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Biology Quotes
Biology
by
Neil A. Campbell4,136 ratings, 4.15 average rating, 319 reviews
Biology Quotes
Showing 1-9 of 9
“time, cost, or safety concerns.
• MasteringBiology: Virtual Biology Labs offer unique
learning experiences in microscopy, molecular
biology, genetics, ecology, and systematics.
• Choose from 20–30 automatically graded, “pre-set”
lab activities that are ready to assign to students, or
create your own from scratch.
• Each “pre-set” lab provides an assignable”
― Campbell Biology
• MasteringBiology: Virtual Biology Labs offer unique
learning experiences in microscopy, molecular
biology, genetics, ecology, and systematics.
• Choose from 20–30 automatically graded, “pre-set”
lab activities that are ready to assign to students, or
create your own from scratch.
• Each “pre-set” lab provides an assignable”
― Campbell Biology
“Demographic transition is associated with an increase in the quality of health care and sanitation as well as improved access to education, especially for women.”
― Biology
― Biology
“Malnutrition and famines are common in some regions, but they result mainly from unequal distribution rather than adequate production, of food.”
― Biology
― Biology
“Our modern lives are very different from those of early humans, who hunted and gathered to survive. Their reverence for the natural world is evident in the early murals of wildlife they painted on cave walls and in the stylized visions of life they sculpted from bone and ivory. Our lives reflect remnants of our ancestral attachment to nature and the diversity of life - the concept of biophilia that was introduced early in this chapter. We evolved in natural environments rich in biodiversity, and we still have a biophilia for such settings. Indeed, our biophilia may be innate, an evolutionary product of natural selection acting on a brainy species who survival depended on a close connection to the environment and a practical appreciation of plants and animals. Our appreciation of life guides the field of biology today. We celebrate life by deciphering he genetic code that makes each species unique. We embrace life by using fossils and DNA to chronicle evolution through time. We preserve life through our efforts to classify and protect the millions of species on Earth. We respect life by using nature responsibly and reverently to improve human welfare. Biology is the scientific expression of our desire to know nature. We are most likely to protect what we appreciate, and we are mostly likely to appreciate what we understand. By learning about the processes and diversity of life, we also become more aware of ourselves and our place in the biosphere. We hope this text has served you well in this lifelong adventure.”
― Biology
― Biology
“If there is truth in science, it is, at best, conditional.”
― Campbell Biology
― Campbell Biology
“cell, for example, has about 2 m
of DNA—a length about 250,000 times greater than the cell’s diameter. Yet before the cell can divide to form genetically identical daughter cells, all of this DNA must be copied, or replicated,
and then the two copies must be separated so that each daughter cell ends up with a complete genome.
The replication and distribution of so much DNA is manageable because the DNA molecules are packaged into structures called chromosomes, so named because they take up
certain dyes used in microscopy (from the Greek chroma,
color, and soma, body) (Figure 12.3). Each eukaryotic chromosome consists of one very long, linear DNA molecule associated with many proteins (see Figure 6.9). The DNA molecule
carries several hundred to a few thousand genes, the units of
information that specify an organism’s inherited traits. The
associated proteins maintain the structure of the chromosome and help control the activity of the genes. Together, the
entire complex of DNA and proteins that is the building material of chromosomes is referred to as chromatin. As you
will soon see, the chromatin of a chromosome varies in its degree of condensation during the process of cell division.
Every eukaryotic species has a characteristic number of
chromosomes in each cell nucleus. For example, the nuclei of
human somatic cells (all body cells except the reproductive
cells) each contain 46 chromosomes, made up of two sets of
23, one set inherited from each parent. Reproductive cells, or
gametes—sperm and eggs—have half as many chromosomes
as somatic cells, or one set of 23 chromosomes in humans. The
Figure 12.4 A highly condensed, duplicated human
chromosome (SEM).
Circle one sister chromatid of the chromosome in this
micrograph.
DRAW IT
Sister
chromatids
Centromere
0.5μm
number of chromosomes in somatic cells varies widely among
species: 18 in cabbage plants, 48 in chimpanzees, 56 in elephants, 90 in hedgehogs, and 148 in one species of alga. We’ll
now consider how these chromosomes behave during cell
division.
Distribution of Chromosomes During
Eukaryotic Cell Division
When a cell is not dividing, and even as it replicates its DNA
in preparation for cell division, each chromosome is in the
form of a long, thin chromatin fiber. After DNA replication,
however, the chromosomes condense as a part of cell division: Each chromatin fiber becomes densely coiled and
folded, making the chromosomes much shorter and so thick
that we can see them with a light microscope.
