NEET Part Test - 6 - NEET MCQ

• Ecology is the study of interaction between living organism and their environment. The basic unit of study in ecology is organism.
• An organism is a single living entity that can carry out all the functions of life, such as obtaining energy and nutrients, responding to the environment, and reproducing.

• This is a large regional unit characterised by a major vegetation type and associated fauna found in a specific climate zone.
• The biome includes all associated developing and modified communities occurring within the same climatic region, e.g., forest biomes, grassland and savanna biomes, desert biome, etc.
• On a global scale, all the earth’s terrestrial biomes and aquatic systems constitute the biosphere.

The population has the same number of individuals in the pre-reproductive post-reproductive age is called a steady population.

• It is the population in which the birth rate is approximately equal to the death rate.
  

• Biological organisms starts with sub-microscopic molecular level like viruses, bacteria etc.
• These organisms are unable to be seen by naked eyes without the help of microscope or even electron microscope. 

Interactions between species can have different outcomes. In mutualism, both species benefit from the interaction. This means that there is a mutually beneficial relationship where both species gain advantages, such as access to food, protection, or reproductive assistance.

Option d) Mutualism is the correct answer because it accurately identifies the type of interaction where both species involved benefit from each other.

Populations grow through births and immigration and decline through deaths and emigration.

When resources become progressively limiting for a population, the growth pattern turns logistic. This means that initially, the population may experience exponential growth when resources are abundant and unlimited.

However, as resources start to become scarce and limiting, the growth rate of the population slows down and eventually levels off. This pattern is known as logistic growth.

• Exponential growth (option b) refers to a rapid and unrestricted increase in population size without resource limitations.
• Constant growth (option c) implies a steady and consistent growth rate over time, regardless of resource availability.
• Declining growth (option d) suggests a decrease in population size over time, often due to factors like limited resources or environmental disturbances.

Intrinsic rate of natural increase (r) is a measure of the inherent potential of a population to grow.

The intrinsic rate of natural increase refers to the rate at which a population grows under ideal conditions, assuming unlimited resources and without any limiting factors such as predation, competition, or environmental constraints. It is a measure of the population's ability to reproduce and survive.

• Birth rate (option b) refers to the rate at which individuals are born in a population.
• Death rate (option c) refers to the rate at which individuals die in a population. While these factors are important in determining population dynamics, the intrinsic rate of natural increase specifically measures the potential for population growth under optimal conditions.
• Carrying capacity (option d) refers to the maximum number of individuals that an environment can sustainably support based on the available resources.

Biotic potential is defined as the physiological capacity of organisms to produce their offspring under natural conditions. It is also called reproductive potential. In nature, the biotic potential of organisms is enormous but all the organisms do not survive due to the lack of food and space. There are also a number of diseases and the predatory organisms, that feed upon other organisms. The carrying capacity is the maximum number of individuals which the environment can support or sustain.

The genetic drift is a drastic change in allele frequency when population size is very small. Its effects are more marked in a small isolated population.

Exponential model is the one in which rate of change in anything is directly proportional to the number of the thing present. Exponential phase shows the exponential growth. Thus the size or the number increases at a constant growing rate.

• Phytoplanktons are small floating photosynthetic unicellular plant.
• In the aquatic ecosystem phytoplankton are producers that fix solar energy by the process of photosynthesis.

Aquatic Food Chain:

Decomposition is the process that involves the breakdown of complex organic matter or biomass from the body of dead plants and animals with the help of decomposers into inorganic raw materials such as carbon dioxide, water, and other nutrients.

The various processes involved in decomposition are as follows:
➢ Fragmentation 

• It is the first step in the process of decomposition.
• It involves the breakdown of detritus into smaller pieces by the action of detritivores such as earthworms.

➢ Leaching

• It is a process where the water soluble nutrients go down into the soil layers and get locked as unavailable salts.

