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Introduction.
Biology as a science.
General characteristics of life.
Biology as a science
Biology is the science of life, of the general laws of the
structure, existence and development of living beings.
The subject of biology research is living organisms, various
living systems, their structure, physiology, behavior, individual
and historical development of organisms, their relationships
with each other and with the environment.
The goal of biology: knowledge of certain patterns of life
activity and development of biological systems.
Biology methods
The main methods in biology are:
1. Descriptive - based on observation and description of
observations
2. Comparative - helped to systematize accumulated data
3. Experimental - the method allows the scientist to actively
influence natural phenomena by conducting experiments
4. Historical - clarifies the patterns of the appearance and
development of organisms, their structures and functions.
General characteristics of life.
Development of ideas about the essence of life.
Definition of life.
Currently, life is defined from the perspective of a
systems approach.
“Living organisms are open, self-regulating,
self-reproducing systems built from
biopolymers - proteins and nucleic acids”
(biologist M.V. Volkenshtein (1965))
Basic properties of living things
1. Chemical composition.
Living things are composed of the same chemical elements as non-living things, but
their ratios are different. The main biogenic elements are H, O, C, N. In addition to
them, Na, Mg, Cl, P, S, K, Fe, Ca, etc. are important.
2. Structural organization.
Living systems are capable of creating order from the chaotic movement of molecules,
forming certain structures. Living things are characterized by order in time and space.
3. Metabolism and energy.
Metabolism is the way living things interact with their environment. Its content
consists of the interconnected processes of assimilation (anabolism) and dissimilation
(catabolism). The result of assimilation is the formation and renewal of the structures
of the body, dissimilation is the breakdown of organic compounds to provide vital
functions with the necessary substances and energy.
4. Self-regulation.
Living organisms have the ability to maintain the constancy of their chemical
composition and the intensity of metabolic processes. When environmental conditions
change, self-regulation of life processes occurs according to the feedback principle,
aimed at restoring homeostasis.
5. Integrity (continuity) and discreteness (discontinuity).
Any biological system (cell, organism, species, etc.) consists of separate interconnected
parts, i.e. discrete. The interaction of parts form an integral, interconnected system. The
lifespan of organisms is limited (the community of humanity is a collection of individual
organisms; the body includes individual organs connected structurally and functionally
into a single whole).
6. Self-reproduction (reproduction).
It is achieved using biological (genetic) information based on cell nucleoproteins (nucleic
acids + protein). The lifetime of any biological system is limited. To maintain life, selfreproduction of biological systems and their elements is necessary.
7. Heredity and variability.
Heredity determines the continuity and stability of life, thanks to the ability to store and
transmit hereditary information with the help of information carriers DNA molecules.
Variability is the ability of organisms to acquire new characteristics and properties.
Variability ensures the adaptation of organisms to their environment and creates the
prerequisites for speciation and evolution (and thereby the existence of life).
8. Growth and development.
Growth is an increase in quantitative characteristics while maintaining general structural
features. Development is an irreversible, directed, natural change, as a result of which a new
qualitative state occurs. A distinction is made between ontogeny and phylogeny.
9. Irritability and excitability.
They determine the individual reactions of living organisms to external and internal stimuli.
In organisms without a nervous system (protozoa and plants):
1) taxis - an active reaction of cells in response to the actions of a stimulus by the directed
movement of organisms or individual cells of multicellular organisms;
2) tropisms - the response of an immobile organism by changing the position and growth
of organs (photo-, geotropism, etc.);
3) nastia - a form of response to irritation inherent in some types of plants (opening and
closing of flowers, curling of sundew leaves, irritation of the leaves of a bashful mimosa
causes them to curl).
For those with a nervous system - in the form of reflexes (conditioned and unconditioned).
Hierarchical levels of life
organization
1.
2.
3.
4.
5.
6.
7.
8.
Molecular.
Cellular
Fabric.
Organ.
Organic.
Population-species.
Biocenotic.
