CONCEPT OF LIVING THINGS
Living things include the organisms that undergo all the processes of life.
Characteristics of Living Things
1. Different levels of organization: Living things are organized in the microscopic level from
atoms which are arranged into molecules, then into macromolecules, which make up
organelles, which work together to form cells. Beyond this, cells are organized in higher
levels to form entire multicellular organisms. Cells together form tissues, which make up
organs, which are part of organ systems, which work together to form an entire organism.
Multicellular organisms, which may consist of millions of individual cells, have an
advantage over single-celled organisms in that their cells can be specialized to perform
specific functions, and even sacrificed in certain situations for the good of the organism as
a whole.
2. Movement: All living things are capable of carrying out one form of movement or the other.
Most animals move from one place to another either in search of food, mates, shelter or to
escape from enemies. Most plants are fixed and can move certain parts of their body such
as roots and shoot in response to growth movement, opening and closing of some flowering.
3. Respiration: All living things need energy for their metabolism. The chemical energy for
work is released by the oxidation of respiratory substrates in living cells.
4. Ingestion: All organisms use a source of energy for their metabolic activities. Some
organisms capture energy from the Sun and convert it into chemical energy in food; others
use chemical energy from molecules they take in.
5. Irritability (Sensitivity): is the ability of a cell, tissue, or organism to respond to a stimulus,
usually in such a way as to enhance its survival. All living organisms respond to changes in
the external and internal stimuli such as light, water, temperature, hunger etc. Movement
toward a stimulus is considered a positive response, while movement away from a stimulus
is considered a negative response.
6. Growth and development: Growth is an increase in size of an organism, either by an increase
in cell size (enlargement) or, much more usually, by an increase in cell number (cell
division). Development on the other hand is the process by which organisms become
transformed from simple unorganised structures to complex, organised, integrated
structures.
7. Excretion: is a process through which all living things are capable of getting rid of unwanted
or waste substances of metabolism from their body. This is because if the waste products
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, are allowed to accumulate in the body of an organism, they will cause harm or death to the
organism.
8. Reproduction: is the process by which living organisms beget or produces new organisms
of their own biological kind. Sexual reproduction involves the fusion of sex cells or gametes
and the exchange of genetic material, thus bringing new vigour to a species. Asexual
reproduction does not involve gametes, but usually the vegetative proliferation of an
organism.
9. Adaptation: is the modification of an of an organism or its part that makes it more fit for
existence under the conditions of its environment. This because adaptation gives all
organisms an advantage in certain environments and enable them to survive in the
environments.
10. Homeostasis: is the ability of an organism or biological system to maintain itself in a state
of stable equilibrium or balance regardless of the changes in the internal or external
environment. An example is maintenance of body temperature or the balance of salts in the
blood.
11. Death: is the cessation or permanent end of all the processes or functions associated with
life. Since all living things have a definite period of existence, if condition becomes
unfavourable or after all processes of life, organisms eventually die off.
Classification of living things
There are over 2,000,000 known organisms today and probably over 1,000.000 are left to be
discovered and named. All living things have different characteristics such as shape, size,
colour and height. It will therefore be extremely difficult to study these millions of things
without arranging them into groups. Biologists, in arranging living organisms into groups have
developed systems of using similarities to unite organisms into groups and using differences to
separate groups.
The science of arranging or grouping living things together based on structural, genetic or
cellular organization is called taxonomy. A group of organisms at a particular level in a
classification system is called a taxon (plural, taxa). The naming of organisms is called
nomenclature, and the systematic assignment or placement of organisms to groups called taxa
is referred to as systematics.
The system of giving two names to an organism is called binomial nomenclature. The
adoption of the strictly binomial nomenclature is due to Carl von Linne, a Swedish botanist
and physician (1707-1778), more commonly called by his Latin name Carolus Linnaeus.
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Living things include the organisms that undergo all the processes of life.
Characteristics of Living Things
1. Different levels of organization: Living things are organized in the microscopic level from
atoms which are arranged into molecules, then into macromolecules, which make up
organelles, which work together to form cells. Beyond this, cells are organized in higher
levels to form entire multicellular organisms. Cells together form tissues, which make up
organs, which are part of organ systems, which work together to form an entire organism.
Multicellular organisms, which may consist of millions of individual cells, have an
advantage over single-celled organisms in that their cells can be specialized to perform
specific functions, and even sacrificed in certain situations for the good of the organism as
a whole.
2. Movement: All living things are capable of carrying out one form of movement or the other.
Most animals move from one place to another either in search of food, mates, shelter or to
escape from enemies. Most plants are fixed and can move certain parts of their body such
as roots and shoot in response to growth movement, opening and closing of some flowering.
3. Respiration: All living things need energy for their metabolism. The chemical energy for
work is released by the oxidation of respiratory substrates in living cells.
4. Ingestion: All organisms use a source of energy for their metabolic activities. Some
organisms capture energy from the Sun and convert it into chemical energy in food; others
use chemical energy from molecules they take in.
5. Irritability (Sensitivity): is the ability of a cell, tissue, or organism to respond to a stimulus,
usually in such a way as to enhance its survival. All living organisms respond to changes in
the external and internal stimuli such as light, water, temperature, hunger etc. Movement
toward a stimulus is considered a positive response, while movement away from a stimulus
is considered a negative response.
6. Growth and development: Growth is an increase in size of an organism, either by an increase
in cell size (enlargement) or, much more usually, by an increase in cell number (cell
division). Development on the other hand is the process by which organisms become
transformed from simple unorganised structures to complex, organised, integrated
structures.
7. Excretion: is a process through which all living things are capable of getting rid of unwanted
or waste substances of metabolism from their body. This is because if the waste products
Page | 1
, are allowed to accumulate in the body of an organism, they will cause harm or death to the
organism.
8. Reproduction: is the process by which living organisms beget or produces new organisms
of their own biological kind. Sexual reproduction involves the fusion of sex cells or gametes
and the exchange of genetic material, thus bringing new vigour to a species. Asexual
reproduction does not involve gametes, but usually the vegetative proliferation of an
organism.
9. Adaptation: is the modification of an of an organism or its part that makes it more fit for
existence under the conditions of its environment. This because adaptation gives all
organisms an advantage in certain environments and enable them to survive in the
environments.
10. Homeostasis: is the ability of an organism or biological system to maintain itself in a state
of stable equilibrium or balance regardless of the changes in the internal or external
environment. An example is maintenance of body temperature or the balance of salts in the
blood.
11. Death: is the cessation or permanent end of all the processes or functions associated with
life. Since all living things have a definite period of existence, if condition becomes
unfavourable or after all processes of life, organisms eventually die off.
Classification of living things
There are over 2,000,000 known organisms today and probably over 1,000.000 are left to be
discovered and named. All living things have different characteristics such as shape, size,
colour and height. It will therefore be extremely difficult to study these millions of things
without arranging them into groups. Biologists, in arranging living organisms into groups have
developed systems of using similarities to unite organisms into groups and using differences to
separate groups.
The science of arranging or grouping living things together based on structural, genetic or
cellular organization is called taxonomy. A group of organisms at a particular level in a
classification system is called a taxon (plural, taxa). The naming of organisms is called
nomenclature, and the systematic assignment or placement of organisms to groups called taxa
is referred to as systematics.
The system of giving two names to an organism is called binomial nomenclature. The
adoption of the strictly binomial nomenclature is due to Carl von Linne, a Swedish botanist
and physician (1707-1778), more commonly called by his Latin name Carolus Linnaeus.
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