2. • Biology, the study of life and living things
(organisms)
• Biology is the scientific extension of the human
tendency to connect to and be curious about life.
• The adventure of biology takes us:
• Into a variety of environments to investigate ecosystems
• To the laboratory to examine how organisms work
• Into the microscopic world to explore cells and the
submicroscopic to explore molecules in cells
• Back in time to investigate the history of life.
1.1 What is biology?
3. • In some ways, biology is the most demanding of all
sciences, partly because living systems are so
complex and partly because biology is an
multidisciplinary science that requires a knowledge
of chemistry, physics, and mathematics.
• Biology is also the science most connected to the
humanities and social sciences.
• The complexity of life is inspiring, but it can be
overwhelming.
• Ten themes cut across all biological fields.
4. 1.2 Branches in biology
Zoology – the study of animals
Botany – the study of plants
Microbiology – the study of microorganisms
Mycology – the study of fungi
Bacteriology – the study of bacteria
Anatomy – study the structure of animals and plants
Taxonomy – classification of organisms
6. 1.3 Brief history of life
• Life can be defined in terms of the
characteristics of living organisms
1. Organisms are composed of cells
Unicellular organisms are composed of a single cell.
Multicellular organisms are composed of several or
great numbers of cells
The cell theory was first described by Schleidan and
Schwann in the 1800s.
1. Living organisms grow and develop
Growth may result from an increase in the number of
cells or in individual cell size
7. Development is the process of change during the life
span of the organism
3. Metabolism includes the chemical processes
essential to growth, repair, and reproduction
The relatively constant internal environment is known
as homeostasis
4. Movement is a basic property of cells
Movement may result from amoeboid motion, cilia or
flagella
Muscular systems allow movement
Some organisms are sessile
8. 5. Organisms respond to stimuli
Responses of animals are more obvious
Plants respond to light, gravity, water, touch, and other
stimuli
6. Organisms reproduce
Life comes from life
Asexual reproduction does not include gamete fusion
Most plants and animals reproduce sexually
7. Populations evolve and become adapted to the
environment
Adaptations may be structural, physiological, and/or
behavioral
10. • Biology can be viewed as having two dimensions: a
“vertical” dimension covering the size scale from
atoms to the biosphere and a “horizontal” dimension
that stretches across the diversity of life.
• The latter includes not only present day organisms but
those throughout life’s history.
• Evolution makes sense of everything we know about
living organisms
• Organisms living on Earth are modified descendents
of common ancestors
The sign of evolution
11. • Evolution is the key to understanding biological
diversity.
• The evolutionary connections among all
organisms explain the unity and diversity of life.
12. • Diversity is a hallmark of life.
• At present, biologists have identified and named about 1.8
million species.
• This includes over 280,000 plants, almost 50,000
vertebrates, and over 750,000 insects.
• Thousands of newly identified species are added each
year.
• Estimates of the total diversity of life range from
about 10 million to over 100 million species.
1. Diversity and unity are the dual faces of
life on Earth
13. • Biological diversity is something to relish and
preserve, but it can also be a bit overwhelming.
Fig. 1.9
14. • In the face of this
complexity, humans are
inclined to categorize
diverse items into a smaller
number of groups.
• Taxonomy is the branch of
biology that names and
classifies species into a
hierarchical order.
• Domains, followed by
kingdoms, are the broadest
units of classification
Fig. 1.10
15. Fig. 1-14
Species Genus Family Order Class Phylum Kingdom Domain
Ursus americanus
(American black bear)
Ursus
Ursidae
Carnivora
Mammalia
Chordata
Animalia
Eukarya
16. • Biologist use a binomial system for naming
and classifying organisms
• Scientific names include a genus name and a
species name
• Carolus Linnaeus developed the system of
classification used today
• Binomial nomenclature describes the genus and
species of the organism
17. The Three Domains of Life
• The three-domain system is currently used, and
replaces the old five-kingdom system
• Domain Bacteria and domain Archaea comprise
the prokaryotes
• Domain Eukarya includes all eukaryotic
organisms
18. • The domain Eukarya includes three multicellular
kingdoms:
• Plantae
• Fungi
• Animalia
• Other eukaryotic organisms were formerly
grouped into a kingdom called Protista, though
these are now often grouped into many separate
kingdoms
20. • Both Eubacteria and Archaea have prokaryotes.
• Archaea may be more closely related to eukaryotes
than they are to bacteria.
• The Eukarya
includes at
least four
kingdoms:
Protista,
Plantae,
Fungi, and
Animalia.
Fig. 1.11
21. • Six-kingdom system
• Kingdom Eubacteria consists of bacteria
• Kingdom Archaea consists of a unique group of
prokaryotic organisms, which biologists recently
have split off from the bacterial kingdom
(Eubacteria)
• Kingdom Protista consists of protozoans and algae
• Kingdom Fungi consists of the mushrooms, molds,
and yeasts
• Kingdom Plantae consists of plants
• Kingdom Animalia consists of the animals
22. • The Plantae, Fungi, and Animalia are primarily
multicellular.
