What type of stimulus is an allergen such as pollen? a) response to a stimulus b) external stimulus c) internal stimulus d) inborn stimulus

B). External stimulus

A stimulus can be defined as any substance or particle that initiates quick action or response in the organism. An external stimulus can be defined as stimulus, which is initiated by foreign agent belonging to the external environment in which the organism interact. Pollen is a fine powder, produced by the flowers. It is a male gamete in flowers. It fertilizes the female gametes in flowers that is ovary, to form seeds and fruits. The pollen exhibit in the form of small grains. Humans have experienced allergic response due to pollen. Pollen being an foreigner agent for the human body, when inhaled, activates the immune system, to fight against it, therefore, it is an external stimulus. This results in an allergic reaction, to expel out the pollen particles from the body. This includes symptoms like sneezing, stuffy nose and watery eyes.

answer: angiosperms

dicots

angiosperms are highly evolved plants, they produce seeds which are enclosed within in a carple. these are the largest group of plants on earth. they include trees, shrubs, herbs and small flowering plants. angiosperms exhibit a flowering stage in their life cycle. the flower serves the function of reproduction and fruit formation in majority of angiosperms. dicot is the term used to describe flowering plants that have two seed leaves. dicots are plants which develop seeds which split into two parts called cotyledons. each cotyledon contains one embryo.

here, a small purple flower development indicates that the plant belongs to angiosperms and having two embryonic leaves indicates it belongs to dicots.  

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.