3 Essays APA Format Two 200 Words and One 500 Words

Chyna45

unitviii_chapter21presentation.pdf_biology.pdf

Home >Biology homework help >3 Essays APA Format Two 200 Words and One 500 Words

A Guide to the Natural World

David Krogh

Chapter 21 • Lecture Outline

Viruses, Bacteria, Archaea, and Protists:

The Diversity of Life 1

Biology

Fifth Edition

21.1 Life’s Categories and

the Importance of Microbes

Life’s Categories and the Importance of

Microbes

• All living things on Earth can be classified

as falling into one of three domains of life:

• Bacteria

• Archaea

• Eukarya

Life’s Categories and the Importance of

Microbes

• All the members of Domains Bacteria and

Archaea are single-celled and microscopic.

• Domain Eukarya is further divided into four

kingdoms:

• plants

• animals

• fungi

• protists

Amazing Diversity in the Living

World

Figure 21.1

Importance of Microbes

• Microbes—living things so small they

cannot be seen with the naked eye—are

indispensable to all life on Earth.

Importance of Microbes

• Microbes produce more than half of Earth’s

atmospheric oxygen.

• The bacteria and archaea among them are

responsible for putting atmospheric nitrogen

into a form plants can use.

Importance of Microbes

• Bacteria and fungi are the most important

decomposers of the natural world.

• They break down dead organic matter, such

as tree branches, and recycle the resulting

elements back into the Earth.

Importance of Microbes

• Microbes live in all environments in which

larger life-forms exist.

• They are present in numbers so immense

that the weight or biomass of all microbes

on Earth exceeds the biomass of all larger

life-forms.

Domain

Bacteria

Domain

Archaea

Kingdom

Protista

Kingdom

Plantae

Kingdom

Animalia

Kingdom

Fungi

Domain Eukarya

gram-

positive

purple

bacteria

methane

producers

salt

lovers

cyano-

bacteria hot acid

lovers diatoms

dinoflagellates

flagellates

foram-

inifera

amoebae

flowering

plants

evergreens

ferns

mosses

vertebrates

inverte-

brates

mushrooms

yeast

Domain Eukarya

(Protists, Plants, Animals, Fungi)

Domain

Archaea

Domain

Bacteria

Universal

ancestor Figure 21.2

21.2 Viruses: Making a Living

by Hijacking Cells

Viruses

• Viruses are noncellular replicating entities

that must invade living cells to carry out

their replication.

• Because viruses can carry out so few of

life’s basic processes on their own, most

scientists do not classify them as living

things.

HIV: The AIDS Virus

• The human immunodeficiency virus (HIV),

which causes AIDS, has two structures

common to all viruses: genetic material and

a protein coat, called a capsid, surrounding

this material.

HIV: The AIDS Virus

• HIV also has one other structural element

that many viruses possess: a fatty

membrane, called an envelope, which

surrounds the capsid.

• HIV does its damage by invading immune

system cells called helper T-cells, which are

then destroyed.

(a) Human immunodeficiency

virus (HIV)

reverse transcriptase

protease

integrase

(b) Life cycle of HIV

receptor (spike)

capsid

genetic material

(2 strands RNA)

envelope

1. HIV binds with

receptors on

T-cell.

receptor

for HIV 2. Viral envelope fuses with T-cell membrane.

3. Capsid disintegrates: viral RNA and enzymes are released.

nucleus 4. HIV’s reverse transcriptase synthesizes DNA from viral RNA.

double-stranded

viral DNA

viral RNA

integrase

5. Integrase splices

viral DNA into

cell’s DNA. integrated

viral DNA

protease

viral components

8. New virus particle buds

off from cell and goes

on to infect more cells.

7. Cell membrane becomes

the envelope for new HIV

particle.

6. Viral DNA and protease begin

turning out materials necessary

to produce viral clones.

HIV: The AIDS Virus

Figure 21.3

Viral Lifecycle

• Most viruses carry out four steps in their life

cycle:

1. They get their genetic material inside a “host”

cell.

2. They turn out viral component parts.

3. They construct new virus particles from these

parts.

4. They move the new particles out of the cell, at

which point the particles go on to infect more

cells.

Influenza A

• Viruses cause a host of human illnesses.

• Health officials worldwide must constantly

be on alert for the emergence of new

members of a particularly dangerous class

of viruses, the influenza A viruses.

• The H1N1 virus was one of these viruses,

and infected people around the world in

2009.

Pandemic

Figure 21.5

21.3 Bacteria: Masters of Every

Environment

Bacteria

• Bacteria are microscopic, single-celled

organisms that are prokaryotes.

• Prokaryotes are organisms whose genetic

material is not contained within a nucleus.

Bacteria

• Other defining features of bacteria are that

they have only a single organelle (the

ribosome) and reproduce asexually through

a simple cell splitting called binary fission.

• Millions of species of bacteria exist.

• Bacteria are metabolically far more diverse

than plants or animals.

