Transcript Chapter 2: Diversity: From Simple to Complex - ahs

UNIT 1: Diversity of Living Things
Chapter 1: Classifying Life’s Diversity
Chapter 2: Diversity: From Simple to
Complex
What are the characteristics of bacteria,
archaea, and protists?
Chapter 3: Multicellular Diversity
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.1
2: Diversity: From Simple to Complex
This mound, a microbialite found in a lake in British
Columbia, is covered with different types of bacteria and
other micro-organisms that trap minerals
from the water to form the solid structures
beneath them. Since microbialites were
common millions of years ago, scientists
hope to gain insight into the history of
Earth and its life forms by studying them.
What does this suggest about
the evolutionary history of
bacterial cells?
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.1
2.1 A Microscopic Look at Life’s
Organization
All species of living organisms, whether unicellular or
multicellular, are comprised of cells and can be studied using a
microscope. Scientists also investigate and classify viruses,
although they are not considered alive since they cannot live
outside of cells. Viruses differ from prokaryotic and eukaryotic
cells in that:
• they are dependent on the internal
physiology of cells
• they are not cellular and thus lack cytoplasm, organelles,
and cell membranes
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.1
Classifying Viruses
Scientists classify viruses by using each one’s unique
characteristics, including:
• size and shape of the capsid (protein coat surrounding
genetic material)
• shape and structure of the virus
• type(s) of diseases the virus causes
• genome (set of genes) and type of genetic material (RNA
or DNA)
• method of reproduction
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.1
Reproduction in Viruses
Viruses undergo replication inside a host cell. Some viruses
replicate by means of a lytic cycle, where they quickly attach,
enter, replicate, assemble, and release from a cell, killing the
cell in the process.
Other viruses replicate by means of a lysogenic cycle, where
they enter and then attach their DNA to the host’s
chromosomes. Now referred to as a provirus, it can lie
dormant within the host chromosome until it re-activates and
continues with the lytic cycle.
Continued…
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Reproduction
in Viruses
Section 2.1
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.1
Viruses and Disease
In multicellular species, lytic viruses burst from host cells
and infect neighbouring cells. Host organisms that are
already damaged are affected more rapidly.
Lysogenic viruses may not cause any immediate effects on
the host organism. HIV (human immunodeficiency virus)
is an example of both a lysogenic virus and a retrovirus.
Continued…
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Viruses and Disease
Retroviruses carry RNA and an enzyme called reverse transcriptase that
causes the host cell to copy the viral RNA into DNA. Then it embeds into the
host’s chromosomes and becomes a provirus. Every descendent cell then has
HIV DNA copied within its genome.
Section 2.1
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Prions: Non-viral
Disease-causing
Agents
Prions, discovered in the1980s,
are proteins and thus are the only
known non-genetic disease agent.
They become harmful when they
change molecular shape. They
remain infectious even after
exposure to radiation. Examples
include Creutzfeldt-Jacob disease
(CJD) and Variant CreutzfeldtJacob disease (vCJD).
Section 2.1
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.1 Review
Section 2.1
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.2
2.2 Comparing Bacteria and Archaea
Comparisons of cell type, morphology (shape), aggregation,
nutrition, habitat, and reproduction show similarities and
differences between the two domains.
Continued…
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.2
Comparing Bacteria and Archaea
Similarities
• prokaryotic
• similar shapes of cocci (spheres), bacilli (rods), and spiral cells
• some species form aggregations
• for energy, species either consume other organisms or use
inorganic compounds
• species live in aerobic or anaerobic habitats
• both found in extreme environments; more archaea live in
extreme habitats (extremophiles), while more bacteria live in
moderate habitats (mesophiles)
• reproduce by binary fission and can exchange genetic
content by conjugation
Continued…
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.2
Comparing Bacteria and Archaea
Differences
• Some bacteria are shaped like pyramids, cubes, or rods with star
cross-sections, while some archaea are shaped like plates or
rectangular rods.
• Some bacteria are photosynthetic, while some archaea are
methanogenetic (produce methane gas as an anaerobic byproduct).
• Bacteria live anaerobically in human guts; archaea live
anaerobically in cattle guts.
Cyanobacteria, such as
Spirulina platensis, contain
chlorophyll and carry out
photosynthesis.
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.2
Three Types of Extremophiles
• Thermophiles live in hot springs and deep
sea vents, enduring temperatures over
100ºC.
Example: Archaea Methanopyrus
• Acidophiles live in volcanic craters
and mine drainage lakes, enduring
pH levels lower than 3.
Example: Archaea Picrophilus
• Halophiles live in salt lakes and
inland seas, enduring salt concentrations
above 20%.
Example: Archaea Halococcus
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.2
Reproduction of Bacteria and Archaea
Reproducing Asexually
Since both domains are
prokaryotic and lack a
nucleus, both reproduce
asexually by binary fission.
