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human developmenthuman development is a continuous procedure that begins when the ovum from a female is fertilised via sperm from a male to form the
multicausal nature of cancer with several dividing cells in the organism and the various proto-oncogenes and tumor suppressor genes that can be
tumor suppressor genes tumor suppressor genes or anti-oncogenes generally inhibit cell division in cooperation with proto-oncogenes the very
proto-oncogenes proto-oncogenes are common genes present in all organisms and emerge to be highly conserved in the course of evolution they have been
mechanism of carcinogenesisin the preceding sub-section you learnt that carcinogenesis is a multistep process even though cancer may be caused by
causes of cancerwe know earlier that a malignant tumor is a large aggregation of cancer cells all of them descended from a single founder cell that
metastasis - characteristics define cancermetastasis is the capability of a malignant cell to detach itself from a tumor and establish a tumor in
anaplasia - characteristics define canceranaplasia is a structural abnormality where cells resemble primitive or embryonic tissue in which adult
characteristics define cancer - hyperplasiahyperplasia is the extreme proliferation of cells which can be observed in normal as well as cancerous
role of hormones in agingaging as well reflects the inefficiency of the endocrine system a change in the hormonal secretions may contribute to the
extracellular agingthe basic components of extracellular space are mucopolysaccharides and fibrous proteins particularly collagen and elastin these
physiological changes - consequences of agingvarious physiological regulatory mechanisms show decreased efficiency due to aging for instance normally
consequences of aging it is hard to enumerate the general consequences of aging in different animals gradual loss of reproductive ability
biochemical changes - consequences of agingseveral biochemical changes are correlated with aging detailed biochemical studies in rats have been
typical form or reparative regeneration - heteromorphosissometimes the part which grows back is not the same as that which was lost the phenomenon is
reasons for uneven distribution of powerthe causes for uneven distribution of the power of regeneration among animals are not noticeably known from a
mammals - regeneration in vertebratesmammals are not capable of regenerating limb or tails however there are a few exceptions where lost tissues are
reptiles - regeneration in vertebratesamong reptiles the lizards like the gecko hemidactylus flaviviridis and anolis carolinensis can again generate
fishes- regeneration in vertebratesseveral different parts of the fish body will re-grow plucked scales are promptly replaced by new ones and
echinodermata - regeneration in invertebratesasteroids starfishes ophiuroids brittle stars and crinoids sea lilies can reproduce their lost arms and
arthropods - regeneration in invertebratesamong arthropods like insects crustaceans centipedes scorpions and spiders the capability of regeneration
segmentation in regenerating annelidsseveral worms as they grow continue to add new segments at the posterior end in these segmentation takes place
annelids - regeneration in invertebratesbetween the segmented worms both the polychaetes and oligochaetes have remarkable powers of regeneration
nemerteans - regeneration in invertebratesnemerteans as well possess remarkable regenerative ability as even a small fragment can regenerate into a
platyhelminthes flatworms - regeneration in invertebratesbetween flatworms the turbellarians mostly fresh water species and fresh water and