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 chordatesInvertebrate 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• 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

Out-of-Africa hypothesisMultiregional continuity 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.

• 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 Summary

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 species-specific 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 white-crowns 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