N represent the carrying capacities of species M and N, respectively, when the other species is absent.
The slopes of the isoclines indicate the per capita effects (α for M on N and β for N on M).

Population Growth:

• If a point lies below a species' isocline, the population of that species is increasing.
• If a point lies above a species' isocline, the population of that species is decreasing.

Point A:

• Located below the isocline of species N: This means that at point A, the population of species N is increasing since it is below its zero-growth isocline.

Point B:

• Located below the isocline of species M: This means that at point B, the population of species M is increasing, as it is also below its zero-growth isocline.

Therefore, Statement 3: "At point B, population of species N increases while that of species M decreases." is incorrect because point B is below the isocline for species M, species M is actually increasing, not decreasing. 

The correct answer is specific leaf area, leaf nitrogen and net photosynthesis rate decrease.

Explanation:

Research on plant species traits has shown trends where longer leaf lifespans are often associated with certain physiological and morphological characteristics:

• Specific Leaf Area (SLA): SLA is the area of leaf per unit of dry mass. Leaves with longer lifespans tend to have a lower specific leaf area because they are typically thicker and tougher to reduce damage and wear over time.
• Leaf Nitrogen Content: Long-lived leaves usually have lower nitrogen content. Nitrogen is a critical component of chlorophyll and proteins involved in photosynthesis. Lower nitrogen content in long-lived leaves is a trade-off for reduced metabolic cost and maintenance.
• Net Photosynthesis Rate: Leaves that live longer often exhibit a lower net photosynthesis rate. This is because they are usually more structurally robust and less focused on rapid growth and turnover, leading to a slower photosynthetic activity rate.

Thus, the correct option is specific leaf area, leaf nitrogen and net photosynthesis rate decrease.

Key Points

Exponential growth

• A population shows exponential growth (there is no limitation on growth, in an idealized unlimited environment.
• Under an ideal unlimited environment, the per capita rate of increase (the number of offspring born per individual) is maximum.
• During exponential growth, the number increases in the geometric progression 2⁰, 2¹, 2², 2³........
• In geometric growth, the rate of increase is expressed as a constant fraction or an exponent by which a particular population is multiplied (like 2, 4, 8, 16, ).
• By contrast, a pattern of growth that increases at a constant amount per unit of time (i.e. 1, 2, 3, 4 or 1, 3, 5, 7...) is called arithmetic growth.
• The exponential form of growth may be represented by the simple model based on the exponential equation:
• Where, W is the population size and ris the intrinsic rate of increase
• dN/dt = rN 
• During exponential population growth under an ideal unlimited environment, per capita rate of increase is maximum and is called the intrinsic rate of increase.
• The maximum value of r is often referred by the less specific but widely used expression (biotic potential, or reproductive potential).
• It is the maximum per capita growth rate in the absence of environmental resistance
• The sum total of all environmental factors that together act to limit the biotic potential of an organism from being realized is called environmental resistance.
• It includes both biotic factors such as predation, competition, parasitism and abiotic factors such as drought, fire, flood etc.
• Biotic potential differs from one species to another e.g. deer populations can grow faster than a population of elephants.
• In a closed population, r is defined as the per capita birth rate (b) minus the per capita death rate (d).
• When per capita birth rate exceeds per capita death rate (b> d), the population is increasing and is positive when death rate exceeds birth rate (d> b), then r is negative and the population is decreasing.
• When per capita birth rate exceeds per capita death rate (b> d), the population is increasing and is positive when death rate exceeds birth rate (d> b), then r is negative and the population is decreasing.

Hence the correct answer is option 2.

Key PointsPopulation  Dispersion 

• Dispersion refers to the spatial and temporal distribution pattern of individuals of a population.
• It describes the pattern of spacing among individuals within the boundaries of the population.
• Individuals in a population may be distributed in three broad patterns - Regular, Random and Clumped (aggregated or contagious).

Regular dispersion

• In regular dispersion (also called a uniform or even distribution), the individuals are more or less spaced at an equal distance from one another.
• Individuals are more evenly spaced than expected by chance.
• This is rare in nature but is common in managed systems like croplands.
• A regular distribution pattern may be the result of competition or social interactions.

 Random dispersion,

• In random dispersion, the position of one individual is unrelated to the positions of other individuals.
• This kind of distribution occurs where the environment is very uniform and there is no tendency to aggregate.
• This is also relatively rare in nature.

