9.3 Evolution's Role in Medicine and Agriculture

Question 1

Studying the ______ of disease can help us understand and control disease ________.

Answer 1

evolution; frequencies

Question 2

Lack of ______ can make crops and livestock ________ to evolutionary forces.

Answer 2

variation; vulnerable

Question 3

Micro-organisms reproduce very ______ (some as little as 20 mins)
Therefore, Microevolution can happen extremely
______

Answer 3

quickly; fast

Question 4

Bacteria and viruses need to be monitored in order to prevent _____________________________

Answer 4

disease outbreaks and pandemics

Question 5

Advances in genetics allows for the study of alleles and how they play in both _____________

Answer 5

causing and preventing diseases

Question 6

Pandemic definition

Answer 6

A disease outbreak over a large geographical area

Question 7

Alleles and Disease Resistance

Answer 7

Some humans/populations show resistance to certain diseases due to natural selection

For example:
-Europeans with CCR5 D32 allele resistant to plague; now resistant to other diseases like HIV
Africans with SCA allele resistant to malaria
-Europeans heterozygous for CF allele resistant to bacterial infections (TB, typhoid fever, salmonella, cholera)

Question 8

Influencing Disease Frequencies

Answer 8

Some diseases may not be selected against due to age of onset or medical interventions

-Huntington’s Disease– adult onset (~40); people have often already reproduced
-Cystic fibrosis – better treatment/management allows affected individuals to survive and potentially reproduce
-Tests for many genetic diseases – can choose to reproduce or not

Question 9

Evolution in Agriculture

Answer 9

Agricultural developments aim to produce as much food as possible

Pesticide resistance and reduced genetic variability are problems that have been encountered

Question 10

Slowing Pesticide Resistance

Answer 10

-New pesticides expensive to develop; only effective for a short period of time
-Refugia: local environments not affected by regional ecological change

For example:
-Most of field sprayed with pesticides, allows some resistant pests to survive
-Part of field not sprayed with pesticides, allows resistant and sensitive species to survive and reproduce
-Therefore, keeps allele frequency lower

Question 11

Refugia definition

Answer 11

local environments not affected by regional ecological change

Question 12

Genetic Diversity in Crops

Answer 12

-Crops are Artificially Selected to have certain traits
-Easy to grow; clones have reduce genetic variability

-E.g. Irish potato famine (1840s) – only one type of potato planted, completely wiped out by blight
-Corn in US (1970) – fungus
-California vineyards (1980s) – insect pests

Question 13

Genetic Diversity in Livestock

Answer 13

-Artificial selection reduces variability in animals as well as plants
-Chickens bred for egg-laying ability need to be cross-bred with other breeds to increase diversity in case of disease outbreaks
-Reproductive technologies like artificial insemination allow for desired traits to be passed on more quickly, but further reduce variation
-However, can allow for breeding that wouldn’t happen in nature (due to location/distance)

Question 14

how does artificial insemination affect diversity?

Answer 14

reduces genetic variation

Question 15

Why are new flu vaccinations needed every year?

Answer 15

the virus mutates so quickly, every year new vaccines have to be created to protect against the new strains

Question 16

Why are Europeans more likely to be resistant
to HIV than Asians or Africans?

Answer 16

-people of European descent carry at least one copy of the D32 allele of the CCR5 gene
-this allele allowed some people to resist plague infections in the past and they were more likely to survive

Question 17

Why do heritable adult-onset diseases such
as Huntington’s disease still occur in the
population?

Answer 17

-in adult-onset genetic diseases, symptoms may occur AFTER reproduction has already taken place. -therefore, the disease-causing allele may have already been passed on to the offspring

Question 18

How does the occurrence of one disease affect
the incidence of another? Provide an example

Answer 18

-20 percent of Europeans and people of European descent have been found to carry at least one copy of the D32 allele of the CCR5 gene

-Scientists think this allele allowed some people to resist plague infections in the past and they were more likely to survive.

-So individuals with the allele were selected for whenever there was an outbreak of the plague

Question 19

How can refugia help reduce pesticide
resistance?

Answer 19

both pesticide-resistant and pesticide-sensitive insects survive in the refuge and they will interbreed.

If the allele for pesticide resistance is recessive,
only about a quarter of the offspring will be resistant.

Thus, over several generations, the proportion of pesticide-resistant insects in the population
will be significantly reduced

Question 20

refugia

Answer 20

Refugia are any local environments that have not been affected by regional ecological change.

In agriculture, refugia are blocks of land in fields that are not sprayed with pesticides

Question 21

Identify two alleles that cause disease yet have
been favoured by natural selection. Explain
why they were favoured

Answer 21

Cystic Fibrosis allele
-evidence shows that heterozygous individuals may be resistant to several serious diseases caused by bacteria, including tuberculosis, typhoid fever, salmonella poisoning, and cholera

D32 allele
-scientists think this allele allowed some people to resist plague infections in the past and they were more likely to survive. So individuals with the allele were selected for whenever there was an outbreak of the plague

Question 22

Provide an example of how artificial
insemination has affected livestock

Answer 22

Using this technique, a single prized male can produce far more offspring than he would have through conventional selective breeding.

