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Insect Midterm 2
| Question | Answer |
|---|---|
| Symbiosis: | Foundation of interspecies relationships involving plants, insects, fungi, and bacteria |
| Symbiotic relationship | interaction between 2+ species |
| Vast insect diversity | vast diversity of insects has led to many kinds of interspecies interactions. Diversity of species also has led to the coevolution of many characteristics necessary for these relationships. Allows insects to coexist and fulfill ecosystem roles. |
| What insects rely on plants | Food resources, Oviposition (egg-laying) sites, Habitats, Camouflage. These relationships are constantly shaped by coevolution. |
| Coevolution | Occurs when 2+ species reciprocally impact each other's evolutionary trajectory. Each species exerts selective pressure on the other. Encompasses many relationship types. |
| Types of Insect-Plant Interactions: | Antagonistic (Insect Herbivory), Antagonistic (Insectivory), Mutualism (Pollination). |
| Antagonistic (Insect Herbivory): | Plants = important food sources for insects. ~50% of all insect species are phytophagous (plant-feeding). |
| Antagonistic (Insectivory): | Insects as food for plants. Insectivorous plants are specialized plants that capture and digest insects while also photosynthesizing. |
| Mutualism (Pollination): | Insect evolution linked to flowering plant evolution. More than 2/3 of flowering plants are insect-pollinated. |
| Insect Mouthparts Components | labrum, mandibles, maxillae, labium. Mouthpart modifications indicate food resources. Many holometabolous insect larvae have chewing mouthparts; adults may not because larvae need to grow rapidly while adults focus on reproduction. |
| Mandibulate (Chewing) Mouthparts: | a basic type of mouthpart from which others are derived. Insects use mandibles to physically bite, chew, and rip plant material. The damage is that they reduce leaf surface for photosynthesis, disrupting plant growth. |
| Piercing-Sucking Mouthparts | Characteristic of order Hemiptera, Modified mandibles and maxillae form stylet (sheathed within labium). Can pierce plant tissue to fluids: xylem and phloem. Contains 2 channels → one for outward movement of saliva and inward movement of liquid. |
| Feeding Challenges for Piercing-Sucking Mouthparts: | Phloem sap is high sugar (carbon), low amino acids (nitrogen), xylem is even lower in nutrients. Must consume large quantities to meet nutritional requirements. Minimal digestion needed (only sucrose hydrolysis). |
| The Filter Chamber (Adaptation to Dilute Diet): | Part of gut looped is back on itself as countercurrent exchanger, separates nutrients from excess water and sugar, residue (mostly water + sugars) excreted as honeydew, well-developed in insects feeding on xylem and phloem. |
| Phloem Feeding Adaptations | Phloem-feeding Hemiptera have gut symbiotic microorganisms, Convert amino acids from sugar. Example: Aphids house Buchnera bacteria (transferred vertically to offspring). |
| Vectors of Plant Diseases: | Piercing-sucking insects can transmit plant pathogens in saliva while feeding, a vector refers to an organism that carries a pathogen, many plant diseases transmitted by Hemiptera, host plants dictate transmission efficacy. |
| Hemiptera Psyllids: | small, sap-feeding insects in the order Hemiptera, also known as jumping plant lice or plant suckers, that possess piercing-sucking mouthparts. Phloem feeders tend to be very host-specific. |
| Asian citrus psyllid: | vector of citrus greening disease, bacteria coevolved with vectors. Reduces citrus quality, flavor, production; causes tree death. Found in Florida (1998), spread across the southern US. |
| Agricultural Pests: | Many plant-feeding insects cause economic damage to crops, Pests and diseases cause up to 40% crop yield losses annually worldwide, Lepidopteran larvae: Among worst chewing agricultural pests, Hemipteran whiteflies: Can vector 80+ plant viruses. |
| Influence of Crop Domestication | Humans began domesticating plants >10,000 years ago, Crop domestication is the human-mediated process of altering plant traits for human preferences, Enabled shift from hunter-gatherer to agricultural-based societies. |
| Domestication-Driven Trait Changes | Larger fruits and seeds, Improved taste, Higher yield, Increased nutritional content, Uniform growth, Enhanced shelf-life. |
| Which Would You Rather Eat | teosinte (wild corn ancestor) has small, tough seeds while modern domesticated corn has large, nutritious kernels. "Which would you rather eat? Insects agree!" shows that domestication made crops more appealing and vulnerable to insect pests too. |
| Consequences for Pest Management | Domesticated plants are MORE susceptible to insect herbivory than wild counterparts. Due to increased nutritional content, reduced plant defenses, reduced genetic diversity, increased dependence on insecticides → insecticide resistance. |
| Modern Pest Management (Shifting Paradigm): | There is a growing global interest in sustainable agriculture. |
| Integrated Pest Management (IPM): | Science-based, environmentally sensitive approach to pest management. Uses information on pest biology and life cycles to choose the most economical and least hazardous pest control methods. |
