Why does the malaria disease persist in the human population quizlet?
Why does malaria persist in the human population? Heterozygote advantage maintains both the normal allele and the sickle cell allele in the population. Which of the following is a step specific to the process of artificial selection? People select which individuals breed and which ones do not.
How does malaria affect the human population?
Nearly half the world's population lives in areas at risk of malaria transmission in 87 countries and territories. In 2020, malaria caused an estimated 241 million clinical episodes, and 627,000 deaths. An estimated 95% of deaths in 2020 were in the WHO African Region.
What characteristic is common of both a genetic bottleneck and founder effect?
What characteristic do a bottleneck and a founder effect have in common? Both involve a decrease in a population's genetic diversity.
What happens when an individual is produced that possesses a trait far away from the mean value?
What happens when an individual is produced that possesses a trait far away from the mean value? A. That extreme individual will likely not survive and reproduce.
Why might a harmful allele persist in a population for many generations?
It's reasonable to think that because they produce phenotypes that make individuals less fit, harmful alleles should disappear from any gene pool. But that tends not to be the case. Because harmful alleles are often recessive alleles, they can persist in a population almost indefinitely.
What does the term genetic drift mean?
Genetic drift describes random fluctuations in the numbers of gene variants in a population. Genetic drift takes place when the occurrence of variant forms of a gene, called alleles, increases and decreases by chance over time.
How does malaria affect the community?
Malaria discourages investments and tourism, affects land use patterns and crop selection resulting in sub-optimal agricultural production, reduces labor productivity, and impairs learning. Malaria can strain national economies, impacting some nations' gross domestic product by as much as an estimated 5–6%.
Why is malaria more common in poor countries?
Malaria occurs when climate and other conditions suddenly favor transmission to areas where people have no immunity to malaria. They can also occur when people with low or no immunity move into areas of intense malaria transmission, for example, refugees and those looking for work.
What impact can the bottleneck effect have on populations?
The bottleneck effect occurs when a population's size is reduced for at least one generation. Undergoing a bottleneck can greatly reduce the genetic variation in a population, leaving it more susceptible to extinction if it is unable to adapt to climactic changes or changes in resource availablility.
What caused the bottleneck effect?
When an event causes a drastic decrease in a population, it can cause a type of genetic drift called a bottleneck effect. This can be caused by a natural disaster, like an earthquake or volcano eruption. Today, it is also often caused by humans due to over-hunting, deforestation, and pollution.
How does a changing environment affect which traits are passed on in a population?
Favorable variations may allow an organism to be better adapted to its environment and survive to reproduce. Beneficial traits are favored in a population so that they may become better represented. Changes in the genetic makeup of a species may result in a new species; this is biological evolution.
What type of environment is being heterozygous in regards to the sickle-cell trait and advantage?
Individuals who are heterozygous for the sickle cell trait have an advantage in certain environments. In what type of environment is being heterozygous in regards to the sickle cell trait an advantage? A. An environment that has malaria.
Why do alleles persist?
While harmful recessive alleles will be selected against, it's almost impossible for them to completely disappear from a gene pool. That's because natural selection can only 'see' the phenotype, not the genotype. Recessive alleles can hide out in heterozygotes, allowing them to persist in gene pools.
Why has sickle cell disease persist in the population?
Its persistence in human populations has been attributed to the resistance it provides to Plasmodium falciparum malaria in its heterozygous state, called sickle cell trait (SCT).
How does genetic drift affect a population?
Genetic drift can result in the loss of rare alleles, and can decrease the size of the gene pool. Genetic drift can also cause a new population to be genetically distinct from its original population, which has led to the hypothesis that genetic drift plays a role in the evolution of new species.
Why does genetic drift happen in small populations?
Small populations tend to lose genetic diversity more quickly than large populations due to stochastic sampling error (i.e., genetic drift). This is because some versions of a gene can be lost due to random chance, and this is more likely to occur when populations are small.
Why is malaria so common in Africa?
It may be surprising that most cases occur on the African continent. Malaria is common in the area south of the Sahara Desert (called sub-Saharan Africa) because the disease spreads almost entirely in poor regions with tropical and subtropical climates. The local weather allows for transmission to occur year round.
Why is the spread of malaria increasing?
An increase in temperature, rainfall, and humidity may cause a proliferation of the malaria-carrying mosquitoes at higher altitudes, resulting in an increase in malaria transmission in areas in which it was not reported earlier.
Which population is most affected by malaria?
Some population groups are at considerably higher risk of contracting malaria and developing severe disease: infants, children under 5 years of age, pregnant women and patients with HIV/AIDS, as well as people with low immunity moving to areas with intense malaria transmission such as migrant workers, mobile …
What causes population bottleneck?
A population bottleneck is an event that drastically reduces the size of a population. The bottleneck may be caused by various events, such as an environmental disaster, the hunting of a species to the point of extinction, or habitat destruction that results in the deaths of organisms.
What caused the human bottleneck?
What caused it? The Toba catastrophe theory offers a convenient answer to the near doom written in our DNA. The hypothesis says an enormous supervolcano eruption occurred around the same time as humanity's biggest bottleneck.
When did the human population bottleneck?
That indicated to the researchers that the first bottleneck occurred as people migrated out of Africa to the Middle East about 50,000 to 60,000 years ago, and the second, 19,000 kilometers away, when they crossed the ancient land bridge in the Bering Strait to the Americas.
When does a population bottleneck happen?
A genetic bottleneck occurs when a population is greatly reduced in size, limiting the genetic diversity of the species. Scientists believe cheetahs have already survived at least two genetic bottleneck events.
How do populations of organisms have changed and continue to change over time?
Organisms that inherit that favorable new gene are likely to become more abundant than others of the species. Sometimes the population of a species becomes separated into two areas, by geography or by climate. Then the two groups no longer breed with each other. The two groups then slowly change by natural selection.
Why do populations change over time?
There are three components of change: births, deaths, and migration. The change in the population from births and deaths is often combined and referred to as natural increase or natural change. Populations grow or shrink depending on if they gain people faster than they lose them.
Why does sickle cell persist in human population?
Its persistence in human populations has been attributed to the resistance it provides to Plasmodium falciparum malaria in its heterozygous state, called sickle cell trait (SCT).
Why those who are heterozygous for sickle cell are immune to malaria?
While the genetic mutation in the beta globin gene producing sickle hemoglobin (HbS) causes severe vascular complications that can lead to early death in individuals who are homozygous (SS) for the mutation, in its heterozygous form (AS), it partially protects against severe malaria caused by P.
Why does the sickle cell allele persist in populations where malaria is not prevalent?
Heterozygotes (AS) with the sickle-cell allele are resistant to malaria. Therefore, they are more likely to survive and re produce . This keeps the S allele in the gene pool.
Why do genetic diseases persist in the human population?
Diseases are thought to persist in human populations primarily because of a balance between mutation, genetic drift, and natural selection, with alleles that contribute to disease introduced by mutation, governed in part by random genetic drift, but eventually eliminated from the population by purifying selection (5, 7 …
Why does genetic drift not affect large populations?
Every population experiences genetic drift, but small populations feel its effects more strongly. Genetic drift does not take into account an allele's adaptive value to a population, and it may result in loss of a beneficial allele or fixation (rise to 100% frequency) of a harmful allele in a population.