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+ Exam #2: Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today 1

Exam #2: Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

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Exam #2: Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today. Chapter 16: Population Genetics and Evolution. Robert E. Ricklefs The Economy of Nature, Fifth Edition. Maintenance of Genetic Variation 1. A paradox: - PowerPoint PPT Presentation

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Page 1: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

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Exam #2: Dec 22. 2-3.30 pm. Exam HallChapters: 7, 10, 11, 12, 13, 14, 16(Adib Kfoury proctoring)

Homework assignment: due today

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Page 2: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

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Chapter 16: Population Genetics and Evolution

Robert E. RicklefsThe Economy of Nature, Fifth Edition

Page 3: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+Maintenance of Genetic Variation 1A paradox:

natural selection cannot produce evolutionary change without genetic variation

however, both stabilizing and directional selection tend to reduce genetic variation: how does evolution continue under such circumstances? does availability of genetic variation ever limit the rate of

evolutionary change?

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Page 4: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+Maintenance of Genetic Variation 2 Mutation and migration supply populations with

new genetic variation. Spatial and temporal variation tend to

maintain variation by favoring different alleles at different times and places.

When heterozygotes have a higher fitness than homozygotes, the relative fitness of each allele depends on its frequency in the population (frequency-dependent selection): alleles are selected for when at low frequency and

against when at high frequency heterozygote superiority is also called heterosis

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Page 5: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ How much genetic variation?

About 1/3 of genes that encode enzymes involved in cellular metabolism show variation in most species: about 10% of these are heterozygous in any

given individual however, most genetic variation is apparently

neutral or has negative effects when expressed thus most variation has no fitness consequences

or is subject to stabilizing selection

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Page 6: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Genetic Variation is Important

Under changing environmental conditions, the reserve of genetic variation may take on positive survival value.

There seems to be enough genetic variation in most populations so that evolutionary change is a constant presence.

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Page 7: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Evolutionary Changes in Natural PopulationsEvolutionary changes have been widely

documented, particularly in species that have evolved rapidly in the face of environmental changes caused by humans: cyanide resistance in scale insects (Chapter 9) pesticide and herbicide resistance among

agricultural pests and disease vectors increasing resistance of bacteria to antibiotics

In each case, genetic variation in the gene pool allowed these populations to respond to changed conditions.

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Page 8: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Useful Conclusions from Population Genetics StudiesEvery population harbors some genetic

variation that influences fitness.Changes in selective factors in the

environment are usually met by evolutionary responses.

Rapid environmental changes caused by humans will often exceed the capacity of a population to respond by evolution; the consequence is extinction.

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Page 9: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

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Chapter 17: Predation and Herbivory

Robert E. RicklefsThe Economy of Nature, Fifth Edition

Page 10: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Consumer-Resource InteractionsAll life forms are both consumers and

victims of consumers.Consumer-resource interactions

organize biological communities into consumer chains (food chains): consumers benefit at the expense of their

resources populations are controlled from below by

resources and from above by consumers

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Page 11: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Some Definitions

Predators catch individuals and consume them, removing them from the prey population.

Parasites consume parts of a living prey organism, or host: parasites may be external or internal a parasite may negatively affect the host but does

not directly remove it from the population

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Page 12: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+More Definitions

Parasitoids consume the living tissues of their hosts, eventually killing them: parasitoids combine traits of parasites and

predatorsHerbivores eat whole plants or parts

of plants: may act as predators (eating whole plants)

or as parasites (eating parts of plants): grazers eat grasses and herbaceous vegetation browsers eat woody vegetation

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Page 13: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Parisitoid wasps develop inside the larvae or pupae of other insects

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Page 14: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Detritivores occupy a special niche. Detritivores consume dead organic material,

the wastes of other species: have no direct affect on populations that produce

these resources: do not affect the abundance of their food supplies do not influence the evolution of their resources

are important in the recycling of nutrients within ecosystems

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Page 15: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Predators have adaptations for exploiting their prey. Predators vary in size relative to their prey:

predators may be much larger than their prey (whales are far larger than krill and small fish)

prey are rarely much larger than their predators: beyond a certain prey size, a predator cannot successfully

subdue and consume the prey cooperative hunters are an exception, taking prey

substantially larger than themselves

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Page 16: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Form and Function Match Diet

