Answer: if i want to breed a rose and i don't have a certain kind of rose, i have to cross between them until i have a kind of rose that express the phenotype i was looking for. Once i've got it, i'll try to cross it with another rose and generate more species like that to cross with the rose that express the phenotype, this favors to generate a specie that have a pure phenotype.
Explanation: The answer is explain by the Mendel's laws.
Mendel's second law:
if you have two roses that are heterozygous and you cross them, their offspring have a 25% probability of generating a homozygous phenotype for a certain recessive characteristic (such as the rich smell of roses that is not a dominant character), 50% of generate heterozygotes with a dominant phenotype, and 25% generate other homozygotes with a dominant phenotype.
Once the offspring with the recessive homozygous character are obtained, it is possible to start making crosses between those of a recessive nature and there Mendel's first law applies
All the homozygous recessive individuals that are crossed will have a 100% homozygous recessive offspring.
Also, if you cross heterozygotes with another heterozygotes the offspring will be 100% heterozygotes
It is called genetic engineering
DDT stands for dichloro-diphenyl-trichloroethane. The first kind of synthetic/artificial insecticides came into use in the 1940s. The earlier usage of DDT include: a) Killing of malarial vectors, b) Combatting Typhus and other insect borne human diseases, c) As a pest control in crops d) as a pest control in garden, live stock production and even at homes.
The negative impact of DDT could be felt for the first time when the pests that were earlier killed by use of DDT have now become pesticides resistant. In the 1950s in USA, the regulatory measures were adopted to reduce the usage of DDTs as its effects as a pesticides were no more long significant and also it was creating detrimental physical and psychological impacts on the human and environment.
It was in 1972 that the U.S. Environmental Protection Agency cancelled the order for banning the usage of DDT based on the adverse impact it produced on the environment, human and other life forms. Since then continuous studies are being conducted to analyse the impact of DDTs. In some later years it was established that DDT is the cause of producing tumors in liver.
Some of the common negative impacts produced by DDT as per the U.S. Department of Agriculture :
a) The non destructive nature – DDT can not be destroyed and thus it remains persistent in the atmosphere
b) It attacks the tissues of living organisms especially the animals and humans ( fatty tissue)
c) It can penetrate the atmosphere to deeper extent.
Now as per the current stuation, The use of DDT is controlled and other alternatives of pest control organisms is being deduced. As per the treaty of Stockholm Convention on POPs (Persistent organic pollutants) , usage of DDT for malarial control is justified but it puts a restrictive use of DDT as pesticides in other areas.
Answer: D.) It allows water to resist freezing and thawing cycles.
The ability of the water molecule to absorb and retain heat is called as heat capacity of water, because of this property the temperature of water remains the same for long, irrespective of the external environment. It allows water to resist freezing and thawing cycles because water molecules will resist change in it's temperature. This temperature regulation will prevent instant heating and cooling, hence, will provide suitable environment for the survival of marine organisms.
Wind isn’t an external force that acts in the rock cycle.
