All questions of Organisms and Population for ACT 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.

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.

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.

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.

The birth rate of a population = new individual added / previous population. Here birth rate= 7/23=0.3043. Hence, birth rate of Salvinia plants is equal to 0.3.###@

Mutualism is a type of interaction between two species in which both species benefit from the relationship. This type of interaction is considered to be mutually beneficial and can occur in a variety of ecosystems and between different types of organisms.


Mutualism is a form of symbiotic relationship where both species involved benefit from the interaction. It is a cooperative interaction that enhances the survival, growth, and reproduction of both species.


There are numerous examples of mutualism in nature, demonstrating the wide range of organisms that can engage in this type of interaction. Here are a few examples:

• Pollination: Bees and flowers have a mutualistic relationship. Bees obtain nectar from flowers, which provides them with a food source, while flowers benefit from the transfer of pollen from one flower to another, facilitating reproduction.


• Cleaner Fish and Host Fish: Cleaner fish, such as cleaner wrasses, remove parasites and dead skin from host fish. The cleaner fish benefits by obtaining food, while the host fish benefits from the removal of parasites, improving its health and well-being.


• Leafcutter Ants and Fungus: Leafcutter ants cultivate fungus gardens by cutting and transporting leaves. The ants feed on the fungus, while the fungus benefits from the constant supply of organic matter and protection provided by the ants.

Mutualism is advantageous for both species involved due to the following reasons:

1. Resource Sharing: Both species share resources, such as food, shelter, or protection, which increases their chances of survival and reproduction.


2. Increased Fitness: By working together, both species can increase their overall fitness and reproductive success. This can lead to population growth and long-term survival.


3. Enhanced Nutrient Cycling: Mutualistic relationships can improve nutrient cycling in ecosystems, benefiting the overall health and productivity of the environment.

Mutualism is a type of interaction that benefits both species involved. It is a cooperative relationship that enhances survival, growth, and reproduction. Examples of mutualism can be found in various ecosystems, demonstrating the importance of this type of interaction in nature.

Red algae are found in deepest ocean waters
because it contains phycoerithrin pigment it can absorbs blue light which penetrates the most deep water for photosynthesis and appears Red because it reflects red light
so Red algae are found in deepest ocean waters

Explanation:
Mychorrhiza is a type of mutualistic relationship between a fungus and the roots of a plant. This interaction is beneficial for both parties involved, as they each provide something the other needs.

Mutualism:
- In a mycorrhizal relationship, the fungus helps the plant absorb nutrients such as phosphorus and nitrogen from the soil.
- In return, the plant provides the fungus with sugars produced through photosynthesis.
This mutualistic interaction is essential for the health and growth of many plant species, as it allows them to access nutrients that would otherwise be difficult to obtain. Mycorrhizae are found in a wide range of plant species and are crucial for the functioning of many ecosystems.

Understanding Resource Partitioning
Resource partitioning is an ecological concept that describes how different species coexist by dividing resources, thereby minimizing competition. This strategy is essential for maintaining biodiversity in ecosystems.
How Resource Partitioning Works
- Division of Resources: Species utilize various resources (like food, water, or space) in different ways or at different times. For example, two bird species may feed on the same tree but at different heights or times of the day.
- Reduced Competition: By partitioning resources, species can avoid direct competition, which often leads to one species outcompeting and eliminating another. This dynamic allows multiple species to thrive in the same habitat.
- Niche Differentiation: Each species occupies a unique niche, which is a specific role in the ecosystem that includes its habitat, resource use, and interactions with other organisms. This differentiation ensures that resources are utilized efficiently without overlap.
Examples of Resource Partitioning
- Temporal Partitioning: Different species may forage at different times, such as nocturnal vs. diurnal feeders.
- Spatial Partitioning: Organisms may occupy different physical spaces within the same habitat, such as tree-dwelling animals versus ground-dwelling animals.
- Morphological Adaptations: Some species evolve specialized traits that allow them to exploit specific resources effectively, such as differing beak sizes in finches that enable them to feed on varying seed types.
Conclusion
Resource partitioning is crucial for species coexistence in ecosystems, allowing diverse species to utilize the same habitat without depleting shared resources, thereby promoting ecological balance and diversity.

