All questions of Organisms and Population for NEET Exam

Organism ....given in ncert

Correct option is (c)
Biological organisation starts with submicroscopic molecular level, where four types of molecules, i.e. carbohydrates, lipids, proteins and nucleic acid are organised into organelles of cell.

Aestivation: Aestivation is summer sleep and during aestivation, animals usually tend to rest in a shady and cool place. ... In aestivation, usually cold blooded animals like reptiles maintain their body temperature by reducing their metabolic activities and protecting themselves from very high temperature.

Answer is c) logistic

Homeotherms: animals who maintain a constant internal body temperature across a wide range of environmental conditions. Most mammals and birds are homeotherms.

Plants adapted to living in dry environments such as succulents are termed xerophytes. However, not all xerophytes are succulents, since there are other ways of adapting to a shortage of water, e.g., by developing small leaves which may roll up or having leathery rather than succulent leaves.

An ectotherm "outside" and  "hot"), is an organism in which internal physiological sources of heat are of relatively small or quite negligible importance in controlling body temperature.] Such organisms (for example frogs) rely on environmental heat sources,which permit them to operate at very economical metabolic rates. Colloquially, some refer to these organisms as "cold blooded" though such a term is not technically correct, as the blood temperature of the organism varies with ambient environmental temperature. Some of these animals live in environments where temperatures are practically constant, as is typical of regions of the abyssal ocean and hence can be regarded as homeothermic ectotherms. In contrast, in places where temperature varies so widely as to limit the physiological activities of other kinds of ectotherms, many species habitually seek out external sources of heat or shelter from heat; for example, many reptiles regulate their body temperature by basking in the sun, or seeking shade when necessary in addition to a whole host of other behavioral thermoregulation mechanisms. For home captivity as pet, reptile owners can use a UVB/UVA light system to assist the animals' basking behaviour.

Commensalism is a type of symbiotic relationship where one species benefits from the association, while the other is neither harmed nor helped. In this type of association, one species derives benefits from the other without causing any harm to the host.

Explanation:

In the given scenario, the small fish gets stuck near the bottom of a shark and derives its nutrition from it. The small fish is not harming the shark, nor is it providing any benefits to the shark. Therefore, this is an example of commensalism.

The small fish is using the shark as a shelter and also gets access to food particles that are present near the shark's mouth. The shark is not affected by the presence of the small fish, and it does not derive any benefit from it either.

In summary, commensalism is a type of symbiotic relationship where one species benefits from the association, while the other is neither harmed nor helped. The small fish getting stuck near the bottom of a shark and deriving its nutrition from it is an example of commensalism.

Logarithmic or Exponential phase : It is characterized by rapid growth in population which continues till enough food is available. But with the increase in reindeer population, there is corresponding decrease in the availability of food and space, which finally become exhausted, which leads to mass starvation and mortality. This sudden increase in mortality is called population crash. Lemming of Tundra, some insect, algal blooms and annual plants also show J-shaped curves. The population growth curve is S- shaped in most of the organisms, Human population also shows S-shaped curve.

Understanding the Lotus Population Dynamics
To solve the problem, we need to calculate the birth and death rates for the lotus plants based on the given data.
Initial Population
- Last year, there were 30 lotus plants.
New Plants Added
- In one year, 25 new lotus plants were added due to reproduction.
Plants that Died
- During the same year, 8 plants died.
Calculating the Birth Rate
- Formula for Birth Rate:
Birth Rate = (Number of New Plants / Initial Population)
- Calculation:
- Birth Rate = 25 new plants / 30 initial plants = 0.8333 (approximately 0.83)
Calculating the Death Rate
- Formula for Death Rate:
Death Rate = (Number of Deaths / Initial Population)
- Calculation:
- Death Rate = 8 plants died / 30 initial plants = 0.2667 (approximately 0.27)
Final Rates
- Therefore, the birth rate is approximately 0.83 individuals per lotus per year.
- The death rate is approximately 0.27 individuals per lotus per year.
Conclusion
The birth and death rates for the lotus population are:
- Birth Rate: 0.83
- Death Rate: 0.27
Thus, the correct answer is option 'A': 0.83 and 0.26 individuals per lotus per year.

