CBSE Questions for Class 12 Medical Biology Organisms And Population Quiz 13 - MCQExams.com

• Symbionts are organisms where two of them live in symbiosis with one another.
• Endoparasites are parasites, such as tapeworm, that lives inside the host.
• Ectoparasites are parasites, such as flea, that lives on the outside of the host.
• Hyperparasites are parasites whose host is also a parasite. This form of parasitism is especially common among entomophagous parasites.

• Mutualism is a mutually beneficial interaction between organisms of two different species with none of the two capable of living separately. For example, Orchid Ophrys and bee pollinators.
• In commensalism, one species is benefited without the other being harmed. For example, epiphytes like mosses, ferns, orchids, etc., perched on other plants for space only to grow.
  
• In parasitism, one organism called parasite obtains nourishment from another organism called as host. For Example, ticks are ectoparasites on dogs.
• Competition is fighting between organisms for obtaining the same resource. For example, Balanus nearly excludes smaller barnacle Chthamalus from the intertidal area. When the Balanus population is reduced or eliminated, Chthamalus begins to flourish.
  
• In predation, one organism called predator that captures and eats another organism called prey. Predators are generally carnivorous animals but some herbivorous which destroy whole plants/ seeds are also called as predators. For example, birds like sparrow feeding on seeds.

• Diapause is a period during which growth or development is suspended and physiological activity is diminished. Example in arthropods mainly in insects.
• Hibernation is an extended period of deep sleep. It is a state of inactivity and metabolic depression in endotherms. Example polar bears show hibernation.
• Phenotypic adaptation involves changes in the body of an organism in response to genetic mutation or certain environmental changes. For example, desert plants have thick cuticles and sunken stomata on the surface of their leaves to prevent transpiration.
• Commensalism is an association between two organisms in which one benefits and the other one neither benefits nor harm. For example, the interaction of an orchid growing on a mango tree where the orchid receives benefits from a mango tree and the mango tree is unaffected.

• The exponential phase is characterized by the vigorous growth of the bacteria where it is in the constant state of division. They undergo the DNA replication and synthesis of new proteins which increases their metabolic rate.
• As the bacterial population continues to grow, all the nutrients in the growth medium are used up by the microorganism for their multiplication. 
• This results in the accumulation of waste materials, toxic metabolites, and inhibitory compounds such as antibiotics in the medium. 
• The reproduction rate will slow down, the cells undergoing division is equal to the number of cell death, and finally, bacteria stops its division completely. 

• In a symbiotic relationship, the two species in the relationship live together. Many organisms are involved in symbiotic relationships because this interaction provides benefits to both species. 
• Symbiotic relationships can be obligate or facultative. 
• Obligate symbiosis is when two organisms are in a symbiotic relationship because they can't survive without each other. 
• Facultative symbiosis is when the species live together by choice. There are four main types of symbiotic relationships: mutualism, commensalism, parasitism, and competition.

Mutualism is an interaction in which both individuals are benefited e.g., hermit crab gains protection from predators by its relationship with the sea anemone and in return provide food to the sea anemone. In a commensal relationship, one organism benefits while the other is unaffected. example e.g., sucker fish by attaching themselves to shark traveled to different places whereas shark remains unaffected. Parasitism is an interaction in which one is benefited at the expense of the other organism e.g., Cuscuta is a parasitic plant which is parasitic on the roots of Cissus. Predation is a biological interaction where a predator feeds on its prey e.g., tiger and deer wherein tiger which is a predator feed on deer which is a prey. Therefore, the correct answer is option B.

• In mutualism, both the host and the predator will get benefitted.
• In commensalism the one get benefited by other but do not harm the other.
• In parasitism it totally depends on the host and may harm the host.
• Competition is not a relationship but fights for something.
• Predation is harming others for the food. 
• Thus, the correct answer is option E.

A. Correct option B
B. Explanation for correct option:

• Agrobacterium tumefaciens is soil-borne gram-negative bacteria that causes crown galls on most of the dicot leaves.
  
• It contains a plasmid also called the Ti (tumour inducing) plasmid, which is used widely in genetic engineering/recombinant DNA technology for creating transgenic plants or genetically modified plants.
• It contains a plasmid also called the Ti (tumour inducing) plasmid, which is used widely in genetic engineering/recombinant DNA technology for creating transgenic plants or genetically modified plants.

• The exponential growth can be mathematically represented as follows: