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108 Cards in this Set
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herbivory |
the consumption of plants by animals |
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economic injury threshold |
amount of damage that causes economic loss |
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insect herbivory |
>99% of herbivore species >99% of plant biomass consumed |
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Major orders of insect herbivores |
1. Coleoptera: beetles, about 90% are specialists on 3 plant families. 2. Lepidoptera: butterflies and moths. 90% are specialists. Monarchs on milkweed; cabbage butterfly on cabbage. Generalists: gypsy moth 3. Diptera: flies - 50% are herbivores, most are specialists 4. Orthoptera: grasshoppers - almost all generalists |
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Leaf cutter ants |
Major herbivore of Central American rainforest Cuts portions of leaves and brings them to ant hill. Grows fungus on leaves and eats fungus |
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Plant Nutritional quality |
Nitrogen limits insect growth. N is 1-7% of plant dry weight because Rubisco needs at least 1% to be functional. Highest in legumes. Insects eat plants with at least 2% N. |
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Phenological changes in leaf nutritional quality |
leaves are most nutritious in the spring and are lower in phenolic compounds. Strong stabilizing selection favors herbivores that are spring feeding. Phenological changes are more common in woody plants than in herbaceous plants. |
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Plant mechanical defenses |
A. Thorns and spines for defense against mammals. eg. Acacia trees and giraffes B. Trichomes - leaf hairs for defense against insects. Non-glandular are like tiny spikes, eg. beans. Glandular secrete oils that may contain toxins, eg. stinging nettle and cannabis. C. basal meristem - for tolerance against grazing mammals. Plant grows from base so that once eaten, the plant can regrow. eg. grasses |
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Plant chemical defenses |
1. Toxicity 2. Deterrence of feeding or oviposition 3. digestibility reduction |
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Toxicity |
contains compounds that will kill or harm the herbivore. eg. black swallowtail will eat wild parsnip but not cabbage or mustard because they contain glucosinolates (sinigrin) which is toxic. |
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Feeding deterrence |
uses chemical compounds to make herbivores not want to eat them. Most toxins are also deterrent because it is more beneficial to prevent feeding than to penalize it. |
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deterrent mimicry |
a plant that does not contain a deterrent compound mimics one that does such that herbivores that do not eat the plant with the deterrent will not. Tomato hornworms without taste receptors will eat non host plants such as dandelions |
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Digestibility reduction |
Protease inhibitors reduce the digestibilities of proteins by insects and mammals. PI's are plant proteins that bind to insect proteins that would break down plant proteins ex. tannins reduce digestibility in mammals |
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Carbon based defenses |
Tannins and phenolics Terpenoids Cardenolides (cardiac glycosides) Furanocoumarins |
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Tannins and phenolics |
- taxonomically widespread -toxic to insects -digestibility reduction in mammals -have aromatic 6 member ring with OH group example: Red maple has a very rare phenolic that protects from caterpillars |
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Terpenoids |
-non-polar, lipid soluble compounds, can pass through membranes -main defense of conifers - very toxic |
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cardenolides (cardiac glycosides) |
-in milkweeds -toxic (nerve cell inhibitors) -sequestered by monarch caterpillars |
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Furanocoumarins |
- in umbellifers - carrot family - toxic when combined with UV to cause DNA cross-linking => grow in sunny areas -contact dermatitis in humans. |
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Nitrogen containing chemical defenses |
Alkaloids Glucosinolates Protease inhibitors more toxic than carbon based on average |
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Alkaloids |
- 6 membered ring with N instead of C -widespread in herbs and some trees -bitter, very toxic -caffeine, nicotine, morphine, cocaine, mescaline, psilocibin -many mimic neuro transmitters |
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glucosinolates |
-in cabbage/mustard familg example: sinigrin mode of action is unknown |
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protease inhibititors |
in legumes (soybeans) because they have sufficient nitrogen to make proteins |
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Why do toxins have a sugar attached in the plant? |
-Limits autotoxicity in plant - Upon ingestion by herbivore, sugar is first ting cleaved off, making the toxin active |
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Temporal Changes in levels of secondary chemicals |
