Describe the process of crossing over during prophase i and explain how genetic recombination occurs.

The correct option is b. Alzheimer's disease

Alzheimer's disease can result from the formation of amyloid plaques and neurofibrillary tangles due to their activity in the brain. Alzheimer's disease can occur when amyloids which are meant to break down and be completely removed piles up to form hard, insoluble plaques. Also, neurofibrillary tangles which are found inside the brain consist of tau (a protein that forms part of a structure called a microtubule). An abnormal state of the tau protein and the breakdown of the microtubule structures will result in Alzheimer's disease.

Pseudostratified columnar epithelial tissue with cilia is located in the linings of the trachea as well as the upper respiratory tract. The presence of pseudostratified columnar epithelium with cilia in the upper respiratory tract protects the lungs from the effects of large dust particles, pollutants,corrosive agents and pathogens as the goblet cells of the epithelium secrete mucus to trap these particles and prevent them from traveling further down respiratory passages.

Pseudostratified columnar epithelial tissue with cilia is found in the lining of the respiratory tract. It has a protective role in preventing unwanted particles from entering the lungs.

Pseudostratified columnar epithelial tissue with cilia is predominantly found in the respiratory tract of humans. This particular type of epithelial tissue is characterized by a single layer of cells that appears layered due to the varying positions of the nuclei within the cells. The role of the cilia on these cells is to trap and transport mucus and dust particles upwards to prevent them from entering the lungs, hence providing a crucial protective role for the respiratory system.

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Answer:

D (characteristics of living things)

Explanation:

All things in existence are made up of matter, which can either be living or non-living depending on whether or not they have LIFE in them. This means that the possession of life distinguishes a living thing from a non-living thing. This life that living things possesses makes them able to perform certain functions called their characteristics.

Based on these, the characteristics of living things have been summarized into an acronym called MR NIGER D with each letter meaning a particular characteristic.

M- Movement (ability to move)

R- Reproduction (ability to produce young ones)

N- Nutrition (ability to absorb nutrients)

I- Irritability (ability to respond to stimulus in the environment)

G- Growth (ability to increase in size, weight and height)

E- Excretion (ability to pass out waste products from the body)

R- Respiration (ability to obtain energy)

D- Death (ability to die)

Looking at all these characteristics, they are possessed by insects, plants, animals, humans etc. Hence, they are all grouped as living things.

According to Chargaff's rules, if the DNA of an organism contains 30% guanine, then it is expected to contain 30% cytosine and 20% adenine, as the remaining 40% is split equally between adenine and thymine.

According to Chargaff's rules, the amount of adenine (A) is equal to the amount of thymine (T), and the amount of guanine (G) is equal to the amount of cytosine (C). This rule is universally true for all DNA, regardless of the organism or species. Therefore, if the DNA of a certain organism has guanine as 30% of its bases, the same percentage, 30%, will be cytosine. Then, the remaining 40% will be divided equally between adenine and thymine, resulting in 20% adenine.

To clarify, the four bases in DNA are adenine, thymine, guanine, and cytosine. Based on Chargaff's rule (A=T and G=C), if guanine makes up 30% of the DNA, then cytosine also makes up 30% of the DNA. Thus, the remaining 40% is shared equally between adenine and thymine, giving 20% adenine and 20% thymine.

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Final answer:

Homologous structures are similar anatomical structures that suggest a common ancestor. They have a common origin and shared basic patterns of bones or genetic sequences. These structures provide evidence for a common ancestor because their similarities can be traced back to a shared evolutionary history.

Explanation:

Homologous structures are similar anatomical structures that appear in different species and suggest a common ancestor. These structures have a common origin and shared basic patterns of bones or genetic sequences. For example, the grasping hands found in both humans and chimpanzees are homologous structures, indicating a common ancestor with the ability to grasp. Homologous structures provide evidence for a common ancestor because their similarities can be traced back to a shared evolutionary history.

Aggressive behavior in animals is often a result of competition for resources such as territory and mates, with intraspecific competition being particularly common. To avoid actual combat, animals use aggressive displays to communicate their strength and discourage others from engaging in a fight. Territorial behavior is widespread in the animal kingdom and these displays are a preferred method to reduce physical conflicts.

Animals may engage in fights, make threatening sounds, and act aggressively due to competition for resources such as territory, water, food, or mates. This competition can be intraspecific, which is among members of the same species, or interspecific, which is between different species. Aggression is an intentional behavior aimed at causing harm or pain, and it sometimes results in serious injuries or death. In many instances, instead of actual physical confrontation, animals utilize aggressive displays to communicate their willingness to fight and their fighting ability. These displays can serve as a mechanism to avoid actual combat by allowing animals to assess each other's strength and fighting prowess, deciding if it is worth engaging in a fight.