Form and function of predators are closely tied to diet: vertebrate teeth are adapted to dietary items:

horses have upper and lower incisors used for cutting fibrous stems of grasses, flat-surfaced molars for grinding

deer lack upper incisors, simply grasping and tearing vegetation, but also grinding it

carnivores have well-developed canines and knifelike premolars to secure and cut prey

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Page 17: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ A predator’s form and function are closely tied to its diet. (a) upper incisors are used to cut plant material; (b) flat-surfaced molars for grinding plant material; (c) knifelike premolars secure prey and tear flesh

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Page 18: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+More Predator Adaptations

The variety of predator adaptations is remarkable: consider grasping and tearing functions:

forelegs for many vertebrates feet and hooked bills in birds distensible jaws in snakes

digestive systems also reflect diet: plant eaters feature elongated digestive tracts with

fermentation chambers to digest long, fibrous molecules comprising plant structural elements

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Page 19: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+Distensible jaws: shift the articulation of the jaw with the skull from the quadrate bone to the supratemporal

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Page 20: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Digestive tracts of consumers are adapted to their diets. Digestive organs of herbivores > carnivores

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Page 21: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Prey have adaptations for escaping their predators.

Prey escape mechanisms are remarkably diverse: in animals:

swift escape capability of early predator detection hiding or seeking refuge sensitive mechanisms for detecting predators

in plants: thorns and defensive chemicals that dissuade herbivores

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Page 22: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ A bombardier beetle sprays a noxious liquid at the temperature of boiling water toward a predator

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Page 23: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Crypsis and Warning Coloration

Through crypsis, animals blend with their backgrounds; such animals: are typically palatable or edible match color, texture of bark, twigs, or leaves are not concealed, but mistaken for inedible objects

by would-be predators

Behaviors of cryptic organisms must correspond to their appearances.

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Page 24: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Cryptic appearances (a) mantid; (b) stick insect; (c) lantern fly

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Page 25: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+Warning Coloration

Unpalatable animals may acquire noxious chemicals from food or manufacture these chemicals themselves: such animals often warn potential predators with

warning coloration or aposematism: predators learn to avoid such animals after

unpleasant experiences certain aposematic colorations occur so widely that

predators may have evolved innate aversions

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Page 26: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Unpalatable organisms 26

Page 27: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+Why aren’t all prey unpalatable? Chemical defenses are expensive, requiring

large investments of energy and nutrients. Some noxious animals rely on host plants for

their noxious defensive chemicals: not all food plants contain such chemicals animals utilizing such chemicals must have their own

means to avoid toxic effects

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Page 28: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Batesian MimicryCertain palatable species mimic unpalatable

species (models), benefiting from learning experiences of predators with the models.

This relationship has been named Batesian mimicry in honor of discoverer Henry Bates.

Experimental studies have demonstrated benefits to the mimic: predators quickly learn to recognize color patterns

of unpalatable prey mimics are avoided by such predators

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Page 29: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+Harmless mantid (b) and moth (c) evolved to resemble a wasp (a)

Page 30: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+Müllerian Mimicry

Müllerian mimicry occurs among unpalatable species that come to resemble one another: many species may be involved each species is both model and mimic process is efficient because learning by

predator with any model benefits all other members of the mimicry complex

certain aposematic colors/patterns may be widespread within a particular region

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Page 31: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Costa Rican butterflies and moths

Page 32: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Parasites have adaptations to ensure their dispersal.Parasites are usually much smaller than

their hosts and may live either externally or internally: internal parasites exist in a benign environment:

both food and stable conditions are provided by host parasites must deal with a number of challenges:

host organisms have mechanisms to detect and destroy parasites

parasites must disperse through hostile environments, often via complicated life cycles with multiple hosts, as seen in Plasmodium, the parasite that causes malaria