Each duplicated chromosome has two sister chromatids,
which are joined copies of the original chromosome
(Figure 12.4). The two chromatids, each containing an identical DNA molecule, are initially attached all along their lengths
by protein complexes called cohesins; this attachment is known
as sister chromatid cohesion. Each sister chromatid has a
centromere, a region containing”
― Campbell Biology
of DNA—a length about 250,000 times greater than the cell’s diameter. Yet before the cell can divide to form genetically identical daughter cells, all of this DNA must be copied, or replicated,
and then the two copies must be separated so that each daughter cell ends up with a complete genome.
The replication and distribution of so much DNA is manageable because the DNA molecules are packaged into structures called chromosomes, so named because they take up
certain dyes used in microscopy (from the Greek chroma,
color, and soma, body) (Figure 12.3). Each eukaryotic chromosome consists of one very long, linear DNA molecule associated with many proteins (see Figure 6.9). The DNA molecule
carries several hundred to a few thousand genes, the units of
information that specify an organism’s inherited traits. The
associated proteins maintain the structure of the chromosome and help control the activity of the genes. Together, the
entire complex of DNA and proteins that is the building material of chromosomes is referred to as chromatin. As you
will soon see, the chromatin of a chromosome varies in its degree of condensation during the process of cell division.
Every eukaryotic species has a characteristic number of
chromosomes in each cell nucleus. For example, the nuclei of
human somatic cells (all body cells except the reproductive
cells) each contain 46 chromosomes, made up of two sets of
23, one set inherited from each parent. Reproductive cells, or
gametes—sperm and eggs—have half as many chromosomes
as somatic cells, or one set of 23 chromosomes in humans. The
Figure 12.4 A highly condensed, duplicated human
chromosome (SEM).
Circle one sister chromatid of the chromosome in this
micrograph.
DRAW IT
Sister
chromatids
Centromere
0.5μm
number of chromosomes in somatic cells varies widely among
species: 18 in cabbage plants, 48 in chimpanzees, 56 in elephants, 90 in hedgehogs, and 148 in one species of alga. We’ll
now consider how these chromosomes behave during cell
division.
Distribution of Chromosomes During
Eukaryotic Cell Division
When a cell is not dividing, and even as it replicates its DNA
in preparation for cell division, each chromosome is in the
form of a long, thin chromatin fiber. After DNA replication,
however, the chromosomes condense as a part of cell division: Each chromatin fiber becomes densely coiled and
folded, making the chromosomes much shorter and so thick
that we can see them with a light microscope.
Each duplicated chromosome has two sister chromatids,
which are joined copies of the original chromosome
(Figure 12.4). The two chromatids, each containing an identical DNA molecule, are initially attached all along their lengths
by protein complexes called cohesins; this attachment is known
as sister chromatid cohesion. Each sister chromatid has a
centromere, a region containing”
― Campbell Biology
“In general, organisms that share very similar morphologies
or similar DNA sequences are likely to be more closely related
than organisms with vastly different structures or sequences.
In some cases, however, the morphological divergence between related species can be great and their genetic divergence small (or vice versa). Consider the Hawaiian silversword
plants discussed in Chapter 25. These species vary dramatically in appearance throughout the islands. Some are tall,
twiggy trees, and others are dense, ground-hugging shrubs
(see Figure 25.20). But despite these striking phenotypic differences, the silverswords’ genes are very similar. Based on
these small molecular divergences, scientists estimate that the
silversword group began to diverge 5 million years ago, which
is also about the time when the oldest of the current islands
formed. We’ll discuss how scientists use molecular data to estimate such divergence times later in this chapter.”
― Campbell Biology
or similar DNA sequences are likely to be more closely related
than organisms with vastly different structures or sequences.
In some cases, however, the morphological divergence between related species can be great and their genetic divergence small (or vice versa). Consider the Hawaiian silversword
plants discussed in Chapter 25. These species vary dramatically in appearance throughout the islands. Some are tall,
twiggy trees, and others are dense, ground-hugging shrubs
(see Figure 25.20). But despite these striking phenotypic differences, the silverswords’ genes are very similar. Based on
these small molecular divergences, scientists estimate that the
silversword group began to diverge 5 million years ago, which
is also about the time when the oldest of the current islands
formed. We’ll discuss how scientists use molecular data to estimate such divergence times later in this chapter.”
― Campbell Biology
“consumption. Fungi are used to ripen Roquefort and other
blue cheeses. A species of Aspergillus produces citric acid used
in colas. Morels and truffles, the edible fruiting bodies of various ascomycetes, are highly prized for their complex flavors
(see Figure 31.16). These fungi can sell”
― Campbell Biology
blue cheeses. A species of Aspergillus produces citric acid used
in colas. Morels and truffles, the edible fruiting bodies of various ascomycetes, are highly prized for their complex flavors
(see Figure 31.16). These fungi can sell”
― Campbell Biology