Understanding Plant Defenses Against Herbivores
Plants have evolved various strategies to protect themselves from herbivores, which can cause significant damage. Among the adaptations listed, thorns on Acacia trees serve as a primary example of a plant defense mechanism.
Thorns on Acacia Trees
- Physical Barrier:
Thorns act as a physical deterrent, making it difficult for herbivores to consume the leaves and stems of the tree. This adaptation helps reduce the likelihood of being eaten.
- Predator Attraction:
In some cases, Acacia trees also have mutualistic relationships with ants. The thorns can provide shelter for these ants, which, in return, defend the tree by attacking herbivores.
Other Options Explained
- High Reproductive Rate of a Parasitic Plant:
This adaptation is not a defense mechanism but rather a strategy for survival and dispersal. Parasitic plants rely on host plants for nutrients, not defending themselves from herbivores.
- Chemical Production in Calotropis:
While this adaptation does harm herbivores, it is more of a chemical defense rather than a structural one. It represents a different category of defense mechanisms.
- Camouflage in Insects like the Monarch Butterfly:
This is an adaptation of the insect and does not pertain to plant defenses. It highlights predator evasion rather than plant strategies against herbivores.
Conclusion
In summary, thorns on Acacia trees exemplify physical defenses that discourage herbivores, while the other options either pertain to different organisms or do not directly relate to plant defense strategies.

Understanding the Population Growth Equation
The equation provided, dN/dt = rN(K-N)/K, is a model used in ecology to describe population growth over time. Each component of this equation has a specific meaning, and understanding these will clarify why 'r' represents the intrinsic rate of natural increase.
Components of the Equation
- dN/dt: This term indicates the change in population size (N) over time (t).
- N: Represents the current population size.
- K: Denotes the carrying capacity of the environment, which is the maximum population size that the environment can sustain.
Role of 'r' in Population Growth
- Definition of 'r': In this equation, 'r' specifically refers to the intrinsic rate of natural increase. This is a measure of how quickly a population can grow under ideal conditions, where resources are abundant and environmental pressures are minimal.
- Impact of 'r':
- If 'r' is high, the population can grow rapidly, as there are fewer limitations on its growth.
- Conversely, if 'r' is low, the population growth will be slower.
Why 'r' is Option B
- Option A (Population density at time Y): This does not define 'r'.
- Option C (Carrying capacity): This refers to 'K', not 'r'.
- Option D (The base of natural logarithm): This is unrelated to population growth.
Thus, option B correctly identifies 'r' as the intrinsic rate of natural increase, making it the correct answer in the context of the population growth equation.

Habitat:
A habitat is the specific place or environment in which a particular organism lives. It refers to the physical location where an organism can find the necessary resources and conditions to survive, reproduce, and interact with other organisms in its ecosystem.

Explanation:
The habitat of an organism is its home, providing everything it needs to survive and thrive. It includes various abiotic (non-living) factors such as temperature, humidity, light intensity, soil composition, and availability of water. Additionally, it encompasses biotic (living) factors such as the presence of food, predators, prey, competitors, and other organisms that may interact with the focal organism.

Importance of Habitat:
The habitat plays a crucial role in determining the distribution and abundance of species. Each organism has specific adaptations that allow it to thrive in particular habitats. These adaptations can include physical characteristics, physiological processes, and behaviors that help the organism survive in its environment.

Components of Habitat:
Habitats can vary greatly in size and complexity, ranging from microhabitats within a small rock crevice to vast ecosystems like a tropical rainforest. Some key components of a habitat include:

1. Physical Features: The physical features of a habitat include the climate, topography, landforms, and geological characteristics of the area. These factors influence the availability of resources and determine the overall suitability of the habitat for different organisms.

2. Food and Resources: The presence of food sources and essential resources is vital for the survival of organisms. Different habitats provide varying amounts and types of food, such as plants, other animals, or decomposing matter, depending on the ecosystems they belong to.

3. Shelter and Cover: Organisms require shelter and cover to protect themselves from predators, extreme weather conditions, and other threats. This can include vegetation, burrows, nests, or specific structures within the habitat that provide protection and safety.

