Answer:
lignified vascular tissue
Explanation:
Stems of Vascular plants are made of vascular tissues and lignin which gives it is characteristics stiffness and the ability to grow tall to access more light and air.
I wish I could help but I speak english.
I am going to assume you meant the "first trophic level" of the ecosystem. The first tropic level of an ecosystem is made up of producers, so the answer is C, Acorns.
Evolution Due to environmental factors, It may not look it, but, needles are leaves, they collect solar radiation to produce glucose through the process of photosynthesis, however, needles are, some would say, evolutionary superior to leaves. Needles themselves hold in more water due to their dense wax coating, they are very difficult for insects and other organisms to eat, one because of their structure, and two because of their acidity, they can catch sunlight all year long due to their winter resilience( they don't fall, during the winter), and they have less surface area for wind to catch, which leaves them better protected from wind than most deciduous trees, however the surface area can also pose a larger problem for less surface area means less sunlight interception, therefore more are needed to compete against regular leaves. But.. I Digress... Plant needles are 'PROBABLY' initially the result of evolution of narrow leaves due to climate or environmental factors.
Sry its so long got carried away! Hope this helps xD
All choices correctly describes physical barriers. Physical barriers after composed of tight junctions wherein it is difficult for the bacteria and viruses to penetrate. Examples of these physical barriers are the skin and the mucous membranes and these work in conjunction with secretions like tears and mucus (as tears and mucus contain IgA, a special type of immunoglobulin that is secreted to fight harmful organisms).