Biosphere.
1. Molecular
The initial level of organization of living things. It is represented by
molecules of nucleic acids, proteins, carbohydrates, lipids found in cells.
Peculiarities:
1. physicochemical specificity - biogenic elements (O, C, H, N) are more
often represented, biogenic molecules have certain specificities;
2. biological specificity of nucleic acids and proteins (universality of the
genetic code, transmission of hereditary information, universality of metabolic
processes, protein amino acids);
3. In plants, radiant energy is converted into the energy of chemical bonds.
2. Cellular
A cell is an elementary structural and functional unit of living
things. Viruses, being a non-cellular form of organization of
living things, exhibit their properties as living organisms only
when they penetrate into cells.
A special feature is the specialization of cells.
At the cellular level, there is a differentiation and ordering of
life processes in space and time.
3. Fabric.
Tissue is a collection of structurally similar cells and
intercellular substances associated with them, united by the
performance of certain functions.
Plants have 4 main
types:
1. meristem;
2. conductive;
3. protective;
4. parenchyma (main).
Animals have 4 main types of
tissue:
1. epithelial;
2. connecting;
3. muscular;
4. nervous..
4.Organ
Tissue systems form organs. An organ is a part of a
multicellular organism that performs a specific function or
functions.
5.Organic
Presented by unicellular and multicellular organisms. At this
level, genetic information is realized and the characteristics of
organisms of a given species are formed. It is very convenient to
use this level when considering the interaction of a living creature
with its environment.
6. Population-species
Organisms unite into populations.
A population is a system of supraorganismal order. This is
understood as the totality of all individuals of one species, forming a
separate genetic system and inhabiting a space with relatively
homogeneous living conditions. A population usually has a complex
structure and is an elementary unit of evolution. The totality of
populations forms a species.
A species is a genetically stable system, a set of populations,
individuals of which are capable of interbreeding under natural
conditions to form fertile offspring and occupy a certain area
of ​geographic space (area).
7. Biocenotic
Species of various living organisms do not exist separately
from each other, and their totality forms a biocenosis.
Biocenosis is a community of organisms of different species
that depend on each other and live in a certain territory. If such
a territorial system also takes into account environmental
factors, i.e., the inanimate component, then they speak of
biogeocenosis.
8. Biosphere
This is the highest level of organization. All the diversity of
biocenoses represents the shell of the Earth in which life exists
and which is called the biosphere. At this level, all living
organisms and the areas of their existence on a planetary
scale are considered.
ORIGIN AND DEVELOPMENT
OF LIFE ON EARTH MAIN
HYPOTHESES ABOUT THE
ORIGIN OF LIFE
1. Biogenesis hypotheses are about the origin of living things
only from living things. They affirm the eternity of life. The origin
of life is most often associated with the act of creation of living
things by the Higher Mind (the ideas of creationism).
2. Abiogenesis hypotheses are about the origin of life from
inanimate nature. They, often without rejecting the ideas of the
creation of life by the Higher Mind, also admitted the possibility
of the spontaneous generation of life, that is, its emergence
from the elements of inanimate nature.
3. The hypothesis of the introduction of life to Earth from
Space (panspermia hypothesis) was put forward in 1895 by
the Swedish physicist S. Arrhenius. It involves the introduction
of living organisms or their spores from outer space along with
meteorites and cosmic dust falling on Earth.
Modern hypotheses about the origin of
life
The hypothesis of the origin of life on Earth, proposed by the famous
Russian biochemist A.I. Oparin (1894-1980) and the English biochemist J.
Haldane (1892-1964), received the greatest recognition and distribution in
the 20th century.
The essence of their hypothesis boils down to the existence on
Earth of a long period of abiogenic formation of organic compounds.
In 1947, the English scientist John Bernal formulated the
hypothesis of biopoiesis.
He identified three main stages in the formation of life:
1. abiogenic occurrence of organic monomers;
2. formation of biological polymers;
3. development of membrane structures and the first organisms.