Though the desired traits are maintained in the population, the genetic diversity within the breed is reduced, since so many individuals have the same father

Question 23

How have outbreaks of diseases such as cholera
affected humans over time?

Answer 23

Cholera was once extremely common in Europe.

Before the invention of antibiotics, those who got cholera had a 50 percent chance of dying from it

It greatly reduced population sizes

Question 24

How have reproductive technologies such
as genetic screening affected the evolution
of diseases?

Answer 24

Tests have been developed for many genetic diseases, including Huntington’s.
People who discover they have a disease-causing allele may choose not to reproduce.
If they do not reproduce, the frequency of the allele in the gene pool will be reduced

Question 25

Suppose herbicide has been developed that
attacks only purple loosestrife. Create a plan
to slow herbicide resistance in these plants,
which have invaded a large marsh

Answer 25

-create a refuge so that both pesticide-resistant and pesticide-sensitive insects survive in the refuge
and they will interbreed.
If the allele for pesticide resistance is recessive,
only about a quarter of the offspring will be resistant.
Thus, over several generations, the proportion of pesticide-resistant insects in the population will be significantly reduced

Question 26

How have modern agricultural practices made
crops vulnerable to evolutionary forces?

Answer 26

Some agricultural practices also reduce the genetic diversity of livestock and crop species, which can leave them vulnerable to evolutionary forces
-e.g. monoculture

Question 27

Pregnant women often experience nausea,
especially in the first three months of fetal
development. The nausea is often triggered by
certain types of food, including spices. Form a
hypothesis about how this nausea might be an
evolutionary adaptation

Answer 27

-morning sickness protects the embryo by causing pregnant women to physically expel and avoid foods that contain chemicals, especially toxic chemicals in strong-tasting vegetables, caffeinated beverages and alcohol

-this helps the fetus become less vulnerable to the effects of chemical disruptions

Question 28

Some people believe that because a new
influenza vaccine is needed each year, there
is no point in getting vaccinated.
(a) Discuss some of the disadvantages in getting
vaccinated each year.

Answer 28

Some vaccines are associated with fever, rash, and achiness. Serious side effects are rare, but may include seizure or life-threatening allergic reaction.

Question 29

Some people believe that because a new
influenza vaccine is needed each year, there
is no point in getting vaccinated.
(b) Why should governments keep investing
money to develop a new flu vaccine each
year?

Answer 29

Because the virus mutates so quickly, every year new vaccines have to be created to protect against the new strains

Question 30

Some individuals who are infected with
malaria develop anemia, which is a deficiency
of red blood cells.
(a) How could anemia benefit these
individuals?

Answer 30

people with sickle cell anemia are resistant to malaria

Question 31

Some individuals who are infected with
malaria develop anemia, which is a deficiency
of red blood cells.
(b) If these individuals then have children,
will the children be anemic? Explain.

Answer 31

since anemia is a recessive disorder, at least one parent has to carry 2 recessive alleles and the second parent must be heterozygous for the children to be anemic

Question 32

Which population of pigs is more vulnerable to
disease? The genetically identical population or the genetically diverse population? Explain

Answer 32

the genetically identical population is more vulnerable to disease

-without genetic variation, a population cannot evolve in response to changing environmental variables or diseases and, as a result, may face an increased risk of extinction

-the greater the variation in genes, the more likely it is that individuals in a population will possess the differentiated genes which are needed to adapt to an environment

Question 33

Scientists have to monitor disease-causing bacteria and viruses because of their ability to _____ quickly

Answer 33

mutate

Question 34

An allele that, when present in both copies, leads to a deadly disease in which sufferers die before they can have children. When present in heterozygous form, however, the allele imparts resistance to many serious diseases caused by bacteria, including cholera. Cholera was very prevalent in ancient Europe, and now one in every 25 people of European descent carry this allele. Which genetic disease is this?

Answer 34

cystic fibrosis

Question 35

An allele that, when present in both copies, leads to a deadly disease in which sufferers die before they can have children, but when present in heterozygous form imparts resistance to many serious diseases caused by bacteria. The survival benefits of this disease allele…

Answer 35

allow the allele to be maintained in the gene pool.

Question 36

What genetically linked disease is most likely to decrease in frequency over time?

a) Childhood disease with treatments available
b) Childhood-onset disease with no treatments developed

Answer 36

b) Childhood-onset disease with no treatments developed

A childhood-onset disease will result in a phenotype of the disease, and likely an individual with compromised health or reproductive abilities. If there are no treatments, the disease will run its course, and it is likely the alleles for the disease will not get passed on to any offspring. Treatable diseases may boost the organism’s health enough to reproduce as well.

Question 37

In the 1340s, Europe suffered from a widespread outbreak of a deadly disease caused by a bacterium. It killed about one-third of Europe’s population. Which disease caused this pandemic?

Answer 37

bubonic plague also known as the black death

Question 38

The white leghorn is the breed most widely used for producing eggs. What is a disadvantage of selectively breeding a chicken to maximize egg production?

Answer 38

It is more susceptible to disease