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Chapter 28.1: Microbiology-VIRUS!
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Viruses
• Viruses are noncellular, nonliving particles
and therefore are not included in the
classification scheme.
• Comparable in size to a large protein
macromolecule, many viruses can be
purified, crystallized, and stored as
chemicals.
Structure of Viruses
• A virus has an outer capsid composed of
protein subunits, and an inner core of
nucleic acid.
• An outer membranous envelope may be
acquired when the virus buds from the cell.
• It may also include enzymes for nucleic acid
replication.
• Viruses are classified by type of nucleic
acid, viral shape and size, and by presence
of an outer envelope.
Adenovirus
• Parasitic Nature
• Viruses are obligate intracellular parasites.
• Viruses are very specific for the type of
cells they infect (e.g., HIV only infects
certain kinds of blood cells).
• Viruses are likely derived from the very
host they infect, and therefore evolved
after cells evolved.
• Some viruses, such as the flu virus, can
mutate rapidly.
Replication of Viruses
• Viruses are specific to a particular host cell
because they bind to a particular plasma
membrane receptor.
• After viral nucleic acid enters the host cell,
it takes over the metabolic machinery of
the host cell so that more viruses are
produced.
•
• Replication of Bacteriophages
• Bacteriophages are viruses that parasitize
bacteria.
• Some undergo two cycles, a lytic cycle and
a lysogenic cycle.
• The lytic cycle is divided into five phases:
attachment, penetration, biosynthesis,
maturation, and release.
• In the lysogenic cycle, the infected
bacterium does not immediately produce
viruses but may do so sometime in the
future; the phage has a latent period and is
called a prophage during this time.
Lytic and lysogenic cycles
• Replication of Animal Viruses
• Entire animal virus penetrates host cell by
endocytosis.
• Once inside, the virus is uncoated to
remove the envelope and capsid.
• The viral genome, either DNA or RNA, is
now free and biosynthesis proceeds.
• The assembled viruses bud from the cell
and acquire envelopes.
•
• Retroviruses are RNA animal viruses that
have a DNA stage.
• They have an enzyme called reverse
transcriptase that carries out RNA →
cDNA transcription.
• Following replication, cDNA integrates into
the host genome until viral reproduction
occurs.
Reproduction of HIV, a retrovirus
• Viral Infections
• Viruses cause infectious diseases of
plants and animals, including humans.
• Some crop diseases are attributed not to
viruses but to naked strands of RNA called
viriods.
• Some diseases in humans and animals
are attributed to prions which are protein
particles.
• Mad cow disease (BSE) in Britain is
believed to be a prion disease.
Chapter 31: Animals: Part II
- Review -
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Evolutionary treeDueterostomes
Echinoderms
• Echinoderms and chordates are on a similar
evolutionany brach because both are deuterostomes.
• In deuterostomes, the first embryonic opening
becomes the anus, and the second is the mouth. In
protostomes, the first opening is the mouth.
• Most echinoderms have radial symmetry.
• Examples are: starfish, sea urchins, and sand dollars.
Evolutionary tree of chordates
Invertebrate chordates
Chordate Characteristics
• Chordates (tunicates, lancelets,
and vertebrates) have:
• a supporting notochord
• a dorsal hollow nerve cord,
• pharyngeal pouches,
• post-anal tail at one time in
their development.
Examples of Invertebrate Chordates
• Lancelets are small animals found in shallow
water along the coasts; they filter feed on
microscopic organisms.
• Tunicates (sea squirts) live on the ocean floor
and filter water entering the animal through an
incurrent siphon.
True Vertebrates
• At some time during their lives, all vertebrates
have the four chordate characteristics.
• The notochord is replaced by the vertebral
column; this endoskeleton demonstrates
segmentation.
• Vertebrates are distinguished in particular
by these features:
• Living endoskeleton
• Closed circulatory system
• Paired appendages
• Efficient respiration and excretion
• High degree of cephalization
Chapter 31: Animals: Part II
- continued -
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Various True Vertebrate Animals
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Jawless fishes (lamprey)
Cartilaginous fishes (sharks and rays)
Bony fishes (tuna, halibut)
Amphibians (frogs, salamanders)
Reptiles (lizards, snakes)
Birds
Mammals
Mammals
• Mammals evolved from reptiles and flourished
after the demise of dinosaurs.
• Mammals have hair that helps them maintain
a constant body temperature.
• Mammals (and birds) have a four-chambered
heart.
• Internal development in the uterus shelters the
young.
• Mammary glands allow mammals to nourish
their young.
Mammals
• Different types of mammals include:
- Monotremes (platypus)
- Marsupials (kangaroos)
- Placental (lions, monkeys, humans)
Monotremes
• Monotremes have a cloaca that is a common area for
feces, excretory wastes, and sex cells.
• Monotremes lay hard-shelled amniote eggs.
• Monotremes are represented by the duckbill platypus
and the spiny anteater.
Marsupials
• Marsupials have a pouch in which
the very immature newborn matures.
Inside the pouch, the newborns
attach to nipples of mammary
glands.
• Marsupials are represented
by the American opossum,
and various Australian
animals such as koalas
and kangaroos.
Placental mammals
Placental Mammals
• Most mammals are placental mammals, which
retain the offspring inside a uterus until birth;
extraembryonic membranes are present,
including the chorion that contributes to the fetal
portion of the placenta.
• The classification of these mammals is based
on methods of obtaining food, and mode of
locomotion.
• Mammals are adapted to life on land and can
move rapidly.
• The brain is enlarged due to the expansion of
the cerebral hemispheres.
• Internal body temperature is constant.
• Mammals have differentiated teeth; the specific
size and shape of the teeth may be associated
with whether the animal is a herbivore, a
carnivore, or an omnivore.
• These features distinguish placental
mammals:
• Body hair
• Differentiated teeth
• Infant dependency
• Constant internal temperature
• Mammary glands
• Well-developed brain
• Internal development
Primates
• Primates are mammals adapted to living in
trees; many have an opposable thumb.
• The snout is shortened, enabling stereoscopic
vision, and cone cells give greater visual acuity.
• During the evolution of primates, various
groups diverged in a particular sequence.
• Prosimians include lemurs, tarsiers, and
lorises; anthropoids include monkeys, apes,
and humans.
These traits distinguish primates from other
mammals:
• Opposable thumb (and sometimes great toe)
• Well-developed brain
• Nails (not claws)
• Single birth (not “litters”)
• Extended period of parental care
• Emphasis on learned behavior
Human Evolution
• The primate evolutionary tree shows that all
primates share one common ancestor and that
the other lines of descent diverged from the
human lineage over time.
• Humans and apes shared a common ancestor.
• Molecular data indicate we are most closely
related to the African apes, whose ancestry
split from ours about 6 MYA.
Primate evolutionary tree
Evolution of Hominids
• To be a hominid, a fossil must have an anatomy
enabling it to stand erect and walk on two feet
(bipedalism).
• Ardipithecus ramidus kadabba is a 5.6 to 5.2
million-years-ago (MYA) hominid found in
Ethiopia; Ardipithecus ramidus ramidus is a 4.4
MYA hominid and less apelike than the older
fossil.
Australopithecines
• Human evolution continued in eastern Africa
around 4 MYA with the evolution of the
australopithecines, a group that is a direct
ancestor to humans.
• Raymond Dart discovered Australopithecus
africanus in southern Africa in the 1920s; this
fossil was the gracile type dated at 2.8 MYA.
• A more robust form, (A. robustus), from 2 to 1.5
MYA, had a brain size of 500cc like A. africanus;
these hominids may have been bipedal but still
had longer forelimbs.
• The most famous australopithecine is “Lucy” or
A. afarensis (3.18 MYA) unearthed in eastern
Africa, whose brain was small (400 cc) but who
walked bipedally.
• Since the australopithecines were apelike above
the waist but humanlike below the waist, it
seems that human characteristics did not all
evolve at once.
• This type of evolution of various body parts at
different rates is referred to as mosaic evolution.
Australopithecus afarensis
Bipedal movement
Evolution of Early Homo
• Fossils are assigned to Homo if the brain size is
600 cc or greater, if the jaw and teeth resemble
those of humans, and if tool use is evident.
• Homo habilis
• Homo habilis, (handy man) present at about 2
MYA, is certain to have made crude flake-like
stone tools.
• Speech areas of the brain enlarged and
contributed to the beginning of society and
culture.
Human evolution
Homo erectus
• Between 1.9 and 0.3 MYA Homo erectus, with a
brain capacity of 1,000 cc, a striding gate, and
a flatter face, was the first to migrate out of
Africa into Asia and Europe about 1 MYA.
• Males were about 6 feet tall and females
approaching 5 feet, much taller than earlier
hominids.
• H. erectus was the first hominid to use fire and
tools of this time were advanced axes and
cleavers.
Homo erectus
Evolution of Modern Humans
• Two contradicting hypotheses have been suggested
about the origin of modern humans, Homo sapiens,
from H. erectus.
• The multiregional continuity hypothesis suggests that
modern humans originated from H. erectus separately
in Asia, Europe, and Africa.
• The out-of-Africa hypothesis states that modern
humans originated in Africa and, after migrating into
Europe and Asia, replaced the archaic Homo species
found there.