Clumped dispersion

• In clumped dispersion (also called a contagious or aggregated dispersion) individuals are aggregated into groups of varying size.
• Most populations exhibit this kind of dispersion.
• A clumped distribution pattern often results from the uneven distribution of a resource.
• Human population show Clumped distribution due to their social behaviours, economic condition and geographic factors.

Explanation:

• In random dispersion, the position of one individual is unrelated to the positions of other individuals.
• This kind of distribution accurse  where the environment is very uniform and there is no tendency to aggregate.

Hence the correct answer is option 2

The correct answer is Option 1 i.e.Early reproduction and slow growth rate 

Explanation-

Snake Predation Pattern:

• Snakes prefer to prey upon large, older individuals of the rodent species that grow continuously over their lifespan.
• This means that larger, older individuals are more vulnerable to snake predation.

Life History Traits in Response to Predation:

• Early reproduction: Rodents with the trait of early reproduction have a higher likelihood of passing on their genes before reaching the vulnerable, larger size. Early reproduction allows individuals to produce offspring at a younger age, potentially reducing the risk of predation for smaller, younger individuals.
• Slow growth rate: The combination of early reproduction and slow growth rate is beneficial in this context. Slow growth rate implies that individuals take longer to reach a larger size, delaying the period when they become more susceptible to snake predation.

Trade-Offs in Life History Traits:

• Life history traits, such as reproduction timing and growth rate, often involve trade-offs.
• In this case, there is a trade-off between reproducing early to avoid predation and having a slower growth rate to delay vulnerability to predation.

Conclusion-Early reproduction and slow growth rate is the most likely life history trait in a rodent species facing a predation pattern where snakes prefer larger, older individuals. This trait allows for reproduction at a younger age and slower growth to delay vulnerability to predation.

Key Points

•  Survivorship curves outline the mortality history of a cohort, or group of people who were born around the same time, as they age.
• A survivorship curve is a graphical representation of the percentage of the cohort's members who live to certain ages.

Important Points:

• ​Survivorship curve of type I:
  • A low mortality rate early in life and a high mortality rate later in life define this sort of curve.
  • In creatures with high levels of parental care and protection, like humans, this kind of curve is typical. specifically elephants.
• Survivorship curve of type II:
  • A relatively steady mortality rate over the cohort's lifetime characterises this kind of curve.
  • This kind of curve is prevalent in species like birds and reptiles that deal with a pretty constant amount of sickness or predation. lizards in this instance.
• type III survivorship curve:
  •  A high mortality rate in the early years of life and a low mortality rate in the later years of life define a type III survivorship curve.
  • This kind of curve is prevalent in organisms like plants and insects that have a large number of young yet offer little to no parental care.
  • Insects in this instance.
  • The use of survival curves in ecological research is crucial because they shed light on the life histories and reproductive tactics of various species.

Hence the correct answer is option 1 

The correct answer is Breeds early and only once in life and produces large number of small-sized offspring.  

Concept:

• An organism's Darwinian fitness is calculated as the number of offspring it leaves behind that, themselves, survive to reproduce.
• In evolutionary terms, it is of no consequence if an organism is a fine, fully mature, physical specimen, or the dominant member of the herd, or even that an individual produces a lot of young but none of them survive.
• In the relay race of evolution, getting as many copies of your genes into the next generation as possible is the only goal.
• As you might imagine, there are many ways to be reproductively successful.
• One way is to become the dominant animal in a pack, and to monopolize mating opportunities, but another way is to be submissive and sneaky, mating with others when the dominant animal is not around to stop you.
• similarly animals also strategize the number of off springs to be produced.

Explanation:

r-selection:

• On one extreme are the species that are highly r-selected.
•  Such a species puts only a small investment of resources into each offspring, but produces many such low effort babies.
• Such species are also generally not very invested in protecting or rearing these young. Often, the eggs are fertilized and then dispersed.
• The benefit of this strategy is that if resources are limited or unpredictable, you can still produce some young.
• However, each of these young has a high probability of mortality, and does not benefit from the protection or nurturing of a caring parent or parents.
• r-selected babies grow rapidly, and tend to be found in less competitive, low quality environments.
• Although not always the case, r-selection is more common among smaller animals with shorter lifespans and, frequently, non-overlapping generations, such as fish or insects.
• The young tend to be precocial (rapidly maturing) and develop early independence.
• Semelparous describes organisms that reproduce exactly once in a lifetime.
• Some examples are female praying mantises eating their mates once eggs are fertilized. 
• Most of r strategists are semelparous.

