Question

What is a human? What is a cell?

Answer 1

Humans:-

The scientific name of humans is homo sapiens.The term homo sapiens was given by carl Linnaeus.Homo sapiens is the only human species still exist.They are anatomically similar and are related to apes.They come under the mammalian class,primates order and Animalia kingdom, family is homonidae,genus is homo,species is H.sapiens.Their reproduction is sexual.male and female gametes are fertilise to form zygote.Humans has double circulatory system with four chamber heart.they have separate digestive system.Their brain is the most developed and complex.They are culture bearing primates.Extinct species of genus include homo erectus.

Cell:-

i.The basic unit of life is cell ,that are present in all living organisms.Unicellular organisms are capable of independent existence and performing the essential functions of life.Anything less than a complete structure of a cell does not ensure independent living.Hence,Cell is the fundamental structural and functional unit of all living organisms.

ii.Anton von leeuwenhoek first saw and described a live cell.Rudolf virchow modified the hypothesis of schleiden and schwann to give the cell theory a final shape:-

a.All living organisms are composed of cells and products of cells.

b.All cells arise from pre-existing cells.

iii.Cells that have membrane bound nuclei are called eukaryotic where as cells that lack membrane bound nucleus are prokaryotic.In eukarotic cells membrane bound distinct structures called organelles like the Endoplasmic reticulum,golgi complex,lysosomes,mitochondria,microbodies,vacuoles are found where the prokaryotic cells lack such membrane bound organelles.

iv.A semi-fluid matrix called cytoplasm occupies the volume of the cell.In cytoplasm cellular activities of both the plant and animal cells occured.

v..Cells differ greatly in size ,shape and activities.smallest cell is mycoplasmas(0.3micro meter).The largest isolated single cell is the egg of an ostrich.