The crossing over mechanism of genetic variation results from the exchange of gene segments between non sister chromatids. The correct answer is A. 
        
                    
             
        
        
        
Answer:
In contrast, major disturbances include large-scale wind events (such as tropical cyclones), volcanic eruptions, tsunamis, intense forest fires, epidemics, ocean temperature changes stemming from El Niño events or other climate phenomena, and pollution and land-use conversion caused by humans.
Explanation:
 
        
             
        
        
        
Answer:
root hairs → 1. absorbs water and nutrients from the soil
vascular tissue → 2. consists of xylem and phloem
chloroplast → 3. the site of photosynthesis inside the cell
stem → 4. holds the leaves up high into the sunlight
leaf → 5. acts like an umbrella to absorb light  
terminal bud → 6. the growing part of the stem
taproot → 7. roots that reach deep into the ground
Explanation:
I have been able to match each term to its correct description.
From the above, we will discover that these are parts of a plant. These parts of the plant enable the plant to carry out photosynthesis and to exist.
The root hairs of the plant absorbs water and nutrients from the soil. When such are absorbed, the vascular tissues help to transport them.
The vascular tissue consists of the xylem and phloem. They  transport fluid and nutrients inside the plant. The vascular tissue is associated with two meristems which are the vascular cambium and the cork cambium. It is at the chloroplast that photosynthesis occur; where light energy is converted to chemical energy. 
The stem holds the leaves firmly in order to project it to the sunlight. The leaf absorb sunlight which is needed for photosynthesis. The terminal bud is actually the part of the stem that is growing out. Taproot reach deep down the ground in search of water for the plant.
 
        
             
        
        
        
Now it is clear that genes are what carry our traits through generations and that genes are made of deoxyribonucleic acid (DNA). But genes themselves don't do the actual work. Rather, they serve as instruction books for making functional molecules such as ribonucleic acid (RNA) and proteins, which perform the chemical reactions in our bodies.Proteins do many other things, too. They provide the body's main building materials, forming the cell's architecture and structural components. But one thing proteins can't do is make copies of themselves. When a cell needs more proteins, it uses the manufacturing instructions coded in DNA.The DNA code of a gene—the sequence of its individual DNA building blocks, labeled A (adenine), T (thymine), C (cytosine) and G (guanine) and collectively called nucleotides— spells out the exact order of a protein's building blocks, amino acids.
Occasionally, there is a kind of typographical error in a gene's DNA sequence. This mistake— which can be a change, gap or duplication—is called a mutation.