Answer:
Arteries carry oxygenated blood away from the heart. Veins carry the blood back to the heart. Veins contain valves that ensure blood flows in only one direction. Arteries don’t require valves because pressure from the heart is so strong that blood is only able to flow in one direction.
Explanation:
Typhoid fever is most common in non-industrialized countries. Travelers to Asia, Africa, Eastern Europe, and Latin America are especially at risk. Salmonella typhi bacteria are shed in the urine or stool of infected persons, including chronic carriers. There are no known animal reservoirs for typhoid fever.
Complete question:
Two species of closely related frogs are found in the same pond high in the Andes of South America. Both species only have teeth on the top jaw. One has small teeth for holding small live prey prior to swallowing. The other species has very large sharp teeth for injuring and killing large prey prior to biting off pieces of flesh for consumption. The above is an example of:
- Directional selection
- Analogous structures
- Character displacement
- Hybridization
- Vestigial structures
Answer:
Explanation:
Competition is an ecological and evolutive process very common in nature. Competition might be intra- or interspecific. Competition between different species in a community or ecosystem might be due to the same resource use, or the same territory, shelter, etcetera. When a resource is useful for two or more species, and limited, they compete to gain it.
The principle of competitive exclusion states that different species with the same requirements sharing the niche can not coexist indefinitely based on the same limited resource. When <u>two competing species coexist, this is because of niche partitioning or niche differentiation</u>.
Differentiation of effective niche is closely related to <u>character displacement.</u>
<u>Character displacement</u> is the result of interspecific competition, in which two or more species that live in the same habitat manage to avoid competition by developing different traits. Morphological divergence, or any adaptative trait development, fixated genetically, is the product of niche segregation. Species tend to differentiate morphologically in the presence of strong competitors. Traits divergence favors coexistence in the same place.
In the exposed example, both species live in the same pond. But to avoid competition and competitive exclusion, species developed different teeth sizes to feed on different prey items.
Answer:
The Leydig cells produce testosterone, which also is responsible for the secondary sexual characteristics of males. In females, FSH and LH cause estrogen and progesterone to be produced. They regulate the female reproductive system which is divided into the ovarian cycle and the menstrual cycle.
Explanation:
