Everything starts from the union of a sperm and an egg, which gives rise to a cell, which has to become an adult organism. For this, this cell divides in such a way that in each division exactly the same genetic information is maintained. The cell is the reproductive unit of living beings. Throughout its life the cells are nourished and increase in size. When a cell reaches the appropriate size, it usually gives rise to two cells similar to the original cell. Cell Theory is one of the fundamental bases of biology and it is where the base of the constitution of living beings and the fundamental role of cells in them is summarized. It is formulated in the first place thanks to observations and formulations of Theodor Schwann ( physiologist) and Matthias Schleiden (botanist).The current third principle of cell theory, formulates that a cell comes from another cell, by cell division or by formation from stem cells. The oldest and most primitive cells in the world are prokaryotes (without a cell nucleus).
Although penguins don't grow from year to year, they increase and decrease in size as they repeatedly form and use energy stores,a significant amount of energy might be stored in fat during part of the year but be missing from the pie chart because it is used later in the year
Allocation of limited endogenous resources causes trade-offs between competing traits, such as reproduction, somatic growth and maintenance
During food deprivation, animals cannot maximize all of their life-history traits and must exhibit adaptive behavioral, physiological and biochemical responses to reduce metabolism and/or the cost of current activities in order to maintain biological value