Some animal species are highly territorial and will defend their living space against intruders of the same species and sex. This territorial behavior often involves aggressive displays that convey a message to other animals to back off, thus reducing the possibility of injuries from physical encounters. For example, male gorillas display aggression through chest beating and ground thumping rather than attacking directly, conserving energy and minimizing the risk of harm. Moreover, birds like the Australian magpies may attack intruders, and certain fish, reptiles, and mammals exhibit similar territorial behaviors.

Lastly, it is important to note that such confrontations can lead to fights over mates or territory, potentially resulting in severe injury or death for one of the participants. Nevertheless, aggressive displays are a common strategy that aims to prevent such drastic outcomes by resolving conflicts before they escalate to physical violence.

Final answer:

Animals may display aggressive behavior due to competition for resources such as territory, water, food, or mates. This behavior can involve physical fighting or aggressive displays. Territorial behavior is also a common cause of aggression in animals.

Explanation:

Aggressive behavior in animals usually occurs as a result of competition. Animals may fight, make threatening sounds, and act aggressively towards members of the same species when they compete for resources such as territory, water, food, or mates. This behavior is known as intraspecific competition.

Intraspecific competition can lead to aggressive displays, such as a dog baring its teeth to intimidate another dog. These displays allow individuals to assess their opponent's fighting ability and determine whether it's worth engaging in a physical fight. It is thought that some of these displays may exaggerate an animal's actual fighting ability and are used to bluff opponents.

Aggressive behavior can also occur when individuals defend their territory. Many animals are territorial and vigorously defend their living space against intruders, especially those of the same species and sex. Territorial behavior is common among birds, fish, reptiles, and mammals.

The crop in earthworms functions as a storage area and has less muscular walls, while the gizzard is heavily muscular to enable it to grind and churn the soil and organic matter. This reflects their different roles in digestion. A similar distinction is seen in birds, where the gizzard contains grit to grind food.

The muscularity difference between the crop and the gizzard of an earthworm centers on their respective functions in the digestive system. The crop is a thin-walled organ that primarily serves as a storage compartment, allowing earthworms to ingest more soil and organic matter than they can immediately digest. It is not heavily muscular as it does not need to contract vigorously. In contrast, the gizzard is a thick, muscular organ designed to churn and grind the soil and organic matter ingested by the earthworm. The muscular walls of the gizzard are much stronger because they must contract powerfully to pulverize the food, which aids in the breakdown and digestion process. This difference in muscularity reflects the different roles these two organs play in the digestion process. Whereas the crop holds food in preparation for digestion, the gizzard actively participates in the mechanical breakdown of food.

In birds, a similar distinction exists. The crop functions as a storage area to moisten and soften food, while the gizzard, often enhanced with swallowed stones or grit, serves the purpose of grinding the food before digestion. Grain-eating birds, for example, possess a well-developed gizzard with ridges to enhance this grinding process, which compensates for the absence of teeth.

Answer:

Extinction of even a single keystone species will cause significant change to the ecosystem. Extinction of a species that is easily replaced by others may have little impact

Explanation:

It's actually Natural Selection

Mature human sperm and ova are similar in that they both have the same number of chromosomes. The human sperm and ova are the reproductive cell in male and female respectively. The sperm cells are motile while the ova are not. A mature human sperm and ova both contain 23 pairs of chromosomes.

Mature human sperm and ova are similar in that they have the same number of chromosomes (23), making them haploid cells. However, there are notable differences in their size, structure, and rate of creation. Specifically, only sperm possess a flagellum for motility and are produced in much larger numbers.

Mature human sperm and ova are similar in that they both have the same number of chromosomes, which is 23. This is half the number present in body cells, making them haploid cells. This is important as it allows the zygote, the cell formed after fertilization, to have the correct number of chromosomes (46).

Regarding size and motility, mature sperm and ova exhibit differences. For instance, sperm cells are much smaller than most cells, including the ovum or oocyte (female gamete). Only the sperm cell possesses a flagellum, a tail-like structure, that provides it motility, enabling it to swim towards the ovum for fertilization.

The production of sperm and ova also varies. Approximately 100 to 300 million sperm are produced daily, whereas typically only one oocyte is ovulated per month in females.

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Viral proteins is produced in a bacterial cell soon after viral RNA appears in the cell

Explanation:

The virus which infects the bacteria is called as bactriophage. When the bactreiophage attaches the bacteria, it releases its RNA into the bacterial cells. As the viral RNA enters the host cell which is nothing but the bacteria, it initiates to replicate due to which proteins are synthesized.

Thus the first product which is produced in a bacterial cell soon after viral RNA is protein. As the protein are made other metabolic process starts and fully developed viruses are synthesized.

Attachment of acetyl groups to histone promotes transcription.

This mechanism is known as histone acetylation and it is a part of gene expression. The lysine residues inside the N-terminal tail from the histone core of the nucleosome are the substrate for enzymes-histone acetyltransferase which transfer an acetyl functional group from another molecule. Acetylation removes the positive charge on the histones and thus decrease the interaction negatively charged phosphate groups of DNA. As a result, chromatin becomes more relaxed structure and transcription is promoted.