1. Phenological changes - tannins increase as oak leaves mature 2. Induced changes - Short-Term - phenolics in aspen increase quickly after damage. Both damaged and undamaged leaves exhibit increase in tomato. Long-term - phenolics in adventitious shoot resins increase following grazing. Paper birch |
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Theory of Stepwise Chemical Coevolution |
1. Plant evolves Chemical 1. 2. Origin of Plant Family 1 3. Insect Breaks Defense 1 4. Origin of Insect Family 1 5. Plant evolves Chemical 2 6. etc.... |
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Why are so many insect herbivores specialists? |
1. the first insects to counter-adapt have access to a resource without competitors and natural enemies so natural selection favors specialization on the new plant 2. Selection then favors using plant chemicals as feeding and oviposition stimulants 3. In rare cases, specialists evolve the ability to store (sequester) plant defenses for their own protection. May evolve aposematic coloration |
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Adaptations for insects that feed on umbellifers |
nocturnal feeding root feeding leaf rolling thicker exoskeleton |
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Stepwise coevolution example |
Umbellifers have 3 chemicals: Hydroxycoumarins - oldest chem typ Linear furanocoumarins - more recently evolved Angular furanocoumarins - most recently evolved Southern armyworm is a generalist and is killed by all of these toxins; Swallowtail is a specialist and is only affected by Xanthotoxin |
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Indirect defense by plants |
1. Cabbage butterfly parasitoids use allyl glucosinolate to locate caterpillars. It is emitted only by damaged plants. The cabbage butterfly uses sinigrin (glucosinolate) to identify host plants for oviposition 2. Some plants call to parasitoids when attacked. Corn senses volicitin in saliva of corn earworm, emits volatiles throughout plants that attract parasitoids Can be toxic to parasitoids ie alkaloid in tomato leads to deformed wasp antenae |
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Predator |
an animal that kills another animal in order to eat it, and does not live inside the body of its prey |
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Parasitoid |
an animal that develops inside another animal (the host) and consumes and kills its host |
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parasite |
an organism that lives inside or on another organism (the host) feeding on parts of it, usually without killing the host |
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pathogen |
a disease-causing parasite |
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Sit and Wait predators |
relatively immobile short burst activity only often use vibration (pressure) example spiders and filter feeders |
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Active foraging predators |
highly mobile sustained aerobic activity often use binocular vision, olfaction (distance cues) Owls, wolves, lions, starfish |
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Predator-prey cycles |
predator lags behind prey, due to longer gestation and smaller clutch size
lemmings and stoats in Greenland |
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Functional response |
individual predator behavior #prey eaten/predator/time |
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Type I Response |
Causes density-independent mortality until the satiation point |
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Type I Response mortality |
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Type II predator response |
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Type II predator response mortaliy |
as groups of prey grow, percent dying decreaases |
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Type III predator response |
switching predator curve |
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Type III predator response mortality |
barred owls |
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Numerical response |
predator population response #predators/area due to predator aggregation and/or reproduction |
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Evolutionary Responses to Predation |
A. Escape in space and/or time (use a refuge) eg. galling insects, wood-boring beetles, vertically migrating zooplankton B. Mechanical defenses - quills, horns, antlers, shells in animals C, Chemical defenses 1. synthesized defenses - bombadier beetle makes hydrogen peroxide and heat; toxins in bites, stings ie poison gland in hymenoptera; alkaloids in amphibian skin (poison arrow frogs) 2. sequestered defenses (monarchs store cardiac glycosides from milkweed); pipevine swallowtail stores arislochic acids from pipevine D. Modification of appearance - 1. crypsis (camouflauge) moth resembles bark 2. aposematic -warning coloration - poison arrow frog 3. batesian mimicry - toxic model and palatable mimic -monarch model, viceroy mimic. Pipevine swallowtail model, black, spicebush, and red-spotted purple mimic 4. mullerian mimicry - two or more toxic species mimic each other 5. aggressive mimicry - wolf in sheep's clothing. Robber's fly looks like bumblebee, eats bumblebee E. Predator satiation 1. colonial nesting in seabirds 2. selfish herd in mammals-wildebeast. 3 mast reproduction - predators satiated during intermittent mast years like mayfly hatch F. Predator confusion - fish schooling, zebra stripes |
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Mutualism |
mutually beneficial association Very common - 90% of plant species 50% of fungal species. Unknown percentage of animal species |