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Page 33: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Parasite-Host Systems: A Balancing ActThe parasite-host interaction

represents a balance between parasite virulence and host defenses: immune system of host can recognize and

disable parasites but parasites may multiply rapidly before an

immune response can be deployed

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Page 34: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Parasites may defeat a host’s immune response. Circumventing the host’s immune system is a

common parasite strategy: some parasites suppress the host’s immune system

(AIDS virus) other parasites coat themselves with proteins that

mimic the host’s own proteins (Schistosoma) some parasites continually coat their surfaces with

novel proteins (trypanosomes)

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Page 35: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Cross-Resistance

Some parasites elicit an immune response from the host, then coat themselves with host proteins before the immune response is fully mobilized: initial immune response by host may benefit the

host later when challenged by related parasites in a phenomenon known as cross-resistance

Once an immune response has been elicited, antibodies can persist for a long time, preventing reinfection.

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Page 36: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Plants have antiherbivore defenses.Plant-herbivore “warfare” is waged

primarily through biochemical means.Full spectrum of plant defenses includes:

low nutritional content of plant tissues toxic compounds synthesized by the plants structural defenses:

spines and hairs tough seed coats sticky gums and resins

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Page 37: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Spines protect the stems and leaves (a) cholla cactus and (b) prickly pear cactus

Page 38: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Digestibility

Animals typically select plant food according to its nutrient content: especially important to young animals, which

have high demands for proteinSome plants deploy compounds that limit

the digestibility of their tissues: tannins produced by oaks and other plants

interfere with the digestion of proteins some animals can overcome the effect of

tannins through production of digestive dispersal agents

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Page 39: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Secondary Compounds

Secondary compounds are produced by plants for purposes (typically defensive) other than metabolism.

Such compounds can be divided into three major classes: nitrogen compounds (lignin, alkaloids,

nonprotein amino acids, cyanogenic glycosides)

terpenoids (essential oils, latex, plant resins) phenolics (simple phenols)

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Page 40: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Induced and Constitutive Defenses

Constitutive chemical defenses are maintained at high levels in the plant at all times.

Induced chemical defenses increase dramatically following an attack: suggests that some chemicals are too expensive to maintain under

light grazing pressure plant responses to herbivory can reduce subsequent herbivory

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Page 41: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Herbivores control some plant populations. Examples of control of introduced plant pests by

herbivores provides evidence that herbivory can limit plant populations: prickly pear cactus in Australia

controlled by introduction of a moth, Cactoblastis Klamath weed in California

controlled by introduction of a beetle, Chrysolina

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Page 42: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Effects of Grazers and Browsers on Vegetation Herbivores consume 30-60% of aboveground

vegetation in grasslands: demonstrated by use of exclosures limiting access to

vegetation by herbivores

Occasional outbreaks of tent caterpillars, gypsy moths, and other insects can result in complete defoliation of forest trees.

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Page 43: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Summary 1

Among consumers, ecologists recognize predators, parasitoids, and parasites.

Predator-prey relative sizes may vary dramatically.

Predators are well-adapted to capturing prey.Prey avoid predation by avoiding detection

and by means of chemical, structural, and behavioral defenses.

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Page 44: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Summary 2

Batesian mimicry involves an unpalatable model and palatable host.

Müllerian mimicry complexes involve two or more unpalatable species that resemble one another.

Parasites have unique adaptations for their way of life.

Parasites and hosts remain in a delicate balance.

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Page 45: Exam #2:  Dec 22. 2-3.30 pm. Exam Hall Chapters: 7, 10, 11, 12, 13, 14, 16 (Adib Kfoury proctoring) Homework assignment: due today

+ Summary 3

Plants use structural and chemical defenses to deter herbivores.

Some herbivores can detoxify secondary plant compounds, enabling them to consume otherwise toxic species.

Herbivores may control populations of plants at levels far below their sizes in the absence of specialized consumers.

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