Organisms that cause disease are carriers. Such as ticks, fleas, lice.
Answer:
Nucleic Acids:
- Uracil
- Adenine
- Guanine
- Cytosine
Explanation:
Since we only have one strand shown, I'm going to assume it is RNA. Both DNA and RNA have nucleic acids, but RNA has 1 different nucleic acid; it replaces Thymine with Uracil. So the 4 nucleic acids are uracil, adenine, guanine, and cytosine.
If the picture shown is a cross-section of DNA, then our 4 nucleic acids are adenine, thymine, guanine, and cytosine.
Meiosis involves crossing over where chromosomes exchange genetic segments, resulting in different sets of chromosomes. Each time an egg or sperm created, it is different due to this recombination. Mitosis on the other hand is non-sex cells replicating exact copies of themselves which lead to no genetic variation as they aren't involved in producing offspring.
Answer:
An index fossil is also known as guide fossils or indicator fossil. They are fossils used to determine and identify geologic periods.
The main characteristics of an index fossil include :
1.It must be distinctive.
2.It must be widespread.
3. It must be abundant
4. It must be limited in geologic time.
Due to trends and studies of most fossil-bearing rocks being formed in the ocean, the major index fossils are mostly marine animal or plant organisms.