Ecology is the branch of biology that studies the relationships between living organisms and their environment. It is concerned with understanding how organisms interact with both the biotic (living) and abiotic (non-living) components of their surroundings.

Understanding Carrying Capacity (K)
The carrying capacity, often denoted as "K," is a crucial ecological concept that defines the limits of a habitat's ability to sustain a population. Here's a detailed explanation:
Definition of Carrying Capacity
- The carrying capacity refers to the maximum number of individuals of a particular species that an environment can support over time without degrading the habitat.
- It is influenced by various factors such as food availability, water supply, habitat space, and the presence of predators and diseases.
Importance of Carrying Capacity
- Understanding carrying capacity helps in the management of wildlife populations and natural resources, ensuring that ecosystems remain balanced and healthy.
- It aids in predicting how changes in the environment (like climate change or human encroachment) can impact species survival.
Factors Influencing Carrying Capacity
- Resource Availability: The amount of food, water, and shelter available directly affects how many individuals can be supported.
- Environmental Conditions: Changes in climate, habitat destruction, and pollution can lower the carrying capacity.
- Species Interactions: Predation, competition, and disease can either increase or decrease the effective carrying capacity.
Consequences of Exceeding Carrying Capacity
- When a population exceeds its carrying capacity, it can lead to overpopulation, resulting in resource depletion, habitat destruction, and a decline in population health.
- This often causes a population crash, where the numbers plummet due to starvation or increased mortality.
In summary, the carrying capacity (K) is essential for maintaining ecological balance, and understanding it allows for better conservation and management strategies.

Logistic growth

Logistic growth is a growth pattern that occurs when resources become progressively limiting in a population. It is a more realistic model of population growth compared to exponential growth, which does not take into account the carrying capacity of an environment.

Understanding logistic growth

Logistic growth is characterized by an initial exponential increase in population size, followed by a slowing down of growth as resources become limited. This is because as a population grows, it will eventually reach a point where there are not enough resources (such as food, water, and shelter) to support further growth.

Factors affecting logistic growth

Several factors influence the occurrence of logistic growth in a population:

1. Carrying capacity: The carrying capacity is the maximum number of individuals that an environment can sustainably support. As a population reaches this limit, resources become increasingly scarce, causing growth to slow down.

2. Density-dependent factors: These are factors that have a greater impact on population growth as population density increases. Examples include competition for resources, predation, and disease. As population density increases due to exponential growth, these factors become more significant in limiting growth.

3. Birth and death rates: In a logistic growth model, birth rates initially exceed death rates, leading to exponential growth. However, as resources become limiting, birth rates start to decline, and death rates may increase due to increased competition and reduced access to resources.

Graphical representation

Logistic growth is often represented graphically using an S-shaped curve. In the initial phase, the curve rises steeply, representing exponential growth. As the population approaches the carrying capacity, the curve levels off and reaches a plateau, indicating the slowing down of growth. At the carrying capacity, the population stabilizes and remains relatively constant.

Significance of logistic growth

Understanding logistic growth is crucial in ecology and population biology. It helps us predict and manage populations, determine the impacts of resource availability on population dynamics, and assess the sustainability of ecosystems. By considering the carrying capacity and the factors that influence population growth, we can make more accurate predictions and develop effective conservation and management strategies.

Understanding Population Density Dynamics
Population density at any given time is influenced by various factors such as births, deaths, immigration, and emigration. The equation provided,
Nt+1 = Nt + [(A + B) - (C + D)],
helps in understanding how these factors affect population density over time.
Key Terminology Explained
- A (Natality): Refers to the birth rate in the population. An increase in natality contributes positively to population density.
- B (Immigration): This is the influx of individuals into a population from other areas. Immigration increases population density.
- C (Mortality): This term represents the death rate. An increase in mortality leads to a decrease in population density.
- D (Emigration): Emigration is the movement of individuals out of a population. Like mortality, it reduces population density.
Analyzing the Correct Option
The equation states that the population density at time t+1 is equal to the density at time t plus the net change from births and immigration, minus deaths and emigration.
- In this context, if we assign:
- A = Natality (births)
- B = Immigration (influx)
- C = Mortality (deaths)
- D = Emigration (outflux)
This fits perfectly into the equation as it correctly reflects the contributions of each factor to population density changes over time.
Conclusion
Therefore, the correct answer is option 'D', where A is natality and D is emigration, as it accurately represents how these factors influence population density:
Nt+1 = Nt + [(Natality + Immigration) - (Mortality + Emigration)].
Understanding these dynamics is crucial for studies in ecology and population biology, especially in the context of NEET.