| Plant-Herbivore Coevolution: | Relationship between insects and plants involves constant evolutionary pressure from both sides. Insects continuously develop new ways to attack and consume plants, while plants evolve defensive mechanisms to prevent being eaten. Leads to coevolution. |
| Plant’s Physical Defenses Against Herbivory: | Thorns or spines, trichomes (hair-like structures) that can be either simple hairs or sticky structures that trap or impede insects |
| Plant’s Chemical Defenses Against Herbivory: | Secondary metabolites that are toxic or deterrent to herbivores, and Herbivore Induced Plant Volatiles (HIPVs) that function as an indirect defense by attracting natural enemies of herbivores, a “call for help” |
| Example of Plant Chemical Defenses: | A notable example is almond plants, which produce the toxic compound cyanide when their tissues are damaged through processes like insect chewing. |
| Steps of Herbivore Induced Plant Volatiles (HIPVs): | 1) Herbivores feed on the plant, 2) the damaged plant performs volatile emission, 3) these volatiles attract natural enemies of the herbivores 4) The natural enemies attack and consume the herbivores, protecting the plant |
| How Insects Overcome Plant Defenses: | they can use detoxification enzymes, behavioral adaptations, and mutations |
| Detoxification Enzymes | Some insect guts contain specialized enzymes that break down plant toxins into harmless byproducts. |
| Behavioral Adaptations | Certain insects have developed behaviors that allow them to avoid or circumvent plant defenses. |
| Mutations | Genetic mutations can make insects insensitive to specific plant defensive compounds. |
| Case Study (Monarchs & Milkweeds): | Monarch butterfly caterpillars can consume milkweed plants that are toxic. They disrupt potassium/sodium ATPase pumps, but monarch caterpillars have evolved mutations that make them insensitive. They can even store them, becoming toxic to predators. |
| Case Study (Tobacco Cutworm & Tobacco Plant): | Tobacco cutworm caterpillars feed on tobacco plants containing nicotine, which disrupts the nervous system of insects. These caterpillars have evolved cytochrome P450 enzymes in their digestive system that detoxify nicotine into harmless byproducts. |
| Case Study (Macaranga Plants & Specialist Caterpillars): | Macaranga plant leaves are covered with hooked trichomes that damage insects. However, specialized caterpillars have evolved the ability to walk over these hooked trichomes without injury. This represents a behavioral adaptation. |
| Insecticide Resistance | occurs when insect populations evolve to become less responsive to insecticides used for pest control. Insects use the same mechanisms that allow them to overcome plant defenses to develop resistance. The Colorado potato beetle is a striking example. |
| Antagonistic Interactions (Insectivorous Plants): | While most plants are exclusively autotrophs, some plants have evolved additional heterotrophic behaviors. Insectivorous plants like pitcher plants and Venus flytraps capture and digest insects to supplement their nutritional needs. |
| Characteristics of Insectivorous Plants | tend to grow in nutrient-poor environments such as bogs and wetlands, can shift between photosynthesizing and consuming insects depending on nutritional availability, Have evolved features that allow them to thrive in nutrient-limiting niches |
| Attracting Insects: | Insectivorous plants use various attractants including nectar, scent, and bright coloration to lure prey. Leaves are adapted to trap insects often using specialized structures like hair and glands. |
| Trapping Mechanisms | Different species employ trapping structures like snap traps (Venus flytraps use leaves that snap shut), sticky traps: Sundews use adhesive secretions on their leaves, and pitfall traps: Pitcher plants use deep cavities filled with digestive fluid |
| Digestion of Insects | Once trapped, plants use digestive enzymes to break down insects and absorb nutrients. Insects provide insectivorous plants with essential nutrients, serving as the primary source for nutrients except carbon, which still comes from photosynthesis. |
| Bladderworts (genus Utricularia): | aquatic insectivorous plants with unique characteristics. They lack roots entirely, have horizontal floating stems containing ‘bladders,’ which use vacuum mechanisms to rapidly suck in and trap small aquatic invertebrates. |
| Ecological Role of Insectivorous Plants | Insectivorous plants contribute to ecosystems by helping control insect populations, influencing species composition within ecosystems, contributing to nutrient cycling in nutrient-poor environments, filling unique ecological niches |
| Pollination: | Transfer of pollen from the anther to the stigma, Sexual reproduction, Allows for fertilization of the ovules → seeds, contained within the ovary, A fruit is an enlarged ovary. |
| Self-Pollination | Self-pollinating plants, like tomatoes, have both male and female reproductive organs in the same flower, allowing them to be fertilized by their own pollen. |
| Cross pollination | Some plants need pollen from a separate individual. An example is apples. |
