101
Most of the living organisms are unicellular. Complex organisms contain millions of cells. Humans are made up of about 70 trillion cells. These cells need a
certain pH range of extracellular fluids, temperature, concentration of mineral ions,
as well as glucose in the extracellular fluid. The cells, as part of the organism, interact in ways that keep internal environment relatively constant, in spite of the
changing external environment. The upholding of a stable internal environment by
an organism is called homeostasis.
Sometimes homeostatic imbalance can occur due to which cells may not obtain
everything they need, or toxic wastes may build up in cells resulting in disease.
Table 3.1 summarizes the types of movement into and out of the cell.
In biological taxonomy (classification of biological organisms), a domain, also
empire or super-kingdom, is the highest taxonomic rank of organisms. It comprises
of Archaea, Bacteria, and Eukarya in three domain classifications. Kingdom is the
second highest taxonomic rank, which is divided into groups called phyla. Some
textbooks list six kingdoms (Animalia, Plantae, Fungi, Protista, Archaea/
Archaebacteria, and Bacteria/Eubacteria) while others list five kingdoms (Fungi,
Plantae, Animalia, Protista, and Monera). The description of each of the term is
given in Table 3.2.
Taxonomic classifications have changed over years and likely to change in the
future. Among the non-living beings, viruses are complicated assemblies of molecules that replicate only in living cells of other life forms.
Requirements of Complex Multicellular Animals
Lives of complex multicellular organisms depend upon the water, oxygen, food,
heat, and pressure described in Table 3.3. As evident, the quantities and qualities of
water, oxygen, food, heat, and pressure are important for health of humans.
In a nutshell, health and un-health are not phenomena that occur only to humans.
Health and un-health are associated with all living beings.
3.3 Microbiology
Microorganisms play a major role in spreading infectious diseases. Understanding
of microorganisms is more important to medical and public health professionals
than carnivores, which may attack humans.
A microorganism is an organism that is invisible to the naked eye, and is microscopic (visible only with a microscope). Study of microorganisms is called microbiology. Microorganisms may be unicellular organisms or multicellular. Some
multicellular organisms are microscopic. But some unicellular organisms are visible
to the naked eye.
Due to the invisibility to the naked eyes, it is hard to understand their movement
and character by common man. Over the millions of years humans have been able
to stay away from or kill carnivores to protect themselves. It is only after the invention of microscope and discovery of microorganisms that the medical practitioners
3.3 Microbiology
Most of the living organisms are unicellular. Complex organisms contain millions of cells. Humans are made up of about 70 trillion cells. These cells need a
certain pH range of extracellular fluids, temperature, concentration of mineral ions,
as well as glucose in the extracellular fluid. The cells, as part of the organism, interact in ways that keep internal environment relatively constant, in spite of the
changing external environment. The upholding of a stable internal environment by
an organism is called homeostasis.
Sometimes homeostatic imbalance can occur due to which cells may not obtain
everything they need, or toxic wastes may build up in cells resulting in disease.
Table 3.1 summarizes the types of movement into and out of the cell.
In biological taxonomy (classification of biological organisms), a domain, also
empire or super-kingdom, is the highest taxonomic rank of organisms. It comprises
of Archaea, Bacteria, and Eukarya in three domain classifications. Kingdom is the
second highest taxonomic rank, which is divided into groups called phyla. Some
textbooks list six kingdoms (Animalia, Plantae, Fungi, Protista, Archaea/
Archaebacteria, and Bacteria/Eubacteria) while others list five kingdoms (Fungi,
Plantae, Animalia, Protista, and Monera). The description of each of the term is
given in Table 3.2.
Taxonomic classifications have changed over years and likely to change in the
future. Among the non-living beings, viruses are complicated assemblies of molecules that replicate only in living cells of other life forms.
Requirements of Complex Multicellular Animals
Lives of complex multicellular organisms depend upon the water, oxygen, food,
heat, and pressure described in Table 3.3. As evident, the quantities and qualities of
water, oxygen, food, heat, and pressure are important for health of humans.
In a nutshell, health and un-health are not phenomena that occur only to humans.
Health and un-health are associated with all living beings.
3.3 Microbiology
Microorganisms play a major role in spreading infectious diseases. Understanding
of microorganisms is more important to medical and public health professionals
than carnivores, which may attack humans.
A microorganism is an organism that is invisible to the naked eye, and is microscopic (visible only with a microscope). Study of microorganisms is called microbiology. Microorganisms may be unicellular organisms or multicellular. Some
multicellular organisms are microscopic. But some unicellular organisms are visible
to the naked eye.
Due to the invisibility to the naked eyes, it is hard to understand their movement
and character by common man. Over the millions of years humans have been able
to stay away from or kill carnivores to protect themselves. It is only after the invention of microscope and discovery of microorganisms that the medical practitioners
3.3 Microbiology