Different Shapes of Bacteria

Figure 21.7

21.4 Intimate Strangers:

Humans and Bacteria

• Bacteria live on and in human beings in

great numbers.

Humans and Bacteria

• In the digestive tract, the relationship

between humans and many bacteria is one

of mutualism: a relationship between two

organisms that benefits both of them.

• Bacteria get food and habitat from this

relationship; human beings get an

efficiently functioning digestive system.

scalp

about 200 species of resident bacteria in mouth

nasal passages

few resident bacteria in stomach because of its acidic pH

digestive

tract

500-1,000 species of resident bacteria in large intestine

rectum

vagina

armpit

skin

Humans and Bacteria

Figure 21.8

21.5 Bacteria and Human Disease

Bacteria and Human Disease

• Only a small proportion of bacteria are

pathogenic or disease causing, but these

bacteria are responsible for some of

humanity’s worst diseases.

Bacteria and Human Disease

• A few pathogenic bacteria cause harm by

invading human cells, but bacteria generally

do their damage by releasing or leaving

behind harmful substances called toxins.

Bacteria and Human Disease

• The primary human defense against

pathogenic bacteria is the class of drugs

known as antibiotics, defined as substances

produced by one microorganism that are

toxic to another.

Antibiotics

• The first antibiotic, penicillin, was

developed in the 1940s.

• Antibiotics work by exploiting the

differences between bacterial and human

cells, such that they kill bacteria while

leaving human cells unharmed.

The Threat of Antibiotic

Resistance

• The power of antibiotics is being threatened

by the emergence of antibiotic-resistant

strains of bacteria.

• These bacteria are evolving in greater

numbers because of an overuse of

antibiotics in medicine and agriculture.

The Threat of Antibiotic

Resistance

• One antibiotic-resistant bacterium,

methicillin-resistant Staphylococcus aureus

(MRSA or “mersa”), is being seen with

increasing frequency in the general public,

in particular among high school and college

athletes.

21.6 Archaea: From Marginal

Player to Center Stage

Archaea

• Archaea were once thought to be a form of

bacteria but are now known to constitute

their own domain of life, standing beside

Domains Bacteria and Eukarya.

Archaea

• Archaea are superficially similar to bacteria

in that they are single-celled prokaryotes

that reproduce through simple cell splitting.

Archaea

• However, archaea are unique in the living

world at the level of the chemical structure

of their cells.

Archaea and the Universal

Tree of Life

Figure 21.9

Domain

Bacteria

Domain

Archaea

Domain Eukarya

(Protists, Plants, Animals, Fungi)

Universal

ancestor

Archaea and Their Habitats

• Archaea exist in large numbers in some

common environments.

• They make up 40 percent of the microbial

life in large portions of the world’s oceans.

• They are seen in large numbers in common

soil, where they join bacteria in carrying out

one phase of the nitrogen-fixing process.

Extremophiles

• Many species of archaea live in extreme

environments and thus are extremophiles:

organisms that grow optimally in

environments whose conditions would kill

most other organisms.

Extremophiles

• Three large classes of extremophiles are:

• Thermophiles—organisms that live in

extremely hot environments.

• Halophiles—organisms that live in extremely

salty environments.

• Anaerobes—organisms that can either do

without oxygen or that actually are poisoned

by it.

21.7 Protists: Pioneers in

Diversifying Life

Protists

• A protist is a eukaryotic organism that does not

have all the defining features of a plant, an

animal, or a fungus.

• This unsatisfactory definition stems from the

fact that the term protist doesn’t refer to a

single evolutionary grouping.

• Instead, it is used as a label for several different

evolutionary lines of organisms, many of which

are only distantly related.

Bacteria

Green sulfur bacteria

Cyanobacteria

Methanococcus

Thermoplasma

Archaea

Protista

Red algae

Protists can be as different from each other as animals are from plants

Plants Fungi

Nucleariid amoeba

Choanoflagellates

Animals

Eukarya

Figure 21.10

Protists

• Protists are mostly microscopic.

• All of them live in environments that are at

least moist, if not aquatic.

Protists

• About 100,000 species are known to exist.

• The small portion of these that are

pathogenic include Plasmodium falciparum,

the cause of malaria, and the intestinal

parasite Giardia, which contaminates water.

21.8 Protists and Sexual

Reproduction

Protists and Sexual Reproduction

• For nearly the first 2 billion years after life

appeared, it consisted solely of bacteria and

archaea.

• Protists were the first life-form to evolve

other than bacteria or archaea.

Protists and Sexual Reproduction

• Protists were the organisms that made

transitions to many of the capabilities and

forms seen in larger organisms today.

• Among these transitions was the change to

sexual reproduction, which protists were the

first to practice.

Protists and Sexual Reproduction + mating type

(haploid) pairing

– mating type

(haploid)

zygote

(diploid)

cell

fusion

Sexual reproduction

begins with the

fusion of two cells

21.9 Photosynthesizing Protists