Answer:
The correct option is A. they evolved from land mammals.
Explanation:
Evolution can be described as a process through which organisms in a species change over a period of time due to the natural selection of the environment. Those organisms that have many similarities in their functions or structures are considered closer to one another and have the same common ancestors.
The properties mentioned in the question about cetaceans resembles the properties of land mammals. For example, cetaceans lack gills and breathe air. Land mammals also do not have gills and need to respire for living. The cetaceans have fin bones which are similar to the limb bones in the land mammals. Hence, these observations show that cetaceas have evolved from land mammals.
Answer:
The sex chromosomes are referred to as X and Y, and their combination determines a person's sex. Typically, human females have two X chromosomes while males possess an XY pairing. This XY sex-determination system is found in most mammals as well as some reptiles and plants.
Men determine the sex of a baby depending on whether their sperm is carrying an X or Y chromosome. An X chromosome combines with the mother's X chromosome to make a baby girl (XX) and a Y chromosome will combine with the mother's to make a boy.
Explanation:
Administer varicella vaccine to the health 6-year old child (who does not have evidence of immunity to varicella) was exposed to a confirmed case of varicella 2 days ago.
Explanation:
It is seen that if a child receives varicella vaccine between 3 to 5 days of exposure, he is safe as disease will not appear in him and would be saved for future infections.
Varicella vaccine is given for prevention against small pox. It is expected once immunised with varicella body will produce antibodies for a span of twenty years or more.
The Sun is the basic source of energy for the Earth which affect the growth of all living things and the Sun also affect the all the biochemical processes. We know that the amount of radiation from the Sun changes day by day due to the distance of the Earth from the Sun. The rate of Solar energy affects the Earth in two ways.
The rate of solar heating which directly affects the processes like the evaporation and condensation and indirectly it affects the cloud forming processes of the Earth. The rate at which the solar energy reaches the Earth is called as the Total Solar Irradiance or TSI. This affects the climate of the Earth in many ways.
The change in rate of cloud formation increases of decreases with the distance of the Sun from Earth and hence a warm, moderate or cold climate is formed
It also affects the formation of winds due to the low or high pressure in the water bodies and hence affect the climate in the coastal areas.
The tropical areas have hot and humid climate due to the equator which has maximum exposure to the Sun’s heat.
Hence, the Sun is one primary feature that affects the climate in the Earth.
A theory in science is a remark on what happened