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How did mutualisms evolve |
from parasitistms example: mycorrhizae evolved from parasitic fungi |
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Obligate mutualism |
mutualist is required for survival Examples: 1. termites and cellulose digesting protozoa - termite can't digest cellulose without protozoa, protozoa not found anywhere else.2. fungus growing leaf cutter ants. 3. wood boring beetles and wood-rotting fungi. 4. some woody plants and mycorrhizal fungi. 5. acacia ants and swollen-thorn acacia trees. 6. lichens-fungus and alga or cyanobacterium. 7. specialized pollination systems ie bucket orchid and male euglossine bees; figs and fig wasps, |
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Facultative mutualism |
mutualism is beneficial but not necessary legumes and rhizobium bacteria most gut symbionts - e. coli in humans => aids digestion, provides vitamin K, some B vitamins many woody plants and mycorrhizal fungi most pollination systems with generalist pollinators |
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Flower |
modified shoot with four whorls of modified leaves Petals, Sepals, Stamens, Carpels |
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Why use a pollinator? |
Disadvantage - risky (but can be self-compatible) Advantages - greater efficiency of pollen transfer, greater pollen dispersal distance, outcrossing |
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Outcrossing |
movement of pollen between individuals of the same species. avoidance of inbreeding depression and using heterozygote advantage |
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Mechanisms that promote outcrossing |
1. dioecy 2. full self incompatibility 3. partial self-incompatibility 4. unisexual flowers on same plant 5. protandry and protygyny |
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Dioecy |
separate male and female plants example - pussywillows |
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Full self-incompatibility |
tomato pollen with same genotype cannot fertilize |
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Partial self incompatibility |
can self pollinate, but own pollen will be at a handicap. bellflower - pollen tubes created by own pollen will lengthen more slowly than tubes created by out cross pollen |
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Unisexual flowers on same plant |
Begonia multiple flowers on plant, some are male, some are female |
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Protandry |
male flower parts mature first so that pollen will not self fertilize fireweed |
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Protygyny |
female flower parts mature first so that they will not be self fertilized plantago |
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constancy |
movement of pollinators between conspecific individuals |
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Plant characteristics that promote constancy |
1. specialized flower shape to restrict access : snapdragon and orchid More common for zygomorphic than for actinomorphic radial species. Some actinomorphic species restrict access by having petals fused into a corolla tube for humminbirds and btterflies 2. Unique flower color, UV patterns - dandelion, morning glory 3. Nectar composition - sugars, amino acids, unique compounds. Orchid was and male euglossine bee sex pheromone; datura alkaloids 4. Unique flower shape and smell. Pseudocopulation in Ophrys and desert wasp |
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Pollinator learning |
with repeated experience with the same flower type, pollinators learn how to better locate and extract rewards. Honeybees learn to locate shapes with rewards Search efficiency increases with experience. Extraction effieciency increases with experience. Memory constraints may prevent simulateneous maximization of efficiency on multiple species |
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Inflorescence |
lots of flowers bunched together may increase pollinator visits per flower (facilitation) Pollinator response to reward variability reduces inbreeding within inflorescence |
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Ecological succession |
the directional, continuous, non-seasonal pattern of colonization and extinction on a site by species populations |
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Heterotrophic succession |
degradative succession external resource input resources are completely used up short time scale example: deer carcass |
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Autotrophic succession |
habitat remains and is occupied during and after succession primary and secondary |
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Primary succession |
at onset, little or no evidence of past communities after volcanoes after glaciers |
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secondary succession |
at onset, habitat contains substantial evidence of past communities after fire old field succession great lakes dune succession |
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3 models of succession |
Facilitation Inhibition Tolerance |
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Facilitation |
early species make it easier for later species to establish post-glacial primary succession in Glacier Bay, AK. Alders fix nitrogen making it easier for spruce trees to establish |
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Inhibition |
