chapter 1

CHAPTER 1 INTRODUCTION

• 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?

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

• 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.


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


• Histology - ?

• Embryology - ?

• Physiology - ?

• Development biology - ?

• Biochemistry - ?

• Cell biology - ?

• Genetics - ?

• Molecular biology , ecology - ?

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.

2. Living organisms grow and develop

Growth may result from an increase in the number of cells or in individual cell size

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

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

order

Evolutionary adaptation

Responseto theenvironment

ReproductionGrowth anddevelopment

Energyprocessing

Regulation

• 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


• Evolution is the key to understanding biological diversity.

• The evolutionary connections among all organisms explain the unity and diversity of life.

• 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


• Biological diversity is something to relish and preserve, but it can also be a bit overwhelming.


Fig. 1.9

• 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

Fig. 1-14Species Genus Family Order Class Phylum Kingdom Domain

Ursus americanus(American black bear)

Ursus

Ursidae

Carnivora

Mammalia

Chordata

Animalia

Eukarya

• 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

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

• 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

(a) DOMAIN BACTERIA

(b) DOMAIN ARCHAEA

(c) DOMAIN EUKARYA

Protists

Kingdom Fungi

KingdomPlantae

Kingdom Animalia

• 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

• 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

• 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.


• 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

• 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.


• 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

• 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.


• 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

• 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

• 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

Populationwith variedinherited traits

1Eliminationof individualswith certaintraits.

Reproductionof survivors.

Increasingfrequencyof traits that enhance survival and reproductive success.

• Natural selection is often evident in adaptations of organisms to their way of life and environment

• Bat wings are an example of adaptation

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

• 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

COMMONANCESTOR

Warb

ler finch

es

Insect-eaters

Bu

d-eater

Seed

-eater

Insect-

eaters

Tree

finch

esG

roun

d

finch

es

Seed

-eaters

Cactu

s-flow

er-eaters

Green warbler finch Certhidea olivacea

Gray warbler finch Certhidea fusca

Sharp-beakedground 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 cactusground finchGeospiza conirostris

Cactus ground finchGeospiza scandens

Small ground finchGeospiza fuliginosa

Medium ground finchGeospiza fortis

Large ground finchGeospiza magnirostris

Warb

ler fin

ches

Insect-

eaters

Seed

-eater

Bu

d-

eater

Green warbler finch Certhidea olivacea

Gray warbler finch Certhidea fusca

Sharp-beakedground 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

Tree

finch

es

Insect-

eaters

Large cactusground finchGeospiza conirostris

Cactus ground finchGeospiza scandens

Small ground finchGeospiza fuliginosa

Medium ground finchGeospiza fortis

Large ground finchGeospiza magnirostris

Cactu

s-flow

er-eaters

Seed

-eaters

Grou

nd

fin

ches

• 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.


chapter 1

Technology

organisms organisms

study of life

things organisms biology

eukaryotic organisms

multicellular organisms

organisms work

brief history of life

complexity of life