When a doctor refuses to care for a certain patient. This can be for numerous reasons, maybe they are not fit to undergo a surgery of some sort, or are being problematic. Either or the doctor nor the patient benefit form this. Doctor misses out on someone to help (i assume that’s the attitude of one working for the greater good) and the patient misses the opportunity to possibly get the help they need.
Seismic waves are waves produced by earthquakes. This occurs
when rocks under the earth suddenly break or explode. There are two MAIN TYPES
of seismic waves called body waves and surface waves.
<span>Body waves have the capacity to travel through the Earth's
inner layers. They have a higher frequency and they are the ones that first
occur under water at the onset of an earthquake. They can be subdivided
into two types, the primary and secondary waves that arrive at seismic records
one after another.
Surface waves can only traverse through the surface of the planet like ripples
in the water. These waves can easily be detected on a seismogram result. These
waves arrive after body waves and they are the ones mostly responsible for
damages and destruction bought by earthquakes.</span>
<span> </span>
Answer:
Answer is option A.
Vestigial features are fully developed and functional in one group of organisms but reduced and function less in a similar group.
Explanation:
- Vestigial structures are anatomical features such as cells, tissues or organs in an organism that are previously functional and performed some important functions in the organism but no longer serve any functions in the current form of the organism and become useless as a result of a large evolutionary change. Examples include the coccyx or the tailbone in humans, the pelvic bone of a snake, wisdom teeth in humans, nipples in human males, the wings of flightless birds such as kiwi, ostrich, etc.
- Homologous features are the features that are similar in different organisms having similar embryonic origin and development and are inherited from a common ancestor that also had that feature. Also, they might have different functions. An example is the presence of four limbs in tetrapods such as crocodiles, birds, etc.
- Analogous features are the features that are superficially similar in different organisms but had separate evolutionary origins i.e., different in origin, but similar in function. An example includes the wings on a fly, a moth, and a bird where the wings were developed independently as adaptations to perform the common function of flying.
- Polygenic features are the traits or features that are controlled by multiple genes that are located on the same or different chromosomes and are also affected by the environment. These features do not follow Mendel’s pattern of inheritance and are represented as a range of continuous variation. Examples of polygenic traits or features include skin color, height, hair color, eye color, etc. For example, there is wide variation in the human skin color (from light to dark) and height (short or tall or somewhere in between).
- Sympatry describes a species or a population that inhabit the same geographic region at the same time. In sympatric speciation, new species are evolved from a surviving ancestral species while both the species inhabit the same place at the same time i.e., in a single population, reproductive isolation occurs without geographic isolation.
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.