early species make it harder for later species to establish primary succession on bare rock in the pacific intertidal zone. Ulva moves on first, prevents Gigartina from moving in |
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Tolerance |
early species have no effect on later species later successional species colonize at same rate with or without early successional species old field succession |
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Describe the pattern of species diversity in old-field succession |
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Ecosystem |
a group of communities and their physical habitats linked by the flow of energy and elements |
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primary production |
the amount of energy (carbon) entering the ecosystem via autotrophs = amount of CO2 fixed by photosynthesis |
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Primary productivity |
rate of primary production |
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Gross primary production |
GPP total amount of carbon fixed by autotrophs (plants) in an ecosystems Global - 103 billion tons of carbon per year. 50% by oceans, 50% by land. NPP for land is 3x grater than that for oceans |
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Net primary production |
net Carbon fixed NPP = GPP - plant respiration =biomass gaied by plants Tropical rainforest and algal beds/reefs have highest NPP per m2 Tropical forests and savannas account for >60% of terrestrial NPP =energy available for heterotrophs NPP = 50% GPP |
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trophic efficiency |
the amount of energy at one trophic level divided by the amount of energy at the trophic level immediately below it. depends on food quality, consumer abundance, and consumer physiology Example: insect herbivore trophic efficiency = 2.5% Mammal herbivores = 2% Carnivores - 10% |
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Why do carnivores have a higher trophic efficiency than herbivores? |
food is easier to digest (less cellulose) easier to convert into biomass (higher N) |
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Why is trophic efficiency higher in aquatic ecosystems than in terrestrial ecosystems? |
higher % of autotrophs consumed in aquatic ecosystems algae are easier to digest than are land plants (less cellulose) algae N>leaf N Aquativ herbivores consume 35% of autotroph biomass (15% trophic efficiency, 5 trophic levels) vs 13% (10% trophic efficiency, 4 trophic levels) in terrestrial ecosystems |
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Nutrient pool |
how much of the nutrient is in that component of the cycle at a given time plant pool might be 10 g N/m^2 |
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flux |
rate of movement of the nutrient between pools eg. soil plant flux might be 5 g N/m^2/yr |
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residence time |
how long a nutrient stays within any component varies among nutrients and ecosystems boreal forests have most soil organic matter; longest residence times Turnover rates of N and P are >100 faster in tropical forest soils than in boreal forest soils |
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Nitrogen cycle |
Major transformations are all done by microorganisms mineralization - breakdown of organic matter into inorganic compounds nitrification - NH4 =>NO3 denitrification - NO3 => N2 |
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Nutrient Cycle Flow |
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Nitrogen cycle flow |
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Species richness |
number of species in the community |
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evenness |
similarity of relative abundance of species |
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Shannon-Wiener index |
H' = -sum(pi*lnpi) pi = proportion of individuals in the ith species s = number of species in the community leaves out: genetic diversity within populations (evolutionary potential) and between populations (species sustainability) also leaves out functional differences between species, like types of species |
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Factors affecting biodiversity |
1. Abiotic stress - latitudinal variation in biodiversity reflects variation in moisture and temperature, but range may be more important than mean. 2. Species interactions - strong interspecific competition may lead to competitive exclusion (invasive species, like spotted knapweed w/ catechin makes it harder for other species to survive. Predation and herbivory (type 3 predator response increases diversity) Pisaster starfist prefers mytilus which is competitively dominant and therefore makes it possible for other species to survive. 3. Habitat structural diversity - ie greater foliage complexity allows more birds, and insect herbivores 4. Disturbance - intermediate disturbance hypothesis says that disturbance that are not too large or too frequent promote greatest diversity. Tree fall vs. glacier.; boulder size and turning over. |
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Major Threats to Biodiversity |