Multiregional continuity hypothesis
Out-of-Africa hypothesis
Multiregional continuity
hypothesis
Out-of-Africa hypothesis
Neanderthals
• The Neanderthals lacked a high forehead and a
significant chin and are classified as Homo
neanderthalensis.
• They had massive brow ridges; their pubic bone was
long compared to that of modern humans.
• Neanderthals had a brain larger than that of modern
humans, and they lived in Europe and Asia during
the last Ice Age.
• Neanderthals lived in caves, made stone tools, and
buried their dead with flowers.
Neanderthals
Cro-Magnons
• Cro-Magnons evolved about 100,000 years ago and
were the first humans (Homo sapiens) to have a
thoroughly modern appearance.
• They made stone tools, including stones attached to
wooden handles; they threw spears, enabling them to
cooperatively hunt larger animals.
• The Cro-Magnon culture included art and beautiful
paintings on cave walls.
Cro-Magnons
Chapter Summary
• Both echinoderms and chordates are
deuterostomes.
• In deuterostomes, the second embryonic
opening becomes the mouth; the coelom
develops by an outpocketing from the primitive
gut.
• Echinoderms develop radial symmetry.
Chapter Summary
• Chordates have a notochord, a dorsal tubular
nerve cord, and a post-anal tail; pharyngeal
pouches occur sometime during the life of
chordates, and in vertebrates, the notochord is
replaced by the vertebral column.
Chapter Summary
• Primates such as pro-simians, monkeys, apes,
and humans are mammals adapted to living in
trees.
• Human evolution diverged from ape evolution in
Africa about six to seven million years ago.
• The australopithecines were the first hominids
and were ancestors to humans.
Chapter Summary
• Homo habilis could make tools; Homo erectus
migrated out of Africa.
• The Neanderthals (H. neanderthalensis) gave
evidence of being culturally advanced, lived in caves,
and hunted large mammals; they buried their dead
with flowers.
• Cro-Magnons are the oldest fossils to be designated
Homo sapiens; they made sophisticated tools and
were accomplished artists and hunters.
Chapter 32: Animal Behavior
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Bases of Animal Behavior
• Genetic
• Learned
• Adaptive
Genetic: Nest-building behavior in lovebirds
Feeding behavior in garter snakes
• Several experiments have been done with the garter
snake, which has two different populations in
California.
• Inland populations are aquatic and feed underwater
on frogs and fish.
• Coastal populations are terrestrial and feed mainly
on slugs.
• In the lab, inland garter snakes refused to eat slugs
but coastal snakes ate them.
• Hybrid offspring showed an intermediate acceptance
of slugs as food.
Learned: Pecking behavior in laughing gulls
The Phenomenon of Learning
• Operant Conditioning and Imprinting
• Operant conditioning, one of many forms of
learning, is the gradual strengthening of
stimulus-response (behavior-reward)
connections.
• Imprinting is another form of learning; chicks,
ducklings, and goslings will follow the first
moving object they see during a sensitive
period after hatching.
Song-Learning in Birds
• Song learning in birds is an active area of
research.
• White-crowned sparrows sing a speciesspecific song, but males of a particular region
have their own dialect; birds were caged into
three groups to see how young birds learn to
sing from older members of their species.
• Birds in the first group heard no singing; when
grown, these birds sang a song that was not
fully developed.
• Birds in the second group heard tapes of whitecrowns singing; when grown, they sang in a dialect,
as long as the tapes had been played during a
sensitive period.
• Birds in the third group were given an adult tutor;
these birds sang a song of even a different species,
no matter when the tutoring began.
• It appears that social influence, along with genetics, is
of great importance in the development of singing.
Song-learning by white-crowned sparrows
• Males can father many offspring because
they produce sperm in great quantity; it
would be expected that they inseminate as
many females as possible.
• Females produce few eggs, so choice of
mate becomes an important consideration.
• Experiments with satin bowerbirds and
birds of paradise support these bases for
sexual selection.
Mating behavior in birds of
paradise
Female Choice
• Courtship displays are rituals that serve to
prepare the sexes for mating; they help
male and female recognize each other so
that mating will be successful.
• Courtship displays also play a role in a
female’s choice of a mate.
• Female choice can explain why male birds
are so much more showy than females;
colorful, lengthy plumes might signify
health and vigor.
Male Competition
• Evolution by sexual selection can occur
either when females have the opportunity
to select among potential mates, and/or
when males compete among themselves
for access to reproductive females.
• Only if the positive effects of male
competition outweigh the negative effects
will the animal have reproductive success.
