Biology 2483A Study Guide - Final Guide: Juncus Gerardii, Distichlis Spicata, Spartina Patens

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8 Dec 2016
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Ecology Final Notes
Competition
- ½ organisms on earth get energy from feeding on others (exploitation one benefits, one directly harms
[potential to reduce growth, survival or reproduction of prey)
- Not all organisms fit into categories, some predators (wolves) also eat berries, nuts and leaves
- Parasitoid: insects that lay eggs in another insect host
- Sit and wait predators: barnacles, carnivorous plants, spiders
- Predators concentrate efforts where high prey (wolf packs follow migration of elk, spiders relocate)
- Specialist predators (preference) lynx eat more hares then expected based on abundance
- Some predators concentrate on prey abundant guppies ate which
was more abundant form search image increase efficiency
- Some cases: prey switching consistent with optimal foraging theory
- Most herbivores feed on a narrow range of plants. Most insect
herbivores feed on only one or a few plant species.
- Other herbivores (e.g., grasshoppers) feed on a wide range of species.
- Large browsers, such as deer, often switch from one tree or shrub
species to another.
- Macroscopic predators 530 MYO pre evolved defenses (body armor and spines)
- Physical Defenses: fast, large, armor, aposematic coloration (learning to not eat
organisms that have toxins), Crypsis (prey is camouflaged), Mimicry (prey resembles
another organism that is toxic)
- Behavioral Defenses: not foraging in open areas, look out, defensive circles
- Trade off b/w physical and behavioral - Snails with thick shells are the last to take refuge.
- Plant Defenses: Masting: plants produce large number of seeds in some years and none
in others, pernicious (nearly invisible) hairs
- Compensation: Removal of plant tissue stimulates new growth less shading
- Full compensationno net loss of plant tissue
- field gentians, early herbivory = compensation, but later in the season it does not. If too
uh tissue is reoed, or there are’t eough resoures for groth, opesatio aot our
- induced defensesproduced in response to herbivore attack. Some cacti increase spine production
after being grazed.
- Secondary compoundstoxic chemicals to reduce herbivory some induced, constituent attract
parasites that will kill herbivores
- Predators counteract by: poisons, mimicry, inducible traits (ciliate adjust size to match prey), enzymes to
digest + tolerate plant toxins
- Beetles in the genus Blepharida have evolved a counterdefense: they chew slowly through leaf
veins with the resin canals, releasing the pressure so gradually that the resin does not squirt from
the plant.
- A leaf-feeding beetle rapidly reduced the density of Klamath weed, an invasive plant that is
poisonous to livestock.
- Anolis lizard predators and their spider prey in the Bahamas - On twelve islands, four had lizards naturally, four
had lizards introduced for the study, and four had no lizards (control), Density of spiders was about 6 times
higher on islands without lizards (13 species extinct on introduced)
- Lesser snow geese summer in salt marshes of northern Canada where they feed on
grasses and sedges. (NPP VS GRAZING - Intermediate = highest)
- The plants are fertilized by the geese feces and grow rapidly after low to intermediate
levels of grazing.
- 1970, lesser snow goose densities increased exponentially; probably because of increased crop production in
their overwintering sites. geese removed vegetation totally
- Golden apple snails were introduced to Taiwan in 1980 and spread rapidly throughout Southeast Asia - snail eats aquatic plants,
algae, and detritus -- Wetlands with high snail densities have few plants, high nutrient concentrations, and high densities of algae --
causes a shift from wetlands with clear water and many plants to wetlands with turbid water, few plants, high nutrients, and high
algal densities, snails affect plants directly by feeding on them, and also release nutrients in their feces that stimulate phytoplankton
growth.
- tested the influence of the snail in enclosures with water hyacinth plus 0, 2, 4, or 6 snails - Water hyacinth biomass increased when
no snails were present, but decreased in all other enclosures -- Phytoplankton increased in enclosures with highest snail density.
- experiments with a mite that eats the herbivorous six-spotted mite, both went extinct prey easy 2 catch - extiction
o strips of vasiline, made harer to get, mites lasted longer population cycle resulted
- some pop cycles due to prey food
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- Snowshoe Hare Cycles 200 years showed population cycle b/w hare and lynx, Hare reproductive rates
reach highest levels several years before hare density reaches a maximum. They reach lowest levels 2 to 3
years after hare density peaks. Hare survival rates show a similar pattern.
- Hypotheses to explain changes in hare birth and survival rates: 1. Food supplies become limiting when hare
population density is high 2. Predation by lynx and other predators can explain drop in survival rates.
