Essential knowledge 4.C.1: Variation in
molecular units provides cells with a wider range of functions.
a.Variations
within molecular classes provide cells and organisms with a wider range of
functions. [See also 2.B.1, 3.A.1, 4.A.1, 4.A.2]
•
Different types of hemoglobin
Sickle cell anemia is caused by a genetic mutation which changed one letter on the gene that codes for hemoglibin. This one mutation made the hemoglobin and blood cells curve, which lessens the amount of oxygen each sickled cell can hold. It does, however, provide a heterozygous advantage in areas where malaria runs rampant. Malaria is a protozoa that is spread by mosquitoes. It invades normal red blood cells and devours hemoglobin, killing the cell. They multiply with every cell they devour and kill, spreading throughout the body and causing the host to die from anemia. When a person contracts malaria without the recessive sickle cell allele, they usually die. Those with homozygous sickle cell alleles are not able to move oxygen through their bodies very efficiently, which is pretty bad.
b.
Multiple copies of alleles or genes (gene duplication) may provide new
phenotypes. [See also 3.A.4, 3.C.1]
Discuss each of the following to explain 4.C.1.b
· A heterozygote may be a more advantageous genotype than a homozygote under particular conditions, since with two different alleles, the organism has two forms of proteins that may provide functional resilience in response to environmental stresses.
· Gene duplication creates a situation in which one copy of the gene maintains its original function, while the duplicate may evolve a new function. Example – antifreeze gene is fish – EXPLAIN.
Sometimes entire genes are duplicated. Since the copied gene is not being used, it will often mutate into a new gene that can code for new traits. A good example of this are fish that have mutated and adapted to below freezing temperature ocean waters. These fish has a trait copied that mutated to allow them to create proteins that kept water inside them from freezing. Since they don't easily freeze, they can live in colder waters with fewer fish to compete with.
Essential knowledge 4.C.2: Environmental factors influence the
expression of the genotype in an organism.
a.
Environmental
factors influence many traits both directly and indirectly. [See also 3.B.2,
3.C.1]
To
foster student understanding of this concept, choose THREE of the illustrative
example below to explain:
•
Height and weight in humans
One environmental factor that affects the expression of genes is food and nutrition availability. If someone only has a limited amount of food like wheat, for example, they are not getting the right amount of nutrients that their body needs to grow and developed. Even though they may be genetically dispositioned to be tall and bulky they would likely be skinny and short due to lacking nutrients to build that tall, bulky frame.
•
Sex determination in reptiles
In turtles, for example, when temperatures are high, more females are hatched and when temperatures are lower, more males are hatched.
•
Density of plant hairs as a function of herbivory
If something chews on a plant, as a defensive reaction it will sprout more spiked hairs to deter the herbivore from eating it. If the herbivore doesn't eat it to begin with, it will not exert the energy to produce thorns.
b.
An organism's adaptation to the local environment reflects a flexible response
of its genome.
To
foster student understanding of this concept, choose an illustrative example to
explain:
•
Darker fur in cooler regions of the body in certain mammal species
in certain mammals, when the temperature drops a gene for the production of darker or lighter fur is produced. When the animal sheds its fur for its winter coat, the color is changed.
•
Alterations in timing of flowering due to climate changes
Flowers are produced when the plant senses warm enough temperatures and light changes. If a plant flowers too early then it will likely be too cold to produce viable fruit, same with if it flowers too late.
Essential knowledge 4.C.3: The level of variation in a population
affects population dynamics.
a.
Population
ability to respond to changes in the environment is affected by genetic
diversity. Species and populations with little genetic diversity are at risk
for extinction.
To
demonstrate student understanding of this concept, make sure you can explain
the following:
●
California condors
California condors are essential in cleaning up dead organisms. Without them, other detrivores' numbers rise and the number of carcasses increase. To increase their numbers, conservationalists captively bred and raised them. When they had enough, they released many of them into the wild. Their genetic diversity is still extremely low and they are still on risk for extinction but it's getting better.
●
Black-footed ferrets
When plague was introduced and their habitats and prey, the prairie dog, declined, they faced extinction. They were thought to be extinct until a small population was discovered. This population has increased the numbers to about a thousand individuals in a captive breeding program.
●
Prairie chickens
Due to overhunting and loss of habitat loss they faced extinction but they have somewhat returned, although genetic diversity has significantly decreased.
●
Potato blight causing the potato famine
Monocropping and a small genetic diversity in potato plants caused the entire crop to fail, starving thousands of people in Ireland.
●
Corn rust affects on agricultural crops
A bacteria that kills corn crops that are not resistant to it.
●
Tasmanian devils and infectious cancer
Tumors that are introduced from devil to devil through fighting. The Tasmanian Devils are so closely related that the devils' bodies don't recognize it as a foreign substance. It spreads throughout the devil and kills it.
b.
Genetic diversity allows individuals in a population to respond differently to
the same changes in environmental conditions.
To
demonstrate student understanding of this concept, make sure you can explain
the following:
●
Not all animals in a population stampede.
These animals are picked of by predators and don't survive to reproduce.
●
Not all individuals in a population in a disease outbreak are equally affected;
some may not show symptoms, some may have mild symptoms, or some may be
naturally immune and resistant to the disease.
c.
Discuss how allelic variation within a population can be modeled by the
Hardy-Weinberg equation(s).
Hardy Weinburg equations represent the alleles in a population of future generations when there is no mutating, immigration, emigration, random mating, and one more thing. It is a mathematical equation that shows dominant homozygous, heterozygous and homozygous recessive trait frequencies.
Essential knowledge 4.C.4: The diversity of species within an
ecosystem may influence the stability of the ecosystem.
a.
Discuss why natural and artificial ecosystems
with fewer component parts and with little diversity among the parts are often
less resilient to changes in the environment.
When there is little diversity in an ecosystem, natural or artificial, if a disease is introduced then the organisms are much less likely to have a mutation that makes them immune to whatever disease is ravaging their species. That mutation would make organisms fit for that environment.
b. Keystone species, producers,
and essential abiotic and biotic factors contribute to maintaining the
diversity of an ecosystem. Discuss the effects of keystone species on the ecosystem are disproportionate
relative to their abundance in the ecosystem, and when they are removed from
the ecosystem, the ecosystem often collapses. Use the example of the Gray
Wolves.
A keystone species is a species with a significant role in an ecosystem. it either provides food for others or controls the population of the others. The grey wolf, for example, keeps the elk population in check. When they were decimated, the elk population soared which ate most of the vegetation. With the vegetation gone, the habitats of many birds and beavers was lost, which caused their populations to plummet. The waters heated up which killed plant life and allowed rivers to erode. With the river eroding, the beavers lose even more of their homes and can no longer build stable dams, which destroys breeding grounds for fish. The whole ecosystem has now collapsed.
Citations:
http://www.cdc.gov/ncbddd/sicklecell/images/sickle-cell-inheritance-pattern_3.jpg
http://www.washingtonpost.com/news/speaking-of-science/wp/2014/09/22/antarctic-fish-have-antifreeze-blood-but-it-might-fill-them-with-ice-crystals-over-time/
http://www.wonderwhizkids.com/resources/content/imagesv4/chemistry/acids+and+bases/hydrangeas.jpg
http://science.kqed.org/quest/files/2012/02/gray_wolf.jpg