As a cell grows, it makes a
copy of its single
chromosome. After
elongating and separating the
two copies, the cell builds a
septum between and splits
into two identical cells.
Continued…
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.2
Reproduction of Bacteria and Archaea
In less favourable conditions, DNA can be exchanged
instead of reproducing by binary fission. In conjugation,
one cell links to another by a pilus (tube) and transfers a
copy of some or all of the chromosomes.
Continued…
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.2
Reproduction of Bacteria and Archaea
In addition, bacteria and achaea house small DNA loops
called plasmids that contain genes different from those of
the chromosome. Plasmids can also be transferred through
conjugation. This results in new genetic combinations and
is an agent for increasing biodiversity.
In some circumstances, bacteria form hard-walled
structures called endospores to protect and store the
genetic material.
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.2
Classifying and Identifying Bacteria/Archaea
The following characteristics are used to classify and identify
these two prokaryotic domains:
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size and shape
nutrition
movement
genetic components
Gram staining
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The Gram stain divides most bacteria into two groups: Grampositive (A) and Gram-negative (B). The Gram-negative group of
bacteria are larger in number and have more diverse species
than the Gram-positive group.
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.2
Classifying and Identifying Bacteria/Archaea
Gram staining works to separate bacteria into two groups;
those species that will stain because they contain a thick
protein layer on their cell wall are Gram-positive (become
purple), and those species that will not stain because they
have a thin protein layer are Gram-negative (become pink).
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Bacteria, Human Health, and
the Environment
Some bacteria can harm human health.
Examples include:
• Clostridium botulinum causes
food poisoning
• Streptococcus pyogenes
causes strep throat
• Streptococcus mutans causes
tooth decay
Section 2.2
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.2
Bacteria, Human Health, and
the Environment
Bacteria are decomposers. They break down organic
molecules and release carbon, hydrogen, nitrogen, and sulfur,
thereby supporting those nutrient cycles. Through the process
of photosynthesis, cyanobacteria are major producers of
oxygen gas on Earth.
Some species in Archaea have enzymes that are of special
use to humans because they can withstand extreme
temperatures, salinity, and acidity. Biotechnologists have
been able to use some of these enzymes for various
procedures in DNA research.
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.2 Review
Section 2.2
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.3
2.3 Eukaryotic Evolution and Diversity
About 2 billion years ago, eukaryotes evolved and this led to
an increase in the diversity of life on Earth.
These organisms are more complex than prokaryotes. They
include more genes, allowing for greater cellular diversity in
terms of size, shape, mobility, and specialized functions.
Scientists examined the important question of how eukaryotic
cells evolved and have come up with some theories supported
by observations and evidence.
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.3
Endosymbiosis
The theory of endosymbiosis suggests that eukaryotic cells
evolved from symbiotic relationships between two or more
prokaryotic cells.
Although one prokaryotic cell engulfed a different, simpler
prokaryotic cell, the engulfed cell survived and became
part of the host cell.
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Chloroplasts and Mitochondria
Chloroplasts and mitochondria may have
been free-living prokaryotes engulfed by
larger prokaryotes. They continued to
perform their cellular activities while
surviving and serving the host cell. A
comparison of chloroplasts, mitochondria,
and prokaryotes shows:
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similar types of membranes
similar types of ribosomes
each reproduces by binary fission
each contains circular chromosomes
gene sequences match
Section 2.3
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.3
Multicellularity
Based on fossil evidence, scientists think that large, complex
eukaryotes first developed about 550 million years ago. They
have also found fossils of simple red algae in the Arctic that
date multicellular eukaryotes as far back as between 1.2 and
1.5 billion years ago.
Scientists hypothesize that the first multicellular organisms
arose from colonies created by individual cells that divided.
Genes within these cells contained
instructions for some cells to
become specialized. With the
passage of time, groups of cells
developed different functions.
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.3
Life Cycles and Reproduction
Eukaryotes reproduce by a number of methods:
• simple asexual reproduction (shown below)
• multiple fission asexual reproduction – where multiple
copies of a cell are made at one time
• sexual reproduction performed by a diploid organism
• sexual reproduction performed by a haploid organism
• sexual reproduction performed by an organism with both a
haploid and diploid stage of life
Continued…
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.3
Life Cycles and Reproduction
In the case of sexual reproduction, the timing of the
production of gametes (egg and sperm) differs as the
organism may be haploid (contain one set of chromosomes
per cell) or diploid (contain two sets of chromosomes per
cell).
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.3 Review
Section 2.3
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.4
2.4 Protists: The Unicellular Eukaryotes
Most protests are unicellular. They are
diverse and are essentially grouped into
one kingdom because they do not fit
well into other kingdoms. There is still
debate about whether multicellular algal
species fit into this kingdom or belong
in the plant kingdom.
