Chapter 11: Organisms and Populations

Ans: Abiotic components are all non-living elements in an ecosystem. Temperature, soil, water, and light are all aspects to consider.

Temperature: This is the most important environmental component in terms of ecology. It changes seasonally on land and gradually diminishes from the equator to the poles, as well as from plains to mountain summits. It varies from sub-zero temperatures in polar regions to high altitudes. Eurythermal animals, such as most mammals and birds, can withstand and thrive in a wide range of temperatures, whereas stenothermal organisms, such as polar bears and amphibians, can only tolerate a small range of temperatures.

Soil: The nature and qualities of soil vary greatly depending on where you are. It is mostly determined by the following factors

• The weather

• The weathering procedure

• The process of soil growth

The soil's water holding capacity and percolation are determined by a variety of factors, including soil chemistry, grain size, and aggregation. The sort of plants that can grow in a particular habitat is determined by these qualities of soil, as well as its pH, mineral content, topography, and other factors.

Water: Water is known to have given birth to life on Earth, and it is impossible to survive without it. The pH, chemical composition, and temperature of water are all vital to aquatic creatures. They are also affected by water salinity, which ranges from less than 5 parts per thousand in inland water to 30-35 parts per thousand in the sea and 100 parts per thousand in some hypersaline lagoons. Euryhaline organisms can tolerate a large range of salinity, whereas stenohaline organisms can only tolerate a narrow range. Because of osmotic difficulties induced by high salt, many freshwater creatures cannot thrive in sea water for long periods of time, and vice versa. A range of factors, including soil chemistry, grain size, and aggregation, influence the water retention capacity and percolation of the soil. These properties of soil, as well as its pH, mineral content, topography, and other elements, affect the types of plants that can flourish in a given habitat. Stenohaline creatures can only survive a narrow range of salinity, but euryhaline species can withstand a wide range of salt. Many freshwater organisms cannot survive in sea water for lengthy periods of time due to osmotic issues caused by excessive salt levels, and vice versa.

Light: The importance of light stems from the fact that all autotrophs rely on it as a source of energy for photosynthesis, which involves the release of oxygen. Because they are obscured by towering, canopied trees, small shrubs and plants growing in forests have adapted to photosynthesis at very low light intensities. The majority of plants rely on sunshine to survive.

Many animals use diurnal and seasonal light intensity variations as cues to time their feeding, reproductive, and migratory activity. Because the sun is the source of both, the availability of light on land is directly tied to that of warmth. The environment is constantly gloomy in deep oceans (> 500m). Solar radiation's spectrum purity is also critical for life.

For marine plants living at different depths of the ocean, different components of the visible spectrum are available. UV light is harmful to many organisms. As a result, distinct species of algae, such as green, brown, and red algae, can be found at the upper, middle, and deep layers of the sea, respectively.

Ans:

(a) Endothermic Animal: Birds such as crows, sparrows, pigeons, cranes, etc. and mammals such as bears, cows, rats, rabbits, etc. are endothermic animals.

(b) Ectothermic Animals: Fishes such as sharks, amphibians such as frogs, and reptiles such as tortoises, snakes, and lizards are ectothermic animals.

(c) Organism of Benthic Zone: Decomposing bacteria is an example of an organism found in the benthic zone of a water body .

Ans : 

• Population: A population can be thought of as a group of individuals belonging to the same species that exist in the same geographical area at the same time and function as a unit. For example, all human beings living at a particular place at a particular time constitute the population of humans.

• Community: A group of individuals belonging to a particular species, living in a particular geographical area. Such individuals can be similar or dissimilar, but cannot reproduce with the members of other species.

Ans:

(a) Commensalism: Commensalism is an interaction between two species in which one species gets benefited while the other remains unaffected. An orchid growing on the branches of a mango tree and barnacles attached to the body of whales are examples of commensalisms.

(b) Parasitism: It is an interaction between two species in which one species (usually smaller) gets positively affected, while the other species (usually larger) is negatively affected. An example of this is liver fluke. Liver fluke is a parasite that lives inside the liver of the host body and derives nutrition from it. Hence, the parasite benefits as it derives nutrition from the host, while the host is negatively affected as the parasite reduces the host fitness, making its body weak.

(c) Camouflage: is a strategy adapted by prey species to escape their predators. Organisms are cryptically coloured so that they can easily mingle in their surroundings and escape their predators. Many species of frogs and insects camouflage in their surroundings and escape their predators.

(d) Mutualism: It is an interaction between two species in which both species involved are benefited. For example, lichens show a mutual symbiotic relationship between fungi and blue green algae, where both are equally benefited from each other.

(e) Interspecific competition: It is an interaction between individuals of different species where both species get negatively affected. For example, the competition between flamingoes and resident fishes in South American lakes for common food resources i.e, zooplankton.

Ans: Yeast cells grown under laboratory conditions commonly exhibit the logistic population growth curve. There are five phases: the lag phase, the positive acceleration phase, exponential phase, negative acceleration phase, and stationary phase.

• Lag Phase: Initially, the population of the yeast cell is very small. This is because of the limited resources present in the habitat.

• Positive Acceleration Phase: In this phase, yeast cells adapt to the new environment and start to multiply. However, at the beginning of this phase, the growth of the cell is very limited.

• Exponential Phase: During this phase, the population of the yeast cell increases suddenly due to rapid growth. Due to sufficient food resources, a constant environment, and the absence of interspecific competition, the population grows exponentially. As a result, the curve rises steeply upwards.

• Negative Acceleration Phase: During this phase, environmental resistance increases and the population growth rate decreases. This occurs because of an increased completion among the yeast cells for food and shelter.

• Stationary Phase: During this phase, the population becomes constant. A population's number of cells equals its number of cells that die. Additionally, the species is said to have reached the carrying capacity of its habitat.

Ans : (d) One organism is benefited, other is affected.

Parasitism is an interaction between two species, in which one species (parasite) benefits from the other. The other species (host) is harmed. For example, ticks and lice (parasites) can be found on the body. This means there is an interaction between parasites and the human body, from which ticks and parasites receive benefit (as they are Feeding on human blood). On the other hand, these parasites reduce host fitness and cause harm to the human body.

Ans: A population is a collection of individuals of the same species living in a specific geographical area at a specific time and acting as a single unit. The population of people, for example, is made up of all human beings living in a specific location at a specific moment.

A population's three most significant qualities are:

(a) Birth Rate (Natality): This is the ratio of live births to total births in a given year.

It is calculated as the number of people added to the population divided by the number of people in the population.

(b) Death Rate (Mortality): This is the ratio of deaths per 100,000 people in a certain location. It's measured in terms of the number of people who have died as a result of the disease.

(c) Age Distribution: This is the proportion of people of various ages in a given population

This is the percentage of people in a population who are different ages. At any given time, a population is made up of people of varying ages. Age pyramids are a frequent representation of the age distribution pattern.