Answer:
A
Explanation:
Because there are two DNA strands in the DNA molecule and they both rotate around each other in a helix formation. So two helixes = double helix.
One group of reptiles, characterized by the fossil Archaeopteryx, led to the evolution of birds. The correct answer is birds
Answer:
<u>Cilia</u>
Explanation:
Cilia and flagellum are made up of microtubules.
Cytoskeletal filaments are structures which allow movement. In cilia and flagella, the cytoskeletal filaments are present in the form of microtubules and the primary work of these structures is to facilitate in movement.
Cilia is also present in mammals to facilitate the movement of fluids in cells.
Structurally, there is no difference between cilia and flagella. The only difference between cilia and flagella is in their lengths.
Answer:
D. DDT
Explanation:
DDT is highly persistent in the environment means that it break down very slowly in the environment. The half-life for DDT is from 2 to 15 years. Half-life is the time needed for the degradation of half of the compound. Persistent bio-accumulative toxic substances (PBTs) are chemicals that break down slowly in the environment and its accumulation in living organisms are toxic. Some PBTs are dispersed through air currents while some uses other environmental pathways, resulting in contamination of regions far from their points of origin.
<h2>Answer:</h2>
The two reasons are given below:
- Natural selection.
- Lack of food
<h3>Explanation:</h3>
Natural selection is the phenomenon of the evolution in which the organisms able to fit in the changing environment survive while other organism died. Hence the survival if the fittest and then these organisms. Further reproduce to give birth organisms more fit to the changing environment.
The long neck giraffe survive but short neck died. So the population of long neck increased while short neck go extinct.
Other reason is the change of food resource. The food resource change from grass to long trees.
