Bacteria are classified into 5 groups according to their basic shapes: spherical (cocci), rod (bacilli), spiral (spirilla), comma (vibrios) or corkscrew (spirochaetes). They can exist as single cells, in pairs, chains or clusters.
Answer:
Mark pathogenic cells for destruction. (Ans. B)
Explanation:
Antibodies are generated by the plasma cells, and once these secreted, they attach quickly to the surface of the toxin and stop the toxin from infecting the normal body cell by blocking key extracellular sites.
Antibodies also help to mark pathogens for destruction by the help of macrophages or neutrophils and they are known as phagocytic cells because they are highly excited to macro-molecules complexed with antibodies.
When a plant opens and closes its stomata, it is maintaining homeostasis. Homeostasis includes the regulation of carbon dioxide and water levels necessary to perform photosynthesis. It also allows the plants to store water to prevent them from dying

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Answer:
They remain in an environment,even as more competitive species arrive
Explanation:
Pioneer species, in ecological succession, are the first set of organisms to colonize a bare area of land or a disturbed area of land. Pioneer species include lichens, grasses, fungi etc.
Pioneer species have unique characteristics that distinguishes them from every other species of organism. These include:
- They facilitate environmental change, making an environment more habitable for other species.
- They tolerate a wide range of environmental conditions.
- They are capable of colonizing a barren environment, as in primary succession.
However, pioneer species do not remain in an environment, even as more competitive species arrive. They rather give way for new species to emerge and dominate.