Answer: a. the lowest trophic level
Explanation:
The keystone species is the one on which the entire ecosystem depends upon. It maintains a balance in the ecosystem. If this species is removed the ecosystem will drastically change. The members of the keystone species are abundantly available at the lowest trophic level. This will help in making a balance in a community or ecosystem. If some members die others will be available to survive others.
It seems that you have missed the necessary options for us to answer this question so I had to look for it. Anyway, here is the answer. Varicose veins seen in the superficial veins of the legs are unsightly and often treated by surgically removing them. however, even without these veins being present, the return of all blood toward the heart from the legs is not diminished primarily because <span>blood can still return via the deep veins. Hope this helps.</span>
Answer:
Xylem cells have no cytoplasm or end walls, meaning they form a tube through which water can pass freely to allow water transport. Lignin strengthens the cell walls, helping to support the plant.
All organisms are grouped into five kingdoms. Those are Monera, Protoctista, Fungi, Plantae and Animalia. The division is made based on 3 criteria. Those are cellular organization, arrangement of cells, and type of nutrition. Cellular organization is whether they are eukaryotic or prokaryotic. Cell arrangement is whether they are unicellular, multicellular, with or without true tissue differentiation etc. Type of nutrition is whether they are autotrophic or heterotrophic. Kingdom Protoctista includes algae, protozoans, oomycota and slime moulds.