• On the other extreme are species that are highly K-selected.
• K refers to the carrying capacity, and means that the babies are entering a competitive world, in a population at or near its carrying capacity.
• K-selected reproductive strategies tend towards heavy investment in each offspring, are more common in long-lived organisms, with a longer period of maturation to adulthood, heavy parental care and nurturing, often a period of teaching the young, and with fierce protection of the babies by the parents.
• K-selected species produce offspring that each have a higher probability of survival to maturity.
• Although not always the case, K-selection is more common in larger animals, like whales or elephants, with longer lifespans and overlapping generations.
• The young tend to be altricial (immature, requiring extensive care).

The correct answer is dN/dt

Concept:

• ​In population ecology and economics, maximum sustainable yield (MSY) is theoretically, the largest yield (or catch) that can be taken from a species' stock over an indefinite period.
• The concept of MSY aims to maintain the population size at the point of maximum growth rate by harvesting the individuals that would normally be added to the population, allowing the population to continue to be productive indefinitely.
• Under the assumption of logistic growth, resource limitation does not constrain individuals' reproductive rates when populations are small, but because there are few individuals, the overall yield is small.
• At intermediate population densities, also represented by half the carrying capacity, individuals can breed to their maximum rate.
• At this point, called the maximum sustainable yield, there is a surplus of individuals that can be harvested because growth of the population is at its maximum point due to the large number of reproducing individuals.

Explanation:

Fig 1: Growth rate varies with population density

• The simplest way to model harvesting is to modify the logistic equation so that a certain number of individuals is continuously removed:

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• Where H represents the number of individuals being removed from the population – that is, the harvesting rate. When H is constant, the population will be at equilibrium when the number of individuals being removed is equal to the population growth rate.
• For low densities (far from carrying capacity), there is little addition (or "recruitment") to the population, simply because there are few organisms to give birth.
• At high densities, though, there is intense competition for resources, and growth rate is again low because the death rate is high. In between these two extremes, the population growth rate rises to a maximum value.
• This maximum point represents the maximum number of individuals that can be added to a population by natural processes.
• If more individuals than this are removed from the population, the population is at risk for decline to extinction.
• The maximum number that can be harvested in a sustainable manner, called the maximum sustainable yield, is given by this maximum point.

Concept:

• The concept is related to the logistic growth model, which is commonly used to describe population growth when there are limited resources available.
• The logistic growth model incorporates a carrying capacity (k), which represents the maximum population size that the environment can sustain.
• In the logistic growth model, population growth starts exponentially, similar to the exponential growth model.
• However, as the population approaches the carrying capacity, the growth rate gradually slows down and eventually levels off.
• This leveling off occurs because resources become limited as the population size increases, leading to competition and constraints on further growth.

Explanation:

• In the logistic growth model, the population growth rate is highest when the population size is halfway between 0 and the carrying capacity (k).
• This midpoint is mathematically represented as N = k/2.
• In the given scenario, the stable population size is 520, which corresponds to the carrying capacity (k).
• Therefore, according to the logistic growth model, the population is expected to reach its highest growth rate when the population size is halfway between 0 and 520, which is 520/2 = 260.

Hence, the correct answer is option 2.

Key Points

• There are two major growth models to explain growth of a population:
  • Exponential - This takes place when the resources are unlimited and the population keeps growing.
  • Logistic - This is a growth model that takes the limitations of resources into account.
• Exponential growth is often represented as density-independent growth, where the growth rate is unaffected by the change in density.
• Density-independent growth is typically observed when the population is far below the carrying capacity of the environment, and the influence of density-dependent factors is minimal.

Explanation:

• The term "dN/Ndt" represents the rate of change of population size (N) over time (t) and is commonly referred to as the instantaneous rate of population growth.
• It is a key concept in understanding exponential growth in populations.
• When a population is growing exponentially, the value of "dN/Ndt" is equal to the population growth rate (r).
• It indicates the fraction of the population that is added or removed per unit of time relative to the current population size.

From the above graphs, we can see that:

• Options 3 and 4 represents logistic growth, while only option 2 shows exponential growth in a population.

Hence, the correct answer is option 2.