ESPM 40 Final Exam

"Intrinsic Yield" vs. "Operational Yield" of crops?

Intrinsic is much higher than operational due to losses from weeds, insects, and pathogens. Insects are responsible for largest reductions in plant productivity.

Agrobacterium tumefaciens

casues crown gall disease by introducing hormone-producing genes into the plant genome during infection

Bacillus thuringiensis toxin

expressed in corn to inhibit corn root and ear worms

Specificity of Bt toxin

may allow reduction in some other pesticides because it facilitates natural biological control

Issue of horizontal transfer of genes in plants?

genes for insect resistance could well confer advantage to weedy recipient

The solution to gene escape?

Transplastomics - chloroplast targeted genes. No transmission through pollen, plastids are maternally inherited - rarely found in pollen (male gamete)

Transgenic vectors

i.e., the construction of transgenic mosquitoes that combine all genetic features to produce highly penetrant, dominant, late-acting, female-specific lethality.

How much food relies on animal pollination?

about a third, particularly fruit and vegetables, coffee and cocoa; also wild flowers need to maintain genetic diversity

Process of pollination?

move pollen from stamen (male) to stigma, successful pollen rain (gametophyte) containing the male gametes gets transferred, germinates and its pollen tube grows down the style to ovary, develops into a seed (embryo).

Angiosperms

flowering plants, approx. 250,000 species

Abiotic pollination

generally by wind

Biotic pollination

animal-mediated

Self-compatible or cross-pollination?

some plants are self-incompatible and need cross pollination to reproduce, others can self pollinate but benefit from cross pollination

Which pollinator is most relied upon?

European honey bee

Bees in relation to wasps?

hymenoptera, bees are highly derived wasps that gave up carnivorous lifestyle for pollen and nectar

When did we begin to use honeybees for pollination?

1980s

Native bees

1500-1700 species, some are colonial but most are solitary, parasitic

Why don't we rely on native pollinators for crop pollination?

bees need nectar to power flight and pollen to feed the next generation, and a place to nest; the central valley is not a great place for bees - not much floral diversity or places to nest

Colony collapse disorder

bees would leave the hive and not come back, up to 85% of hives were lost - bee shortage

Cause of colony collapse disorder?

the way we do agriculture, our food system, the landscape is bad for honeybees and humans, bringing hives together increases spread of pathogens and parasites, pest outbreaks require pesticides to be sprayed

Hedgerows

planting native plants to make landscape better for bees; more nectar and nesting sites; increase species richness, abundance of rare species, species persistence and colonization,

Why are insecticides needed?

insects without control would destroy a third of crops, we need food for an expanding population, insects transmit diseases of humans, livestock and plants

Safe insecticides?

Insect specific molecular targets: Bt - ingested by larva acts on gut permeability, muscle Ca2+ channel; mammal detoxifies much faster

Types of insecticides?

contact insecticides - penetrate cuticle; stomach poisons- ingested; insect growth regulators - block development but slowly; protection by detoxifying enzymes

Lipophilic nerve and muscle poisons

cuticle - wax over chitin/protein contact insecticides are organosoluble, chitin synthesis inhibitors are growth regulators - slow; nerve - about 80% of insecticide action, sensitive, coordination, selective, poor detoxification, rapid action; muscle - Ca2+ channels block contraction

Insecticides target molecular interactions

targets are enzyme receptors, designed to reach the target and bind with high affinity, nicotinic receptor

Health benefits of entomophagy?

alternatives to mainstream meats, rich in protein and good fats and calcium iron zinc, already part of many diets

Environmental benefits of entomophagy?

emit fewer GHGs and ammonia, does not require land clearing for production, efficient at converting feed into protein (cold-blooded), can be fed organic waste, less water, few animal welfare issues, low risk of zoonotic infections

Livelihood of entomophagy?

harvesting/rearing is low-tech, low-capital investment for even poorest of society, women and landless

Why is entomophagy more common in the tropics?

larger insects, significant numbers easy to harvest, variety year round, harvests and locations are predictable

Insects as a resource?

not unlimited: edible insects are also hosts or prey of other insects, overexploitation, damage to habitat - forest degradation, pollution

Conservation and management of insects

important but little paid attention to, promotes growth of insects through labor and skill but not cultivation (tending), palm trees felled deliberately

Diptera

flies

Hymenoptera

ants, bees, wasps

Hemiptera

true bugs

Orthoptera

grasshoppers, crickets

Lepidoptera

moths and butterflies

Odonata

dragonflies and damselflies

Coleoptera

beetles

Evolution in 3 words

descent with modification

Why do insect species have sexual reproduction?

recombination, genetic variation

Refuge area - refuge concept?

pests will build resistance so, integrate GMO corn with adjacent non GMO corn, resistant breeding with non resistant = rr - small population of resistance (25%)

The insecticide treadmill?

the treadmill represents the negative side effect of pesticides; as you use more pesticides, insects will evolve resistance; the greater the selective pressure, the faster resistance is evolved

Algor mortis

Change in temp following death

What are drawbacks of Exoskeleton?

1. Growth must occur in distinct stages 2. size limiting factors and surface area to volume problem: 3. mass increased faster than muscle strength 4. over stress of exoskeleton leads to buckling 5. pin joints are under excessive stress 6. limits to respiration rate