1
普通生物学
CH 1 An Introduction To Life On Earth
1.1 What is Life?
Biology: “bio”->life “logy”->the study of
Life is the quality that distinguishes a vital and functioning being from a dead body.
Living things are more than the sum of their parts; living organisms are not a mere collection of
inanimate materials.
The complexity and ordered interactions of parts in living things give rise to certain properties.
Characteristics of living things:
● Complex, organized, and composed of cells
● Acquire and use materials and energy
● Maintain a relatively constant internal conditions through homeostasis
● Sense and respond to stimuli
● Grow and reproduce
● Can evolve
Organization
The cell is the basic unit of life.
All cells contain:
● Genes: provide information to control the life of the cell
● Organelles: small, specialized structures that perform specific functions
● A plasma membrane: encloses the fluid cytoplasm and organelles from the outside world
Levels of biological organizations:
● Atoms
● Molecules
● Organelles / Cells
● Tissues
● Organs
● Organ Systems: e.g. the digestive system
● Organisms
● Populations: all the individuals of a particular species
● Ecosystems: consists of all the living things in a particular area
● Communities: the entire array of organisms inhabiting a particular ecosystem is called a
biological community
● Biosphere
Organisms Acquire and Use Materials and Energy
Organisms obtain energy from:
● Air, water, soil, photosynthesis (plants and some single-celled organisms)
,2
● The bodies of other living things (consume energy-rich molecules in the bodies of other
organisms): herbivores and carnivores (vore: “vorae”, for devour)
All energy that sustains life comes directly or indirectly from the sun.
Life neither creates nor destroys matter, materials are continuously exchanged and recycled
among organisms and their nonliving surroundings.
Some energy is lost as heat at each transfer.
Organisms use energy to:
● Build parts of cells
● Move around
● Generate heat
● Maintain homeostasis
● Grow, develop, and reproduce
Organisms Maintain Homeostasis（稳态）
Homeostasis (homeo: similar; stasis: the state of equilibrium or inactivity caused by opposing
equal forces): the ability of an organism to maintain its internal environment within the limits
required to sustain life.
Organisms must maintain relatively constant internal conditions.
To maintain homeostasis, cell membranes constantly pump specific substances in and others
out.
Homeostasis include:
● Sweating in hot weather or dousing oneself with cool water
● Metabolizing more food, basking in the sun, or turning up the thermostat in cold weather
● When AMP/ATP ratio is increases, cells increase catabolic processes (such as fatty acid
oxidation), while decreasing anabolic rates (fat synthesis)
Organisms Sense and Respond to Stimuli
Organisms sense and response to internal and external environmental stimuli
● Sensory organs in animals can detect and respond to external stimuli like light, sound,
chemicals, etc
● Internal stimuli in animals are perceived by stretch, temperature, pain, and chemical
receptors
● Plants and bacteria respond to stimuli as well (e.g. plants grow toward the light, bacteria
move toward available nutrients in a medium)
● When the brain detects a low level of sugar in our blood (internal stimuli), it causes our
mouth to water at the smell of food(external stimuli).
Organisms Grow
Growth involves the conversion of acquired materials to molecules of the organisms body
(increased anabolic activity)
● Plants, birds, and mammals grow by producing more cells to increase their mass
● Bacteria grow by enlarging their cells; they also divide to make more individuals
,3
Organisms Reproduce
Ways to reproduce:
● Dividing in half
● Producing seeds
● Bearing live young
● Producing eggs
Organisms give rise to offspring of the same type
The parent’s genetic material (DNA) is passed on to the offspring, creating continuity of life.
Hereditary molecule: deoxyribonucleic acid (DNA)
Organisms Can Evolve
Evolution is the change in DNA that occurs in a population over time.
The genetic composition of a whole species changes over many generations.
Mutations and variable offspring allow a species to evolve
1.2 What is Evolution?
Evolution is the process by which modern organisms descended, with modifications, from
preexisting forms of life.
Darwin and Wallace formulated the basis of our modern understanding of evolution
Three Natural Processes Underlie Evolution
● Genetic variation among members of a population due to differences in their DNA
● Inheritance of those variations by offspring of parents carrying the variation
● Natural selection of individuals whose survival and enhanced reproduction are due to the
favorable variations they carry.
