Answer:
Underground stem, Aerial stem, and subaerial stem.
Explanation:
Plant stems can be Underground stem, Aerial stem, and subaerial stem due to its presence and strength of the stem. Underground stem are thick stems that run below the ground surface. e.g rhizome. Aerial stems are thin stems that can not stand erect. Examples include watermelon and strawberry etc. Subaerial stems are very thin stems that do not rise up but grow just above the ground. for example, water plantain, flowering rush etc.
Material through which water flows is permeable. This material can be either natural or artificial. Naturally permeable material can be clean sand and gravel for example, or a sandstone and in the latter case the sandstone can have both porosity which is not synonymous with permeability as the pores must be connected to be permeable. An impermeable membrane could be used to line ditches for example to prevent leakage near mines.
<span>A psychological response to an out-of-the-ordinary stressor defines the posttraumatic stress disorder (PTSD).
When people are exposed to a traumatic event, such as war, or sexual assault, or generally any type of threat or tragedy, they may develop PTSD as a result. This means that the person will still have strong and negative emotions, such as fear, or hatred, months or years after the event occurred, and it is very difficult to treat.
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Insect populations can develop resistance to insecticides over time. The evolution of resistance is associated with an increase in the frequency of adaptive genes in the population.
- In the case above described it is expected that a few mosquitoes in the population were resistant to DDT before it was ever used (Option a is correct).
- Dichlorodiphenyltrichloroethane (DDT) is a pesticide used in agriculture.
- After exposure to DDT, those individuals in the mosquito population that didn't carry gene variants (i.e., alleles) associated with the resistance to this pesticide died.
- Subsequently, insects having adaptive alleles associated with DDT resistance survived and reproduced, thereby increasing the frequency of adaptive genes/alleles in the population.
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