<span>My pea plant has an unknown genotype for flowers, whether it has two dominant traits for white flowers (WW) or one dominant and one recessive (Ww) leading to white flowers; therefore I am doing a testcross in order to determine the genotype of my pea plant. The best plant to do this with is one that has a phenotype of purple flowers (ww) - that is, it is homozygous for the recessive trait.
If I use a homozygous recessive plant, I know exactly what its genotype is. I don't have to worry about whether it's got one or two dominant alleles; I know that at least half of my alleles are going to be the recessive w.
This makes identifying the offspring's genotype very simple. If I find that the offspring have at least some purple flowers among them, I know that my original plant had to be Ww; that is it had to have one dominant and one recessive allele for the flower color gene. If, however, all of the offspring are white flowers, I know that my original pea plant had both dominant alleles (WW).</span>
Answer:
This is correct. The remaining portion:
Sympatric species that form interrelationships undergo coevolution.
Allopatric species in different environments can undergo convergent evolution.
Allopatric species in small populations and under intense environmental conditions can undergo genetic drift.
Explanation:
On the basis of geographical distance, speciation is of two major types:
- Sympatric
- Allopatric
Sympatric Speciation:
Sympatric speciation is the formation of new species with no gergraphical separation from the ancestor. The new and parent species both exist in the same environment but do not interbreed due to mechanisms of reproductive isolation. These involves both prezygotic and post zygotic barriers to reproduction such as timing of mating, sensitivity to pheromones, choice of mating sites or infertility and mismatched gametes. Species formed through sympatric speciation can form interrelationships and undergo coevolution i.e. the evolution of ones species is dependent on the other.
Allopatric Speciation:
It involves the geographical separation of the parent and new species. These species could be geographically separated by a river, mountain range or land mass.
Although, allopatric species evolve independently, they may develop similar characteristics that serve different functions. Allopatric species in radically different environments undergo convergent evolution i.e. species evolve similar characteristics without any ancestral homology.
Allopatric species that reside in small populations and are under harsh environmental pressures undergo a rapid genetic revolution i.e. genetic drift. This includes the Founder's and bottleneck effect that involve the continuation of a species from very few individuals after a drastic, sudden environmental change.
The hormone calcitonin is controlled by a negative feedback mechanism because it's release leads to the decrease of calcium blood levels.
<h3>What is negative feedback mechanism?</h3>
A negative feedback mechanism is the defined as a type of regulatory mechanism in the body where by the increased output of a system leads to a decrease of another system.
Therefore, the release of the hormone calcitonin (increased level of calcitonin in the blood) will lead to decrease in blood levels of calcium.
Learn more about hormones here:
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Answer:
first drop down:
a. mass
second drop down:
b. weight
third drop down:
a. strength of gravity increases
fourth drop down:
b. weight decreases
