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Helen [10]
3 years ago
6

An infectious disease is an infection that impairs the normal state of health.

Biology
1 answer:
Kitty [74]3 years ago
3 0
I think the answer is {b.false}
Infectious diseases are diseases that spread from one person to other either directly or indirectly. I think this is the answer.
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Consider a species of sparrow that originally lived only in Alaska but recently expanded its range through North America, then C
Shtirlitz [24]

Answer:

North America is the one with the highest heterozygosity frequency for most loci, followed by Central America, and finally, South America with the lowest heterozygosity level.  

Explanation:

Some different forces or mechanisms might alter H-W equilibrium and lead to evolution, such as mutation, natural selection, migration, and genetic drift.

In the exposed example, we have a species of sparrow that migrates from Alaska to North America. Migration is unidirectional, which means that the movement occurs in only one direction: from Alaska to North America. We should also consider that the first immigrants colonized the area for the first time, meaning that there was not a receiving population of the same species already established. Finally, we need to consider that Alaska´s environmental conditions are very different from North America´s environmental conditions.

When a species arrives at a new place, it needs to adapt. The establishment and dispersion of the species in the new area depend on previous adaptation. So, when the firsts sparrow individuals arrived in North America, they faced new environmental conditions that acted as selective pressures that drove to the occurrence of mutations. A mutation implicates a stable and inheritable change in the genetic material. A mutation introduces changes, new alleles in the population, variability. But mutation rates are very low and have no evolutive direction, so they need another force to increase or decrease the mutant allelic frequencies. Natural selection benefits new advantageous alleles and transmits them to new generations changing their relative frequencies. <em>So, sparrows arrive in North America, mutated, and natural selection favored the beneficial mutations leading to a better adaptation to the environment.</em> This means that the heterozygosity level in this new recent population is very high.

As animals adapt to the new habitat and have better dispersal genes, they get to disperse even more. So they start new migration south, to Central America and South America. Again, they are moving to new regions with new conditions, and to establish they need to suffer new adaptations. But remember that we are talking about a recent event in time. Probably the animals migrating south are just a few.  They have not spent enough time yet in the new area, to adapt to the new environment and to include new genes into their population. What is even more, as they are a small new population moving south, they are more vulnerable to genetic drift events. Genetic drift acts on a population decreasing the variability between individuals, hence, decreasing the heterozygosity. <em>This small population suffers low mutation, has not enough time to establish, and is more vulnerable to genetic drift events.</em> The heterozygosity level is probably inferior to North America´s one.

Comparing the three areas, we could say that North America is the one with the highest heterozygosity frequency, followed by Central America, and finally, South America with the lowest level of heterozygosity.

8 0
2 years ago
Water is essential for life. Its special properties make water the single most important molecule in plant life. Which of the fo
Maslowich

Answer:

Because water exhibits cohesive behavior.

Explanation:

Cohesive behavior can be explained as a behavior where molecules are attracted to each other.

And this means that,  water molecules are attracted to each  other because of their cohesive behavior. This makes them to be  attracted to other substances, such as the walls of the xylem of plants.

In this case, it is believed that the water molecules behave this  way because they are polar, that is, there is an electronegativity difference between the bonded atoms. And this enables it to move from the roots to the leaves of the plants.

7 0
2 years ago
Representative organism Type of symmetry (Radial, Bilateral, or None) Type of skeleton (ENdoskeleton, EXoskeleton, or None) Type
Galina-37 [17]

Answer:

Sponge; Radial Symmetry; Endoskeleton; Absent Appendages; Absent Segmentation

Cnidarians; Radial Symmetry; No Skeleton; Non-Jointed Appendages; Absent Segmentation

Roundworms; Radial Symmetry; No skeleton; Absent Appendages; Absent Segmentation

Annelids; Radial Symmetry; No skeleton; Absent Appendages; Present Segmentation

Mollusks; Bilateral Symmetry; Exoskeleton; Non-Jointed Appendages; Absent Segmentation

Arthropods; Bilateral Symmetry; Exoskeleton; Jointed Appendages; Present Segmentation

Echinoderms; Bilateral Symmetry; Endoskeleton; Non-Jointed Appendages; Absent Segmentation

Vertebrates; Bilateral Symmetry; Endoskeleton; Jointed Appendages; Absent Segmentation

8 0
3 years ago
Glycans are a virulence factor for which group of organisms?
zloy xaker [14]

Answer:

<h3>C.bacteria</h3>

Explanation:

because bacterial glycans are attractive pathogen-specific targets. Bacterial cells are coated with an impressive array of glycan structures that comprise their cell wall

4 0
2 years ago
Which current would help an explorer sailing westward from Europe across the Atlantic Ocean?
puteri [66]

Answer:

The North Atlantic Drift, more formally known as the North Atlantic Current.

Explanation:

The current is pretty strong and increased travel speed significantly, especially back in the day when cross-atlantic travel took months.

3 0
2 years ago
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