4. Interactions: Habitats are dynamic environments where organisms interact with each other and their surroundings. These interactions can be cooperative (symbiosis), competitive (for resources), or predatory (hunting for food). The presence of other species and their roles within the ecosystem can significantly affect an organism's survival and reproduction.

5. Environmental Conditions: The environmental conditions within a habitat, such as temperature, humidity, pH levels, and availability of water, greatly influence an organism's ability to survive. Different species have specific tolerance ranges for these conditions, and the habitat must provide suitable conditions for their survival.

In conclusion, a habitat is the specific place where an organism lives, providing the necessary resources, conditions, and interactions for its survival and reproduction. It is a fundamental concept in ecology and plays a vital role in shaping the distribution and abundance of species in ecosystems.

Understanding Predation
Predation is a fundamental ecological process involving the interaction between predators and their prey. Among the given statements, option 'B' accurately describes a significant aspect of predation.
Correct Statement: Predators Prevent High Prey Densities
- Population Control: Predators help maintain the balance of ecosystems by controlling prey populations. Without predation, certain species could reproduce unchecked, leading to overpopulation.
- Resource Availability: By keeping prey numbers in check, predators ensure that resources such as food and habitat remain available for other species, fostering biodiversity.
Analysis of Other Options
- Option A: Predation is not mutualism. In mutualism, both species benefit, while in predation, the predator benefits at the expense of the prey.
- Option C: Herbivores are indeed considered predators in ecological terms as they consume plant material, impacting plant populations and dynamics.
- Option D: While overexploitation can lead to declines in prey populations, it typically does not result in the extinction of both predator and prey species. Predators can adapt or switch to alternative prey if one species becomes scarce.
Conclusion
In summary, option 'B' is correct because it highlights the crucial role of predators in preventing prey populations from reaching unsustainable levels, thus maintaining ecological balance. Understanding these interactions is essential for grasping the complexities of ecosystems and the importance of biodiversity.

Explanation:

Definition:
- Aestivation: Aestivation is a state of inactivity and dormancy in response to high temperatures and arid conditions.
- Hibernation: Hibernation is a state of inactivity and dormancy in response to low temperatures and limited food availability.

Characteristics:
- Aestivation: Organisms undergoing aestivation will reduce their metabolic rate, conserve energy, and wait for more favorable conditions.
- Hibernation: Organisms undergoing hibernation will lower their body temperature, slow down their heart rate, and enter a state of torpor to conserve energy.

Environmental Conditions:
- Aestivation: Aestivation is typically seen in animals living in hot and dry environments where water and food sources are scarce.
- Hibernation: Hibernation is common in animals living in cold climates where food is limited during the winter months.

Examples:
- Aestivation: Examples of animals that undergo aestivation include snails, earthworms, and certain amphibians during the dry season.
- Hibernation: Examples of animals that hibernate include bears, squirrels, and bats during the winter months.

In conclusion, organisms may adopt aestivation to avoid high temperatures and hibernation to avoid low temperatures as adaptive strategies to survive in challenging environmental conditions.

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.

- Humans and Gut Bacteria:
Humans have a mutualistic relationship with the bacteria that live in our guts. These gut bacteria help us digest food, produce essential vitamins, and boost our immune system. In return, they have a stable environment and a constant food source within our bodies.

- Mutualistic Relationship:
A mutualistic relationship is a type of symbiosis where both organisms benefit from each other's presence. In the case of humans and gut bacteria, both parties rely on each other for survival and well-being.

- Benefits of Gut Bacteria:
The bacteria in our guts help break down complex carbohydrates, produce vitamins like vitamin K and some B vitamins, and regulate our immune system. Without these bacteria, humans would struggle to digest certain foods and absorb essential nutrients.

- Importance of Mutualistic Relationship:
The mutualistic relationship between humans and gut bacteria is crucial for maintaining our overall health. Disruptions in the balance of gut bacteria can lead to various health issues, including digestive problems, weakened immune system, and even mental health disorders.

- Conclusion:
In summary, humans do exhibit mutualistic relationships, particularly with the bacteria that live in our guts. This symbiotic relationship is essential for our well-being and highlights the interconnectedness of different organisms in nature.