➢ Catabolism

• It is a process in which bacteria and fungi degrade detritus through various enzymes into smaller pieces.

➢ Humification

• The next step is humification which leads to the formation of a dark-coloured colloidal substance called humus, which acts as reservoir of nutrients for plants.

➢ Mineralization

• The humus is further degraded by the action of microbes, which finally leads to the release of inorganic nutrients into the soil.
• This process of releasing inorganic nutrients from the humus is known as mineralization.

Option A: Mineralization is the process in which humus is further degraded by some microbes and release of inorganic nutrients occur.

Option B: The degradation of the detritus into simple inorganic substances, by bacterial and fungal enzymes, is known as catabolism.

Option C: If the breakdown of the detritus by detrivores is called fragmentation.

Option D: Leaching is the process by which the water-insoluble inorganic nutrients go down into soil horizon and get precipitated as unavailable salts.

Hence,option B is correct.

In a food chain, energy stored at the producer level is called as primary productivity (PP). Net primary productivity (NPP) is the rate of storage of organic matter except which is utilized for the respiration by plants.

In detritus food chain, speed of decomposition will be fast if detritus is rich in simple sugar that can be easily decomposed into glucose by saprophytes that includes bacteria and fungi.

Pyramids of biomass are comparatively more fundamental, as they, instead of geometric factor, show the quantitative relationships of the standing crops. In grassland and forest, there is generally a gradual decrease in biomass of organisms at successive levels from the producers to the top carnivores. Thus, pyramids of biomass and number are upright in terrestrial ecosystems.

Mr. X eating curd / yoghurt should be considered as occupying third trophic level. Producers or greeen plants (first trophic level) are consumed by herbivore (second trophic level). And from them curd, yoghurt (made from dairy breed) is consumed by third trophic level like man.

The second law of thermodynamics states that whenever energy is transformed, there is a loss energy through the release of heat. This occurs when energy is transferred between trophic levels as illustrated in a food web. When one animal feeds off another, there is a loss of heat (energy) in the process. Additional loss of energy occurs during respiration and movement. Hence, more and more energy is lost as one moves up through trophic levels. If this pyramid is inverterved, it would violate the law of thermodynamics. Hence the pyramid can never be inverted.
The pyramid of numbers depicts the relationship in terms of the number of producers, herbivores and the carnivores at their successive trophic levels. There is a decrease in the number of individuals from the lower to the higher trophic levels. The number pyramid varies from ecosystem to ecosystem. Since the amount if energy flowing through the system is not indicated, the pyramid can be inverted.
These are the diagrammatic illustrations of connection between different trophic levels in terms of energy, biomass and number of an organism. The base of each pyramid represents the producers or the first trophic level. Apex represents tertiary or top level consumers. If any species belongs to two or more trophic level, it can causes differences and issues in energy flow and numbers. 
Saprophytes are organisms which feed on dead and decaying matter and these pyramid exhibit interaction between the living components and decomposers interact with dead organisms at all level. This makes it difficult to place it in the ecological pyramid. Hence, they are not given any place in ecological pyramids even though they play a vital role in the ecosystem.
So the correct option is 'none of these'.

The components of the ecosystem are seen to function as a unit when the aspect is energy flow. It is the calorific amount of energy that moves from the sun and up to each subsequent level of the food chain in an environment.

Interaction of biotic and abiotic components result in a physical structure, that is characteristic of each type of ecosystem. Components of ecosystem function as one single unit. Four important functional aspects of the ecosystem are:
(i) Productivity,
(ii) Decomposition,
(iii) Energy flow and
(iv) Nutrient cycling.
Ecological pyramids are graphical representation of number, biomass and energy flow in an ecosystem.

• Industrial melanism is an adaptation where the moths living in industrial areas develop melanin pigments to match their body to the soot covered surroundings.
• In this case, moths with dark coloured will be selected by nature and hence they will be reproductively successful as compared to moths of light colour. Hence it is an example of protective colouration.