1. Habitat destruction - Humans have impacted ; 75% of Earth's land surface (agriculture); 10% of forests are designated for biodiversity conservation. Total forest area is decreasing, but the global net loss rate is slowing. 80% gain in China, 25% loss in Brazil. Primary or contributing cause for 85% of threatened birds, amphibians, mammals 2. Climate Change - 1.5d increase=> 10-30% of Earth's species possibly committed to extinction. 3.0d increase=>20-50% of Earth's species possibly committed to extinction 3. Invasive species - 1% of introduced species become invasive, like zebra mussels. Especially damaging on islands - 67% birds on oceanic islands threatened, 17% on continental islands, 8% on continents. No anti-predator behaviors or defenses. Cats have been the worst invasive species. Kill 1.2 billion birds per year. Feral cats on islands are responsible for 14% of bird, mammal, reptile extinctions. Burmese python in Everglades caused 90% reduction in local mammals (rabbits, opossum, fox, bobcat, deer). Climate change will benefit invasives more than native. Gypsy moth in Utah. 4. Overexploitation - involved in 45% of documented animal extinctions. Mammals Harvested for bushmeat and homeopathic medicinal use. Birds, amphibians harvested for pet trade, food. Whales overexploited. Many marine fish, like Atlantic cod. Industrialized fisheries reduce community biomass by 80% in 15 years. Shark finning. Recovery is very difficult for species with low realized r. |
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Vertebrate groups most threatened |
12% of birds 21% of mammals 28% of reptiles >/= 20% of freshwater fish Most vulnerable: amphibians, 32% of species threatened |
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Plant groups most threatend |
33% of gymnosperms ?% angiosperms |
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Reactive conservation |
prioritize high vulnerability environments, like Brazilian Cerrado, Andes Mtns, African savannah, Mediterranean, most of India, south Pacific islands. |
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Proactive conservation |
prioritize areas with current low vulnerability Picks Amazonas, Northern Canada, Southwest US, African rainforest, northern Australia. Inverse of reactive places. |
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Coral triangle |
Southeast Asian coral region Centers of greatest endemism lie outside of coral triangle |
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Milankovitch cycles |
Cause of long-term climate change Orbit - elliptical or spherical (100,000 year cycle) Tilt- how much the earth is tilting. Usually around 23.5d (40,000 year cycle) Precessions - wobble of the earth around its axis. (23,000 year cycle) |
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Patterns of Recent Climate Change |
Global Temperature has risen 0.9dC in the last 100 yrs. 2 major periods of warming (1905-1940; 1975 - present) and one period of insignificant change (1940-1975) 16 warmest years in history - 2001-2015 and 1998 (super el nino) Severe rainstorms have become more common. Floods and drought have also increased since 1950 Cryosphere melting => positive feedback by reduced albedo. decrease in arctic sea ice. 97% of world's glaciers are retreating. |
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Maunder minimum |
temporary reduction in solar output which caused the Little Ice Age from 1550 through 1800. |
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Carbon cycle |
Out of balance due to burning of fossil fuels. Deforestation and fossil fuel burning put 10 bty into atmosphere; ocean and land take in 6 bty. Ocean is acidifying. |
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Greenhouse effect |
CO2, CH4, N2O, HFCs, PFCs, water vapor, etc. Allow visible wavelengths pass through atmosphere => surface converts light energy to heat => GHGs absorb and re-radiate infrared. Some greenhouse effect is necessary for life on Earth. |
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A1F1 scenario |
business as usual increase of 4.5dC Big decrease in precipitation in Central America, Mediterranean, and Southern Africa |
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B1 scenario |
paris agreement Increase of 2dC |
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Effects of climate change |
1. Altered precipitation patterns - increase in high latitudes, decrease in some regions under high emissions scenario. Winter rainfall increase, summer rainfall decrease. Extreme drought more common. 2. More days with higher temperatures. Every summer is hottest on record |
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Ecological consequences of climate change |
a. phenological shifts - marmot hibernation ends earlier, robin arrives in spring earlier. Plants flowering earlier. Non-responders decreasing in number. Potential loss of synchrony with mutualists, food sources ie butterflies and herbs. b. range shifts - shifts to higher latitudes and altitudes. eg forest transition zone on Vermont mountains. Northern hardwoods replacing high elevation boreal |
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Species that are particularly vulnerable to climate change |
1. Species that have nowhere to go - high latitude species may have nowhere to go (ice-obligate species, high altitude species) 2. Species that live in coral reefs - both warming and ocean acidification can cause bleaching 3. Species that live in the tropics - narrow thermal tolerance, so are vulnerable to even small climate change, most likely to experience disappearing climates |
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Solutions to climate change |
A. Forests grown as carbon sink - stop deforestation => not a solution B. Energy conservation => only delays outcome C. rapid and large emission reductions/aggressive expansion of alternate energy sources |