The rest of the kingdom can be
grouped as follows:
• animal-like protists
• fungus-like protists
• plant-like protists
Can you identify the type of
protist shown in the photo?
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Animal-like Protists
The protozoans (animal-like) are
heterotrophic and consume
prokaryotes, other protists, or
organic wastes. Some are
parasitic and consume nutrients
from the organism they live in.
Four phyla will be highlighted:
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Cercozoa
Ciliophora
Zoomastigina
Sporozoa
Continued…
Section 2.4
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.4
Animal-like Protists
Phylum Cercozoa includes the amoebas. Using pseudopods
(“false feet”) they change shape to move and engulf food. They
inhabit various environments, including freshwater, saltwater,
and humans (as parasites).
When amoebas detect food, they form pseudopods
from the cell membrane and engulf their target.
Continued…
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.4
Animal-like Protists
Phylum Ciliophora includes the ciliates such as paramecia. The
surface of the cell has hair-like projections called cilia that are
used for locomotion and food sweeping. These protists inhabit
various environments, and some are parasites. They are large and
complex organisms.
Paramecia use cilia
to move through the
water and to move
food into the gullet.
Continued…
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.4
Animal-like Protists
Phylum Zoomastigina contains species with hard protective
coverings over their outer membrane. These protists are called
flagellates because they have one or more whip-like flagella,
used for locomotion. They live in a variety of environments and
conditions, including mutualistic relationships where both
organisms benefit.
Phylum Sporozoa includes parasitic protists. They are unique in
that they alternate between asexual and sexual reproduction that
often occurs in different hosts. One sporozoan species causes
malaria in humans.
Continued…
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Animal-like Protists
Section 2.4
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.4
Fungus-like Protists
These protists absorb nutrients from living organisms, dead
organisms, and wastes and are thus considered heterotrophic.
They are similar to fungi in that they produce spores. However,
the structure of their cell wall is different from those of fungi.
They are classified generally into two categories: slime moulds
and water moulds. Three phyla will be highlighted:
• Myxomycota
• Acrasiomycota
• Oomycota
Continued…
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.4
Fungus-like Protists
Organisms in phylum Myxomycota are also known as the
plasmodial slime moulds. Visible to the unaided eye as tiny
slug-like organisms, they creep and stream over decaying plant
matter in forests and engulf small particles. A plasmodium
contains many nuclei.
Hemitrichia clavata
can be found on
rotting logs.
Continued…
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.4
Fungus-like Protists
Organisms in phylum Acrasiomycota are also known as the
cellular slime moulds. They differ from Myxomycota in many
ways; for example, their cells contain only one nucleus. They live
as separate cells and behave like amoebas until food is scarce,
when they join together as a slime mould.
Continued…
This slime mould is
likely a member of
the genus Fuligo.
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.4
Fungus-like Protists
Organisms in phylum Oomycota (oh-oh-my-cota) are
filamentous water moulds that consume dead organic matter.
However, some species are parasitic and draw nutrients out of
their hosts by extending fungus-like threads into their tissues and
releasing digestive enzymes.
This species of
saprolegnia is
digesting a goldfish.
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.4
Plant-like Protists
Unicellular, plant-like protists include diatoms, dinoflagellates,
and euglenoids. They all contain photosynthetic pigments in
their chloroplasts, many of which contain chlorophyll. Three
phyla will be highlighted:
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Chrysophyta
Pyrrophyta
Euglenophyta
Continued…
The many species of
diatoms have different
shapes and sizes
based on differences
in their silica walls.
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.4
Plant-like Protists
Organisms in phylum Chrysophyta are also called
phytoplankton. They are a diverse group of free-living aquatic
diatoms that are an
important source of food for
many marine organisms.
They all contain a rigid cell
wall with an outer layer
of silica. They can
reproduce asexually
and sexually (when
conditions become
less favourable).
Continued…
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.4
Plant-like Protists
Organisms in phylum Pyrrophyta are also called dinoflagellates.
Two flagella, extending at right angles on the organism, produce a
spinning movement during locomotion.
When food is plentiful, these organisms reproduce quickly and
cause great algal blooms. While dinoflagellates are photosynthetic,
some live in mutualistic relationships with coral.
Dinoflagellates, such as
Gonyaulax catenella, can
cause red tides, during
which many marine
organisms can die and
shellfish can become toxic.
Continued…
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.4
Plant-like Protists
Organisms in phylum Euglenophyta are mostly freshwater
species. They tend to be autotrophs in sunlight and heterotrophs in
the dark. They have chloroplasts for making food by day and can
absorb nutrients at night.
UNIT 1 Chapter 2: Diversity: From Simple to Complex
Section 2.4 Review
Section 2.4