HSC EV Biology 2nd Paper 4th Chapter Note. Human Physiology, Blood and Circulation. The center of the circulatory system is the heart, which is the main pumping mechanism. The heart is made of muscle. The heart is shaped something like a cone, with a pointed bottom and around the top. It is hollow so that it can fill up with blood. An adult’s heart is about the size of a large orange and weighs a little less than a pound. The heart is in the middle of the chest. It fits snugly between the two lungs.
Most are aquatic and autotrophic and lack many of the distinct cell and tissue types, such as stomata, xylem, and phloem, which are found in land plants. The largest and most complex marine algae are called seaweeds, while the most complex freshwater forms are the Charophyta, a division of green algae which includes, for example, Spirogyra and the stoneworts.
This is necessary for sexual reproduction because each parent must give only half of the required genetic material, otherwise, his offspring would have too much DNA, which can be a problem. These different types of cell division are discussed below. Organisms can be classified as unicellular (consisting of a single cell; including bacteria) or multicellular (including plants and animals). While the number of cells in plants and animals varies from species to species, humans contain more than 10 trillion (1013) cells. Most plant and animal cells are visible only under a microscope, with dimensions between 1 and 100 micrometers.
HSC EV Biology 2nd Paper 4th Chapter Note. Human Physiology, Blood and Circulation
A cell is the smallest working unit of all living organisms on our planet earth, which is capable of performing life functioning. Hence it can also be defined as a fundamental unit of life. The term cell was first observed and identified by an English physicist Robert Hook in the year 1665. There were many theories developed for the cell. Later in the year 1839 a two German scientist – Schwann and Schleiden provided few basic principles of the cell.
A microscopic living organism. Examples include bacteria, protozoa, and some fungi and parasites. Viruses are also called microbes. Microbes are tiny forms of life that surround us — too small to be seen by the naked eye. They are found in water, in the soil, and in the air. The human body is also home to millions of these microbes, also called microorganisms. Some microbes make us sick, others are important for our health.
An electrochemical cell consists of two half-cells. Each half-cell consists of an electrode and an electrolyte. The two half-cells may use the same electrolyte, or they may use different electrolytes. The chemical reactions in the cell may involve the electrolyte, the electrodes, or an external substance (as in fuel cells that may use hydrogen gas as a reactant). In a full electrochemical cell, species from one half-cell lose electrons (oxidation) to their electrode while species from the other half-cell gain electrons (reduction) from their electrode.
There are many cells in an individual, which performs several functions throughout life. The different types of the cell include- prokaryotic cell, plant and animal cell. The size and the shape of the cell range from millimeter to microns, which are generally based on the type of function that it performs. A cell generally varies in their shapes. A few cells are in spherical, rod, flat, concave, curved, rectangular, oval and etc. These cells can only be seen under a microscope.
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