Introduction:
The growth of a population is influenced by various factors. While some factors can limit population growth, others can promote it. This question asks which of the given options is not a factor that would limit population growth.

Explanation:
Immigration:
Immigration refers to the movement of individuals into a population from another area. It can contribute to an increase in the population size and counteract the limiting factors. When individuals immigrate into a population, they bring their genetic diversity, which can help the population adapt to changing environments and increase its resilience. Immigration can also introduce new individuals that may increase the available workforce, stimulate economic growth, and contribute to the overall development of the population. Therefore, immigration does not limit population growth but rather facilitates it.

Food Shortage:
Food shortage is a significant limiting factor for population growth. When there is a scarcity of food resources in a population, individuals may struggle to obtain adequate nutrition for survival and reproduction. This can lead to decreased birth rates, increased mortality rates, and overall population decline. Food shortage can be caused by various factors such as environmental changes, overexploitation of resources, or competition among individuals within the population. It is a crucial factor that can limit the carrying capacity of an ecosystem and, consequently, the growth of the population.

Disease:
Diseases can exert a significant impact on population growth. When a population is affected by diseases, it can lead to increased mortality rates and decreased reproductive success. Infectious diseases, for example, can spread rapidly within a population and cause widespread illness and death. This can result in a decrease in population size and limit population growth. Additionally, diseases can also affect the health and well-being of individuals, leading to reduced fertility and birth rates. Therefore, disease is a limiting factor for population growth.

Famine:
Famine refers to a widespread scarcity of food in a population, often caused by factors such as drought, crop failure, or political instability. Like food shortage, famine can lead to a lack of adequate nutrition, increased mortality rates, and reduced reproductive success. It can have severe consequences on population growth, causing population decline and impacting the overall health and survival of individuals. Therefore, famine is a limiting factor for population growth.

Conclusion:
Among the given options, immigration is not a factor that would limit the growth of a population. On the contrary, immigration can contribute to population growth by introducing new individuals, genetic diversity, and enhancing the workforce and overall development of the population.

Understanding Logistic Growth
Logistic growth is a model that describes how a population grows in an environment with limited resources. The Verhulst-Pearl logistic growth equation is essential in understanding this concept.
Key Features of Logistic Growth:
- Initial Slow Growth: The population starts with a slow increase due to limited resources available for growth.
- Acceleration Phase: As resources become more available, the growth rate accelerates.
- Deceleration Phase: Eventually, the population growth slows down as it approaches the carrying capacity of the environment.
Equation Explanation:
The correct equation representing Verhulst-Pearl logistic growth is:
- dN/dt = rN(K-N)/K
Here’s a breakdown of the components:
- dN/dt: Rate of change of the population size over time.
- r: The intrinsic growth rate of the population.
- N: Current population size.
- K: Carrying capacity of the environment.
- (K-N): Represents the remaining resources available for growth; as N approaches K, (K-N) decreases, slowing down the growth rate.
Why Option A is Correct:
- Option A accurately incorporates both the intrinsic growth rate (r) and the effect of limited resources on the population growth, making it a comprehensive representation of logistic growth.
- Other options either misrepresent the relationship between population size and carrying capacity or fail to include the intrinsic growth rate effectively.
Conclusion:
Understanding the logistic growth model is crucial for predicting population dynamics in ecology, particularly in contexts where resources are limited. The Verhulst-Pearl equation provides a robust framework for these predictions.

In logistic growth the population seldom grows beyond the carrying capacity of the ecosystem.