| Animal Pollinators & Increased Crop Yields | Many crops REQUIRE an animal pollinator, Others do not but could still benefit, Example: Bees can increase soybean yields by 20%. 84% of global crops have increased yields from insect pollinators. |
| Incomplete Pollination | Incomplete pollination causes uneven fruit shape. Apparent in fruits with multiple seeds (each pistil leads to at least one ovule that needs to be fertilized). |
| Why does Incomplete Pollination lead to Uneven Shapes? | A plant's growth is determined by hormonal signals released by developing seeds. If only some of the ovules are fertilized, the fruit will only expand and develop properly in the areas where seeds are forming. |
| Pistil | the female organs of a flower, comprising the stigma, style, and ovary. |
| Pollen Transfer | As pollinators collect nectar from flowers, they pick up pollen. While some insects intentionally collect pollen as a food source, pollination is accidental. The vast majority of pollinators are insects! (99% of pollinator species). |
| Bees as Pollinators | Over 20,000 of bee species, Monophyletic clade → Anthophila, Many specialized to eat certain plants, While many people associate bees with social living, only a minority of species form colonies. The vast majority of bees are solitary. |
| Apple Pollination | Need cross pollination, Honeybees pollinate most apple flowers, But native bees can further increase yields, Native bees provide a failsafe for honeybees lost to colony collapse |
| Native Bees | Native to a specific range, not introduced (Honeybees are a non-native species in North America). Many different body sizes, shapes, colors, and behaviors. Majority solitary, but some are sub-social or primitively eusocial |
| Are Honeybees Native? | Native bees are species vital to ecosystems and agriculture, unlike the non-native honeybee. While honeybees were introduced to North America by European settlers, native bees have evolved alongside native plants and are highly effective pollinators. |
| Polylectic Pollinators | Generalist pollinators, Collect pollen from a wide variety of plant species, Example: Honeybees (Apis mellifera), Pollinate more than 130 types of crops. |
| Oligolectic Pollinators | Specific pollinators, Preference for pollen from only a single family or genus, Unique adaptations to pollinate specific flowers, Example: Squash bees are specialists of Cucurbita (squash and gourds) |
| Bee Nutrition | Nectar (carbohydrates), Pollen (protein), Bees collect a ratio of both food sources to meet their nutritional goals |
| Emergence Timing | Seasonal emergence of different bee species, Correlated with food sources, The crops we eat also have varied blooming times, Early season bees provide pollination before honeybees start to forage |
| Buzz Pollination (Sonication): | Vibration of thorax releases pollen from anthers, Used by bumblebees and other native bees such as Augochloropsis, Especially helps self-pollinating crops, Electric toothbrush mimics buzz pollination, used on tomato flowers. |
| Bombus impatiens — The Common Eastern Bumblebee: | Native pollinator in Eastern North America, Favor colder climates, can forage earlier and later in the season, Primitively eusocial |
| Primitively eusocial | have a colony structure that meets the basic criteria for eusociality but often lacks distinct, permanent castes and morphological differences between queens and workers. Roles can be flexible, and workers may have the ability to reproduce. |
| Eusocial Colony | showing an advanced level of social organization, in which a single female or caste produces offspring and nonreproductive individuals cooperate in caring for the young. Only a few hundred individuals per nest. Worker bees are sterile. |
| Bee Life Cycle | Queens diapause over the winter, Emerge the following spring to start a new colony, Previous colony dies out (annual colonies) |
| Bombus impatiens Pollination | Coevolved with native plants in Eastern North America, Use buzz pollination to pollinate a wide variety of commercial crops, Used in greenhouses to pollinate fruit crops, especially tomatoes |
| Buzz Pollination | a method where insects like bumblebees use powerful vibrations from their flight muscles to shake pollen from flowers with poricidal anthers, releasing sticky pollen that other pollinators can't access. |
| Commercial Bumblebees | Captive bumblebee colonies used in greenhouses. Increase fruit yield and shape quality. You can buy different species online depending on region → in North America, you can only get Bombus impatiens because that’s the native species. |
| Pollen Baskets (Corbicula → Bumblebee Morphological Adaptation): | Structure for carrying pollen on the tibia of the hind legs, Wet pollen with nectar to make it stick, Found in family Apidae: includes honeybees and bumblebees, Polished cavity with fringed hairs |
| Fuzzy Bodies (Bumblebee Morphological Adaptation): | Pollen sticks to hairs on body, Hair also provides insulation from the cold, Allows bumblebees to forage in colder temperatures than honeybees |
| Pollinators Under Threat (Reasons): | Death by a thousand cuts: no one single cause for pollinator declines Mix of factors: Pesticides, climate change, habitat loss, disease, drought, pollution etc. 28% of bumblebee species in North America are considered threatened |