- Evolution is a factor: experiments with rotifer predator and algal prey, found pops cycled but not in
synchrony predator pops peaked when prey pops reached lowest levels and vice versa
o Algal genotypes most resistant to predators were poor competitors, increased at high predator density
Parasitism
- Clown fish with critter in mouth
- Symbionts: live in or on other organisms more tha ½ earth’s speies, parasite: consume tissue or fluids
- Parasite includes herbivores such as aphids or nematodes that feed on one or a few host plants (macro vs micro)
- Fungi ectoparasites attack crop plants - mildews, rists and smuts grow and extend hyphae get nutrients
- Plant ectoparasites: Aphids, whiteflies, scale insects, nematodes, beetles, and juvenile cicadas herbivore and
parasites, plant endoparasite: bacterial pathogens - rot
- Animals also have ectoparasites: athletes foot fungus, fleas, mites, lice and ticks some transmit disease
- Endoparasite: tapeworm, bacteria that causes plague, tuberculosis
- Ectoparasites disperse more easily (lice), endo disperse through complex life cycles, feces, enslaver
- Ecto exposed to more things ex aphids eaten by birds, insects, attacked by parasites, parasitoids, endo immune system
- Host defenses: ex regulate biochemistry: vertebrae host has protein called transferring that removes iron from blood serum and
stores it so bacterial and fungal endoparasites a’t get it but some parasites steal iron from transferrin
- Plant defenses: resistant genes, nonspecific immune responses, chemicals Lignin barrier to spread, chemicals that warn of attack
- Plants have secondary compounds not essential to primary function some animals eat to treat or prevent infections Woolly
bear caterpillars switch from their usual food plants to poison hemlock when parasitic flies lay eggs on their bodies.
- Chimpanzees infected with nematodes seek out and eat a bitter plant that contains chemicals that kill or paralyze the nematodes
- Some hosts encapsulate endoparasites, or eggs to make harmless some insects have lamellocytes (blood cells) that can form
multicellular capsules around large objects such as nematodes
- Parasitoid wasps that attack fruit flies avoid encapsulation by injecting virus-like particles that infect the
lamellocytes and cause self-destruction -- Others lay eggs covered with filaments that embed i host’s fat
cells so not detected by circulating lamellocytes.
- Australia European rabbits (introduced 1859) pop exploded and control mechanisms failed, Myxoma virus
(1950) killed 99.8%
o Overtime, rabbits evolved resistance, rabbit mortality rate decreasing with # of epidemics
experienced now
- New Zealand lakes: change in frequencies of trematode worm and snail host, found parasites infected snails from their home lake
more effectively than other lakes, snails evolved in response to parasites, abundant genotype changed lab experiment: parasites
infect snails with common genotype vs rare drive pop down so frequencies change
- Arms race may stop because of trade-offs trait that improves defense of parasite may reduce growth, survival or reproduction
- Asia: fungal pathogen causes chestnut blight wiped out most chestnut populations, reduced geographic range (used to dominate)
- Parasites can humpact host population cycles study that manipulated numbers of parasites in red grouse populations (tend to
crash every 4 years) parasite trematode was known to decrease
survival and reproduction of the birds
o When grouse was expected to crash, two pops treated with
drug to kill parasite, in control #s crashed, parasite removal in
other pops reduced fluctuations
- Parasites can change species interactions, community composition, physcial environment
- Species interactions: experiments with flour beetles and protozoan parasite when parasite was absent
,one beetle outcompeted the other driving to extinction, parasite absent? opposite
- parasites change predator prey interactions by decreasing physical condition of one
- parasites can change behavior of host protozoan makes rats less wary of cats, some worm parasites
cause amphipods to move from sheltered areas to bright light more likely to be eaten
- Ecosystem engineer:change environment: when beaver builds Dam changes # ponds
o Amiphipod corophium is ecosystem engineer in tidal mudflats hold mud together preventing
erosio ad forig ud islads at lo tides, he parasite, these dissapear
Mutualism and Commensalism
- Ant farmers nourish, protect, eat fungi species a’t surie ithout eah other underground gardens feed 2-8mill ants
- Leaf-cutter ants ut leaes ad rig to fugi, pulp ad fertilize  droppigs eed fugal gardes to control invaders
- Fungi produce gongylidia on which ants eat, ants scrape wax from leaves fungi cant do, fungi digests and detox chemicals plants
use to deter insect herbivores, study: parasitic fungus (E) attacks fungal gardens of leaf-cutter ants, parasite transmitted from
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gardens death of ant colony ants respond by increasing weeding rate, enlist help of others, ants have bacteria that inhibit
parasite and promote growth of fungus
- Bacteria benefit b/ get plae to lie at’s eoskeleto + food gradular seretios fro at, bac = 3rd mutualist
- Facilitation: positive interactions (benefits > cost) divided into mutualism and commensalism
- Mutualism: mutually beneficial (+/+) (cora + algae, coral provides algae w home, nutrients (P+N) and sunlight, algae gives carbs)
- Commensalism: (+/0) (lichens that grow on trees or bacteria on skin, forest many depend on trees for habitat)
- Symbiosis: 2 species live in close physiological contact w/ each other coral + algae (+/-)(+/0)(+/+)
- Most plants have mycorrhizae: symbiotic b/w roots and various fungi increase surface area of plant to take up nutrient hyphae
- Ectomycorrhizae: The fungus grows between root cells and forms a mantle around the root.