Hence the correct option is "D" 

According to abiogenesis theory of origin of life, life originated from non-living matter like gases, inorganic substance and water at particular temperature and pressure.

Hardy-Weinberg equilibrium cannot be disturbed by vegetative propagation as the all new offspring are clone of each other having same gene. Migration, genetic drift, mutation and natural selection affect the equilibrium of alleles in a population.

• This graph indicates stabilizing selection. As we can see, the peak gets higher and narrower.
• In this selection, most of the individuals acquire mean character value.

Narrow utility of biodiversity:
The narrow utility of biodiversity refers to specific benefits or uses that can be derived from biodiversity. Among the given options, both fiber production and taxol production are examples of narrow utility of biodiversity. Here is a detailed explanation:
1. Fiber production:
- Biodiversity plays a crucial role in fiber production as different plant species provide various types of fibers such as cotton, jute, hemp, and flax.
- These fibers are used in the textile industry to produce fabrics, clothing, and other materials.
- The diversity of plant species ensures a wide range of fiber properties, allowing for different uses and applications.
2. Taxol production:
- Taxol is a compound derived from the bark of the Pacific yew tree (Taxus brevifolia).
- It has anti-cancer properties and is used in chemotherapy treatments.
- The production of taxol relies on the biodiversity of the Pacific yew tree and its ecosystem.
- Protecting the biodiversity of these trees is essential for ensuring a sustainable supply of taxol for medical purposes.
Therefore, both fiber production and taxol production are examples of narrow utility of biodiversity as they represent specific uses and benefits derived from plant species.

• George David Tilman is an American ecologist.
• He performed long-term ecosystem experiments using outdoor plots.
• Through his plots, he provided some tentative answers such as increased diversity contributed to higher productivity.

Explanation:
The biodiversity of a given region is influenced by various factors, and the options provided in the question - climate and topography, possibility for dispersal, and evolutionary history - are all important contributors to the outcome of biodiversity in a region. Here's a detailed explanation of each factor:
1. Climate & topography:
- Climate refers to the long-term weather patterns in a region, including temperature, rainfall, and seasonality.
- Different climates support different types of organisms, as they have specific adaptations to survive in specific environmental conditions.
- Topography refers to the physical features of the land, such as mountains, valleys, and rivers. It affects the distribution of habitats and the movement of organisms.
2. Possibility for dispersal:
- Dispersal refers to the movement of organisms from one place to another.
- The ability of organisms to disperse to different areas is crucial for the establishment of diverse populations and the colonization of new habitats.
- Factors that affect dispersal include the presence of barriers (such as mountains or oceans), availability of suitable habitats, and the ability of organisms to travel long distances.
3. Evolutionary history:
- Evolutionary history refers to the cumulative changes in organisms over time.
- The biodiversity of a region can be influenced by its historical connection to other regions and the movement of species over evolutionary timescales.
- Regions with longer evolutionary histories may have higher levels of biodiversity due to the accumulation of diverse lineages and adaptations.
Conclusion:
All of the factors mentioned - climate and topography, possibility for dispersal, and evolutionary history - interact and contribute to the biodiversity of a given region. Therefore, the correct answer is option D: All of the above.

Introduction of Nile perch (an exotic predatory fish) into lake Victoria (South Africa) threatened the entire ecosystem of the lake by eliminating several native species of the small Cichlid fish species that were endemic to this fresh water ecosystem. 

The last twenty years alone have witnessed the disappearance of 27 species. Careful analysis of records shows that extinctions across taxa are not random; some groups like amphibians appear to be more vulnerable to extinction. Adding to the grim scenario of extinctions is the fact that more than 15,500 species world-wide are facing the threat of extinction.

Total number of biodiversity hotspots in the world to 34. Three of these hotspots – Western Ghats and Sri Lanka, Indo-Burma and Himalaya – cover our country’s exceptionally high biodiversity regions.