NEET Part Test - 6 - NEET MCQ

The place where a particular organism lives called a habitat.

• It is a place where an organism can find shelter, food, mates for reproduction and, protection from predators.
• It depends on both biological and physical factors present within it.

• 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. 

Natural selection operates on the population level to evolve desired traits. While individual organisms have to cope with changes in their environment, it is at the population level that natural selection acts to shape the genetic composition and traits of the population over time.

Population ecology, links ecology to population genetics and evolution. It is at the population level that variations in traits occur due to genetic diversity and interactions with the environment. Individuals with traits that confer advantages in survival, reproduction, and adaptation are more likely to pass on those traits to the next generation through interbreeding.

An age pyramid with a wide base and narrow top indicates a population that is growing rapidly.

In an age pyramid, the width of each age group represents the proportion or percentage of individuals in that specific age group. A wide base indicates a larger population of young individuals, while a narrow top indicates a smaller population of older individuals.

When the base of an age pyramid is wide and the subsequent age groups gradually decrease in width towards the top, it suggests that there is a higher proportion of young individuals compared to older individuals. This is indicative of a population that is growing rapidly because there is a high birth rate.

A population's birth rate refers to the number of births per capita. A population has birth rates and death rates, and these rates are expressed as changes in numbers (increase or decrease) with respect to members of the population.

To calculate the birth rate, the number of births is divided by the population size or the number of individuals in the population. The birth rate per capita provides a measure of the average number of births per individual in the population.

Interactions between different species living within a particular area may be useful as in case of mutualism, fatal as in case of parasitism or neutralin which no one is harmed.

Interacting members of species live close to each other in commensalism, predation and parasitism.

The levels of organization are described below from the smallest to the largest:

• A species is a group of individuals that are genetically related and can breed to produce fertile young. Individuals are not members of the same species if their members cannot produce offspring that can also have children. The second word in the two word name given to every organism is the species name. For example, in Homo sapiens, sapiens is the species name.
• A population is a group of organisms belonging to the same species that live in the same area and interact with one another.
• A community is all of the populations of different species that live in the same area and interact with one another. A community is composed of all of the biotic factors of an area.
• A biome is a community of plants and animals that have common characteristics for the environment they exist in. They can be found over a range of continents. Biomes are distinct biological communities that have formed in response to a shared physical climate.

Hence, Option A is correct.

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.

Natality in population ecology is the scientific term for birth rate. Along with mortality rate, natality rate is used to calculate the dynamics of a population. They are the key factors in determining whether a population is increasing, decreasing or staying the same in size. Natality is the greatest influence on a population’s increase. Natality is shown as a crude birth rate or specific birth rate. Crude birth rate is used when calculating population size (number of births per 1000 population/year), whereas specific birth rate is used relative to a specific criterion such as age. By calculating specific birth rate, the results are seen in an age-specific schedule of births.

Formula = the rate of change in population size) = (the contribution of each individual to population growth) x (the number of individuals in the 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.

The density of a population in a given habitat during a given period changes due to changes in four basic processes, two of which (natality and immigration) contribute to an increase in population density and two (mortality and emigration) to a decrease. In a zero population growth density natality is balanced by mortality. 
 

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.

The pyramid of biomass in an aquatic system is always inverted. A sharp decrease in biomass results in inverted pyramids.

• At a constant temperature, soil moisture content shows a parabolic affect on decomposition rates with a maximum rate at intermediate levels of moisture.
• High moisture content limits soil gas exchange leading to low oxygen concentrations and potentially anaerobic conditions.
• At low moisture content, the lack of water limits microbial metabolism; however, many microorganisms can remain active to much lower soil water potentials (at -3.0 MPa) than plants (at -1.5 MPa).

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.

In a marine aquatic ecosystem, the biomass of phytoplanktons (producers) is smaller than that of zooplanktons (primary consumers) and the biomass of zooplanktons is smaller than that of secondary consumers. This results in the inverted pyramid of biomass in an aquatic ecosystem. This shape is the consequence of the very short life spans of phytoplanktons, which are consumed almost as rapidly as they are formed. Also phytoplanktons have high reproductive potential, i.e., they reproduce rapidly.

The given pyramid represents pyramid of biomass in an aquatic ecosystem. In this pyramid, biomass of phytoplanktons, i.e., producers (represented by A) is smaller than that of zooplanktons, i.e., primary consumers (represented by B). Phytoplanktons support zooplanktons as the latter feed upon them.

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 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.

• 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" 

• The Hardy-Weinberg principle states that allele and genotype frequencies in a population will remain constant from generation to generation in the absence of other evolutionary influences.
• It operates in the absence of mutation, natural selection and recombination.

Process of evolution of different species in a given area starting from a point and radiating to another area of geography (habitats) is called adaptive radiation.  Example : Darwinian finches and Australian marsupials.

• 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.

The materials or substances occurring in nature that exist without the actions of humankind are known as natural resources. The conservation of natural resources is important for the preservation of natural, biological diversity.

Genetic variation is advantageous to a population because it enables some individuals to adapt to the environment while maintaining the survival of the population.
Speciation occurs from standing genetic variation when reproductive isolation between 2 or more populations evolves from alleles already present within the common ancestral population, rather than from new mutations. This seasonal difference contributes to strong (although still incomplete) reproductive isolation.
Mutations are changes to an organism's DNA and are an important driver of diversity in populations. Species evolve because of the accumulation of mutations that occur over time.
This mutation has introduce a new allele into the population that increases genetic variation and may be passed on to the next generation.

Both domesticated crops and agricultural weeds have arisen from wild plants, but domesticated crops are different, as they are mostly human inventions selected for certain traits through thousands of years. We will first describe the crop domestication process and the evolution of agricultural weeds in general, contrasting “domestication” with “weediness” traits acquired during the dedomestication or ferality process, including a review of their genetic basis. Then for a select group of crop plants we will examine the degree of inferred domestication (ratio of domestic acquired to retained weediness traits).

Those species whose number of individuals is greatly reduced recently and is decreasing continuously and are at a high risk of endangerment in the wild are known as vulnerable species. Some examples of vulnerable species are Barasingha, Nilgiri Langur, Yak, Olive Ridley Turtle, Sloth bear, etc.