Dominance Hierarchy
• Male and female baboons within a troop
have separate dominance hierarchies in
which a higher-ranking animal has greater
access to resources than a lower-ranking
animal.
• Dominant male baboons generally
monopolize females when they are fertile,
although males that help rear offspring
sometimes have breeding access during
less fertile times.
• Dominance is decided by confrontations.
A male olive baboon displaying full
threat
Female choice and male
dominance among baboons
Territoriality
• A territory is an area that is defended
against competitors.
• Territoriality includes the type of defensive
behavior needed to defend a territory.
• Vocalization and displays, rather than
outright fighting, may be sufficient to
defend a territory.
• Red deer stags may actually lock antlers
and push against each other to repel
challengers.
Competition between male red
deer
Communicative Behavior
• Communication is an action by a sender that
affects the behavior of a receiver.
• Chemical communication uses chemical
signals, such as pheromones; an advantage is
that this form of communication works both
night and day.
• Auditory (sound) communication is fast and
effective, and can be easily modified.
Use of a pheromone
A chimpanzee with a researcher
• Visual communication involves signals used by
species active during the day.
• For example, defense and courtship displays
are exaggerated and are always performed in
the same way so their meaning is clear.
• Tactile communication occurs when one animal
touches another.
• Honeybees use a combination of methods of
communication, but especially tactile ones, to
impart information about food distance and
direction.
Communication among bees
Altruism Versus Self-Interest
• Altruism is behavior that has the potential to
decrease the lifetime reproductive success of
the altruist while benefiting the reproductive
success of another member of the group.
• Genetic relatedness appears to underlie
altruism; an altruistic act is best targeted at a
close relative sharing the same genes.
• Direct selection is natural selection that can
result in adaptation to the environment when
the reproductive success of individuals
differs.
• Indirect selection is natural selection that can
result in adaptation to the environment when
individuals differ in their effects on the
reproductive success of relatives.
• Inclusive fitness of an individual includes
personal reproduction and reproduction of
relatives.
Inclusive fitness
• Inclusive fitness is measured by the genes
an individual contributes to the next
generation, either directly by offspring or
indirectly by way of relatives.
• Many of the behaviors once thought to be
altruistic turn out to be examples of
indirect selection and are adaptive.
• Song learning in birds involves various
elements, including a sensitive period
during which the bird is primed to learn, and
the effect of social interactions.
• Since genes influence the development of
behavior, it can be assumed that behavioral
traits, such as mate choice, are among
those subject to natural selection.
• Evolution by sexual selection can occur
either when females have the opportunity
to select among potential mates, and/or
when males compete among themselves
for access to reproductive females.
• Territoriality includes the type of defensive
behavior needed to defend a territory.
• Vocalization and displays, rather than
outright fighting, may be sufficient to
defend a territory.
• Animals that form social groups use
chemical, auditory, visual, or tactile
communication, and communication fosters
cooperation that benefits both sender and
receiver.
• In most cases, individuals of a society act to
increase their own reproductive success by
helping relatives who share their genes.
• Altruistic behavior has a benefit in terms of
inclusive fitness.
Lab Ex 17: Porifera (sponges)
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•
Sponges are mainly marine animals at the cellular
level of organization.
• The sponge body wall has:
1) an outer layer of epidermal cells; a middle layer
consisting of semi-fluid matrix where amoeboid cells
transport nutrients, produce spicules and form sex
cells
2) and an inner layer of collar cells with flagella that
wave water through pores and out an osculum.
Collar cells also engulf food particles and pass them
to amoeboid cells.
• Sponges are classified according to type of
spicules.
• Chalk sponges have spicules made of calcium
carbonate; glass sponges have spicules that
contain silica.
• Most sponges also contain spongin fibers
made of collagen.
• Sponges are sessile filter feeders.
• They reproduce asexually by budding or by
fragmentation.
Lab Ex 18: Cnideria
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• Cnidarians are mostly coastal marine animals with a
tissue level of organization and radial symmetry.
• They may be a polyp or a medusa or may alternate
between the two forms.
• They have cnidocytes that discharge stinging
nematocysts, long threads that may have spines and
contain a poison.
• Cnidarians are diverse and include sea anemones,
coral, and jellyfishes.
Cnidarian diversity
• Hydra
• A hydra polyp has an outer layer of epidermis derived
from ectoderm and an inner layer called gastrodermis
derived from endoderm.
• Mesoglea lies between the two layers and contains a
nerve net that communicates with muscle fibers so that
the animal is able to move.
• Digestion begins in a gastrovascular cavity and finishes
in gastrodermal cells.
• Nutrients and gases are distributed from layer to layer
by diffusion.
Anatomy of Hydra