• Protista is primarily unicellular but includes the
multicellular algae in many classification schemes.
• Most plants produce their own sugars and food by
photosynthesis.
• Most fungi are decomposers that break down dead
organisms and organic wastes.
• Animals obtain food by ingesting other organisms.
23. • Underlying the diversity
of life is a striking unity,
especially at the lower
levels of organization.
• The universal genetic
language of DNA unites
prokaryotes, like
bacteria, with
eukaryotes, like humans.
• Among eukaryotes,
unity is evident in many
details of cell structure.
Fig. 1.12
24. • Above the cellular level, organisms are variously
adapted to their ways of life.
• This creates challenges in the ongoing task of
describing and classifying biological diversity.
• Evolution accounts for this combination of unity
and diversity of life.
25. • The history of life is a saga of a restless Earth
billions of years old, inhabited by a changing cast
of living forms.
2. Evolution is the core theme of biology
• This cast is revealed
through fossils and other
evidence.
• Life evolves.
• Each species is one twig
on a branching tree of life
extending back through
ancestral species.
Fig. 1.13
26. • Species that are very similar share a common
ancestor that represents a relatively recent branch
point on the tree of life.
• Brown bears and polar bears share a recent common
ancestor.
• Both bears are also related through older common
ancestors to other organisms.
• The presence of hair and milk-producing mammary
glands indicates that bears are related to other
mammals.
• Similarities in cellular structure, like cilia, indicate
a common ancestor for all eukaryotes.
• All life is connected through evolution.
27. • Charles Darwin published On the Origin of
Species by Means of Natural Selection in 1859
• Darwin made two main points:
• Species showed evidence of “descent with
modification” from common ancestors
• Natural selection is the mechanism behind “descent
with modification”
• Darwin’s theory explained the duality of unity
and diversity
28. • Darwin observed that:
• Individuals in a population have traits that vary
• Many of these traits are heritable (passed from parents
to offspring)
• More offspring are produced than survive
• Competition is inevitable
• Species generally suit their environment
29. • Darwin inferred that:
• Individuals that are best suited to their environment are
more likely to survive and reproduce
• Over time, more individuals in a population will have
the advantageous traits
• In other words, the natural environment “selects”
for beneficial traits
31. • Natural selection is often evident in adaptations of
organisms to their way of life and environment
• Bat wings are an example of adaptation
32.
33. The Tree of Life
• “Unity in diversity” arises from “descent with
modification”
• For example, the forelimb of the bat, human, horse and
the whale flipper all share a common skeletal
architecture
• Fossils provide additional evidence of anatomical
unity from descent with modification
34. • Darwin proposed that natural selection could
cause an ancestral species to give rise to two or
more descendent species
• For example, the finch species of the Galápagos
Islands
• Evolutionary relationships are often illustrated
with tree-like diagrams that show ancestors and
their descendents
35. COMMON
ANCESTOR
Warblerfinches
Insect-eaters
Bud-eater
Seed-eater
Insect-eaters
TreefinchesGroundfinches
Seed-eaters
Cactus-flower-
eaters
Green warbler finch
Certhidea olivacea
Gray warbler finch
Certhidea fusca
Sharp-beaked
ground finch
Geospiza difficilis
Vegetarian finch
Platyspiza crassirostris
Mangrove finch
Cactospiza heliobates
Woodpecker finch
Cactospiza pallida
Medium tree finch
Camarhynchus pauper
Large tree finch
Camarhynchus psittacula
Small tree finch
Camarhynchus parvulus
Large cactus
ground finch
Geospiza conirostris
Cactus ground finch
Geospiza scandens
Small ground finch
Geospiza fuliginosa
Medium ground finch
Geospiza fortis
Large ground finch
Geospiza magnirostris
37. Mangrove finch
Cactospiza heliobates
Woodpecker finch
Cactospiza pallida
Medium tree finch
Camarhynchus pauper
Large tree finch
Camarhynchus psittacula
Small tree finch
Camarhynchus parvulus
Treefinches
Insect-eaters
38. Large cactus
ground finch
Geospiza conirostris
Cactus ground finch
Geospiza scandens
Small ground finch
Geospiza fuliginosa
Medium ground finch
Geospiza fortis
Large ground finch
Geospiza magnirostris
Cactus-flower-
eaters
Seed-eaters
Groundfinches
39. • Population evolve as a result of selective pressures
from changes in the environment
• Descent with modification accounts for both the
unity and diversity of life.
• In many cases, features shared by two species are due to
their descent from a common ancestor.
• Differences are due to modifications by natural
selection modifying the ancestral equipment in different
environments.
• Evolution is the core theme of biology - a unifying
thread that ties biology together.