- Arbuscular mycorrhizae: The fungus grows into the soil, extending away from the root; and also penetrates into some of the plant
root cells
- Herbivores (cattle/sheep) bacteria in gut to metabolize cellulose, Wood-eating insects gut protists to digest cellulose
- Mutualism can arise from host-parasite interaction (strain of amoeba that was infected by bacteria, caused host to be smaller, grow
slow and often killed but then bacteria evolved to be harmless to amoeba, and amoeba evolved to depend for things need each
other now) obligate (not optional some positive interactions)
- Tropical figs pollinated by fig wasps cant reproduce without each other coevolved wasps have complex reproductive
behaviors in the fig receptacle that ensures pollination, wasp larvae develop by eating some of the fig seeds
- Many mutualisms and commensalisms are facultative (not obligate) and show few signs of coevolution in deserts shade of adult
plants create cooler and moister conditions, seeds of many can only germinate in shade, adult called nurse plant one species of
nurse plant may protect seedlings of many other species desert ironwood (165 different species) may evolve little
- Large herbivores (deer/moose) eat trillium seeds disperse through feces sporadic +
facilitative little evidence of coevolve
- Soil temperature can affect if wetland plants are commensals or competitors
- Wetland soils can be anoxic. Some plants such as cattails aerate soils by passively
transporting oxygen through continuous air spaces in the leaves, stems, and roots some
o2 becomes available to other plants
- Experiment: cattails (Typha) and forget-me-not (Myosotis) that lacks air spaces were
grown at different temps -- At low temperatures, soil oxygen increased when cattails were
present, but not at the higher temperatures, low temps cattails helped FMN, high temps it
decreased growth
- Mutualisms can be categorized by the type of benefits that result
o Trophic: mutualist receives energy or nutrients from partner (leaf cutter ants/fungus, mycorrhizae)
o Habitat mutualism: one provides shelter, living space or habitat (pistol shrimp and goby fish goby = refuge + on lookout)
o Service mutualism: one partner preforms ecological service for other (pollination, dispersal, defense) fig-fig wasp
- Sometimes cost = providing reward for service: during flowering milkweeds use up to 37% of energy gain from
photosynthesis to produce nectar that attracts insect pollinators
- If environment changes and benefit changes for mutualism, outcome may change important in facultative
(not obligate)
- Some ants protect treehoppers fro predators, ad the treehoppers serete hoede sugar solution),
which the ants feed on if predators are few, shifts from +/+ to +/0
- Mutualist may withdraw reward in high nutrient places, plants can get nutrients and may reduce carb
reward to mycorrhizal fungi
- Cheaters are individuals that increase offspring production by overexploiting their mutualistic partner. =
Yucca and yucca moth (pollen and eggs), cheating if moths lay too many eggs (larvae eat too many seeds),
penalty: yucca aborts flowers
- Positive interactions affect abundances and distributions of populations + composition of communities
- Drosophila neotestacea has a bacterial symbiont that protects it from a nematode parasite. The nematode
can reduce mating success, but if the bacterial symbiont is present, egg production remains high.
- Ants + acacia trees: The ants live in the large thorns on the tree, and the tree produces high-protein Beltian
bodies on the leaf tips, which the ants gather to feed their larvae,
in exchange ant patrols 24 hours attack insect and mammal
herbivores, ants use mandibles to eat plants 10-150cm from tree-
competitor-free zone
- Acacias without ant colonies are often killed by herbivores in 612
months, ants cant survive w/o trees
- + interactions community composition: coral reef fish have
service mutualisms with smaller organisms (cleaners) that remove
parasites from fish(clients) benefit greater then energy if were to eat
- manipulated mycorrhizal fungi -- plant biomass and phosphorus uptake increased as the number
of fungal species increased (y=shoot, root biomass + phosphorus, x = fungi#)
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