d) a vascular plant that uses pollen to produce seeds that are not enclosed in protective fruits
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Answer:
Yes, two hydrogen bonds could form between thymine and cytosine.
Explanation:
Cytosine is a pyrimidine base found in both DNA and RNA, and Thymine is a pyrimidine base found in only DNA. Electronegative Oxygen and Nitrogen atoms with free lone pairs are potential hydrogen bond acceptors. Hydrogen atoms attached to very electronegative atoms like Oxygen and Nitrogen have strong partial positive charge and are potential hydrogen bond donors.
One hydrogen bond could form between the C4 carbonyl group on thymine which is a hydrogen bond acceptor and the C4 amino group on cytosine which is a hydrogen bond donor. Also, another hydrogen bond could be formed between N3 of thymine which is a hydrogen bond donor and the N3 of cytosine that is a hydrogen bond acceptor.
It is important to note that hydrogen bond cannot be formed between them because the C2 carbonyl groups found on both bases are both hydrogen bond acceptors.
Answer:
1. <u>Highest population</u>: Primary producers (e<em>.g.</em> plants). In the case of animals: Primary consumers (<em>e.g</em>. grasshoppers).
2. <u>Lowest population</u>: Third-level consumers (Top predators). <em>E.g.</em> An eagle.
Explanation:
There are two types of ecological pyramids that illustrate the correlation between trophic levels and biomass in a healthy ecosystem:
- Energy pyramid: illustrates the <u>flow of energy at each trophic level</u>. That is, <em>energy is passed up from lower to higher.</em>
- Biomass pyramid: illustrates the amount of <u>biomass at each trophic level.</u><em> Less energy, less organisms.</em>
In a healthy ecosystem, plants are located at the bottom of the pyramid because they produce their own food; while top predators are located at the top.
<u>Plants (trees and bushes)</u>, for example, will have high population levels and will pass energy to the next level of the pyramid. <u>As we go up the trophic levels, organisms tend to be larger in size but fewer in numbers.</u> This means that the top predators or third-level consumers, such as <u>eagles, lions, or bears</u>, are indeed bigger but have lower biomass or population numbers.