Natural selection: the process by which individuals that inherit certain characteristics
tend to survive and reproduce better than other individuals.
Genetic Variability
Genes, which are specific segments of DNA, are the basic units of heredity.
Changes in genes (mutations) alter the informational content
Mutations arise from a number of sources:
● Copying errors in DNA
● Ultraviolet rays from sunlight
● Radiation released from a damaged nuclear power plant
● Toxic chemicals from cigarette smoke
● Occur spontaneously
Most mutations to genes are either harmful or neutral.
E.g. hemophilia, sickle-cell anemia, cystic fibrosis (harmful)
Eye color (neutral)
Effects of mutation:
● No effect (harmless)
, 4
● Loss of function
● Death of the organism
● Dominant negative effect
● Gain of function
Mutations occurring over millions of years and passed through many generations cause
members of a species to be slightly different
Natural Selection
Natural selection is the process by which organisms with certain inherited traits survive and
reproduce better than others in a given environment.
Organisms that best meet environmental challenges leave the most offspring.
Natural selection preserves genes that help organisms flourish.
Adaptations are structures, physiological processes, or behaviors that help an organism survive
and reproduce in a particular environment.
Adaptations that are good for one environment may be poor in another
Species that cannot adapt to environmental change go extinct
Darwin hypothesised: different forms of life may evolve if a population becomes fragmented and
groups of individuals are subjected to different environments.
Development of biodiversity: the many different habitats coupled with evolutionary adaptive
processes produce species variety, or biodiversity.
Humans are responsible for accelerating the rate of environmental change, and the rate of
extinction of species.
1.3 How Do Scientists Study Life?
Life May Be Studied at Different Levels
● Atom
● Molecule
● Cell
● Tissue
● Organ
● Organ System
● Multicellular organism
● Population
● Species
● Community
● Ecosystem
● Biosphere
All matter consists of elements, substances that cannot be broken down or converted into
smaller substances.
An atom is the smallest particle of an element that retains all the properties of that element.
Atoms may combine in specific ways to form molecules
普通生物学
CH 1 An Introduction To Life On Earth
1.1 What is Life?
Biology: “bio”->life “logy”->the study of
Life is the quality that distinguishes a vital and functioning being from a dead body.
Living things are more than the sum of their parts; living organisms are not a mere collection of
inanimate materials.
The complexity and ordered interactions of parts in living things give rise to certain properties.
Characteristics of living things:
● Complex, organized, and composed of cells
● Acquire and use materials and energy
● Maintain a relatively constant internal conditions through homeostasis
● Sense and respond to stimuli
● Grow and reproduce
● Can evolve
Organization
The cell is the basic unit of life.
All cells contain:
● Genes: provide information to control the life of the cell
● Organelles: small, specialized structures that perform specific functions
● A plasma membrane: encloses the fluid cytoplasm and organelles from the outside world
Levels of biological organizations:
● Atoms
● Molecules
● Organelles / Cells
● Tissues
● Organs
● Organ Systems: e.g. the digestive system
● Organisms
● Populations: all the individuals of a particular species
● Ecosystems: consists of all the living things in a particular area
● Communities: the entire array of organisms inhabiting a particular ecosystem is called a
biological community
● Biosphere
Organisms Acquire and Use Materials and Energy
Organisms obtain energy from:
● Air, water, soil, photosynthesis (plants and some single-celled organisms)
,2
● The bodies of other living things (consume energy-rich molecules in the bodies of other
organisms): herbivores and carnivores (vore: “vorae”, for devour)
All energy that sustains life comes directly or indirectly from the sun.
Life neither creates nor destroys matter, materials are continuously exchanged and recycled
among organisms and their nonliving surroundings.
Some energy is lost as heat at each transfer.
Organisms use energy to:
● Build parts of cells
● Move around
● Generate heat
● Maintain homeostasis
● Grow, develop, and reproduce
Organisms Maintain Homeostasis（稳态）
Homeostasis (homeo: similar; stasis: the state of equilibrium or inactivity caused by opposing
equal forces): the ability of an organism to maintain its internal environment within the limits
required to sustain life.