| Climate Change & Bees | Bumblebees may continue to move to cooler latitudes due to increasing temperatures. Climate change affects bees by driving range shifts in bumblebees, creating a mismatch between bee emergence and floral resources, and causing population declines. |
| Toxic Nectar | Plants absorb toxins from the environment, Heavy metals and systemic pesticides like neonicotinoids accumulate in nectar, Bees ingest the toxins |
| Sub-lethal effects (Bees & Toxins): | foraging and learning disruption |
| Lethal effects (Bees & Toxins): | death |
| The European Honeybee, Apis Mellifera: | generalist pollinator, model organism for social behavior — lives in eusocial communities. |
| The Superorganism (Bees): | colony members are comparable to how cells make up a single biological unit. The human body is made up of skin cells, kidney cells, etc. The colony is made up of queens, drones, and workers. NOT DRIVEN BY INDIVIDUAL BEHAVIORS. |
| Bee Colony | highly organized social structure consisting of a queen, drones, and thousands of work bees that work together as a single organism. |
| The Queen | reproductive unit of the hive, can lay up to 2,000 eggs per day. Spermatheca allows for long term storage of sperm from multiple males. Elongated body and larger abdomen. Uses pheromones to prevent worker reproduction and elicit retinue behavior. |
| Drones | haploid males, robust stocky body, large thorax, eyes meet at the top of the head, one purpose → mate then die. |
| Worker Bees: | colony labor force → care for brood and queen, construct comb and care for the structural integrity of the hive, thermoregulate, collect resources. Most numerous members of the hive, non-reproductive. |
| Caste Differentiation | reproductive division of labor in female bees, drones do not experience division labor = not a caste. Case differentiation is heavily influenced by larval nutrition. |
| Caste Differentiation (Larvae & Eggs): | diploid eggs are genetically identical, workers build worker or queen-specific cells for the queen to lay her eggs in, queen larvae are kept on a diet of royal jelly. |
| Royal Jelly | contributes to an activation of genes that are associated with queen-specific traits. |
| Task Allocation: Nurse Bees: | typical younger bees, care for the queen and broad, construct comb, clean the hive, process nectar |
| Task Allocation: Forager Bees: | at nurse’s age, they start guarding the entry and take orientation flights to help develop navigation skills. Foragers collect water, resin, nectar, and pollen. Bees that forage for food may be nectar or pollen-biased. |
| Nectar: | carbohydrate source |
| Pollen: | protein source |
| Waggle Dance | communication is essential for colony success – the queen and brood use chemical signals to communicate their needs to workers. Some argue that waggle dance is an effective way for foragers to communicate the distance and direction of floral resources. |
| Waggle Dance Effectiveness | many bees fail to decode the dance or completely ignore it. Bees do ‘dance,’ but its importance or effectiveness in communication is debated. |
| Task Allocation: Role Reversal | foragers can transition back into nurses, generally occurring when bees swarm. Swarming = colony reproduction. Old queens leave with mostly reverted nurses to help set up a new hive. |
| Task Allocation: Precocious Foraging | stress hives engage in precocious foraging, nurses transition to foragers earlier, limits behavioral and learning development (bees do not learn landscape features needed for navigation, less successful foraging trips, more prone to predation). |
| Colony Collapse (CCD): | precocious foraging is only a piece of the puzzle, in 2006-2007, beekeepers noticed an absence in worker bees, queen and brood are unable to survive without worker contributions. |
| CCD Contributors | poor nutrition, habitat fragmentation, monoculture, urbanization, pathogens & parasites, pesticide uses. From beekeeping practices: overcrowding and migratory transport. |
| Times Article | The TIMES released an article titled, “A World Without Bees” that emphasized the importance of bees and the loss of them. One minor issue is that the cover only depicted one bee instead of multiple species. |
| Beekeeping | hobby beekeepers, manage a few hives. Recent rise in urban beekeeping in order to protect the bees, like in New York. |
| Large-Scale Beekeeping | commercial, can manage hundreds of hives, provide seasonal pollination services, while it supports agriculture and provides economic benefits, it can also pose serious threats to the health of honey bees and native wild pollinator populations. |
| How is Large-Scale Beekeeping Harmful? | It can cause increased stress on honeybees, unsustainable colony losses, increased pesticide exposure. |
| Save The Bees | honeybees were introduced to the US by European colonists. Less effective pollinators than native bees. Managing pollinator populations for short-term agricultural benefit can endanger native bee species and their broader ecological role. |
| Honey Bees Vs. Native Bees | honeybee colonies are of thousands of individuals, paired with the effects of large-scale beekeeping practices and environmental stressors, honeybees compete with native bees and add stress to already declining native bee populations. |
Created by:
smurtab