Organisms must maintain relatively constant internal conditions.
To maintain homeostasis, cell membranes constantly pump specific substances in and others
out.
Homeostasis include:
● Sweating in hot weather or dousing oneself with cool water
● Metabolizing more food, basking in the sun, or turning up the thermostat in cold weather
● When AMP/ATP ratio is increases, cells increase catabolic processes (such as fatty acid
oxidation), while decreasing anabolic rates (fat synthesis)
Organisms Sense and Respond to Stimuli
Organisms sense and response to internal and external environmental stimuli
● Sensory organs in animals can detect and respond to external stimuli like light, sound,
chemicals, etc
● Internal stimuli in animals are perceived by stretch, temperature, pain, and chemical
receptors
● Plants and bacteria respond to stimuli as well (e.g. plants grow toward the light, bacteria
move toward available nutrients in a medium)
● When the brain detects a low level of sugar in our blood (internal stimuli), it causes our
mouth to water at the smell of food(external stimuli).
Organisms Grow
Growth involves the conversion of acquired materials to molecules of the organisms body
(increased anabolic activity)
● Plants, birds, and mammals grow by producing more cells to increase their mass
● Bacteria grow by enlarging their cells; they also divide to make more individuals
,3
Organisms Reproduce
Ways to reproduce:
● Dividing in half
● Producing seeds
● Bearing live young
● Producing eggs
Organisms give rise to offspring of the same type
The parent’s genetic material (DNA) is passed on to the offspring, creating continuity of life.
Hereditary molecule: deoxyribonucleic acid (DNA)
Organisms Can Evolve
Evolution is the change in DNA that occurs in a population over time.
The genetic composition of a whole species changes over many generations.
Mutations and variable offspring allow a species to evolve
1.2 What is Evolution?
Evolution is the process by which modern organisms descended, with modifications, from
preexisting forms of life.
Darwin and Wallace formulated the basis of our modern understanding of evolution
Three Natural Processes Underlie Evolution
● Genetic variation among members of a population due to differences in their DNA
● Inheritance of those variations by offspring of parents carrying the variation
● Natural selection of individuals whose survival and enhanced reproduction are due to the
favorable variations they carry.
Natural selection: the process by which individuals that inherit certain characteristics
tend to survive and reproduce better than other individuals.
Genetic Variability
Genes, which are specific segments of DNA, are the basic units of heredity.
Changes in genes (mutations) alter the informational content
Mutations arise from a number of sources:
● Copying errors in DNA
● Ultraviolet rays from sunlight
● Radiation released from a damaged nuclear power plant
● Toxic chemicals from cigarette smoke
● Occur spontaneously
Most mutations to genes are either harmful or neutral.
E.g. hemophilia, sickle-cell anemia, cystic fibrosis (harmful)
Eye color (neutral)
Effects of mutation:
● No effect (harmless)
, 4
● Loss of function
● Death of the organism
● Dominant negative effect
● Gain of function
Mutations occurring over millions of years and passed through many generations cause
members of a species to be slightly different
Natural Selection
Natural selection is the process by which organisms with certain inherited traits survive and
reproduce better than others in a given environment.
Organisms that best meet environmental challenges leave the most offspring.
Natural selection preserves genes that help organisms flourish.
Adaptations are structures, physiological processes, or behaviors that help an organism survive
and reproduce in a particular environment.
Adaptations that are good for one environment may be poor in another
Species that cannot adapt to environmental change go extinct
Darwin hypothesised: different forms of life may evolve if a population becomes fragmented and
groups of individuals are subjected to different environments.
Development of biodiversity: the many different habitats coupled with evolutionary adaptive
processes produce species variety, or biodiversity.
Humans are responsible for accelerating the rate of environmental change, and the rate of
extinction of species.
1.3 How Do Scientists Study Life?
Life May Be Studied at Different Levels
● Atom
● Molecule
● Cell
● Tissue
● Organ
● Organ System
● Multicellular organism
● Population
● Species
● Community
● Ecosystem
● Biosphere
All matter consists of elements, substances that cannot be broken down or converted into
smaller substances.
An atom is the smallest particle of an element that retains all the properties of that element.
Atoms may combine in specific ways to form molecules
